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Fatigue and Fracture

2006;():1-10. doi:10.1115/ESDA2006-95034.

In Low Density Polyethylene (LDPE) plant, the ethylene gas is compressed up to a pressure of 3000 bar. This is achieved by compressing the ethylene gas using two stages as primary [18 °C (64.4 °F), 1700 bar] and secondary [90 °C (194 °F), 3000 bar] stage compressors. The studs under investigation were used to clamp the flange of the suction and discharge valves to the cylinder head (Studs from the Flanges of 1st Stage - Secondary Hyper Compressor). Six cylinders are present in each stage and 6 studs are used to fix each flange on the suction or discharge valve to the cylinder head. The material used to fabricate these studs was B7 and the threads were produced by rolling. In the 1st stage cylinders frequent failures of studs started within two months of operation. Since the start up about 11 studs from different location have been failed. A metallographic examination using optical and scanning electron microscopy as well as energy dispersive spectrometry (EDS) revealed that the failure was due to fatigue.

Commentary by Dr. Valentin Fuster
2006;():11-18. doi:10.1115/ESDA2006-95035.

Fatigue life investigations have been made for hollow rollers in pure normal loading. Different hollowness percentages between 20% and 80% have been tested to find the optimum percentage hollowness that gives the longest fatigue life. Two main models were built for this purpose. Model 1 with two identical sized rollers and Model 2 with two non identical sized rollers. In each model, two cases have been studied, when both rollers are hollow and the case when one roller is hollow while the other one is solid. The Ioannides-Harris (IH) theory was used to calculate the relative fatigue life of the hollow rollers with respect to solid rollers under same loading. Investigations have been made for five different materials, CVD 52100, Carburized steel, VIMVAR M50, M50NiL and Induction-hardened steel. The finite element package ABAQUS has been used to study the stress and deformations in the loaded rollers. In general, the optimum hollowness percentage with the longest fatigue life ranges between 60% and 70% based on the kind of the material, whether the rollers are same size or different size and whether both rollers are hollow or only one of them is hollow. Using IH theory for fatigue life calculation resulted in having infinite fatigue life for those rollers made of Induction-hardened steel that relatively has high fatigue limit value. Rollers in the optimum range are flexible enough to get the best redistribution the stress in the contact zone. For models of a hollow cylindrical roller in contact with a solid roller, the optimum hollowness is around 70%. When both cylindrical rollers are hollow, the optimum hollowness decreases to be between 60% and 65%. At the optimum hollowness, small differences in the fatigue life have been found between models of one hollow roller and models of two hollow rollers. Even though, having both rollers hollow means less weight, saving more material and more stability for the system.

Commentary by Dr. Valentin Fuster
2006;():19-23. doi:10.1115/ESDA2006-95086.

In this study, the influence of crack conduction method on behavior of reinforced concrete (RC) frame under iterative high impact loading were experimented. To investigate the structural behavior through large deformations and progressive damage and to identify the failure modes, the falling weight and falling height were set more than the structural strength in elastic state. A comprehensive scheme which indicated influence of location of initial cracks on behavior and failure mode of structure was developed. Falling weight impact test was conducted on twenty-one laboratory scaled RC frames which were categorized in four series regard to considered scheme. Concrete volume and compressive strength, number of longitudinal and transverse rebar were constant factors in all specimens. Deformed shape and crack patterns, developed on the side surface of the RC frames, were sketched and total deflections vs. cumulative input energy of the RC girder were plotted. The results revealed the influence of crack conduction on improving the structural behavior and extending the endurance of RC frames against iterative high impact loading.

Commentary by Dr. Valentin Fuster
2006;():25-33. doi:10.1115/ESDA2006-95089.

In general, aeroegine casings may experience an axial force, a bending-moment and radial loading. Under these loads, the high stress regions of these complex aerongine casings will experience local stress and strain concentrations, with various load combinations. The stiffness will also depend on the loading mode. Hence, careful design is required to avoid the various types of failure such as buckling, crack initiation and propagation must be taken into account when designing an aeroengine casing structure. In addition, aerongine casings require extremely high reliability in service and adequate strength under extreme load conditions, i.e. Fan-Blade-Off (FBO) condition, must be demonstrated. Under radial loading of aeroengine casings, which have spoke to shell connections, these are the most likely sites for plastic deformation to occur and cracks to initiate. Also, the load path for each spoke to shell connection within the casing structure changes during loading. Based on these observations, this paper concentrates on the behavior which occurs in spoke to shell connections, referred to as local joints. The intention is first to characterize the local joint behavior and then to incorporate this into a global casing model. The work reported in this paper includes studies of mesh sensitivity, predictions of load path at each local joint under radial load, FE failure loci, upper bound techniques for predicting limit loads and stresses-strains predictions at local casing notches under elastic-plastic and creep situations using approximate notch methods. Hence, the global responses of a casing structure were predicted by utilizing a “repeated local joint” technique in conjunction with simplified global models.

Commentary by Dr. Valentin Fuster
2006;():35-43. doi:10.1115/ESDA2006-95114.

This paper presents a thermomechanical model to predict the surface temperature evolution of a specimen during a fatigue test. In particular, the aim of this theoretical approach is to evaluate the amount of accumulated fatigue damage in the material, on the basis of its temperature growth indicated as damage parameter. To do that, a thermomechanical model has been developed and applied to a unidimensional steel specimen, with rectangular cross-section, fatigued by alternate axial stresses. Temperature variation along the thickness of the specimen has been disregarded. Thermomechanical differential equation has been integrated by applying both initial and boundary conditions. Temperature evolution of steel specimens measured during fatigue tests by means of thermographic techniques has been compared to the corresponding predicted by the theoretical model.

Commentary by Dr. Valentin Fuster
2006;():45-53. doi:10.1115/ESDA2006-95125.

Localized heating during welding, followed by rapid cooling, usually generates residual stresses in the weld and in the base metal. Residual stresses in welding processes give significant problems in the accurate manufacture of structures because those stresses heavily induce the formation of cracks in the fusion zone in high strength steels. Therefore, estimating the magnitude and distribution of welding residual stresses and characterizing the effects of certain welding conditions on the residual stresses are deemed necessary. In this work, residual stresses and distortions on butt welded joints are numerically evaluated by means of finite element method. The FE analysis allows to highlight and evaluate the stress field and his gradient around the fusion zone of welded joints, higher than any other located in the surrounding area. Temperature-dependent material properties, welding velocity, external mechanism constraints, technique of ‘element birth and death’ and latent heat of fusion are also taken into account. Some numerical results are compared with experimental data showing a very good correlation.

Commentary by Dr. Valentin Fuster
2006;():55-60. doi:10.1115/ESDA2006-95146.

This paper presents a study for predicting crack initiation angle in the case of mixed mode fracture i.e., opening and sliding mode. Experimental and numerical analyses were carried out using photoelasticity and ANSYS finite element program, respectively. Polycarbonate specimens with a thickness of 3mm and different angles of inclinations namely 0° and 22.5° were considered in this analysis. Predicting the crack initiation angles is dependent on the value of stress in the vicinity of the crack tip. As a result, stress intensity factor is considered as the most significant parameter in this regard because it represents the stress level at the crack tip. In experimental analysis Schroedl and Smith method is used to calculate the pure opening mode stress intensity factor (KI ) and Smith and Smith method for the mixed mode case (KI & KII ). Then, SIF’s for straight and inclined crack are determined numerically using ANSYS. After that, the values of stress intensities are incorporated in minimum strain energy density criterion (S-Criterion) to find the crack’s angle of initiation.

Commentary by Dr. Valentin Fuster
2006;():61-66. doi:10.1115/ESDA2006-95149.

Nonlinear finite element analysis was performed to predict the thermal fatigue for leadless solder joint of TFBGA Package under accelerated TCT (Temperature Cycling Test). The solder joint was subjected to the inelastic strain that was generated during TCT due to the thermal expansion mismatch between the package and PCB. The solder was modeled with elastic-plastic-creep property to simulate the inelastic deformation under TCT. The creep strain rate of solder was described by double power law. The furthest solder away from the package center induced the highest strain during TCT was considered as the critical solder ball to be most likely damaged. The effects of solder meshing on the damage parameters of inelastic strain range, accumulated creep strain and creep strain energy density were compared to assure the accuracy of the simulation. The life prediction equation based on the accumulated creep strain and creep strain energy density proposed by Syed was used to predict the thermal fatigue life in this study. The agreement between the prediction life and experimental mean life is within 25 per cent. The effect of die thickness and material properties of substrate on the life of solder was also discussed.

Commentary by Dr. Valentin Fuster
2006;():67-79. doi:10.1115/ESDA2006-95176.

Many important engineering applications such as nuclear reactors, ships, pipes and pressure vessels are shell-like structures made with weldments. For such a structure, a major problem is the development of residual stress and distortion due to welding. Residual stresses in weldments significantly affect stress corrosion cracking, hydrogen-induced cracking and fatigue strength in welded structures. As-welded components generally have certain amount of residual stresses caused by the application of intense heat or thermal loading at the weld joint, formed due to non-uniform cooling rates at different points in the weld metal and heat affected zones. Presence of residual stresses in a component is detrimental as they may lead to failure below the design stress value and also affect many important properties including the life of a welded component. Welding induced residual stresses can significantly increase the fracture driving force in a weldment and also contribute to brittle fracture. The thermal cycle imposed on any welded object causes thermal expansions and contractions which are not uniform. Quantitative measurement of residual stresses is essential to take remedial measures such as change in the welding technique, optimizing welding parameters (heat input, electrode diameter etc,), change in the weld groove design and post-weld heat treatment for minimizing the residual stresses. Residual stress measurements after post-weld treatment would also ensure the adequacy of stress relief treatment. To have an investigation into these aspects, residual stresses due to Manual Metal Arc Welding and Submerged Arc Welding were measured nondestructively with Ultrasonic technique. Residual stress distribution for Shielded Metal Arc Welding and Submerged Arc Welding were compared and the present studies emphasized, that Shielded Metal Arc Welding gave higher compressive stresses than Submerged Arc Welding. Further, to substantiate the studies, commercial finite element analysis software ANSYS 5.6 was used for modeling of manual metal arc welded joint. The results obtained by ANSYS were compared with those by Ultrasonic method.

Commentary by Dr. Valentin Fuster
2006;():81-88. doi:10.1115/ESDA2006-95239.

The kinematic hardening theory of plasticity based on the Prager model and incremental isotropic damage is used to evaluate the cyclic loading behavior of a beam under the axial, bending, and thermal loads. This allows damage to be path-dependent. The damage and inelastic deformation are incorporated and they are used for the analysis of the beam. The beam material is assumed to follow linear strain hardening property coupled with isotropic damage. The material strain hardening curves in tension and compression are assumed to be both identical for the isotropic material. Computational aspects of rate independent model is discussed and the constitutive equation of the rate independent plasticity coupled with the damage model are decomposed into the elastic, plastic and damage parts. Return Mapping Algorithm method is used for the correction of the elastoplastic state and for the damage model the algorithm is used according to the governed damage constitutive relation. The effect of the damage phenomenon coupled with the elastoplastic kinematic hardening is studied for deformation and load control loadings.

Topics: Kinematics , Hardening
Commentary by Dr. Valentin Fuster
2006;():89-98. doi:10.1115/ESDA2006-95263.

The present work attempts to investigate some aspects of the fracture behavior of cracked pipe bends under the action of in-plane bending moments, with and without internal pressure. The results of the elastic-plastic FE analysis of the defect free elbow under the action of in-plane opening and closing bending moments are presented with the emphasis on the hoop and axial stress distribution at various salient locations in the elbow. A severity matrix is outlined subsequently, correlating the various possible cracked configurations and the loading patterns. Parametric studies on the cracked elbows are carried out, in which the parameters, such as ratio of crack depth to elbow thickness (a/t), angle of the part-through wall crack, bend factor ‘h’ and the internal pressure ‘P’ are varied. The variations of the J-integral versus load and load versus load line displacement are presented. The crack initiation load is determined from the material specific critical value of the J-integral. A non-dimensional parameter is suggested as ratio of plastic collapse load to the crack initiation load, which increases with the increase in the internal pressure both in case of the throughwall flawed elbow as well as in the part-throughwall flawed elbow.

Commentary by Dr. Valentin Fuster
2006;():99-103. doi:10.1115/ESDA2006-95303.

Body force method is a method based on principle of superposition. In the body force method the actual condition is treated as an imaginary condition i.e. the semi-infinite plate with hole is treated as a plate without hole; the actual hole is regarded as imaginary on whose periphery boundary forces are applied. The problem is solved by superimposing the stress fields of the boundary forces and concentrated force acting at an arbitrary point to satisfy the prescribed boundary conditions so that the stress condition of the actual plate is approximately equal to that of the imaginary plate. The flamant problem with hole is shown below in Fig. 1.The complex variable method of stress analysis is a versatile technique for stress analysis Problem. The formulas for flamant problem are derived and described. Complex potentials are used for stress analysis. In the present paper, semi-infinite plate with hole is considered for analysis by body force method.

Topics: Force
Commentary by Dr. Valentin Fuster
2006;():105-114. doi:10.1115/ESDA2006-95470.

In the present paper different damage criterions, recorded in literature, are compared, distinguishing the philosophical approach to thermo-mechanical fatigue (TMF) in energetic methods and phenomenological methods. TMF is the combination of mechanical and thermal stresses that takes place in most of mechanical components, especially in automotive engines. The presence of thermal together with mechanical cycling can worsen fatigue and ageing phenomena. In order to describe the TMF behavior of a material or of a component it is necessary to take into account different phenomena contributing to progressive damage as plastic strain, thermal strain, creep and oxidation. In literature it is possible to find different definitions of damage: strain accumulated energy, volume unit damage, residual life. Many papers on TMF are available like experimental studies, analytical investigations, analytical models of damage, life prediction models. The present paper aims to make a first selection of TMF life assessment criteria by means of literature critical analysis. Then, by means of numerical model of actual TMF component, i.e. an exhaust manifold, a comparison between the selected methods is done. Using a set of experimental and numerical analyses of exhaust manifolds collected in literature papers, a comparison and results discussion are done.

Topics: Fatigue
Commentary by Dr. Valentin Fuster
2006;():115-123. doi:10.1115/ESDA2006-95606.

This paper investigates the state of stress induced by oxidation of a typical plasma sprayed thermal barrier coating. At high temperature a thin layer of thermally grown oxide forms in the barrier, and growth with time. Observation of specimens after laboratory tests gave important information about the shape of the oxide layer and about the oxidation law. The oxide is the main responsible for the stress in the thermal barrier coating. A finite element model of a TBC has been developed with temperature-depending material properties, simulating the strain due to lateral growth of the oxide and considering the sintering of the ceramic materials. Time dependent behavior, such as oxide creep, has been taken into account with a simplified model. Simulation has been done for both isothermal ageing and thermal cycles. The location of the maximum stresses in the model are consistent with the location of crack propagation observed in the experimental tests.

Commentary by Dr. Valentin Fuster
2006;():125-131. doi:10.1115/ESDA2006-95633.

In this research the Charpy impact properties of the two steel wheels of grade B2N and R7 were investigated. The dynamic toughness levels of test materials were measured experimentally according to the general recommendations of International Union of Railways (UIC) test standards. To do this, two sets of standard Charpy U-notch impact specimens were taken from the original rail vehicle steel wheels (made from B2N and R7) in their circumferential direction. As the conventional Charpy impact machine gives only one output (i.e., total fracture energy), an instrumented Charpy rig was used for conducting the impact experiments. This provided novel impact test data as well as full failure information (appeared for the first time in the literature for rail vehicle steel wheels). The obtained data included elastic strain energy, fracture initiation, and fracture propagation energy. All these parameters were calculated by double integration of load history captured by a high frequency digital oscilloscope during impact tests. The results showed that the impact toughness of both steel wheels was above the minimum toughness specified by the UIC leaflet. Detailed analysis of instrumented fracture test data showed that a significant portion of total measured Charpy energy (more than 75%) was consumed in fracture initiation and non-related fracture processes in each test material. This is a direct result of high strain-hardening capacity of B2N and R7 steel wheels and their characteristics, which allows the material to absorb high amounts of energy and to deform plastically before any fracture initiation. The total fracture energy of the R7 wheel steel was 160% higher than the B2N (21J against 13J), which was indicative of better dynamic crack resistance of R7 wheel material.

Commentary by Dr. Valentin Fuster

Heat Transfer

2006;():133-141. doi:10.1115/ESDA2006-95012.

In contrast to existing methods which do not take into account multiconnectivity in a broad sense of this term, we develop mathematical models and highly effective combination (BIEM and FDM) numerical methods of calculation of stationary and quasi-stationary temperature field of a profile part of a blade with convective cooling (from the point of view of realization on PC). The theoretical substantiation of these methods is proved by appropriate theorems. For it, converging quadrature processes have been developed and the estimations of errors in the terms of A.Ziqmound continuity modules have been received [6]. For visualization of profiles are used: the method of the least squares with automatic conjecture, device spline, smooth replenishment and neural nets. Boundary conditions of heat exchange are determined from the solution of the corresponding integral equations and empirical relationships. The reliability of designed methods is proved by calculation and experimental investigations heat and hydraulic characteristics of the gas turbine first stage nozzle blade.

Commentary by Dr. Valentin Fuster
2006;():143-158. doi:10.1115/ESDA2006-95037.

A number of turbulence models offered by the commercial code STAR-CD have been tested on the measurements published in the literature with the objective to compare their capabilities for the simulation of a flow and heat transfer in multiple impinging jets. Numerical predictions of the single jet and jet array air impinging heat transfer have been compared with experimental data. The comparison shows that only turbulence models with additional limiters for turbulence production in the stagnation zone are able to correctly predict the jet impingement heat transfer. Suga’s k-ε turbulence model with Yap-correction, k-ε RNG, V2F and SST turbulence models with different near wall modifications are in acceptable agreement with experiments. The deviations from the experimental data, which provide all the turbulence models, are analyzed.

Topics: Cooling , Simulation
Commentary by Dr. Valentin Fuster
2006;():159-164. doi:10.1115/ESDA2006-95100.

Heat transfer enhancement by nanofluids is an emerging and innovative technology for traditional heat transfer problems. However, researches of nanofluids for refrigeration applications are rare either theoretically or experimentally. In this paper, the physical model of a freezing chucker is considered as a two-dimensional domain which is consist of the top and bottom copper plates, and a channel for flowing of copper nanofluids. Inlet flow passes through the left hand side and exhausts to the outlet at right hand side. Three kinds of transverse rib structures, e/Dh = 0.1, 0.2, 0.3, are attached on the internal top wall of the channel for heat transfer enhancement of the coolant flows. To investigate this problem, the transient heat transfer of this channel flow is analyzed and transport problems are solved numerically for the ethylene-glycol (EG) based nanofluids mixture of copper nano-particles with volume fractions of 0%, 0.5%, 1%, 5%, respectively. The smooth channel problem is analyzed and compared to the ribbed channel problem. Analyses of the highest decay rate, the lowest temperature, and temperature distributions of the top-plate surface of a freezing chucker are shown.

Commentary by Dr. Valentin Fuster
2006;():165-175. doi:10.1115/ESDA2006-95202.

This paper aims to investigate the effect of the flow pattern on the mixed convection heat transfer. A 28 thermocouples wire were installed along a 900mm copper tube to measure the temperature distribution. Three insulation layers of fiber glass, asbestos and gypsum were used to minimize to heat lost to the surrounding. A forced convection at the entrance region of a fully developed opposing laminar air flow was investigated to evaluate the flow direction effect on the Nusselt number. The investigation covered a wide range of Reynolds number from 410 to 1600 and heat flux varied from 63W/m2 to 1260W/m2 , with different angles of tube inclination of 30°, 45°, 60°, and 90°. It was found that the surface temperature variation along the tube for opposed flow higher than the assisted flow but lower than the horizontal orientation. The Reynolds number has a significant effect on Nusselt number in opposed flow while the effect of Reynolds number was found to be small in the case of assisted flow. The Nusselt number values were lower for opposed flow than the assisted flow. The temperature profiles results have revealed that the secondary flows created by natural convection have a significant effect on the heat transfer process. The obtained average Nusselt number values were correlated by dimensionless groups as Log Nu against Log Ra /Re .

Commentary by Dr. Valentin Fuster
2006;():177-187. doi:10.1115/ESDA2006-95229.

A free convection from the inside surface of vertical circular tube with a uniformly heated surface (constant wall heat flux) was investigated experimentally for laminar air flow in the ranges of RaL from 6.9 × 108 to 5 × 109 . The effect of restriction lengths placed at top position of the heated tube on the surface temperature distribution and the local and average heat transfer coefficient were studied. The experimental apparatus consists of aluminum tube with 900mm length and 30mm inside diameter. The entry restrictions were included a circular tube of same diameter as the heated tube but with different lengths of 60cm, 90cm, 120cm, 150cm, and 180cm. It was found that the surface temperature along the tube surface higher values for restriction with length of 180cm and smaller values for the restriction with length of 120cm. The results showed that the local Nux and average Nusselt number Nu were higher values for the restriction with length of 120cm and smaller values for the restriction with length of 180cm. The results obtained are correlated by dimensionless groups as Log NuL against Log RaL for each case and proposed a general correlation for all cases.

Commentary by Dr. Valentin Fuster
2006;():189-196. doi:10.1115/ESDA2006-95231.

Laminar free convection heat transfer from vertical and inclined arrays of horizontal isothermal cylinders in air was investigated experimentally and numerically. Experiments were carried out using Mach-Zehnder interferometer and the FLUENT code was used for numerical study. Investigation was performed for vertical and horizontal cylinder spacing from 2 to 5 and to 2 cylinder diameter respectively. The Rayleigh number based on the cylinder diameter varied between 103 and 3×103 . The effect of vertical and horizontal cylinder spacing and Rayleigh number on the local heat transfer from each individual cylinder was investigated. It was seen that the local heat transfer coefficient of each cylinder strongly depends on its position relative to the others. This variation of the local heat transfer coefficient was explained by the interaction of plume’s temperature and velocity profiles.

Commentary by Dr. Valentin Fuster
2006;():197-204. doi:10.1115/ESDA2006-95238.

An artificial neural network (ANN) was applied successfully to predict laminar free convection heat transfer coefficient from an isothermal horizontal cylinder of elliptical cross section confined between two adiabatic walls. Neural networks were used since they constitute a general, powerful function-approximator tool proving able to represent a convectional heat transfer coefficient precisely in the present case. The input database for the network includes 171 experimental data points. The experiment is carried out using Mach-Zehnder Interferometry. Tube axis ratio, wall spacing to miner axis ratio of tube and Rayleigh number are variable parameters or the experimental study. The values of the average Nusselt numbers predicted by the network are in very good agreement with the available experimental data. Therefore the network is used to predict the unavailable data points within the range of our experimental results.

Commentary by Dr. Valentin Fuster
2006;():205-214. doi:10.1115/ESDA2006-95255.

Subsea oil and gas production systems are becoming more complex and more automated. At ocean depths down to 2300m reliability and dependability are of utmost importance. During a production shut-down the production fluid in the subsea equipment will be cooled off by the surrounding ocean water. Simultaneous presence of light hydrocarbons and water in a cold environment with relatively high pressure can create hydrates that are ice like substances capable of blocking the production piping and prevent fluid flow. The equipment is therefore thermally insulated to slow down the cooling process. Field operators are challenging subsea equipment makers to break new boundaries with respect to passive thermal insulation and to increase reliability of the thermal performance. This paper will present the methodology and results of a thermal insulation design project conducted for Total E&P Angola. The project aimed to meet cool down times in excess of 20 hours in areas where 8 hours were previously the norm. In order to meet such a stringent requirement, a system approach to thermal design had to be adopted and reliance on computational analyses tools had to be strengthened. Following a design phase in which the computational analyses tools CFD and FE were used to design the thermal insulation, a full scale cool down test was performed with a subsea Manifold. The simulated cool down results generated by CFD and FE compared well to the results of a full scale cool down test.

Commentary by Dr. Valentin Fuster
2006;():215-224. doi:10.1115/ESDA2006-95257.

The present paper outlines a practical methodology for improved virtual prototyping, using as an example, the recently re-engineered, internally-cooled 1st stage blade of a 40 MW industrial gas turbine. Using the full 3-D CAD model of the blade, a CFD simulation that includes the hot gas flow around the blade, conjugate heat transfer from the fluid to the solid at the blade surface, heat conduction through the solid, and the coolant flow in the plenum is performed. The pressure losses through and heat transfer to the cooling channels inside the airfoil are captured with a 1-D code and the 1-D results are linked to the three-dimensional CFD analysis. The resultant three-dimensional temperature distribution through the blade provides the required thermal loading for the subsequent structural finite element analysis. The results of this analysis include the thermo-mechanical stress distribution, which is the basis for blade life assessment.

Commentary by Dr. Valentin Fuster
2006;():225-230. doi:10.1115/ESDA2006-95265.

A 3-dimensional Eulerian finite volume approach is used to predict heat and mass transfer in a laminar two-phase gas-vapor-drop flow in a ribbed tube. It is well known that extending heat transfer area enhances heat transfer and this is the base of studying ribbed faces. It is shown that ribbed faces can be more effective in two phase mist flows since evaporation and deposition of droplets mostly take place near hot surface [1]. Parallel ribs are analyzed. Vapor mass concentration and droplets diameter are calculated by separate transport equations. Analysis is continued from thermally inlet to fully developed vapor gas flow. This model can be used in many applications to understand the effects of changing parameters of hydrodynamics and thermodynamics of the flow, when the flow regime is changed from turbulent to laminar. The results are compared to single phase gas flow.

Commentary by Dr. Valentin Fuster
2006;():231-239. doi:10.1115/ESDA2006-95284.

The aim of this experimental work is to study the pattern dynamics in the Bénard-Marangoni convection. The free surface deformation fields were visualized by interferometry and the temperature fields by infrared thermography. The influence of the aspect ratio, Rayleigh, Biot and Prandtl numbers, was considered. More dynamics are found to be induced by increasing the Biot number. Conversely, increasing the Prandtl number reduces the dynamics. The deformation magnitude and the wavenumber increase as functions of the gradient of temperature. Two behaviours of the deformation, as a function of Prandtl and Biot numbers, were observed, depending on the value of the gradient of temperature.

Commentary by Dr. Valentin Fuster
2006;():241-247. doi:10.1115/ESDA2006-95286.

The aim of this study is to recognize the flow states and the transition mechanisms between them in a simulated Czochralski convective system. We considered the influence of the crystal rotation effects (up to Reynolds number, Re = 3.9 × 103 ) and the buoyancy (up to Rayleigh number, Ra = 7.2 × 107 ) on the flow. Using velocity fields, obtained by an ultrasonic method, the corresponding 2D Fourier spectra and a correlation function; steady, quasi-periodic and turbulent states were recognized as the Reynolds number was increased. The orthogonal decomposition method was applied to these velocity fields. The numbers of modes involved in the dynamics of turbulent states were calculated. From these results, we have concluded that the rotation effects tend to stabilize the flow, and the thermal gradients play a destabilizing role.

Commentary by Dr. Valentin Fuster
2006;():249-261. doi:10.1115/ESDA2006-95290.

This paper reports the results of a study of the transient removal of contaminant particle from enclosures. These results are the basic instruments for finding a model for contaminant particle removal from an enclosure containing an obstacle. A numerical CFD code is developed and validated with different cases, then proper two- and three-dimensional cases are modeled and improvements are done. The improvements are done by proper positioning the inlet/outlet vents. The size and position of the obstacle affect the order of magnitude of the convection-diffusion terms in the Navier-Stokes equations, hence results in different phenomena while removing the particles. One of these phenomena, the step effect, is more detailed in reference [41]. The results of these two papers may be compacted into one whole theory, describing the particle removal efficiency from an enclosure as a function of obstacle position and size.

Commentary by Dr. Valentin Fuster
2006;():263-271. doi:10.1115/ESDA2006-95291.

This paper reports the results of a study of the transient removal of contaminant particle from enclosures containing an obstacle. We study specially a phenomena occur sometimes called the step effect. This phenomenon may occur if the size of the obstacle is small enough in comparison with the length or height of the enclosure. These results are the basic instruments for finding a model for contaminant particle removal from an enclosure containing an obstacle. A numerical CFD code is developed and validated with different cases, and then proper two- and three-dimensional cases are modeled. The size of the obstacle affect the order of magnitude of the convection-diffusion terms in the Navier-Stokes equations, hence results in different phenomena while removing the particles. It may end to a simple removal of the particles from the enclosure or it may contain two or three steps in removal, which is due to increase in scale of magnitude of the convection terms in the Navier-Stokes equations. The results of this paper and Ref. [3] may be compacted into one whole theory, describing the particle removal efficiency from an enclosure as a function of obstacle position and size.

Commentary by Dr. Valentin Fuster
2006;():273-280. doi:10.1115/ESDA2006-95394.

The risk assessment regarding overheating in underground structures is becoming quite common among the designers, when internal heat gains are severe or they occur for a long time. Typical is the case of subway tunnel networks, but many other recent examples may be easily found. Quite often however, not only the air temperature pattern is relevant, but also humidity may play an important role, especially if underground water infiltrations are not negligible. In fact, water evaporation or condensation may significantly affect the temperature profiles; on the other hand, high humidity ratios may hamper some activities performed in the cavities. The present paper aims to present a design tool to simulate the hygro-thermal behaviour of ventilated underground cavities. The model can be used to simulate steady-state or transient conditions: it solves the heat and mass transfer equations in the cavity, providing also a criterion for the evaluation of the fog in the air.

Topics: Cavities
Commentary by Dr. Valentin Fuster
2006;():281-287. doi:10.1115/ESDA2006-95398.

The vehicle HVAC systems have a fundamental role for demisting operation, eventually even more important than assuring thermal comfort because it guarantees the correct visibility for the drivers in the respect of the global security, towards the passengers and the pedestrians. Fiat Auto regulation follows the Standard CEE 78/317 performance test that the HVAC systems must respect to assure windshield demisting. The performance is evaluated by means an experimental test in climatic chamber. This test usually requires either waste of time and of money, since it has to be performed in climatic chambers. Only afterwards, if this first test is satisfied, thermal comfort performances of the vehicle are analysed. The goal of the present work is to describe the CFD virtual model developed to predict the demist performance of an HVAC system coupled with the virtual vehicle cabin, once the cabin CAD surfaces are available (draft surfaces are enough), and not after the vehicle manufacturing. A suite of routines for the prediction of environment moist condensation and evaporation on solid surfaces is presented. The physical problems require the solution of the air flow field along a (cold) solid surface, the evaluation of the unsteady conduction through the solid itself, and the development of a suitable model for the heat and mass transfer within the thin water layer on the fogged surface. The routines for the unsteady simulation of the water layer evolution are designed as a purely interfacial procedure, minimizing the exchange of information with the flow and conductive solver. This allows the coupling with different solvers. Here, the model is used in connection with a commercial CFD solver, in order to predict the defogging process of a car windshield. The water layer is modelled as a collection of closely packed tiny droplets, leaving a portion of dry area among them. The effect of the contact angle is taken into account, and physical assumptions allow to define the local ratio between wet and dry surface for both the fogging and defogging process. The model for the misted layer simulation is derived from a numerical method developed for the aeronautical de-icing systems. Fluid domain, solid domain and liquid film are simultaneously solved, and the problem of the conjugated thermal exchange through solid-fluid domains is carried out by means of opportune interpolations and information exchange on the boundary conditions. Finally this model has been successfully validated with respect to the experimental results.

Commentary by Dr. Valentin Fuster
2006;():289-295. doi:10.1115/ESDA2006-95436.

Interferometric methods are non-intrusive optical measurement techniques, which find extensive use in flow and heat transfer visualization. The present work originates from the idea that by a suitable experimental system and data analysis method, the interferometric technique can be used to estimate its thermal conductivity. A method is developed to obtain the thermal conductivity of a transparent medium using the optical technique of differential interferometry. The basis is of this method is the measurement of the local interference fringe shift values along an isothermal flat plate surrounded by the medium to visualize the heat transfer field. The local Nusselt number distribution along the plate is estimated from fringe shift and compared with theoretical local Nusselt number distribution along an isothermal plate, and this comparison is used to estimate the thermal conductivity of the medium.

Commentary by Dr. Valentin Fuster
2006;():297-304. doi:10.1115/ESDA2006-95438.

Polymer films possess excellent optical properties, such as high transparency, and thermal characteristics, like low heat conductivity, as well as further polymer specific advantages. Consequently, polymer films have an outstanding potential for many solar applications. They are already used for encapsulation of photovoltaic (PV) cells, as convection barrier in solar collectors and as substrate or adhesive layers for glazing. In translucent polymers, energy can be transferred internally by radiation in addition to conduction. Since radiant propagation is very rapid, it can provide energy within the layer more quickly than diffusion by heat conduction. Thus, the transient thermal response of a layer for combined radiative and conduction may be extremely different from that of conduction alone. In this paper, the behavior of a heat conducting, absorbing, and emitting layer of Polypropylene is investigated during the transient interval when both conductive and radiative heat transfer are considered. The governing differential equations include the equation of radiative heat transfer within the material coupled to the transient energy equation, which contains both radiative and conductive terms. The solution procedure is based on nodal analysis and Hottel’s zonal method extended by the ray tracing method. The transient energy equation including the radiative internal energy source is solved using a time marching finite difference procedure with variable space and time increments. In addition, effects of variable parameters including optical thickness and thermal conductivity of the layer are investigated carefully.

Commentary by Dr. Valentin Fuster
2006;():305-313. doi:10.1115/ESDA2006-95475.

A thermoelectric generator (TEG) produces electric power directly out of a heat flux across a certain temperature difference. This thermoelectric effect is based on interlinking effects of thermodynamic forces and fluxes (Seebeck and Peltier effect). Within the present work, a prototype unit using Bi2 Te3 semiconductor elements is installed at the biomass combined heat and power (CHP) plant in Güssing, Austria. Different operation points are examined according to a specific test program in order to find operating figures and describe the technical and economical potential of the TEG. A model of the TEG is implemented in the simulation software IPSEpro and verified with results from the experiments. Based on the model, the test plant is extrapolated to the size of possible demonstration plants for which electric output and energetic efficiency are calculated. For the entire CHP plant, the costs for retrofitting standard heat exchangers to TEGs are calculated and compared to the expected revenues from feeding the additional electricity into the grid. It can be concluded that the TEG gives way for new concepts and ideas but the expenses, especially with respect to the high material costs of the semiconductor, do not support a technically efficient and economically lucrative application of the TEG combined with decentralized heat and power production at present time.

Commentary by Dr. Valentin Fuster
2006;():315-324. doi:10.1115/ESDA2006-95480.

The possibility of exploiting an electrohydrodynamic (EHD) technique of heat transfer enhancement for obtaining a high-performance heat sink is investigated in this work. The proposed heat sink is an evolution of a water-cooled cold plate (CP), designed by Daimler-Benz Aerospace (DBA) for the International Space Station (ISS). The dielectric liquid considered for the design process is perfluorohexane, also known as FC-72, a widely-used refrigerant, space-qualified, and present on the Japanese Experiment Module (JEM) of the ISS. The mechanical interfaces for accommodation on the ISS have been taken into account, along with the dynamic loads typical of the critical launch phase, defined by a given power spectral density (PSD) curve. The thermostructural behavior of the CP has been evaluated by the finite element method (FEM). The numerical analysis has been validated on the reference DBA model, whose performance data are available. The hydraulic results are based on simple calculations of pressure drops in ducts, arranged in series or in parallel. The step-by-step conceptual evolution to the final design solution is described in detail. Also, it is explained how to employ the global thermal resistance reduction for decreasing the pumping power, increasing the heat load or reducing volume and weight of the CP.

Commentary by Dr. Valentin Fuster
2006;():325-336. doi:10.1115/ESDA2006-95502.

A numerical investigation of mixed convection in air in a convergent vertical channel, due to the interaction between a buoyancy flow and a moving plate induced flow, is presented. The plate moves at a constant velocity along the buoyancy force direction and the principal inclined walls of the channel are heated at uniform heat flux. The numerical analysis is carried out by means of the finite volume method, using the commercial code Fluent. The effects of the channel spacing, wall heat flux, moving plate velocity and converging angle are investigated. Heated wall temperature increases at increasing converging angle, except for natural convection in a 10 mm minimum channel gap. The effect of the converging angle on the wall temperatures is less marked at the larger channel spacing. Maximum temperature of the moving plate is attained in the parallel wall channel for a 30 W m−2 wall heat flux, both in the 10 mm and 40 mm channel, whereas for a 220 W m−2 wall heat flux in the 40 mm channel in mixed convection, maximum wall temperatures are exhibited for a 10° angle. Nusselt, Reynolds and Richardson numbers are correlated by a monomial equation for each converging angle and a unique monomial correlation for all investigated angles in the 2.1·10−2 – 5.1·105 Richardson number range is presented.

Commentary by Dr. Valentin Fuster
2006;():337-347. doi:10.1115/ESDA2006-95526.

In this paper an experimental investigation on natural convection in air in inclined channels with rectangular transversal section and lower wall heated at uniform heat flux is carried out. Wall temperature measurements and flow visualization are presented. The results allow investigating on the effect of the distance between the two principal parallel walls and of the inclination angle. The experiments are accomplished for two channel gap values: 20 and 40 mm. The inclination angle is equal to 80° and 88°. The flow development and the shape of flow transitions along the channel are visualized. Flow visualization allows to describe the secondary motion inside an inclined channel. Flow separation region along the lower heated plate begins at lower axial coordinate as the wall heat flux, the inclination angle and the channel gap are greater. The flow separation depends also on transversal coordinate. The detected secondary structures pass from thermals to plumes and vortices. Along the plane parallel to the heated wall, the visualization shows that thermal plumes split in V-shaped structures. For the largest considered channel gap value the instability phenomena in the channel are stronger and chaotic motion in the channel outlet zone is observed. When the channel gap value increases wall temperatures become lower because the higher distance between the walls determines a greater mass flow rate and an increase in the heat transfer.

Commentary by Dr. Valentin Fuster
2006;():349-360. doi:10.1115/ESDA2006-95531.

Mixed convection in air in a convergent channel with the two principal flat plates at uniform heat flux is analyzed numerically by Fluent code. In the considered system two parallel adiabatic extensions are placed downstream of the convergent channel. The forced flow is obtained by imposing a pressure drop between the inlet and the outlet of the channel. The flow in the channel is assumed to be two-dimensional, turbulent and incompressible. A k-ε turbulent model is employed. Results in terms of dimensionless wall temperature distribution as a function of the walls converging angle, the Grashof number, the pressure drop and the channel aspect ratio are presented in the ranges: 0° ≤ θ ≤ 10°; 4.10 102 ≤ Gr ≤ 32.1 105 , 0 ≤ ΔP ≤ 8.82·107 , 10.15 < Lw /bmin < 58.0. Results show that Reynolds number, and then the mass flow rate flowing in the channel, increases at decreasing aspect ratios, Lw /bmin . The converging angle that optimizes the fluid-dynamic within the channel is equal to 5°. Dimensionless maximum wall temperature values decreases at increasing Reynolds number and the larger the aspect ratio, the larger the decrease. The Reynolds number over which natural convection become negligible, with respect to forced convection, increases at increasing converging angle and at decreasing aspect ratio.

Commentary by Dr. Valentin Fuster
2006;():361-369. doi:10.1115/ESDA2006-95575.

In this paper some analytical and numeric analyses of a high temperature heat exchanger are performed. This heat exchanger should be employed in a test loop of a EFCC (Externally Fired Combined Cycle), placed in a experimental facility owned by the Italian electric utility, ENEL. The heat exchanger is the crucial element in this cycle, as it undergoes temperatures above 1000°C and pressures of about 7 bars. The enthalpy of the combustion products of low cost fuels, such as coal, bottom tar, residuals from refineries, is used to heat a clean working fluid, in this case pressurized air. There are some outstanding benefits for the turbine, in regard to the manufacturing and maintenance costs, and also for its life. The heat transfer components are some bayonet tubes, assembled in 4 modules. A half of them is made of ceramic materials, the others of an advanced metallic material (ODS), due to the burdensome operating conditions. First of all, the heat exchanges are evaluated by means of a simplified analytical model. The radiant contribution also has been taken into account, due to the presence of non-transparent gases. Subsequently, the in-tube fluid temperature increase is calculated for all the heat exchanger modules, through an enthalpy balance and with some simplifying assumptions. Moreover, a comparison is made between the analytical solution and the results of a numerical model implemented in a CFD code. A good agreement is found, which indicates that the analytical model is reasonably valid. In fact, the whole heat exchanger temperature change is determined by means of the two methods with a difference of about 7% for both the streams. Finally, these results are to be compared with the experimental data which should be available in the near future, when the facility will begin working. Also, by this way, the developed calculation model would get a validation.

Commentary by Dr. Valentin Fuster
2006;():371-382. doi:10.1115/ESDA2006-95585.

In this paper a parametric analysis of natural convection in air in a channel-chimney system symmetrically heated at uniform heat flux, obtained by means of a numerical simulation, is carried out. The analysed regime is two-dimensional, laminar and steady-state. The numerical procedure employs the full Navier-Stokes and energy equations in terms of the stream function-vorticity approach. Results are presented in terms of wall temperature profiles in order to show the more thermally convenient configurations which correspond to the channel-chimney system with the lowest maximum wall temperature. The analysis is obtained for a Rayleigh number in the range between 102 and 105 , for a channel aspect ratio equal to 5, 10 and 20 and the extension and expansion ratios between 1.0 and 4.0. Correlations for dimensionless mass flow rate, maximum wall temperature and average Nusselt number in terms of Rayleigh number, aspect ratio, extension and expansion ratios are presented. Geometric optimal configurations, for assigned Rayleigh number and aspect ratio, are estimated as a function of the extension ratio. For considered Rayleigh number the difference between the highest and the lowest maximum wall temperatures increases increasing the channel aspect ratio. This behaviour is as greater as the extension ratio is. These differences decrease significantly for the highest Rayleigh number value. The optimal expansion ratio values depend strongly on Rayleigh number and extension ratio values and slightly on the aspect ratio.

Commentary by Dr. Valentin Fuster
2006;():383-390. doi:10.1115/ESDA2006-95604.

A compact and efficient heat exchanger for exhaust gas recovery energy was needed to raise the total efficiency of a thermo-photovoltaic system TPV (Thermo-Photo-Voltaic) for automotive applications (see [1]). In order to respect the strict condition of a high heat transfer surface to volume ratio, a heat exchanger configuration with a plate compact multi-pass counter flow and locally cross-flow recuperator has been chosen. The goal of this work is the understanding of the behaviour of the heat exchanger with numerical and experimental analysis for different geometrical and operating conditions. A high number of dimensions and manufacturing constraints was evaluated before reaching a definite design of a compact and efficient heat exchanger to be tested in the lab for initial experiments. The experimental work was needed in order to validate the numerical model. As the material needed for the real application could not be easily manufactured and instrumented in a workshop, a simplified real model, made of brass, was built, in order to compare numerical results and experimental findings. It was supposed that results obtained in this way would be sufficient to be considered valid when extrapolated in the real heat exchanger high temperature operating conditions and manufacturing material. The experimental results have been successfully compared with numerical ones obtained with the Fluent CFD code (release 6.2.16) Curves of performance (ε-NTU diagram plotted as a function of the ratio between the minimum and the maximum thermal capacities of the flows and pressure drop -mass flowrate diagram as a function of the average temperature) have been obtained and were useful to choose the adequate configuration for different applications, depending on the requested heat transfer and maximum allowable pressure drop. The output of the investigation was: heat transfer, outlet temperatures for both air flows, heat exchanger efficiency, differential pressure drop for both hot and cold sides. After this validation final numerical simulations have been carried out in order to understand the dependence of the heat exchanger efficiency on other geometrical parameters and operating conditions such as plates dimensions, numbers and height of vanes, operating pressure and so on.

Commentary by Dr. Valentin Fuster
2006;():391-399. doi:10.1115/ESDA2006-95634.

In this paper a three-dimensional steady state incompressible turbulent air flow is considered in a large single room. The buoyancy affected turbulent air flow is simulated by solving governing equations numerically. The turbulence modeling includes both k–ε and zero-equation models and their results are compared to the experimental data. The paper reviews several aspects such as displacement of radiator system performance, temperature and flow field distribution and comfort. The results show that the best temperature distribution and comfort obtain when radiator is installed under the window and its height be equal to or greater than that of the window.

Commentary by Dr. Valentin Fuster
2006;():401-411. doi:10.1115/ESDA2006-95729.

Pressure vessels are common equipment in oil, gas and petrochemical industries. In a hot containing fluid vessel, excessive temperature gradient at junction of skirt to head (weld line), can cause unpredicted high thermal stresses; Thereby fracture of the vessel may occur as a result of cyclic operation. Providing a hot box (air pocket) in crotch space is a economical, applicable and easy mounted method in order to reduce the intensity of thermal stresses. Natural convection due to temperature difference between the wall of pocket, will absorb heat near the hot wall (head of the vessel) and release that near the cold wall (skirt of the vessel), then the skirt wall conducts heat to the earth as a fin. This conjugated heat transfer removes the temperature gradient boundary at welded junction. This phenomena will lead the temperature gradient on the weld line from a sudden to smooth behavior, thereby the skirt-head junction, that is a critical region, could be protected from excessive thermal stresses. In this paper the profit of hot box and conjugated heat transfer in cavity has been demonstrated experimentally. As a result it is shown that the conductive heat transfer through the skirt (which acts as a fin) ensures the continuation of natural convection in the box. Also the governing equations has been solved numerically and compared with experimental results.

Commentary by Dr. Valentin Fuster
2006;():413-422. doi:10.1115/ESDA2006-95749.

A 2-d rectangular slab, internally cooled by circular tubes of different diameters, is used as a benchmark to perform a numerical thermal optimization procedure on a heat transfer configuration obtained by “constructal” considerations. Three different geometric arrangements are investigated: in the first one, all cooling holes have the same diameter; in the second, there are two hierarchies of holes with two different diameters; in the third, yet another series of smaller holes is added. To assist the user in systematically assembling multiple configurations, a custom user interface utility for generating constructal geometries has been developed. Thermal boundary conditions are assigned as if the slab were the axial cross-section of an elongated prismatic body, and as if the ducts were internally cooled by forced convection. For each case (single diameter of the cooling holes, 2 and 3 different diameters) a series of numerical simulations has been run to assess and compare the performance of different values of the geometrical parameters (location of the holes, slab aspect ratio, etc.). The best performing configurations for each case have then been compared with those identified for the other cases, the objective function being the average temperature of the slab “volume”. All results consistently indicate that, under the specified design conditions, the configuration obtained by a simple constructal optimization is the best performing one at each configuration level (1, 2 or 3 series of cooling holes).

Commentary by Dr. Valentin Fuster
2006;():423-430. doi:10.1115/ESDA2006-95798.

The goal of the present work was to perform a thermal and fluid dynamic analysis of a refrigerated warehouse used for cheese conservation and ripening at a cheese factory close to the city of Cagliari. Air cooling is obtained by means of cooling units located under the cooler rooms ceiling, where the air distribution is realized by means of tubular pipes made of micro-porous material. An electronic control system allows keeping temperature and humidity within the desired range. As a first step, in order to verify the operation of the cooling system, an investigation was performed through a numerical simulation of the 3D and turbulent flow within the warehouse by solving the Reynolds Averaged Navier-Stokes (RANS) equations; this task was performed by employing the commercial code Fluent. The simulation allowed to represent the temperature and the velocity maps of the air flow inside the cooler room; the most relevant result mainly consists of a strong temperature gradient along the vertical direction. Some possible interventions for improving the air distribution are also suggested.

Commentary by Dr. Valentin Fuster
2006;():431-437. doi:10.1115/ESDA2006-95821.

In this paper an analysis of the fluid flow and the heat transfer in the next generation micro-sized heat sinks is presented. The analysis includes three different geometries for the channels of the heat sinks: rectangular, triangular and trapezoidal, with water as the cooling work flow. A constant heat flux typical of the current high-intensive computational chips (such as the current Pentium chips) is applied at the bottom of the heat sink in a small 1 cm × 1 cm area, an area also typical of the current contact area between electronic devices and the heat dissipaters. The analysis aims to determine the effect of geometry at microscopic scales. It is found that the temperature at the bottom of the dissipater increases approximately in a linear fashion and that by increasing the Reynolds number this temperature decreases. On the contrary, by having a decay in the Reynolds number the temperature of the working fluid increases, bringing a decrease in the viscosity allowing in turn a decrease in the friction losses since the friction coefficient decreases.

Commentary by Dr. Valentin Fuster

Internal Combustion Engines

2006;():439-445. doi:10.1115/ESDA2006-95017.

In the present article, the performance analysis of a bi-fuel spark ignition engine is investigated. An originally gasoline-fuelled car is used for experimental tests. It is converted to a bifuel vehicle which may run both on natural gas and gasoline. The wheel and motor power of the car are measured before and after conversion together with exhaust emissions. It is observed that the engine power reduces not only in gas but also in gasoline state after the conversion in comparison with the base engine power. The effect of gas/air mixer design is fully explained. The results of closed-loop and open-loop gas supplying systems are compared. The influence of ignition timing on the power loss is discussed. The optimum timing advance for natural gas is obtained through laboratory experiments. The power and emissions of the converted vehicle are compared with the base power and emission values for a series of engine speeds. The reasons for the power loss are discussed and some useful methods are recommended to decrease the amount of power loss.

Commentary by Dr. Valentin Fuster
2006;():447-452. doi:10.1115/ESDA2006-95115.

The ABAQUS gasket elements are an efficient and flexible tool to study gasket applications. Nevertheless their usage is not limited to gasket analysis, but it provides an effective improvement in structural analysis. The results point out that both the predicted contact pressure and the predicted stress distribution depend on the mesh topology. Several combinations of mesh dimension and topology are investigated. The purpose is the definition of a calculation methodology and the demonstration of the application efficiency. Complex models analysis highlights that the defined methodology represents an effective tool for the design and the optimisation of the head gasket, the cylinder head and the engine block. The methodology is then applied to an actual case. A layout modification to prevent a sealing issue is validated by the FEM analysis. The modification was introduced in the actual component. The qualitative and quantitative evidences provided by the calculation were confirmed by the experimental results obtained by colour films (not running engine with assembly loads at room temperature) and by the test bench (actual working conditions).

Commentary by Dr. Valentin Fuster
2006;():453-461. doi:10.1115/ESDA2006-95118.

Thermo mechanical fatigue problem is treated to define an analysis methodology permitting the strength evaluation by reliability viewpoint. The main difficulty is the lack of both theoretical and experimental information; consequently the problem is treated verifying continually the validity and the limits of the developing solution method. The chosen application was the exhaust manifold of an IC engine; FE analyses were executed following the standard methodology consolidated by this time in CRF. In particular a time transient thermal analysis was performed taking into account the exhaust gas fluid dynamics inside the manifold; the thermo structural analysis took into account both geometrical and material non linearities; the contact between the manifold and the cylinder head was simulated and the bolts pre load was applied. The evaluation of the thermal fatigue damage is executed adapting methods developed to face isothermal fatigue, analysing also energetic criteria. A preliminary reliability evaluation was executed, on the base of numerical results and of experimental information. The results permitted the individuation of critical areas of the manifold and a preliminary evaluation of the number of cycles allowable before the rupture. Since the several criteria furnished different durations, a more accurate evaluation may be deferred to the execution of experimental tests.

Commentary by Dr. Valentin Fuster
2006;():463-476. doi:10.1115/ESDA2006-95215.

During most of the operating conditions occurring on a vehicle driving cycle, a reciprocating IC engine works at low load and low speed, with poor fuel efficiency. In this regard downsizing appears as a major way of improving fuel consumption of Spark Ignition Engines. In fact, downsized engines have smaller friction surfaces and can work on the same vehicle and on the same driving cycle with higher mean effective pressure and higher efficiency. In this paper the main technical trends and problems related to SI engine downsizing are reviewed and discussed. Assuming a stoichiometric boosting, a simulation code is used to outline a strategy to improve low end torque of a downsized DISI engine. In the numerical experiments volumetric efficiency is enhanced by an optimal configuration of the inlet system. For the same objective, assuming a Variable Valve Timing, a proper selection of maximum lift and opening duration of the inlet valve allows a reduction of the reverse flow of fresh mixture. The optimization of the exhaust system and of the lift diagram of the exhaust valve leads both to the enhancement of volumetric efficiency and to the reduction of residual exhaust gas, with beneficial effects on knock phenomenon. An evaluation of fuel consumption gains resulting from downsizing is made as well, with reference to a New European Driving Cycle.

Commentary by Dr. Valentin Fuster
2006;():477-485. doi:10.1115/ESDA2006-95217.

The main objective of the present paper is to describe the research work accomplished to develop a combined experimental/numerical calibration method, which has the capability to validate combustion models embedded in an advanced 3-D numerical engine simulation tool. The first part of the paper describes the background for the necessity to use 3-D numerical simulation techniques as well as the basic setup requirements for both the virtual engine model and the real engine experimental support. The paper continues with a description of the method used to derive a 3-D flame front propagation function from direct true-color combustion visualizations. Finally a validation of the suggested method is presented by comparing the obtained results with those produced by an independent thermodynamic computation approach.

Commentary by Dr. Valentin Fuster
2006;():487-495. doi:10.1115/ESDA2006-95352.

Turbocharging of gasoline engines has been improved less than diesel engines due to some difficulties, especially knock phenomena. They require wider air flow range and faster response too. A computer code is developed to simulate turbocharged gasoline engine behavior. A three zone combustion model is employed. Different performance curves at speed and equivalence ratio ranges are prepared. By this code naturally aspirated and turbocharged behavior are compared. A turbocharged aftercooled engine has been studied in various cases to complete the investigation. Some aftercooler effects are described experimentally. Modeling and experimental results are compared providing valuable achievements.

Commentary by Dr. Valentin Fuster
2006;():497-506. doi:10.1115/ESDA2006-95407.

In recent years the problem of studying particle formation and evolution in turbulent flames has become increasingly important, for both environmental and technological reasons. Information on particle size and morphology is often required, since these characteristics largely influence the effects of particulate matter on human health and global climate in the case of soot. A mathematical model able to describe the evolution of these particulate systems must solve the population balance equation within a Computational Fluid Dynamics (CFD) code that predicts the temperature, composition and velocity fields of the flame. In this work, the recently proposed Direct Quadrature Method of Moments (DQMOM) is applied to the study of soot formation in turbulent non-premixed flames. The model takes into account nucleation, molecular growth, oxidation and aggregation of soot particles; simplified kinetic rates are employed, while velocity and scalar fields are computed by simulations based on the solution of the Reynolds Averaged Navier Stokes (RANS) equations. Different population balance formulations are implemented and compared and results show that DQMOM is a suitable modelling tool; comparison of predictions with experimental data shows that the model accurately describes the morphological properties of soot aggregates.

Commentary by Dr. Valentin Fuster
2006;():507-516. doi:10.1115/ESDA2006-95467.

Multiphase systems, such as sprays and aerosols, are characterized by the existence of a continuous primary phase and a disperse secondary phase. The interaction between the two phases and/or the chemical reactions can affect both composition and characteristic velocity of the primary and secondary phases, as well as the size distribution of the secondary phase. In order to describe these systems, the continuity, mass balance and momentum balance equations as well as additional equations for turbulence, must be solved. Nevertheless if there is the need to account for the evolution of the secondary phase because of continuous and discrete events the population balance equation must be solved. In this work two very efficient ways to cope with these issues will be presented. In particular the use of the quadrature method of moments coupled with the mixture multiphase model, and the multi-fluid model will be presented and discussed.

Commentary by Dr. Valentin Fuster
2006;():517-525. doi:10.1115/ESDA2006-95479.

The aim of this paper is to investigate the use of fast-response pressure transducers for measuring the instantaneous pressure in different sections of a common-rail diesel injection system, both for a single injection and for multiple injections. The influence of the pressure transducer onto the measured pressure is evaluated numerically by comparing the pressure history computed without the pressure transducer and that computed with the presence, and thus with the disturbance, of this sensor. A new electric circuit is proposed in substitution of the standard electronic central unit, which allows to modify the injection parameters and to perform injections on a test rig, as done in the automotive applications. Experimental results are provided both for a single injection and for multiple injections, to demonstrate the capabilities of the proposed test bench for the unijet injectors.

Commentary by Dr. Valentin Fuster
2006;():527-535. doi:10.1115/ESDA2006-95556.

The aim of this work was the modelling and the simulation of the Piezo injector, developed by Siemens VDO Automotive for “spray guided” Gasoline Direct Injection (GDI) systems. The development of the model was based on a 1D lumped parameter approach, which was performed in the AMESim environment. The injector was accurately modelled in its three subsystems, namely the piezo actuator, the thermal compensator and the valve body, in order to have a complete control on its behaviour. The reliability and the accuracy of the models of each subsystem were evaluated through comparisons with experiments for various operating points. The last part of this work describes some applications where the model was used and it demonstrates how accurate modelling and simulation may allow a real contribution in the understanding and optimization of the injector behaviour, reducing time and costs that are involved in an only experimental analysis.

Commentary by Dr. Valentin Fuster
2006;():537-545. doi:10.1115/ESDA2006-95558.

The objective of the present work is the development of a closed-loop individual cylinder spark advance control strategy that allows maximizing torque production while keeping the knocking phenomenon at levels considered safe for the engine components. The research activity has consisted of several phases: the first one was focused on the analysis of the relationship between knocking level and indicated mean effective pressure. The main result of this preliminary phase is a methodology for identifying target values of the chosen in-cylinder pressure based knocking index. A subsequent phase of the work has been devoted to a correlation analysis between pressure-based knocking indexes and knocking indexes obtained by processing other combustion-related signals (engine block vibration and ion current), showing that the ion current based system that has been developed allows reaching high correlation levels. Finally, in order to achieve the target knocking levels, the spark advance control strategy proposed here consists of two parallel contributions: a slower, adaptive and statistically-based contribution, and a fast but range-limited term. The process of designing the controller has been particularly fast and cost-effective, due to the development of a specific software environment that allows verifying the performance the controller would achieve when applied to the actual engine. Such structure may be described as a software rapid control prototyping environment, since an experimental database has been used to reproduce in a simulation environment the response of the controlled system (the engine) coupled to the spark advance control system. The proposed control strategy has been successfully implemented on a V12 6.0 liter high performance engine, allowing to maximize output torque while protecting engine components from knock-related damage.

Topics: Torque
Commentary by Dr. Valentin Fuster
2006;():547-556. doi:10.1115/ESDA2006-95582.

The monitoring of several vehicle and engine operation parameters has been a key factor for the successful introduction of electronic control of the most important car performances. Among the several measured quantities, the measurement of fluid mass flow still requires sophisticated and expensive transducers, no convenient and low cost technologies having been available so far. The recent invention of the concept of bi-layer ribbons, has allowed to adjust the sensitivity of magneto-elastic sensing elements to be employed in the construction of bending sensors, in order to match their metrological properties to the wanted application. Due to their low production cost, small size and good reliability, magneto-elastic bi-layer sensors proved to be a promising technology for the large scale production of fluid flowmeters, which can be used in the automotive industry and are operated in a very wide temperature range, with temperatures spanning from −25 to 115 °C. In the present research, two main application domains have been taken into consideration namely the flow metering of the air streaming into engine air intake manifolds and the measurement of the flow rates of refrigerant fluid in the cooling loop of car air conditioning systems (HVAC). The technical feasibility of agglutinated bi-layer flow sensors, has been investigated and evaluated, by means of experimental testing under real like operating conditions. The present paper briefly describes the manufacturing process and the experimental methodologies. Preliminary results are given and future developments are foreseen, while further research guidelines are established.

Commentary by Dr. Valentin Fuster
2006;():557-565. doi:10.1115/ESDA2006-95590.

The high-pressure hydraulic circuit of the Multi-jet Common Rail (C.R.) system has thoroughly been investigated in the last few years by researchers of the automotive field. However, shortage of knowledge is still present about the high-pressure pump performance. Hydraulic-mechanical efficiency of the pump is only known as mean value and no published data are available on the Radial-jet compression volumetric efficiency. Due to the fact that part of the pumped fuel is partially expelled by the pressure-control valve and because of the presence of the oil flowing in the cooling and lubrification circuit, the determination of the compression volumetric efficiency seems to be a hard task. In the present paper a detailed description of the Radial-jet performance has been provided. The dependence of the flow rate sucked by the high-pressure pump, on speed and load has been studied and the characteristic curve of the cooling-lubricant circuit has been determined. A special procedure was designed and applied for the experimental evaluation of the fuel leakages from the pumping chambers, so as to allow the calculus of the volumetric efficiency. The actual head-capacity pump curves at different revolution speeds were plotted and compared with the electroinjector flow-requirements so as to allow the evaluation of the efficiency of the pressure-control strategy. Furthermore the pump mechanic-hydraulic efficiency dependence on head and speed was also experimentally assessed.

Commentary by Dr. Valentin Fuster
2006;():567-574. doi:10.1115/ESDA2006-95648.

This paper presents a novel monitoring approach to diesel engine combustion based on acoustic measurement of exhaust systems. It investigates the acoustic characteristics from the measurements of individual sensors and their combination based on a linear one port acoustic source model. It has been found that the strength, in terms of pressure, of the acoustic source gives a more accurate representation of engine acoustics because it is obtained by minimizing the reflection effects in the exhaust system. Therefore, the pressure waveform produces more accurate monitoring results for abnormal combustions such as those caused by faults in engine fuel injection systems.

Commentary by Dr. Valentin Fuster
2006;():575-581. doi:10.1115/ESDA2006-95657.

In the field of engines for light motorcycles, two-stroke cycle survival is submitted to the application of direct fuel injection and charge stratification, even in the case of low-cost small engines. However, charge stratification is a difficult target in two-stroke engines, chiefly because timings of late injection (necessary for charge stratification) and of early injection (necessary for homogeneous charge) are much closer than in four-stroke engines. The compatibility between stratified and homogeneous charge operations needs a thorough CFD study of injection and mixing processes, with the support of techniques of spray visualization. Results strongly depend on the possibility of optimising the interaction between in-cylinder gas-dynamic field and spray; experimental activity is necessary as data source and verification of computational prediction. This paper shows the latest CFD investigation, experimental tests and results concerning a 50 cm3 engine for light motorcycles. The injection is of the liquid type with wall-and-air guided spray produced by a swirl injector. The research has been focused on the attainment of charge stratification at every engine speed. Spray actual characteristics have been investigated, attesting suitable repeatability and proper variation versus backpressure. Engine satisfactory behaviour even at light loads in unthrottled condition is proved by good fuel economy and engine stability in dynamometric bench tests. Exhaust gas analysis and indicated pressure behaviour confirm stratification and combustion correctness.

Commentary by Dr. Valentin Fuster
2006;():583-595. doi:10.1115/ESDA2006-95716.

Mixture preparation is a crucial aspect for the correct operation of modern DI Diesel engines as it greatly influences and alters the combustion process and therefore, the exhaust emissions. The complete comprehension of the spray impingement phenomenon is a quite complete task and to completely exploit the phenomenon a mixed numerical-experimental approach has to be considered. On the modeling side, several studies can be found in the scientific literature but only in the last years complete multidimensional modeling has been developed and applied to engine simulations. Among the models available in literature, in this paper, the models by Bai and Gosman [1] and by Lee et al. [2, 3] have been selected and implemented in the KIVA-3V code. On the experimental side, the behavior of a Diesel impinging spray emerging from a common rail injection system (injection pressures of 80 MPa and 120 MPa) has been analysed. The impinging spray has been lightened by a pulsed laser sheet generated from the second harmonic of a Nd-YAG laser. The images have been acquired by a CCD camera at different times from the start of injection (SOI). Digital image processing software has enabled to extract the characteristic parameters of the impinging spray with respect to different operating conditions. The comparison of numerical and experimental data shows that both models should be modified in order to allow a proper simulation of the splash phenomena in modern Diesel engines. Then the numerical data in terms of radial growth, height and shape of the splash cloud, as predicted by modified versions of the models are compared to the experimental ones. Differences among the models are highlighted and discussed.

Commentary by Dr. Valentin Fuster

Manufacturing

2006;():597-605. doi:10.1115/ESDA2006-95002.

In forging processes, several operations are often required to achieve gradual metal flow from a simple shape of initial billet to a more complex shape of the desired final forging. Amongst various kinds of preforming operations, the blocker is the stage that is normally used before the finishing operation. The geometry of the blocker cavity is often similar to that of the finisher. An appropriate design of the blocker preform can lead to a defect-free metal flow in the final forging operation and complete die-filling with minimum metal loss and die wear. However, the optimum design of the blocker die is an extremely difficult task and is known to be an art by itself, requiring skills that are achieved only by years of extensive experience. This paper presents a blocker die design using the backward deformation method. This method employs the finite element analysis during each reverse deformation step. It involves an alternative boundary node release criterion in the finite element simulation of backward tracing of forging processes to reduce the die wear in the finishing operation. The procedure starts with the forward simulation of a candidate preform into the final forging shape. A record of the boundary condition changes is produced by identifying the time that a particular segment of the die makes contact with the workpiece surface in forward simulation. Also the wear profile on the die surface during forging is calculated by implementing friction work model into a finite-element user written subroutine. Recorded time sequence is then optimized with the aim of releasing those nodes that are located on the segments of the die which have higher wear profile, in the first stages of the backward simulation. The modified boundary conditions are finally used as the boundary condition that controls the criterion for the inverse deformation simulation. Two examples of the blocker preform design for two forging components are performed and presented in this paper.

Topics: Deformation , Forging , Design
Commentary by Dr. Valentin Fuster
2006;():607-612. doi:10.1115/ESDA2006-95026.

On of the most typical forming processes used for the production of long, straight semi-finished products in the form of various section geometries is extrusion. Hot extrusion is a thermo-mechanical process whish involves complicated interactions between process parameters, tooling and deforming material /1,2/. In the present paper, FEM simulation is performed in the aluminum extrusion using circular dies with different geometries in order to extract quantitative simulating results regarding various forming parameters. Most specifically the parameters that are investigated are the die design-geometry, the process parameters (i.e. ram speed, container temperature, billet temperature) and the product quality (i.e. extruded shape, surface condition). The finite element modeling is based on 3D simulation tools using the DEFORM 3D software /3–5/. The used work piece is the aluminum AA6061 in cylindrical form with a diameter of 14 mm. The used material for the extrusion die is the hot work steel AISI H13. The geometry of the die is circular with a variation in die angle. The container and the billet temperature will vary from 450 to 550 degrees, and the mandrel (ram) speed will be at the range of 2 mm/sec. On the basis of simulating results such as pressure distribution on the extrusion die, effective stresses on the billet and product quality, new and improve die geometry will be introduced. Although the simulation problem is an axisymmetric one the authors decide to proceed with 3D FEM simulation in order to examine and verify the 3D simulating results. This paper is the first part of a further research project in which more complicated die geometries will be used as simulating and experimental specimens. In addition to simulating results, experimental results will be presented in the next few months.

Commentary by Dr. Valentin Fuster
2006;():613-620. doi:10.1115/ESDA2006-95063.

The new type of mechanisms — the variable structure mechanisms (VSM) possess a unique possibility of rapid and practically instantaneous transformation of the motion law of actuating link under influence of insignificant non-force displacement of one of the kinematical elements without breaking up the entire kinematical chain. The main feature of VSM is in its ability to fulfill two and more laws of motion by output link. The change of motion law for lever mechanisms occurs without disruption in the kinematical chain and thus enables to expend less effort and time. Whereas the couplings, brakes and other power impact elements control the block of interacting mechanisms till now, this results in disruption of entire kinematical chain. A considerable part of power will be required to put these elements into action. This results in decrease of machine efficiency and, especially, extremely influences the machine parts’ durability. The variable structure mechanisms (VSM) exclude such supplementary operative power consumption elements.

Topics: Machinery , Mechanisms
Commentary by Dr. Valentin Fuster
2006;():621-628. doi:10.1115/ESDA2006-95077.

Flexible manufacturing systems (FMS) have already proved their great success in a large number of manufacturing industries. Realizing the importance of FMS in increasing productivity, quality, the high investment and the potential of FMS as a strategic competitive tool makes it attractive to engage in research in this area. Scheduling of flexible manufacturing systems (FMSs) has been one of the most attractive areas for both researches and practitioners. A considerable body of literature has accumulated in this area since the late 1970s when the first batches of papers were published. A number of approaches here been adopted to schedule FMS. The FMS scheduling problem has been tackled by various traditional optimization techniques and non-traditional approaches. The traditional method can give an optimal solution to small-scale problem; they are often inefficient when applied to larger-scale problem. The non-traditional approaches such as genetic algorithm generate optimal schedule to large-scale problems. Articles emphasizing many methodological perspectives are critically reviewed. The review is done from multiple viewpoints covering different approaches like simulation, artificial intelligence and genetic algorithm. Comments on the publications and suggestions for research and development are given. A comprehensive bibliography is also presented in the paper.

Commentary by Dr. Valentin Fuster
2006;():629-635. doi:10.1115/ESDA2006-95081.

In this paper, global welding buckling distortion of a thin wall aluminum butt joint is investigated. To determine longitudinal residual stresses, a thermo-elastoplastic model is employed; analysis of thermal model and elastic-viscoplastic (Anand) model are decoupled. By using birth and death element method and time dependent model, molten puddle motion (speed of welding) is modeled. Three dimensional nonlinear-transient heat flow analysis has been used to obtain temperature distribution. By applying thermal results and using three dimensional Anand elastic-viscoplastic model, stress and deformation distributions are obtained. Residual stresses are applied on a structural model and by using eigenvalue methods, global buckling instability of butt welded joint is determined. The result of buckling investigation in the numerical model is compared with the result of an experiment.

Commentary by Dr. Valentin Fuster
2006;():637-645. doi:10.1115/ESDA2006-95116.

For calibrating an angular rotary table, either a high precision standard table or a laser interferometer and related optics are normally employed at high cost. This paper establishes a novel, simple and low cost technique to calibrate a 4-degrees-of-freedom errors of a rotary table (three angular motion errors and one displacement error) for a 360° full circle by employing one reference rotary table, one 1D grating and two 2D (2 dimensional) position-sensing-detectors. With this technique, no highly accurate reference table with good repeatability is needed. After two full circle tests, the 4 DOF errors of the target rotary table and the reference table can be calculated respectively. The angular uncertainty of the measurement system can be less than 1.5 arc sec, while the displacement uncertainty can be up to 1.5 μm.

Commentary by Dr. Valentin Fuster
2006;():647-654. doi:10.1115/ESDA2006-95122.

In this work we suggest a synthesis of recent results obtained on the application of soft-computing techniques to solve typical automatic machines design problems. Particularly, here we show an optimization method based on the application of a specialized algorithms ruled by a generalized software procedures, which appears able to help the mechanical designer in the first part of the design process, when he has to choose among different wide classes of solutions. In this frame, among the different problems studied, we refer here about the choice of the best class of motion profiles, to be imposed to a cam follower, which must satisfy prefixed design specifications. A realistic behaviour of the system is considered and the parameter model identification is set up by a soft computing procedure. The design, based on theoretical knowledge, sometimes is not sufficient to fulfil desired dynamical performances, in this situation, a residual optimization is achieved with the help of another optimizing method. The problem of a cam-follower design is presented. A class of motion profiles and the best theoretical motion profile is selected by an evolutionary algorithm. A realistic model is considered and its parameter identification is achieved by a genetic algorithm. The residual optimization is achieved by a servomotor optimized by another genetic algorithm. Evolutionary approach is used during all the design process and, as was shown, it allows really interesting performance in terms of simplicity of the design process and in terms of performance of the product.

Topics: Design
Commentary by Dr. Valentin Fuster
2006;():655-662. doi:10.1115/ESDA2006-95134.

Elbows, which belong to butt-welded steel pipe joints, are used in piping of various plants. Elbows are mainly manufactured by hot mandrel bending. In hot mandrel bending, short straight pipes are inserted into an inner tool of mandrel and are bent at specified bending radius, while they are compressed by pusher from one end of pipes and their outer diameter are expanded. Elbows manufactured by this bending process have small deviation in wall thickness and also high accuracy in roundness, even when they are processed into short bending radius. Shape and dimension of mandrel are designed by trial and error through many experimental tests. However, there are a few research works on hot mandrel bending. We focus on expansion ratio and bending radius ratio of mandrel, which are main variables, and greatly affect deformation behavior of hot mandrel bending. And we conducted experiment and numerical analysis using mandrels which have several kinds of expansion ratio and bending radius ratio. Following items are clarified by this research work: At extrados, axial strain decreases slightly, when expansion ratio increases. As a results, neutral axis of bending moves from extrados toward intrados by increasing of expansion ratio. And at intrados, wall thickness strain at intrados decreases, when expansion ratio increases. Wall thickness strain at intrados decreases, when bending radius ratio increases. Forming load increases, when expansion ratio increases and with bending radius ratio decreases. When experimental conditions do not coincide with optimized expansion ratio and bending radius ratio, deviation of wall thickness occurs in elbow.

Commentary by Dr. Valentin Fuster
2006;():663-672. doi:10.1115/ESDA2006-95150.

This research applies ATOS, an optical scanning device, to scan fan blades which possess overlapped geometry between blades. The surfaces to be investigated include a pressure surface, a suction surface and two hub surfaces adjacent to the pressure and suction surfaces respectively. Through numerous scanning practices, rules are found to position the fan blades in proper orientations so that data points of the four types of fan-blade surfaces can be completely obtained. The scanning sequence include: (1) rotate the fan with respect to the z-axis so that the fan can be set parallel to the straight-line connecting the two cameras of ATOS, (2) rotate the fan with respect to the x-axis so that the whole pressure surface can be located inside the scanning region of cameras, (3) rotate the fan w.r.t. the z-axis to let the suction surface be completely scanned, (4) rotate the fan w.r.t. the y-axis so that the hub surface can be located inside the camera scanning region, and (5) rotate the fan w.r.t. the z-axis so that the other hub surface can be scanned. To verify the proposed scanning sequence, this research uses Pro/Toolkit and Visual C++ to develop the programming codes so that the positioning angles for the four different types of surfaces can be automatically found from the Pro/ENGINEER part model of a fan. The goal of automatic positioning for scanning of fan blades can thus be achieved. It is concluded that the research results contribute the possibility of scanning overlapped fan blades in an automation manner, and also in little time-span.

Topics: Blades
Commentary by Dr. Valentin Fuster
2006;():673-681. doi:10.1115/ESDA2006-95163.

The key to successful manufacturing of complicated geometry in numerically controlled machines lies in the control and quality of operations planning. Process planning, as it is considered plays an important role in the innovation process. It is the interface between product development and manufacturing system development. Hence, in this paper, process planning is considered to be an active part in the concurrent development of products and their manufacturing systems, not only as an activity where manufacturing resources are selected. The authors focus on the use of the new standard; ISO 14649, to address the process planning and machining of turn/mill discrete components. This paper identifies a view of how ISO 14649 can be used to combine turning and milling operations to achieve the complete machining of rotational asymmetric components at a single turning centre. The use of the individual parts of the evolving standard ISO 14649, namely Parts 10, 11, 12, 111 and 121 has been investigated to provide the means to represent STEP-compliant turn/mill component programs.

Topics: Machining , Turning
Commentary by Dr. Valentin Fuster
2006;():683-691. doi:10.1115/ESDA2006-95172.

This paper details the current research on size tolerances of component parts machined through peripheral end milling using a prototype simulation software for virtual end milling based on previously reported cutting force and surface generation models. Firstly, the simulation software was employed for predicting the size tolerances of a prismatic component by varying one controllable variable at a time and then, the relationship between the size tolerance and the variable changed was monitored. When a distinct relationship was noted it was verified both analytically and experimentally. The results indicated that while the average size variation, which contributed to the variation of the basic size of component parts, was always proportional to the metal removal rate, the range of size variations that contributed to the size tolerance was not. Thus, there is scope for increasing the metal removal rate without sacrificing the size tolerances. The knowledge acquired through this research can be applied for selecting an optimum cutting condition using the simulation software when the size tolerances of component parts are specified.

Topics: Milling
Commentary by Dr. Valentin Fuster
2006;():693-700. doi:10.1115/ESDA2006-95241.

Magnesium alloy parts have the merits of low specific gravity, high specific strength, electromagnetic wave-proof shelter, and recyclability; therefore, it has been extensively applied to 3C and car industries. However, the processing and forming of magnesium is quite difficult to control due to magnesium’s hexagonal close-packed (HCP) structure, making the slipping face of itself less than the FCC material. Currently, common processing methods of magnesium alloys are die casting, semi-solid forming, and plastic forming. In the employment of a fixed-speed method for extrusion, the extruded sheet had serious defects in the forms of cracks on the surface. Hence, in this research, AZ31 magnesium alloy sheet metals were processed by hot extrusion using a variable speed method. The formability of AZ31 sheets under converging dies was investigated. Three converging dies with semi die angle of 20°, 30°, and 40° were used. Experiments were conducted and analyzed utilizing the Taguchi method. L9 orthogonal array was used to design the experiments under extrusion ratio of 35.9. Four important process parameters considered in this research are the heating temperature of the billet (320°C, 340°C and 360°C), the temperature of the container (300°C, 350°C and 400°C), the initial speed of extrusion (2mm/sec, 3mm/sec and 4mm/sec), and the lubricants (boron nitride, molybdenum disulphide and graphite) applied in the extrusion. The influences of these parameters to the extrusion load and the resulting mechanical properties were investigated. Moreover, the microstructure of the extruded sheets was observed to provide better insight of the formability. As a result, the optimal combinations of the process parameters were determined for the maximum tensile strength.

Commentary by Dr. Valentin Fuster
2006;():701-709. doi:10.1115/ESDA2006-95246.

A model for drilling of viscoplastic materials is presented. An analytical model is developed for predicting thrust force and torque in the drilling with a twist drill. The thermomechanical properties are accounted for describing the material flow in the primary shear zone and at the element-chip interface. A temperature friction law is introduced. The approach is based on the representing the cutting forces along the cutting lips as a series of oblique elements. Similarly, cutting in the chisel region is treated as orthogonal cutting with different speeds depending on the radial location. The section forces obtained by the model are combined to determine the overall thrust force and drilling torque. The results of the proposed model are compared with experimental results and a good agreement is obtained.

Topics: Torque , Thrust , Drilling
Commentary by Dr. Valentin Fuster
2006;():711-717. doi:10.1115/ESDA2006-95256.

A typical grinding process is an essential manufacturing operation and has been considered to be a precise and economical means of shaping the parts into the final products with required surface finish and high dimensional accuracy. The need to economically process hard and tough materials which can withstand varying stress conditions to ensure prolonged service life of parts has become a real challenge for researchers and practitioners. In this context, with the advance development and automation of grinding processes, use of appropriate modelling and optimization techniques has been continually emphasized. In view different types of end product and process requirements in grinding processes, optimization often becomes non-linear, multiple response constrained problem with multi-modal distribution of response quality characteristics. The objective of this study is to apply back propagation neural network modelling technique for prediction of a computer numeric-controlled (CNC) rough grinding process behaviour, and thereby determine overall near optimal process design using real coded genetic algorithm. The study proposes an integrated approach using back propagation neural network algorithm, composite desirability function, and real-coded genetic algorithm. The effectiveness and suitability of the approach is determined based on data analysis of a single-pass 6-cylinder engine liner CNC rough grinding (honing) operation in a leading automotive manufacturing unit in India.

Commentary by Dr. Valentin Fuster
2006;():719-726. doi:10.1115/ESDA2006-95259.

Underwater vehicles have been used in many ocean exploration and rescue applications. Recent researches are trending toward the vehicle’s application in smaller regions. As size of the parts decreases, challenges exist in the manufacturing of critical components which are hard to obtain commercially. This paper focuses on developing the propulsion systems of the micro underwater vehicle, and exploring the feasibility of the manufacturing. The target hull size of the micro underwater vehicle that the propulsion systems use is less than 50×30×30mm. In this research, two types of propulsion systems, propeller-type and jet-type, were investigated. In the propeller-type propulsion system, a propeller with the selected electric motor was designed to generate sufficient thrust, and the blade section was based on NACA four-digit airfoils. The outer diameter of the propeller is 25 mm with a minimum blade thickness of 0.9 mm. The thin 3D blade geometry is hard to achieve by traditional manufacturing approaches. As a result, Shape Deposition Manufacturing (SDM) process, a layered manufacturing technique, was used to generate the complex 3D propeller. The thrust performance of the fabricated propeller was also compared with the theoretical thrust. The jet-type propulsion system utilized the concept of piezoelectric-actuated valveless micro-pump, and a special design with 3 inlets from the side and one outlet in the back was implemented in order to satisfy the micro underwater vehicle application. The 3D geometry of the channel with minimum width of 80 μm creates great challenges in fabrication and poses difficulty when done by traditional micro fabrication techniques. SDM process is also applied to manufacture the chamber and channels of the micropump. The piezoelectric buzzer was attached to the fabricated valveless micropump chamber for testing back pressure and flow rate. This research provides solutions to manufacture propeller-type and jet-type propulsion systems for micro underwater vehicle applications. SDM process was proved to be the suitable approach to generate small complex 3D propellers and a pre-assembled valveless micropump structure with micro channels.

Commentary by Dr. Valentin Fuster
2006;():727-733. doi:10.1115/ESDA2006-95272.

Dockside container cranes have huge complex structures which have various kinds of types and lots of parameters for design. Moreover the finite element analysis must be carried out on the structures. An integrated CAD/CAM system for crane’s structures is introduced in this paper. A CAD platform of 3D parametric model family is built to allow generation of feasible configurations of crane products. Using Visual C++ and the second exploiting software kit, an integration method of CAD/CAE which includes regeneration of 3D parametric model, synchronous updating and analysis of FEA model is achieved.

Commentary by Dr. Valentin Fuster
2006;():735-742. doi:10.1115/ESDA2006-95304.

We are working in the design process of progressive dies to make that process more structured and, by this way, to be able to automate the different design phases. The basic phases that it’s necessary to follow in the design of a progressive die could be divided into two groups: 1. The strip layout design. This phase involves several steps such as to obtain blank development, to find the best layout, to define the sequence of operations, to calculate the forces... 2. The die design according to the strip layout previously designed. The characteristics’ die depends on the tools are necessary to use (standard or specific for each die), maintenance... These two phases are not independent between them, and the final and optimal design is achieved improving iteratively these phases. In the first phase, the strip layout design, one of the more important steps is to define all the operations that it’s necessary to carry out and the sequence that these operations have to follow to get the part with the wanted characteristics. In the present paper it’s presented a methodology and the software with its application. This methodology consists of extracting all data are going to be use to manufacture the part from its solid modeling or 3D representation. These data are used to create a relational diagram (or relational tree) that shows the relationship among the different features that form the part. Once this tree is represented, it’s used to define the operations that are going to be made and to obtain a first approximation to the sequence of operations that the designers could change according their experience.

Commentary by Dr. Valentin Fuster
2006;():743-749. doi:10.1115/ESDA2006-95322.

In this paper, a method of quantitative evaluation of surface roughness based on computer vision system is presented. A low cost computer vision system consisting of flat bed desktop scanner connected to personal computer (PC) is used. A large number of surface specimens such as EN-8, EN-9, cast iron, copper, brass, aluminium, C-20, C-45 steel etc. were carefully prepared by using various machining processes like planing, shaping, turning, milling, grinding, polishing etc. to generate a database of surface specimens with different lay-types and surface roughness values. This database is evaluated for conventional surface roughness parameters like Rt , Ra , Rq and for RGB colour component values at each pixel over the digital images of these produced surfaces. By using the technique of multiple linear regression analysis, the conventional roughness values and colur component values were correlated with each other to form a multiple linear regression equation for Rt . The value of surface roughness Rt obtained for a given specimen using this equation was then crosschecked and confirmed with the results obtained by using conventional method for the same specimen. When any test surface is introduced for surface roughness evaluation, the developed method relates the colour component values obtained from its surface image, to the conventional values like Rt , Ra , Rq . In addition to this, surface topographical representation and summits are also presented. Using this method even the evaluation of the surface roughness in the nano-metre level can be carried out to fulfill the requirements of experimental field of 0.001 to 50 microns.

Commentary by Dr. Valentin Fuster
2006;():751-755. doi:10.1115/ESDA2006-95349.

The operation error of a robot manipulator that occurs inevitably due to the manufacturing tolerance needs to be controlled within a certain range to achieve proper performance. The reduction of manufacturing tolerance, however, increases the manufacturing cost in return. Therefore, system design engineers try to solve the problem of maximizing the tolerance to reduce the manufacturing cost while minimizing the operation error to satisfy the performance requirement. In the present study, a revolute joint model considering the variation of joint axis orientation due to joint clearance is employed to perform a tolerance analysis of the robot manipulator operation. This paper presents a hybrid method which employs the sensitivity-based analytic method and the single Monte-Carlo simulation. The proposed method provides rapid implementation and the accurate statistical properties using the only single integration or single iteration for one sample set, whereas the Monte-Carlo method necessitates integrations as the number of samples and cases. Significant reduction of computing time can be achieved with the proposed method. The present method is especially effective if sensitivity information is hard to be obtained for the analysis.

Commentary by Dr. Valentin Fuster
2006;():757-762. doi:10.1115/ESDA2006-95375.

In the last decade sheet metal forming market has undergone substantial mutations since the development of more efficient strategies in terms of flexibility and cost reduction is strictly due. Such requirements are not consistent with traditional metal stamping processes which are characterized by complex equipment, capital and tooling costs; thus the industrial application of such processes is economically convenient just for large scale productions. For this reason most of the research work developed in the last years has been focused on the development of new sheet forming processes able to achieve the above discussed goals. Contemporary, with particular reference to the automotive industries the requirement of light components and the engineering of the outer skin parts of the vehicles have determined the growing utilization of tailored blanks characterized by either different material or different sheet thickness. In the paper SPIF processes of FS welded aluminium blanks are investigated in order to analyse the product properties in terms of strength and formability. A proper experimental investigation has been carried out and interesting guidelines have been highlighted in the next paragraphs.

Commentary by Dr. Valentin Fuster
2006;():763-770. doi:10.1115/ESDA2006-95382.

In the recent years Friction Stir Welding (FSW) has become an important joining technique since it allows to weld light weight alloys rather difficult to be welded or even “un-weldable” with the classic fusion welding operations. In the paper the authors present the application of the FSW process to the joining of 3D complex shapes typical of the industrial environment. In particular the research was aimed to highlight the joint mechanical strength at the varying of the 3D geometry of the welding line.

Topics: Friction , Welding
Commentary by Dr. Valentin Fuster
2006;():771-780. doi:10.1115/ESDA2006-95388.

In the recent past great study has been dedicated to porosity formation in laser welding. Using impressive apparatus for the experimentation Japanese authors have pointed out the main phenomenological causes of porosity produced by laser keyhole welding. Moreover, they have evidenced the effect of process parameters and bead configuration on porosity formation. Keyhole oscillation and consequently local vaporisation of the molten pool have been found to be present in all metals (stainless steel, carbon steel, aluminium and magnesium alloys) and in all process conditions (CO2 or Nd:YAG systems, continuous wave or pulsed lasers). Since keyhole porosity can not be totally avoided, the laser welding process should be accurately selected and process parameters designed in such a way as to minimise pore formation. The paper is aimed at studying the effect of laser configuration, single beam or dual beam, on the keyhole porosity. A dual beam system, allowing the laser beam to be divided in two beams, both of them working in keyhole mode, has been studied and compared to the traditional single beam welding process. In order to compare the two laser configurations, quantitative features of pores have to be individuated. Since the pores in the bead are supposed to have a negative effect on fatigue strength of the welded component, the main characteristics of investigated porosity were the porosity percentage and the pore diameter. The experimental results show that the dual beam configuration is effective in pore area reduction, if the related process parameters (inter-beam distance and feed rate) are accurately selected.

Commentary by Dr. Valentin Fuster
2006;():781-786. doi:10.1115/ESDA2006-95404.

There are two basic methods of forming the face spiroid gears. The first one, well known, is based on cutting the gear with multi-point cutting tool on the gear hobbing machine. The second method is based on machining with single-point cutting tool applying continuous indexing on universal NC machine tool and with application of NC rotary table. The second method is recommended for piece production because of the simple, cheap and universal cutting tool. There is also known the method of forming the face gears with involute tooth line obtained by machining with the inclined tool axis in relation to the face surface of the gear. The methods of forming face toothing in spiroid gear with the tool axis parallel to gear surface (according to author’s proposal) has been presented in the article. In this method the tool axis is located against the machined wheel at the same position as the worm is located in the gear and this is the greatest advantage of this method. For both methods there have been elaborated special machining programs for four axis NC milling machine of FYN 50ND type, together with NC rotary table of FNd-400 type. Then the obtained gears have been tested and investigated. Three types of such gears have been investigated, all of them with ratio 1:90. Two versions of the face spiroid gears have been assembled in the rotary table and then positioning accuracy has been measured. Additionally, for comparison reasons, the double pitch worm gear has been investigated using the same measuring instruments. There have been presented the chosen accuracy investigation of the gears in the range of one full rotation of the spiroid wheel that is connected with table disc (measurement by 4°) and in the range of two worm rotations (measurement by 0,1°) General evaluation of the chosen methods concerning the manufacturing of the face wheels in spiroid gears has been presented too. The data have been obtained from literature and from author’s own researches.

Topics: Gears
Commentary by Dr. Valentin Fuster
2006;():787-789. doi:10.1115/ESDA2006-95428.

The noise and vibration problems created by injection molding machines can be moderated by the installation of absorbers. The pull rods of the machine, which are guided to the molding movements, might be a better location for mounting a spring, rubber or hybrid elastomer for energy absorption and reduction of noise and vibration. In this paper, some special washers are designed to fit the guide rods and performance tests are carried out. The results show that noise and vibration decreased over 10 dB and 2 times, respectively.

Commentary by Dr. Valentin Fuster
2006;():791-797. doi:10.1115/ESDA2006-95442.

Ultrasonic-vibration upsetting is a process in which a cylindrical specimen is compressed by an axial force while the ultrasonic vibration is simultaneously applied to the die. Homogenous deformation is difficult to achieve during this process because of the friction at the interface between the specimen and the die. An extrapolated compression test was performed in this study on aluminum alloy specimens to explore the effect of superimposing ultrasonic-vibration during upsetting. Experimental results indicate that ultrasonic-vibration reduced the compressive force when the friction was eliminated by the extrapolated compression test. The specimen size also influences the force-reducing effects of ultrasonic-vibration. The decrease in the compressive force is smaller for a larger specimen. The barreling profile of the specimen after test indicates that the interface friction will increase during ultrasonic-vibration compression. Additionally, the raised material temperatures are caused by ultrasonic-vibration. Experimental results of the hot extrapolated compression test and the hot ring compression test indicate that the drop in the flow stress and the increase in the interface friction are caused by the increase in the temperature of the material under ultrasonic vibration.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2006;():799-808. doi:10.1115/ESDA2006-95476.

An Integrated Pilot Plant (IPP) for agile production of customized footwear is discussed. Such a system integrates all the functions of an advanced shoe manufacturing company, starting from ERP/PDM, CAD/CAM till job dispatching, factory automation, supply chain management. In particular the innovative job dispatching and monitoring functionalities and tools are here presented. Such an environment specializes on the production of extremely small production batches — usually in fact they are one-pair orders. Each order is directly received from the final consumer via an Internet based Point of Sales, launched into production as-soon-as-possible, and delivered directly to destination into a personalized box. Each order is potentially different from the preceding, so the fast and automatic set-up of each machine involved in the process is a mandatory requirement for an efficient and effective production. Such a workflow imposed innovative solutions for scheduling, job dispatching, and monitoring, based on a strong integration among the various layers of the architecture: ERP/PDM to organize production requests and technological data, CAD/CAM to guarantee the coherence of geometry among the various components of a shoe, SCM/MES to coordinate the dispatching of production and technological data, internal-logistics and line-control to coordinate job-advancement, SCADA and cell automation to actually apply the transported technological information.

Commentary by Dr. Valentin Fuster
2006;():809-813. doi:10.1115/ESDA2006-95486.

In traditional machining drilling is a major and common holemaking process in which lubrication and cooling are very important to improve the machining. The idea proposed in this paper regards the metal heating during the drilling operation by means of an infrared lamp. In this way a reduction in thrust force and torque is expected, since the material properties have been changed. Some experimental tests are carried out on Al 6082 in dry drilling operation, using a conventional milling machine and cobalt-coated HSS twist drills 2.5, 5, 7 mm in diameter. The spindle speeds range from 5000 to 15000 Rpm, the feeds range between 0.0076–0.042 mm/rev, the temperature is varied in the range of 40–140°C. Besides, Flat-top cylinder Indenter for Mechanical Characterization (FIMEC) tests for material characterization are carried out to obtain the yield stress of material varying temperature. The main result is a significant reduction of the thrust force (from 10 to 34% depending on the process conditions). By analysing the data of forces as a function of temperature, a minimum value of force is always found in correspondence of a temperature depending on drill diameter and feed. The influence of each parameter is investigated. The experimental data in terms of force are also correlated to the measured yield stresses to study the influence of material properties on drilling machining. Further study must be developed to investigate the torque, the mechanisms of chip formation and the tool wear.

Commentary by Dr. Valentin Fuster
2006;():815-823. doi:10.1115/ESDA2006-95519.

New type of face worm gear drive with double-lead worm is proposed. The advantages of that gear in comparison to contemporary known gears are also mentioned. The shaping process of the face worm gear is carrying out by means of a single point tool. The same insert is used for cutting the duplex worm. Using a single point tool instead of hobbing cutter considerably reduces the manufacturing cost, in which the share of tool production plays the main role. The shaping process is performed on a CNC milling machine with or without additional equipment. Two main methods of shaping depended on setting up the tool machine are presented. One of them requires no special equipment but a single point tool with insert of specific tool included angle, whilst the second uses a constructed tooling. There are also described 3 methods of shaping the face toothing, which depends on the used technology. Geometry of that face worm gear drive is presented and described. The tooth depth is constant along the whole tooth line. Nominal width of tooth section as well as its location depends on the lead difference of the worm. Provided scheme can be used to calculate those parameters. The total length of the duplex worm is calculated by taking into consideration the internal and external diameters of the worm gear and the additional length which is needed to reduce the backlash. The shape and size of the single point tool is determined according to the worm and the necessary geometric model is provided. There are also given criteria, which limit the maximum length of worm and its maximum lead angle. A complete algorithm describing the designing process of that type of gear is presented in the final part of the article.

Topics: Worm gears
Commentary by Dr. Valentin Fuster
2006;():825-830. doi:10.1115/ESDA2006-95520.

Plane spiroid gears currently applied in feed motion rotary drives are roughly described in this paper. The theoretical possible methods of backlash adjustment in this kind of gear are mentioned. Referring to industry experience the only applied method, which uses the eccentric, is described. Its advantages as well as disadvantages related to operation and wearing process are pointed. The disadvantages are mainly connected with changing the gear axis distance while rotating eccentric in order to adjust backlash. A graph depicting the movements of the worm in the direction of backlash reducing and in the perpendicular one, which changes the axis distance, is given. In order to provide some information about the influence of changing axis distance on the mating of face toothing with the worm, mathematical model was created. Some effects of numerical calculations based on that model and showing the bearing contact of the face gear drive supplied with eccentric backlash adjustment are depicted. It can be noticed, how changing the axis distance influences the bearing contact. It can be also estimate if within the chosen range of eccentric rotation the theoretical bearing contact is still acceptable to operate correct. A simplified model presenting the wearing process is also provided. It reveals that after some operating time an edge contact appears while reducing backlash. It significantly decreases the operating time till the next adjustment. There are two methods of backlash reducing described: the first is typical whilst the second is improved and proposed by the author. The advantage of the proposed method is lengthening the operating time between two backlash adjustments. In the end a new type of spiroid gear mating with double-lead worm and deprived of aforesaid disadvantages is mentioned.

Topics: Gears
Commentary by Dr. Valentin Fuster
2006;():831-838. doi:10.1115/ESDA2006-95528.

Milling is a widely used manufacturing process with the main purpose of generating high precision mechanical components of shapes and sizes given by the numerical control programmed cutting tool trajectory. These mechanical components frequently needs the application of milling operations in order to satisfy the technical specifications that corresponds to their dimensional, geometrical and surface quality requirements. For that reason, the effects of different factors such as cutting tool dynamics, fixturing system design, workpiece material behaviour and applied cutting forces on the desired dimensional precision must be studied, as well as cutting tool and machine tool performance. In this work, the relation between machine tool inaccuracies and geometrical tolerances is analyzed, and a methodology is proposed for improving flatness in planing operations by the correction of imperfections detected in cutting tool displacement according to machine tool axis. These machine tool error correction methodology could be implemented in the current CAD/CAM/CAPP techniques as a means of increasing the milling process performance by identification and correction of CNC milling machine imperfections. The deviations in machine tool displacement during cutting process are identified by metrological analysis, and a modified trajectory for cutting tool is defined by direct numerical control (DNC) from systematic error compensation in machine tool.

Commentary by Dr. Valentin Fuster
2006;():839-846. doi:10.1115/ESDA2006-95537.

The problem of efficiency evaluation of water jet nozzles has been dealt in the present work and a novel Laser Doppler Velocimetry (LDV) technique has been proposed in order to acquire high-speed water velocity at the exit of the cutting head nozzles. A standard LDV technique has been implemented for the first experimental trials with the aim of applying the theoretical approach to measured velocity values. A novel LDV technique has been proposed outlying of the critical aspects to be taken into account for future developments and improvements in measurement dynamic range, resolution, and accuracy.

Commentary by Dr. Valentin Fuster
2006;():847-854. doi:10.1115/ESDA2006-95609.

Electro-Discharge machining (EDM) is a thermal process with a complex metal removal mechanism that involves the formation of a plasma channel between the tool and the workpiece electrodes and the melting and evaporation of material resulted thus in the generation of a rough surface consisting of a large number of randomly overlapping craters and no preferential direction. EDM is considered especially suitable for machining complex contours, with high accuracy and for materials that are not amenable to conventional removal methods. However, certain phenomena negatively affecting the surface integrity of EDMed workpieces, constrain the expanded application of the technology. Accordingly, it has been difficult to establish models that correlate accurately the operational variables and the performance towards the optimization of the process. In recent years, artificial neural networks (ANN) have emerged as a novel modeling technique that is able to provide reliable results and it can be integrated into a great number of technological areas including various aspects of manufacturing. In this paper ANN models for the prediction of the surface roughness of electro-discharge machined surfaces are presented. A feed-forward artificial ANN trained with the Levenberg-Marquardt algorithm was finally selected. The proposed neural network takes into consideration the pulse current and the pulse-on time as EDM process variables, for three different tool steels in order to determine the center-line average (Ra ) and the maximum height of the profile (Rt ) surface roughness parameters.

Commentary by Dr. Valentin Fuster
2006;():855-858. doi:10.1115/ESDA2006-95614.

In this paper the manufacturing of a side impact beam, with the aid of local heat treatment, is described. The beam has two areas where the risk of fracture is high. Two zones of the blank, corresponding to these areas, are therefore heat treated before stamping to reduce the risk of fracture. The material is a martensitic steel with a virgin tensile strength of 1200 MPa. The heat treatment is made by laser to an approximate temperature of 850° Celsius. This heat treatment reduces the strength of the material to a tensile strength of approximately 650 MPa after cooling. The formability is increased accordingly. The method of local heat treatment with the objective to increase formability in selected areas can be seen as an alternative to the use of conventional tailor welded blanks.

Commentary by Dr. Valentin Fuster
2006;():859-863. doi:10.1115/ESDA2006-95619.

Fibre heating can be employed to optimise composite fabrication in hand lamination. In order to show the fibre heating effect on the properties of hand laminated composites, dynamical and mechanical tests were performed on simply cured glass fibre reinforced laminates and on treated ones. In this second case the fibre content was heated before composite lamination by means of a hot parallel plate press. All the specimens were room temperature cured. A significant increase in storage modulus was observed as an effect of fibre heating as well as a data dispersion reduction. Additionally a lower thickness was measured due to the higher resin fluidity.

Commentary by Dr. Valentin Fuster
2006;():865-869. doi:10.1115/ESDA2006-95622.

A new approach for manufacturing of shell fender is proposed and has been examined numerically and experimentally. The new suggested method is based on sheet hydroforming process, which has a lot of advantages over conventional deep drawing process. After defining the shape of initial blank using an inverse finite element program, numerical evaluation of the proposed sheet hydroforming process for production of shell fender has been carried out using an explicit finite element code considering fluid pressure, boundary conditions and tools. Then experimental evaluation has been carried out using down sized specimen and the results have been compared with results of previous simulations. It has been shown that there are similar trends between finite element and experimental results.

Topics: Design , Automobiles , Shells
Commentary by Dr. Valentin Fuster
2006;():871-876. doi:10.1115/ESDA2006-95682.

Ball milling is a material processing method that allows near room temperature process of elements in powder and permits to synthesize materials with peculiar properties otherwise difficult or impossible to obtain. Due to the repeated fractures and cold welding of the reactants particles, solid solutions, amorphous alloys and equilibrium nanostructured materials can be obtained. Products coming from mechanosynthesis process can be advantageously applied as high performance structural and functional materials. Different milling devices can be utilized for the powder processing: planetary mill, attritor, horizontal ball mill, 1D and 3D vibrating machines. The wide differentiation in configuration of the mills obstacles the development of a unified model on powder transformation kinetics in the milling process and then most of processing procedures are still developed by using a trial and error method. The focus of this paper is on a horizontal fixed vial ball mill; in this configuration a high speed rotor launches several tumbling against the vial wall. During hits, a quantity of energy is released to the trapped powder and the solid state reactions are promoted. To characterize the powder transformation process, knowledge of the kinematics of the balls system must be inferred. For this purpose an experimental setup based on digital image acquisition was constructed and the movement of balls inside the vial was filmed. Particle trace analysis methodology permitted to obtain balls trajectories, velocity vector field and total hit frequency. The kinetic energy of the impacting balls inside the vial was quantified, so that the energy released to the powder in a milling experiment can be estimated.

Commentary by Dr. Valentin Fuster
2006;():877-881. doi:10.1115/ESDA2006-95683.

Corner shaping is a necessary operation in manufacturing of most mechanical components. Edge radiusing is the principal way to reduce stress concentration in components like gear, crank shaft, ball bearing, to permit assembly and disassembly of parts, to avoid local damage and to reduce the possibility of hurting the operators. Often precise values of corner radius are specified in component design. Deterministic operations such as chipping, plastic deformation and non traditional ones such as electro discharge machining, abrasive jet deburring are well established technology. Yet, sometimes, it results not economic or even impossible to perform these operations due to the complicated part geometry, difficulty in part clamping and tool path, large number of parts to be produced. Barrel finishing is technique able to improve the roughness of parts of complicated shape by means of a soft mechanical action over the surface performed by abrasive media. The main features of this technology is that the parts do not need to be fixed. Radiusing is, in turn, a potential application area for barrel finishing which has been investigated in this paper. Experimental tests were conducted on finished specimens with sharp corners in order to achieve information about corner radius evolution as a function of the time for different set parameters. The radius values have been assessed by analyzing the acquired profiles with a proprietary fitting procedure. It has been found a square root relation between radius and working time and, by assessing the influence of single parameter, a radiusing model has been proposed.

Commentary by Dr. Valentin Fuster
2006;():883-889. doi:10.1115/ESDA2006-95801.

Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, and for creating internal profiles in tubes. Among parameters affecting process variables, the die geometry is of fundamental importance and greatly influences variables such as forging load, stress distribution on the dies, metal flow during deformation, and surface finish of the forged product. In this paper a generalized slab method analysis of radial forging process is presented which can handle this process with curved shape dies. Results for dies with various curves are presented and it is shown that the analysis reduces to that of Lahoti and Altan [2] when the die has a linear profile.

Topics: Forging , Slabs , Shapes
Commentary by Dr. Valentin Fuster

Technology and Society

2006;():891-897. doi:10.1115/ESDA2006-95005.

In China, the national engineering and technology view has great influences on formulating and executing all kinds of engineering and technology developing strategies, policies and plans. The People’s Republic of China has been founded for more than 50 years. During this period Chinese science and technology, economy and society have gained remarkable changes, yet, there were many frustrations and backslides in the progress of development either. The evolution of engineering and technology view in P. R. China is characterized by “period”. This kind of “period” is correlated tightly with the political and economic conditions home and abroad, reflecting the ideologies of different period, and plays a very important role on the direction, scale and speed of the development of engineering and technology in each period. This paper divided the engineering and technology view into 6 periods from the foundation of P.R. China, analyzed them periodically according to cases and statistical data, and compared them. Finally, this paper carried on a further discussion and prediction on the engineering and technology view of the new century.

Topics: China
Commentary by Dr. Valentin Fuster
2006;():899-906. doi:10.1115/ESDA2006-95432.

In the present paper unique data about initial shortcomings in the design and application of different industrial and consumer products are presented. The research area covers all of the products’ development stages beginning with factory automation and equipment control systems, and continuing with the design and realization of light fittings up to follow-up on the product development of office machines. The statistical results of this research are presented. Further the essence of the synergy-based approach to the design process, focussing on the most common human faults/mistakes, is clarified. Evidence is presented to show that the reason for human shortcomings is either the lack of synergy in teamworking or problems in inner personal communication. A detailed definition of the concepts of positive and negative synergy, with examples from both categories is given. Guidelines are given to reduce human risks at the conception of interdisciplinary systems design to avoid bad engineering. A framework for the synergy-based design of interdisciplinary systems is presented capable of adapting to the competences of the design team.

Commentary by Dr. Valentin Fuster

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