ASME Conference Presenter Attendance Policy and Archival Proceedings

2017;():V010T00A001. doi:10.1115/DETC2017-NS10.

This online compilation of papers from the ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (IDETC/CIE2017) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

2017 ASME International Power Transmission and Gearing Conference: Gear Analysis, Materials, Fatigue

2017;():V010T11A001. doi:10.1115/DETC2017-67003.

This study investigates the role of the tribo-dynamic behavior in the contact fatigue crack nucleation for spur gears. To describe this fatigue phenomenon, a six-degree-of-freedom (DOF) lumped parameter dynamics formulation is coupled with a set of mixed elastohydrodynamic lubrication (EHL) governing equations. The former provides the dynamic tooth force to the EHL analysis, and the latter yields the gear mesh damping as well as the friction excitations that are required in the gear dynamics simulation. The converged tribo-dynamic surface normal pressure and tangential shear are then used to determine the multi-axial stress fields using the potential theory based closed-form stress formulation for half space. Lastly, the stress means and amplitudes are implemented in a multi-axial fatigue criterion to assess the fatigue damage.

Commentary by Dr. Valentin Fuster
2017;():V010T11A002. doi:10.1115/DETC2017-67049.

This paper presents a numerical approach to calculate the distribution of the surface temperature of worm gears, which is needed to determine the scuffing load capacity. The simulation model used for the heat transport as well as its boundary conditions are explained. Exemplary results for various operating conditions and temperature courses over time are presented. A comparison of the simulation model with another model from literature reveals deviating results. It is shown that the deviations can be attributed to limitations of the model from literature. These limitations do not apply to the numerical simulation model that is presented in this paper.

Commentary by Dr. Valentin Fuster
2017;():V010T11A003. doi:10.1115/DETC2017-67080.

Conventional hypoid gear design approach utilizes specific commercial programs provided by gear machine providers. Those programs typically have a set of assumptions as the starting point for the hypoid gear design. That type of approach works well when the overall system performance matches the assumptions.

The gearing systems have been evolving significantly to reach ever-higher customer demands. The condition challenges the engineering community to go beyond the conventional wisdom. As the breakthrough ideas come into the system concept, the conventional hypoid gear design assumptions might not be sufficient to represent the actual performance. Unexpected failure modes and reliability of the products could cause serious consequences. Hypoid gear design based on system concept becomes a more effective approach under such conditions.

This paper presents examples of how system approach helped analyzing and designing hypoid gears for modern powertrain systems in heavy vehicle applications. The effectiveness of such approach makes those systems realistic and reliable to meet extremely strict customer demands.

Conventional hypoid gear design tools require the system to be sufficiently rigid to duplicate the actual gear tooth contacts as observed on the gear tester. Typical relationship between the gear set is represented by E, P, G, and α, which represents three linear displacements and one angle displacement as shown in Figure 1 [1]. This approach works well if the system performance meets all the assumptions defined by the tools.

As the complexity of the system increases, more considerations for hypoid gear design become critical. Analytical tools that take into consideration other components beyond the gear set provide an effective way to understand the hypoid gear performance in different conditions closer to the reality. Figure 2 is an example analytical model of a heavy vehicle carrier [2].

Gear performance could be predicted in advanced engineering stage and compared to experimental results at a later stage of the product development. This approach provides insight into potential risks earlier in a product development cycle and cuts the product development cycle time significantly. Another advantage of this type of approach is the possibility to understand the gear set performance under different operating conditions. Conventional hypoid gear design tools focus primarily on vehicle driving condition. The heavy vehicle industry faces more diversified operating conditions based on customer needs. Figure 3 is one example showing the analysis results of one testing condition where ring gear concave side drives pinion convex side (coast mode).

Commentary by Dr. Valentin Fuster
2017;():V010T11A004. doi:10.1115/DETC2017-67176.

In order to measure the transmission error of bevel gear pair, a measurement method of transmission error based on the best mounting distance was introduced. The algorithm of adjustment of the best mounting distance was presented, and the single flank testing of bevel gear pair was carried out on this position. The evaluation of transmission error and frequency spectrum was described. Measurement and control software was developed including the function of data acquisition and processing and graphic display, optimizing search of best mounting distance and SPC statistical analysis. The class diagram, the sequence diagram, the test case diagram and the main interface of the software was designed. The experiment was carried out that the mounting distance on 130.0mm of pinion is the best mounting distance according to the value of the factor F 0.699. Under the best mounting distance, the total tangential composite deviation is 79.27μm. The method and the software mentioned in this paper can be used in measurement of the bevel gear pair or the face gear pair.

Commentary by Dr. Valentin Fuster
2017;():V010T11A005. doi:10.1115/DETC2017-67191.

Automotive differential gears are usually operating at very low speed and high load conditions and hence are usually designed to be protected against the root bending fatigue failure. Depending on application requirements and lubrication regime surface failures may occasionally be encountered as well. Mainstream existing design procedures published by AGMA is based on analyzing one single gear pair engagement while up to four potential engagements, between two side gears and two differential pinions, exist. There are also differential designs with three or four differential pinions that increase potential number of engagements to respectively six and eight. Usually the hypoid gear loading is divided by number of side gears, two, differential pinion loads are also usually assumed to be equal; this is a good estimate when no misalignments are present. When misalignments are present however, load sharing between the differential pinions become greatly imbalanced. This study tries to come up with a simplified analytical approach to evaluate overload factor between the differential pinions as a result of misalignments realized by differential gears inside a differential case. The total indexing runout quality of gears is also studied through treating it as a source of misalignment. This study will help designers to evaluate the effects of tolerancing limits and differential case machining errors on differential gear bending lives.

Commentary by Dr. Valentin Fuster
2017;():V010T11A006. doi:10.1115/DETC2017-67724.

Plastic gears bring some interesting advantages compared to metal gears. However, they also have some drawbacks, many of them related to the dependency of their mechanical properties with the temperature. Among other reasons, the friction between the gear teeth causes a heat flux that heats the gears and produces temperature variations within the gear geometries. These temperature variations have effects on the mechanical response of the gears, that must be taken into account when designing plastic gear drives.

In this work, two different finite element models have been proposed to perform heating contact analysis, that is a coupled thermal-stress analysis that takes into account the heating produced by friction and the non-linear properties of the material. As a result of these models, the temperature field of the gears can be determined at any running time, as well as other interesting results, such as the transmission error function or the instantaneous power loss.

Commentary by Dr. Valentin Fuster
2017;():V010T11A007. doi:10.1115/DETC2017-67911.

The paper presents a computational method to predict the cyclic life of gears subjected to single tooth bending fatigue, using VEXTEC’s VPS-MICRO® software. The project was a collaborative effort between Eaton - Vehicle Group and VEXTEC Corporation to replicate physical testing virtually, more specifically to virtually determine bending fatigue curves of gears made from different steels.

VPS-MICRO is based on VEXTEC’s patented Virtual Life Management® (VLM®) technology which includes computational microstructural damage models to simulate the fatigue performance and calculate the lifetime of various product configurations. The framework probabilistically estimates the fatigue behavior of a range of Eaton gears and other products.

Commentary by Dr. Valentin Fuster
2017;():V010T11A008. doi:10.1115/DETC2017-68354.

Here, a load distribution model of planetary gear sets is presented capable of dealing with planetary gear sets with any component level and gear set level design variations such as component supporting conditions, different kinds of gear modifications and planetary gear sets with different numbers of equally or unequally spaced planets as well as different gear set kinematic configurations while considering gear mesh phasing. It also accounts for classes of planetary gear set manufacturing and assembly related errors associated with the carrier or gears, i.e. pinhole position errors, run-out errors and tooth thickness errors. Example analyses are provided to indicate the need for a model of this type when studying load distribution of planetary gear sets due to unique loading of the gear meshes associated with planetary gear sets. Comparisons to measurements existing in the literature are provided.

Commentary by Dr. Valentin Fuster

2017 ASME International Power Transmission and Gearing Conference: Gear Dynamics and Noise

2017;():V010T11A009. doi:10.1115/DETC2017-67034.

Gear transmission is a key component in locomotive where it delivers the traction or braking forces between the motor and the wheelset. Its working performance has a direct effect on the operating reliability and safety. Therefore, investigation on the dynamic characteristics of the gear transmission in locomotives is very meaningful. In this study, a gear transmission-locomotive-track spatial coupled dynamic model is established based on the classical locomotive-track coupled dynamics and the gear dynamics theory. Based on this model, the dynamic responses of the gear transmission can be analysed under excitations from different track geometrical irregularity, and the dynamic performance of the gear transmission can be obtained. This paper also studies the effect law of the track irregularity on the vibration of the gear transmission by using statistical indicators RMS (Root Mean Square) and PtP (Peak-to-Peak). The results indicate that the track geometrical irregularity has an obvious impact to the dynamic performance of gear transmission. The dynamic response of the gear transmission will increase violently when the locomotive runs on the track in a worse condition. The results are expected to be capable of providing some references for fatigue life prediction and reliability analysis of the gear transmissions in locomotive.

Topics: Gears , Locomotives
Commentary by Dr. Valentin Fuster
2017;():V010T11A010. doi:10.1115/DETC2017-67043.

Time-varying mesh stiffness (TVMS) is a key component of gear transmission system for gear dynamic response. When the machine starts working, stop working or goes into an unstable working condition, the load will be varying. In order to investigate the impact of different loads on TVMS, a numerical method based on FEM is proposed in this paper to study the effect of TVMS. The dynamic mesh forces and dynamic displacements along the action line direction at each mesh point are extracted. The calculated TVMS is validated by comprising with the TVMS calculated by the analytical method (AM). The results show that TVMS increases with the rise of input moment which can be intruded in gear dynamic behavior study under different load condition.

Commentary by Dr. Valentin Fuster
2017;():V010T11A011. doi:10.1115/DETC2017-67045.

As braking components, friction plates are key components in automobile transmissions. Due to tough working conditions, i.e. high speed, high friction, fracture and plastic deformation are easily observed in friction plates. However, most of previous studies mainly focused on the chemical analysis of the fracture friction plate, the researches on impact damage have rarely published in the listed literature. In order to investigate the impact damage for friction plate, a dynamic model for a friction plate of a 6-speed planetary gear train is established based on multi-body theory. The dynamic model of planetary gear transmission mechanism is constructed. The rotating speed of the inner hub is obtained. Furthermore, the contact force between the friction plate and the inner hub is calculated. The relationship between the vibration characteristics of the friction plate and operation conditions are studied.

Commentary by Dr. Valentin Fuster
2017;():V010T11A012. doi:10.1115/DETC2017-67054.

In this paper, a method to determine the optimal rib layout of gearbox for the noise reduction is proposed based on acoustic contribution analysis and topology optimization. Firstly, the radiated noise is simulated using the finite element method (FEM) and boundary element method (BEM). The field point with maximum sound pressure is taken as the objective field point. Secondly, the surface of gearbox is divided into different regions and the region with maximum acoustic contribution to the sound pressure on the objective field point is found by acoustic transfer vector analysis and acoustic contribution analysis. Thirdly, the topology optimization model is established to reduce the velocities on the region with maximum acoustic contribution. Lastly, the topology optimization model is solved using the SIMP method and the ribs can be arranged according to the results of topology optimization. The simulation results show that the sound pressure on objective field point is reduced remarkably by using this method.

Commentary by Dr. Valentin Fuster
2017;():V010T11A013. doi:10.1115/DETC2017-67063.

RV reducers are widely used in high-precision gear transmissions. Assembly errors and elastic deformation of the components have great influence on the transmission accuracy, which is an important indication on the evaluation of performance. A RV reducer dynamic transmission accuracy analysis model is established which is based on the rigid-flexible coupled multibody dynamics. For the modelling, the input gear shaft, the planetary gear, the crankshaft, the cycloid gear and the pin gear are considered as flexible bodies, while other components are identified as rigid bodies. Based upon the model, the influence of geometric errors of key load-carrying components such as the cycloid gear, the pin gear and the crankshaft on the dynamic transmission accuracy are studied. Through the sensitivity analysis, a control method on the dynamic transmission accuracy of the RV reducer is proposed, which provides a theoretical support for further optimization of the transmission performance for RV reducer.

Commentary by Dr. Valentin Fuster
2017;():V010T11A014. doi:10.1115/DETC2017-67231.

In order to reduce the resonance of aviation bevel gears, designing frictional interfaces for gear systems is an important approach through dissipate vibration energy. One emerging technology uses ring dampers, which are ring-like substructures constrained to move inside a groove at the rim of the gear. Ring dampers are in contact with the rim of the gear due to centrifugal force, and they create nonlinear dissipation by relative motion between the ring and the gear.

The analysis of the dynamic response of nonlinear structures is commonly done by numerical integration of the equations of motion, which is computationally inefficient, especially for steady-state responses.

In this paper an efficient methodology to predict the effect of the ring damper based on energy method, predicting the dissipated energy by friction force, converting into equivalent damping and to identify the main design parameters affecting the damper performance is proposed. The approach is based on expressing the vibration energy dissipated by nonlinear forces per vibration cycle as equivalent nonlinear damping ratio. This method avoids computing the forced response of the gear with ring damper in the frequency domain, that can increase the efficiency of the ring damper design.

The methodology is applied to an aviation bevel gear. The effect of the principal design parameters of the ring damper is identified.

Topics: Dampers , Design , Gears , Aviation
Commentary by Dr. Valentin Fuster
2017;():V010T11A015. doi:10.1115/DETC2017-67256.

Gear drive is a mechanism transmitting a power and a motion through the teeth contact. The number of teeth in contact changes during a mesh cycle. That raises a discontinuity of the mesh stiffness, and causes a gear vibration. The discontinuity implies a direct relationship with the contact ratio of the gear pair. In general, the high contact ratio more than two decreases the discontinuity of the mesh stiffness. Therefore, the increase of the contact ratio is able to reduce the vibration and the noise in the gear drives. An adoption of a helical gear pair is a method to obtain two or more contact ratio. However, that provides a thrust force and a difficulty to machine and assemble. For a spur gear pair, though it is possible to increase the contact ratio by stretching the tooth depth, the tooth thickness may reduce or be excessively sharp at the tooth tip on the addendum circle.

In this study, we designed and made a high contact ratio spur gear pair with an asymmetric tooth profile. The gear pair has a large tooth depth to increase the contact ratio, and the asymmetric tooth profile to prevent the sharpness of tooth at the tip circle. In the running test, the vibration and the noise were measured. Consequently, we succeeded in a reduction of vibration and noise in spur gear drives with the asymmetric tooth profile.

Topics: Vibration , Spur gears
Commentary by Dr. Valentin Fuster
2017;():V010T11A016. doi:10.1115/DETC2017-67305.

Gravity is usually neglected in the dynamic modeling and analysis of the transmission system, especially in some relatively lightweight equipment. The wind turbine gearbox weight up to tens of tons or even hundreds of tons, and the effects of gravity have not been explored and quantified. In order to obtain accurate vibration response predictions to understand the coupled dynamic characteristics of the wind turbine gear transmission system, a comprehensive, fully coupled, dynamic model is established using the node finite element method with gravity considered. Both time-domain and frequency-domain dynamic responses are calculated using the precise integration method with various excitations being taken into account. The results indicate that gravity has a significant impact on the vibration equilibrium position of central floating components, but the changing trends are different. Gravity does not change the composition of the excitation frequency, but will have a certain impact on the distribution ratio of the frequency components. And the high frequency vibrations are hardly affected by gravity. In addition, the load sharing coefficient is greater when gravity is taken into account, both of internal gearing and external gearing system. When the planet gears have a certain position error in accordance with certain rules, the load sharing performance of the system will be better.

Commentary by Dr. Valentin Fuster
2017;():V010T11A017. doi:10.1115/DETC2017-67314.

This paper complements recent investigations [Handschuh et al (2014), Talbot et al (2016)] of the influences of tooth indexing errors on dynamic factors of spur gears by presenting data on changes to the dynamic transmission error. An experimental study is performed using an accelerometer-based dynamic transmission error measurement system incorporated into a high-speed gear tester to establish baseline dynamic behavior of gears having negligible indexing errors, and to characterize changes to this baseline due to application of tightly-controlled intentional indexing errors. Spur test gears having different forms of indexing errors are paired with a gear having negligible indexing error. Dynamic transmission error of gear pairs under these error conditions is measured and examined in both time and frequency domains to quantify the transient effects induced by these indexing errors. Both measurements indicate clearly that the baseline dynamic response, dominated by well-defined resonance peaks and mesh harmonics, are complemented by non-mesh orders of transmission error due the transient behavior induced by indexing errors.

Commentary by Dr. Valentin Fuster
2017;():V010T11A018. doi:10.1115/DETC2017-67984.

This study investigates the planetary gear housing vibration for rotorcraft systems with equally spaced and diametrically opposed planets using a finite element/contact mechanics model. This approach permits accurate housing deflection calculations at each time instant that result from the changing contact conditions on all gear teeth and elastic deformations of each gear. Planetary gears with diametrically opposed planets have larger amplitude vibrations and more frequency content than those with equally spaced planets. Parametric studies show that although the frequency content does not change with changes in the system’s parameters, the amplitudes of response at these frequencies are meaningfully impacted. The frequency components of the acceleration spectra can have additional content when the planetary gear has manufacturing and assembly errors. Each error case results in different frequency content in the acceleration spectra. Understanding these housing vibrations is beneficial for interpreting measured accelerometer signals to detect and classify damage.

Commentary by Dr. Valentin Fuster
2017;():V010T11A019. doi:10.1115/DETC2017-68245.

The need to reduce weight in internal combustion (IC) engines introduces new or increased NVH challenges. In particular, gear-related noise such as rattle and whine need to be addressed.

This paper discusses a methodology aimed at simulating a novel “split gear” system designed to counteract the rattle noise typically generated in accessory drive gears on combustion engines. In particular, the focus is on the increased gear whine associated with this system.

The ‘split gear’ system is simulated as a multi-body system incorporating contact force prediction developed by Siemens. It enables efficient identification of the contact between gear teeth based on their intrinsic involute geometry, including the effects from microgeometry corrections as well as relative displacements and misalignments of the gears. The gear contact force is evaluated taking into account both compliances for the global bulk and local contact. The multi-body approach and dedicated modeling technique permitted the investigation of interaction between gears of the ‘split gear’ system and appropriate replication of the operational boundary conditions.

The activity presented in this paper consisted of two main phases, measurements of the dynamic behavior of the split gear system and multi-body simulations. The former allows gathering reference data for validation of the simulation model built in the latter phase.

The results show the potential of the new method to analyze gear systems in view of NVH performance.

Topics: Gears , Springs
Commentary by Dr. Valentin Fuster
2017;():V010T11A020. doi:10.1115/DETC2017-68421.

This work will introduce two methods for calculating the gear mesh stiffness which includes the potential energy method and Finite Element/ Contact Mechanics method. The elastic theory of Muskhelishvili will be used to calculate the elastic deformation from the gear body during one mesh cycle for the gear pair in the potential energy method. Also the involute curve, the geometric and kinematics properties of the gear mesh pair will be taken into account of these two methods. The quasi-static time-varying mesh stiffness considering the deflection of gear rim body is learned in detail. Results from both two methods will show the importance of gear rim body elasticity on the gear pair mesh stiffness and the comparison of the results will reveal the validity and efficiency of the methods. Then lumped-parameter model is presented for studying the whole system dynamic behaviors. The effect from the body elastic deformation from component itself on the macro rigid body motion of the system is investigated. The conclusion from the results shows that the elasticity from gear rim body will take prominent effects on the gear pair dynamic behaviors, which should be regarded as an important factor during the design process.

Topics: Gears , Stiffness
Commentary by Dr. Valentin Fuster
2017;():V010T11A021. doi:10.1115/DETC2017-68515.

A computational model of a planetary gearset is developed to investigate the influence of gear tooth pitting on the dynamic response from transmissions that consist of planetary gearsets. The computational model is capable of simulating the system response due to pitting damage under static, quasi-static, and dynamic conditions. Both off-resonant and resonant dynamic conditions have been exploited to understand the influence of resonant dynamics on the transmission vibroacoustic response. Observations on the likelihood of damage detectability under dynamic conditions have been made.

Commentary by Dr. Valentin Fuster

2017 ASME International Power Transmission and Gearing Conference: Gear Geometry

2017;():V010T11A022. doi:10.1115/DETC2017-67051.

The relief surfaces of the cutting teeth of a dual-cone double enveloping hourglass worm gear hob cannot be ground automatically until now because all of teeth have different profiles and different spiral angles with each other. The land width and the relief angle of the hob are two important factors when using the hob to hob a worm gear. In order to improve the precision of this type worm pair, the land width and the relief angle of the hob need to be machined accurately and effectively. For the purpose that the land width and the relief angle could be machined precisely, an incomplete design and generating theory of the relief surfaces of the dual-cone double enveloping hourglass worm gear hob is put forward in this paper. The mathematical model of the incomplete design and generating theory of the relief grinding of the hob is built. According to the model, a series of data of the motion parameters when grinding different points of the land edges of the different hob teeth are solved out. Using those data of the motion parameters on a four-axis hourglass worm-grinding machine, a machining simulation is built and the results of the simulation show that the relief surfaces of the hob can be ground continuously, and the land width and the relief angle are consistent with the design.

Topics: Worm gears , Design
Commentary by Dr. Valentin Fuster
2017;():V010T11A023. doi:10.1115/DETC2017-67053.

All of the cutting edges on an hourglass worm gear hob have different shapes and spiral angles. If the spiral angles are small, straight flutes are usually adopted. But for the hob with multiple threads, the absolute values of the negative rake angles at one side of the cutting teeth will greatly affect the cutting performance of the hob if straight flutes are still used. Therefore, spiral flutes are usually adopted to solve the problem. However, no method of determination of the spiral flute of the hourglass worm gear hob has been put forward till now. Based on the curved surface generating theory and the hourglass worm forming principle, a generating method for the spiral flute of the planar double enveloping worm gear hob is put forward in this paper. A mathematical model is built to generate the spiral flute. The rake angles of all cutting teeth of the hob are calculated. The laws of the rake angles of the cutting teeth of four hobs with different threads from one to four threads are analyzed when straight flutes and spiral flutes are adopted respectively. The laws between the value of the negative rake angles of the hob with four threads and the milling transmission ratio are studied. The most appropriate milling transmission ratio for generating the spiral flute is obtained. The machining of the spiral flutes is simulated by a virtual manufacturing system and the results verify the correctness of the method.

Topics: Worm gears
Commentary by Dr. Valentin Fuster
2017;():V010T11A024. doi:10.1115/DETC2017-67073.

The research objective of this study is involute beveloid gears in marine gearbox with small shaft angle. Based on the theory of gear geometry and the generation mechanism, the mathematical models of beveloid gear pairs are derived according to the tooth surface equations of the imaginary counterpart rack. Then a parametric modeling programs of beveloid gears are developed to automatically generate exact model of tooth surface, so as to establish gear solid models. Subsequently, the assembly models are established according to the spatial geometry relation of beveloid gear pairs with intersected axis and crossed axis respectively. On this basis, the finite element models of beveloid gear pairs with intersected axis and crossed axis are established, and the dynamic contact force, dynamic stress distribution and dynamic transmission error are obtained by dynamic contact finite element analysis.

Commentary by Dr. Valentin Fuster
2017;():V010T11A025. doi:10.1115/DETC2017-67463.

In this paper, calculation of no-load transmission error (TE) of planetary gear train is studied. The theory computational model of the eccentric planetary gear train with single planet gear (SPG) under no-load conditions is constructed initially for acquiring the formulas of no-load transmission ratio error and unloaded transmission error (UTE) of internal and external gear pairs. Then computational formula of the UTE of planetary gear train with SPG caused by eccentricity is presented. Through simulation TE and the developed formula of UTE, the eccentricities and initial phasing are uncoupled by curve fitting. Simultaneously, formula of UTE of planet gear train with SPG is validated. At the same time, different groups of initial phasing are analyzed to acquire the relatively good initial phasing group. In addition, the UTE of planetary gear train with multiple planet gears (MPG) caused by eccentricity is developed.

Commentary by Dr. Valentin Fuster
2017;():V010T11A026. doi:10.1115/DETC2017-67793.

The face-hobbing cutting method is widely applied for generation of spiral bevel and hypoid gears due to its high productivity. Among face-hobbing processes, Cyclo-Palloid™ system allows either line contact or localized bearing contact through application of a dual head-cutter where two separate rotating centers are considered. Another face-hobbing process known as Cyclo-Cut™ is based on the application of a single and tilted head cutter for localization of the bearing contact. Computerized generation models of spiral bevel gears through the Cyclo-Palloid and the Cyclo-Cut systems are compared here. Application of tooth contact and backlash analyses will bring to light the similarities and differences between both processes, and the possibility to substitute a Cyclo-Palloid gear by a Cyclo-Cut gear in a Cyclo-Palloid spiral bevel gear drive, and viceversa. Several numerical examples are presented.

Commentary by Dr. Valentin Fuster
2017;():V010T11A027. doi:10.1115/DETC2017-68326.

This paper is the first that uses the new conjugation curvature theory [1] to directly synthesize conjugate tooth profiles with the given relative curvature that determines the Hertzian contact stress. Conjugation curvature theory offers a systematic methodology to synthesize the relative curvature for a tooth pair. For any given relative curvature between the contact tooth profiles, a generating point can be located on an auxiliary body. Under the rolling motion among the pinion pitch, the gear pitch and the pitch on the auxiliary body, the generating point will trace fully conjugate profiles on the pinion and gear bodies with the given relative curvature at the instant of the contact. Full conjugation throughout the contact of the profiles is guaranteed with the three instant centers remaining coincident [1]. The methodology is demonstrated with a planar tooth profile synthesis with given relative curvature. One may find that the Wildhaber-Novikov tooth profile, which is known to have low relative curvature and Hertzian contact stress, and its variations become special cases under such methodology.

Topics: Stress , Gears
Commentary by Dr. Valentin Fuster
2017;():V010T11A028. doi:10.1115/DETC2017-68407.

Hypoid gears are effectively used in cross axis power transmission systems. Design of hypoid gear parameters is complex and dependent on designers’ experiences. In this paper, an easy approach to design the parameters of hypoid gear to obtain the minimum of maximum principle normal contact stress and peak to peak transmission error is presented. An improved Particle Swarm Optimization (PSO) and Back Propagation (BP) algorithm is proposed to predict the stress and the transmission error if certain design parameters are given. The predictive accuracy is evaluated by Root Mean Square Error (RMSE) equation. The results show that the predictive accuracy is in reasonable agreement with the values calculated by the software [1]. Based on the prediction model, the optimization model for the design parameters of hypoid gear is established. This paper proposes a method to design a set of hypoid gears with minimum of maximum principle normal stress and peak to peak transmission error.

Commentary by Dr. Valentin Fuster

2017 ASME International Power Transmission and Gearing Conference: Gear Manufacturing

2017;():V010T11A029. doi:10.1115/DETC2017-67048.

Gear rolling process is a state-of-the-art technology on track for the future due to the productivity, high material unitization rate and high profile qualities. The pitch error has been one of main concern to fabricate high precision gears. The initial stage is to divide the angular position of teeth, and it has significant impact to pitch error of the formed gear as well as fatigue life of the rolling tools. This paper is aimed to study the two geometrical requirements of dividing teeth in the initial stage that are the phase difference of rolling tools and the contact ratio. The contact ratio is modeled with consideration of the geometric of the forming tool, bite depth, size of the workpiece, etc. A speed-controlled forced synchronization system is proposed for forming large module gear and the rolling experiments demonstrates its effectiveness. Finally, some discussions and conclusions are given.

Topics: Gears , Errors
Commentary by Dr. Valentin Fuster
2017;():V010T11A030. doi:10.1115/DETC2017-68067.

The machining process monitoring, especially the tool wear monitoring, is very critical in modern automated gear machining environment which needs instant detection of cutting tool state and/or process conditions, quick final diagnosis and appropriate actions. It has been realized that the non-uniform hardness of the workpiece material due to the improper heat treatment can cause expedited tool wear and unexpected tool breakage, which greatly increases difficulties and complexities in monitoring the tool conditions in gear cutting. This paper provides a solution to detect the wear conditions of the gear milling cutter in the cutting of workpiece materials with hardness variations using the audible sound signals. In this study, cutting tools and workpieces are prepared to have different flank wear classes and hardness variations respectively. A series of gear milling experiments are operated with a broad range of cutting conditions to collect sound signals. A machine learning algorithm that incorporates support vector machine (SVM) approach coupled with the application of time and frequency domain analysis is developed to correlate observed sound signals’ signatures to specified tool wear classes and workpiece hardness levels. The performance evaluation results of the proposed monitoring system have shown accurate predictions in detecting tool wear conditions and workpiece hardness variations from the sound signals in gear milling.

Topics: Wear , Machinery , Gears , Milling , Signals
Commentary by Dr. Valentin Fuster

2017 ASME International Power Transmission and Gearing Conference: Gearbox Design, Reliability, and Diagnostics

2017;():V010T11A031. doi:10.1115/DETC2017-67012.

In this paper, a method to determine the axial profiles of the grinding wheels for machining the screw, roller and nut in planetary roller screw mechanism is proposed. Firstly, the thread fillets of the screw, roller and nut are defined and there is a continuous first-order derivative at any point of the fillets. The equations of thread surfaces are derived. Secondly, the position relationship between grinding wheel and workpiece is described by using a coordinate transformation matrix. Thirdly, according to the theory of gear engagement, the equations of meshing for the grinding of the screw, roller and nut threads are developed. A parameterized program is designed by the meshing equations and the axial profiles of the grinding wheels are calculated. Finally, a specific example is provided and the influence of center distance and axis angle on the grinding wheel profiles is analyzed. The results show that the center distance has little influence of the grinding wheel profile.

Commentary by Dr. Valentin Fuster
2017;():V010T11A032. doi:10.1115/DETC2017-67052.

In this paper, the tapered roller bearing supported on the output shaft of the dual clutch transmission was studied. During the operating process of the DCT (Dual Clutch Transmission) gearbox, the heat generation of the bearing is very large due to the large operating load and high operating speed, which will easily result in bearing failure, such as pitting and abrasion, so it is necessary to investigate the lubrication performances and thermal characteristics of the tapered roller bearing. The simulation models considering or not considering the roller’s spinning (the rollers rotating on their own axles) were established based on Ansys Fluent software. The influences of the roller’s spinning on the lubrication performances of the bearing were analyzed. Furthermore, the transit heat transfer properties of the bearing were simulated and analyzed. The roller’s spinning and transit heat boundary specification were realized by using UDF (user-defined functions). At the same time, the lubrication performances and heat transfer properties of the bearing with different operating conditions are presented and analyzed.

Commentary by Dr. Valentin Fuster
2017;():V010T11A033. doi:10.1115/DETC2017-67072.

The aim of this paper is to investigate the influence of structure parameters on the vibration characteristics and improve the dynamic performance of marine gearbox. A finite element model was established to solve the dynamic response by using modal superposition method. Based on the theory of multi-objective optimization design, the structure sensitivity analysis model of marine gearbox was established, which takes the structure parameters of the housing as design variables. The modal and response sensitivity was obtained by using the optimal gradient method. According to the results of sensitivity analysis, a modal and response optimization model of marine gearbox was established. The objective was to avoid natural frequencies from the excitation frequencies and minimize the root mean square of vibration acceleration of the evaluating points on the surface of housing. Then the modal optimization and response optimization of gearbox were carried out by using zero-order and first-order optimization method. The results indicate that the dynamic optimization of the gearbox can be achieved. After optimization, the amplitude of vibration acceleration of the evaluating points on the housing surface has been reduced and the resonance of marine gearbox can be avoided.

Commentary by Dr. Valentin Fuster
2017;():V010T11A034. doi:10.1115/DETC2017-67076.

In this paper, the internal dynamic excitation of the gear pair in a helical gear reducer of bridge crane is numerically investigated, taking into account of time-varying mesh stiffness, comprehensive gear error and meshing shock. The integral finite element model of bridge crane reducer gearbox is built by ANSYS software using APDL language. The internal dynamic excitations are imposed on the contact line of gear pair to solve the dynamic response of the gearbox. Using the results of dynamic response as boundary excitation conditions, the acoustic boundary element model is established. The surface sound pressure of gearbox and the radiated noise of field points are solved with SYSNOISE software. In order to verify the feasibility of the simulation method, a vibration & noise test is carried out. With the constant center distance as well as the similar total transmission ratio, the surface sound pressure of gearbox and the radiated noise of field points are calculated with different modules and helix angles. The effects of module and helix angle on the noise radiation of the gearbox are analyzed and discussed. The results provide a useful theoretical guidance for the design of gearboxes.

Commentary by Dr. Valentin Fuster
2017;():V010T11A035. doi:10.1115/DETC2017-68060.

Linear and bilinear time-frequency distributions (TFDs) have been employed in planetary gearbox fault diagnosis. For linear TFDs, there is a trade-off between the time localization and frequency resolution and the spectrogram may not have correct energy marginals. For bilinear TFDs, they cannot be interpreted as an energy distribution because of the existence of possible negative values even though they are designed for energy density representation. To overcome these shortcomings, TFDs based on copula theory have been reported in the literature. In this paper, we analyze two simulated data sets using linear TFD and copula-based TFD. The results show that the constructed copula-based TFD has desirable properties of being positive, free from cross-term interference, having high time-frequency resolution and matching well with true marginals. The copula-based TFD is also able to locate fault-induced impulses by vertical lines over a certain frequency range in the time-frequency domain. Consequently, this study confirms the advantages of the copula-based TFD as an energy distribution and its capability in fault detection for planetary gearboxes.

Commentary by Dr. Valentin Fuster

2017 ASME International Power Transmission and Gearing Conference: Lubrication and Efficiency

2017;():V010T11A036. doi:10.1115/DETC2017-67002.

In this work, the impact of the surface micro-dimple arrays on the frictional behavior under the mixed elastohydrodynamic lubrication condition is examined, considering a point contact problem. The interested geometric parameters of the micro-dimple arrays include the dimple center distance and the dimple depth. To quantify the influence of these parameters on the friction coefficient, a computational approach is implemented. In addition, different surface texture combinations, namely micro-dimpled and polished surface versus polished surface, polished surface versus polished surface and ground surface versus ground surface, are compared to determine any advantage or disadvantage of micro-dimpled surfaces on the aspect of the friction performance under the typical gearing application operating conditions.

Commentary by Dr. Valentin Fuster
2017;():V010T11A037. doi:10.1115/DETC2017-67016.

In various gear applications, water contaminated lubricants are a well known problem leading to a significantly decreased lubricant performance under certain circumstances. In FVA-research projects 488/I and 488/II (FVA-Forschungsvereinigung Antriebstechnik: German research association for transmission technology) the influence of a defined water content ranging from 1 000 ppm to 20 000 ppm in typical gear lubricants on the pitting load carrying capacity of case carburized gears was investigated. Regarding the test series with a relatively high water content from 5 000 to 20 000 ppm, a generally negative influence was observed. This influence was differently distinctive for the investigated base oil types. Especially non-polar lubricants were affected negatively. Subsequently, non-polar lubricants, such as polyalphaolefines and mineral oils, were chosen for further investigations as the water content was also lowered on more practice-relevant levels ranging from 1 000 to 2 900 ppm. The water contamination still influenced the pitting load carrying capacity in the upper range with water contents resulting in a relative humidity significantly higher than 100% (absolute water contents from 2250 to 2900 ppm). At the level of 1 000 ppm (rel. humidity approx. ≥ 100%), no significant influence was detected. Thus, it was possible to derive critical threshold limits for the water contamination of non-polar lubricants in practical applications, as from which, the water contamination may affect the pitting load capacity. The water-induced reduction of the pitting load carrying capacity seems to be primarily dependent on the blended additives. The used non-polar base oil type only had a subordinated impact. Based on the results of theoretical investigations, it was possible to derive and expand a general model of damaging mechanisms of water contamination in lubricants, which is split into: interaction lubricant-water, chemical-material-technological influence and tribological influence. In short, it describes the possible impact of water contamination on the lubricant, the material and lubricating-film properties. The results of additional measurements indicate some damaging mechanisms to be dominant under the herein performed test conditions. In detail, decomposition effects of additive components and an increased oil aging effect were identified to be crucial factors, while the influence on the material properties like the measured residual stresses in the gear material seemed to be subordinated.

Undissolved water is supposed to affect the pitting load carrying capacity more negatively than dissolved water. Therefore, the relative humidity is recommended as a suitable characteristic of lubricants to evaluate, whether measured water contents in practical gearbox applications may lead to a reduced pitting performance. Based on the results of the experimental and theoretical investigations a threshold limit for the relative humidity of 100 % appears to be reasonable, given that the additive system of the lubricants is not affected negatively.

Topics: Lubricants , Gears , Water
Commentary by Dr. Valentin Fuster
2017;():V010T11A038. doi:10.1115/DETC2017-67518.

An experimental investigation of spur gear behavior was conducted with the aim of quantifying the impact of lubrication methods and conditions on the power losses and contact fatigue lives. Variations of dip and jet-lubrication were defined and these behaviors were observed as a function of the lubrication conditions. All measurements were performed using the same back-to-back test machine and the same spur gear test articles such that all evaluations were correlated. Power loss experiments were performed under both loaded and unloaded conditions to determine both load-independent (spin) and load-dependent (mechanical) losses. Sets of long-cycle contact fatigue experiments were performed under the same lubrication conditions to determine macro-pitting lives in a statistically meaningful manner. Results indicate that the spin power losses are impacted by the lubrication method significantly while the mechanical losses are not influenced. Contact fatigue lives from jet-lubricated tests are comparable to those under dip-lubricated conditions ones as long as jet velocities are sufficient.

Commentary by Dr. Valentin Fuster
2017;():V010T11A039. doi:10.1115/DETC2017-67646.

Elastohydrodynamic lubrication phenomenon in spiral bevel gears was modeled in this study. The coefficient of friction calculated from the elastohydrodynamic (EHL) lubrication model is time varying. Friction is expected to have a greater impact on the spiral bevel gears than on any other right angled geared system due to the reversal of the contact area over a full tooth-to-tooth engagement cycle. The coefficient of friction formulated from an EHL model of spiral bevel gears depends upon lubricant properties, mesh forces and rotational speeds of the pinion and gear. Hence in this present study, a full elastohydrodynamic lubrication model was used to calculate the coefficient of friction in spiral bevel gears. The geometric and kinematic input data required for the EHL simulations were obtained from tooth contact analysis. Full numerical elastohydrodynamic lubrication simulations were carried out using the asymmetric integrated control volume (AICV) algorithm to compute the contact pressures and the coefficient of friction. The elastic deformations on the gear contact surfaces were calculated by circular convolution using a Fourier transform technique. The computed pressures, film thickness and the effective viscosity were used to calculate the time varying coefficient of friction for the spiral bevel gears. Parametric studies were conducted by varying the speed, torque applied, lubricant properties, temperature and slide to roll ratio to identify their impact on the time varying coefficient of friction.

Commentary by Dr. Valentin Fuster
2017;():V010T11A040. doi:10.1115/DETC2017-67818.

Rotorcraft gearbox efficiencies are reduced at increased surface speeds due to viscous and impingement drag on the gear teeth. This windage power loss can affect overall mission range, payload, and frequency of transmission maintenance. Experimental and analytical studies on shrouding for single gears have shown it to be potentially effective in mitigating windage power loss. Efficiency studies on unshrouded meshed gears have shown the effect of speed, oil viscosity, temperature, load, lubrication scheme, etc. on gear windage power loss. The open literature does not contain experimental test data on shrouded meshed spur gears. Gear windage power loss test results are presented on shrouded meshed spur gears at elevated oil inlet temperatures and constant oil pressure both with and without shrouding. Shroud effectiveness is compared at four oil inlet temperatures. The results are compared to the available literature and follow-up work is outlined.

Commentary by Dr. Valentin Fuster
2017;():V010T11A041. doi:10.1115/DETC2017-67971.

The lubricating ability of one halogen-free and one halogen-containing phosphonium-based ionic liquids are investigated as neat lubricants, lubricant additives and thin lubricant layers in steel-steel contact. The use of the ionic liquids in any of the three lubricating methods reduced friction and wear compared to a base mineral oil. The halogen-free ionic liquid outperformed the halogen-containing ionic liquid in the three methods of lubrication. The highest friction and wear reduction were obtained when ionic liquids were used as neat lubricants. Under this condition, friction reductions of 37.21% and 25.73 %, and wear reduction of 47.12% and 41.18% compared to the based mineral oil were obtained for the halogen-free and halogen-containing ionic liquids respectively. The wear mechanisms and surface interactions are discussed in terms of ionic liquid-metal surface interactions from optical and SEM images and EDS analysis.

Topics: Friction , Wear , Lubricants
Commentary by Dr. Valentin Fuster
2017;():V010T11A042. doi:10.1115/DETC2017-68006.

The efficiency analytical model of the inverted planetary roller screw mechanism is formulated based on the friction torque calculation. Firstly, the friction torque model considering the load distribution of thread teeth is established including the components such as curvature friction torque, friction torque due to spinning sliding, pure sliding friction torque between rollers and carriers, friction torque generated by the viscosity of lubricant, and preload torque. Secondly, the contribution of the friction torque components and torque distribution on the roller thread teeth are investigated. Finally, efficiency analysis is conducted by discussing the influences of structure parameters of the inverted planetary roller screw mechanism and operating conditions. Computational results reveal that the total friction torque and efficiency are influenced by axial load, number of roller thread teeth, nut speed, contact angle, and helix angle of nut with different extents. This study provides an understanding of the relationship between friction torque, transmission efficiency, and system design parameters, which can be employed to enhance the inverted planetary roller screw mechanism optimization design.

Commentary by Dr. Valentin Fuster
2017;():V010T11A043. doi:10.1115/DETC2017-68345.

In this study, load-independent (spin) power losses of a gearbox operating under dip-lubrication conditions are investigated experimentally using a final-drive helical gear pair from an automotive transmission as the example system. A dedicated gearbox is developed to operate a single gear or a gear pair under given speed and temperature conditions. A test matrix that consists of sets of tests with (i) single gears (spur, helical, or representative disks with no teeth), and (ii) helical gear pairs is executed at various temperatures, immersion depths and pinion positions relative to its mating gear. Power losses from single gears and gear pairs at identical operating conditions are compared to quantify the components of the total spin loss in the form of losses due to gear drag, gear mesh pocketing, and bearings and seals.

Commentary by Dr. Valentin Fuster

2017 ASME International Power Transmission and Gearing Conference: Transmission Systems Including Novel Concepts

2017;():V010T11A044. doi:10.1115/DETC2017-67015.

Energy crisis and environment pollution are closely correlated with the widespread use of internal combustion engine (ICE) vehicles. Considering multi-factors, developing hybrid electric vehicle (HEV) is an ideal solution to solve the problems since its environmental protection and practicability. Integrated Starter Generator (ISG), integrated by two motors between engine and mechanical transmission system, performs better in efficiency and economy. This paper attempts to design a parameter matching method of hybrid electric system according to its dynamic performance, driving condition and control strategy. An ISG model and the model of parameter matching HEV system are proposed in this paper.

Topics: Generators
Commentary by Dr. Valentin Fuster
2017;():V010T11A045. doi:10.1115/DETC2017-67179.

Experiment on a test bench is one of the key points during the research and development of a transmission. This paper designs a new real-time dynamic test bench based on MATLAB/Simulink® for testing and developing a novel seamless two-speed automatic mechanical transmission (AMT) for electric vehicles (EVs). Structure of the transmission allowing seamless shifting between two gears is also proposed. According to the transmission structure and the real-time testing requirements, hardware components and software system of the test bench are designed. A real-time executable and flexible model of the EV that is more suitable for hardware-in-the-loop (HIL) simulation, is built to run on Simulink Real-Time platform. The EV model is combined with two induction motors adopting direct torque control (DTC) technique to emulate the dynamic driving conditions of the transmission on the test bench. Simulation and experimental results show that the test bench responds well to the real-time dynamic requirements and it is very useful for testing and developing the proposed transmission.

Commentary by Dr. Valentin Fuster
2017;():V010T11A046. doi:10.1115/DETC2017-67488.

This paper applies the bond graph theory to construct a dynamic stiffness calculation model for the planetary roller screw mechanism with factors such as structural stiffness and contact stiffness of screw, clearances, geometry errors, rolling-sliding friction, and load distributions on the roller threads and a group of rollers under two installation modes. In addition to predicting how dynamic stiffness varies with the load frequency and load amplitude under two installation modes, how does it change with the structural parameters such as screw diameter, helix angle, contact angle and number of roller threads under two installation modes are also investigated. The results can provide theoretical basis for the design of planetary roller screw mechanism considering dynamic stiffness with the influences of clearances, geometry errors, friction and installation modes.

Commentary by Dr. Valentin Fuster
2017;():V010T11A047. doi:10.1115/DETC2017-67887.

This paper presents a new 3-dimensional multi-body dynamic model of a chain-type continuously variable unit (CVU). The modeling requirements and assumptions are presented first. Then, the paper discusses the approaches developed to mathematically represent the chain, pulleys, and their interactions in terms of contact and friction. Three dimensional representation of the chain is given. Actual geometries of the pins and pulleys are captured, including crowning on either member. The model is then used to investigate the effects of different operating conditions, including speed ratio and torque, on the quasi-static performance of a CVU. Several metrics are discussed to characterize the behavior of an example CVU under practical operating conditions; these include torque capacity and the ratio of clamping forces. The predictions presented show the sensitivity of the model to these operating conditions. Finally, trends that describe the CVU quasi-static behavior are explained in context of the parameters studied.

Commentary by Dr. Valentin Fuster
2017;():V010T11A048. doi:10.1115/DETC2017-68001.

The focus of this work is development of a comprehensive tooth contact analysis model and characterization of lubricant performance in a Pericyclic mechanical transmission utilizing modified straight bevel gears. The Pericyclic drive is kinematically similar to an epicyclic bevel gear train, and is characterized by load sharing over large number of teeth, large shaft angles (175°-178°), nutational gear motion, and high reduction ratio. The load sharing calculation model described in this paper takes into account contact outside involute region and is easily generalized to all bevel epicyclic gear drives. The resulting contact stress field, calculated using Hertz contact stress theory, was validated against FEA solution. A 3-D kinematic analysis of the pericyclic drive was carried out to determine rolling and sliding velocities at contact points. Thereafter, Elastohydrodyamic lubrication (EHL) characteristics viz. film thickness, friction coefficient, and flash temperature were calculated for a sample lubricant. Power losses due to film friction are calculated to determine mesh efficiency. Finally, the effect of input power and profile crowning parameter was studied for all of the above mesh characteristics. The friction coefficient values were found to be in the lower range of EHL contact leading to high efficiency values and a small flash temperature for surfaces in contact.

Commentary by Dr. Valentin Fuster

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