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ASME Conference Presenter Attendance Policy and Archival Proceedings

2015;():V014T00A001. doi:10.1115/IMECE2015-NS14.
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This online compilation of papers from the ASME 2015 International Mechanical Engineering Congress and Exposition (IMECE2015) 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to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.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

Emerging Technologies: Energy, Electronics, Design and Education

2015;():V014T06A001. doi:10.1115/IMECE2015-50173.

The Internet of Things (IoT) consists of embedded low-power devices that collect and transmit data to centralized head nodes that process and analyze the data, and drive actions. The proliferation of these connected low-power devices will result in a data explosion that will significantly increase data transmission costs with respect to energy consumed and latency. Edge computing performs computations at the edge nodes prior to data transmission to interpret and/or utilize the data, thus reducing transmission costs. In this work, we seek to understand the interactions between IoT applications’ execution characteristics (e.g., compute/memory intensity, cache miss rates, etc.) and the edge nodes’ microarchitectural characteristics (e.g., clock frequency, memory capacity, etc.) for efficient and effective edge computing. Thus, we present a broad and tractable IoT application classification methodology and using this classification, we analyze the microarchitectural characteristics of a wide range of state-of-the-art embedded system microprocessors and evaluate the microprocessors’ applicability to IoT computation using various evaluation metrics. We also investigate and quantify the impact of leakage power reduction on the overall energy consumption across different architectures. Our work provides insights into the microarchitectural characteristics’ impact on system performance and efficiency for various IoT application requirements. Our work also provides a foundation for the analysis and design of a diverse set of microprocessor architectures for IoT edge computing.

Commentary by Dr. Valentin Fuster
2015;():V014T06A002. doi:10.1115/IMECE2015-51816.

The described research is a light weight, inexpensive portable and collapsible wind turbine, small enough to be carried in a backpack, ruck sack or within the storage compartment of a vehicle, which can be used to recharge batteries and provide off-site, emergency, or campsite power. As a means to extend the battery life of electronic equipment while moving away from the power grid and extra battery storage, a power generating unit is needed. Current approaches are to carry the anticipated number of spare batteries, to use solar cells or any number of small generating thermionic devices. While each of these have a place in the market, they also have negative cost, size, and weight drawbacks.

The objective of this research is to create a power generating/storage wind turbine device for recreational, emergency, and military use that can easily be collapsed and transported as needed. The device is a lightweight, collapsible wind turbine constructed of rugged materials to be used on camp sites, remote locations etc. and carried within a pack for travel. It is of a size and weight to be part of an emergency or survival pack. The wind turbine, in its preferred embodiment, is a self-starting/sustaining device that starts at low wind speeds so no monitoring or priming of the device is necessary. In addition to the novelty of it being collapsible, the wind turbine device employs advanced features to increase its wind energy capture efficiency and its energy storage and delivery system, along with unique design features that make it rugged, lightweight and easily assembled.

Commentary by Dr. Valentin Fuster
2015;():V014T06A003. doi:10.1115/IMECE2015-52394.

Data centers are expensive to build and operate. Large data centers cost $9–13/W to build [1] and can consume more than forty times, and up to over two hundred times, the amount of energy and resources consumed by a typical building [2], [3]. Therefore, space and energy considerations need to be accounted for when evaluating competing designs for high-performance computing (HPC) installations.

This paper describes the results of an incremental cost and energy savings analysis conducted using data collected from a real-world case study to evaluate the impacts of efficient resource planning and implementing a total cost of ownership (TCO) model in the analysis of IT equipment and systems. The analysis presented demonstrates the advantages of using the latest technologies and IT strategies when planning the growth of new HPC installations at an enterprise level. The data also indicates an efficient design can significantly reduce the space, power, and cooling requirements of the HPC deployment while maintaining the performance and reliability criteria.

Topics: Density , Design
Commentary by Dr. Valentin Fuster
2015;():V014T06A004. doi:10.1115/IMECE2015-53021.

RTCP (rotation tool center point), which is one of the necessary functions for high-grade CNC machine tools, can effectively decrease nonlinear errors caused by the motion of the rotation axis and improve the accuracy of the machinery. Based on the characteristic that the cutting tool tip point is relative to the manufacturing workpiece, the RTCP trajectory is proposed to conveniently measure the displacement of the tool tip point. The scheme is utilized to study the dynamic performance of machine tools, and a simulation that shows the relationship between the tool tip error trajectory and the factors influencing the dynamic performance of the machine tool is presented based on the servo system model. Then, the experiment is carried out, and the tool tip point error variation is found to be consistent with the simulation result. This study provides theoretical support for dynamic performance detection of five-axis CNC machine tools.

Commentary by Dr. Valentin Fuster
2015;():V014T06A005. doi:10.1115/IMECE2015-53237.

Modeling machining processes with conventional finite element methods (FEM) is challenging due to the severe deformations that occur during machining, complex frictional conditions that exist between the cutting tool and the workpiece, and the possibility of self contact due to chip curling. Recently, the Smoothed Particle Hydrodynamics (SPH) method has emerged as a potential alternative for modeling machining processes due to its ability to handle severe deformations while avoiding mass and energy losses encountered by traditional FEM. The method has been implemented in several commercial finite element packages such as ABAQUS and LS-DYNA for solving problems involving localized severe deformations.

Numerous control parameters are present in a typical SPH formulation. The purpose of this work is to evaluate the effect of the three most important parameters, namely, the smoothing length, particle density, and the type of SPH formulation. The effects of these parameters on the chip morphology and stress distribution in the context of orthogonal machining of AISI 1045 steel are investigated. The LS-DYNA finite element package along with Johnson-Cook material model is used for this purpose. Results from the parametric study are presented and compared with the previously reported results in the literature. In addition, the sensitivity of chip morphology and stresses to Johnson-Cook parameters for AISI 1045 steel is also investigated by considering five different sets of values reported in the literature for this steel.

Commentary by Dr. Valentin Fuster
2015;():V014T06A006. doi:10.1115/IMECE2015-53463.

A rapid development in wind turbine technology took place during the Second World War and oil crisis of 1973. It continued during twentieths century, which resulted in turbines with bigger size and more advanced technology. Today, large wind turbines are becoming more competitive in the field of electricity generation because of economical production of electricity and availability at rural and remote locations. They have occupied remarkable share in world renewable power generation among various renewable energy sources. On the other hand small wind turbines are not accepted well because of lack of assured performance, cost, efficiency, etc. Therefore some researchers are trying to develop new wind turbine systems to convert wind energy in to electricity. Innovations in the design wind turbine to make them compatible for household use and also to favor their installations by building more eye-catching, efficient and economical wind turbine. To increase acceptability of wind turbines, wind turbine should satisfy the most of the criteria listed in the present study such as, ability to catch the wind from all the direction, self starting, light weight, inexpensive, maintenance free, low weight tower-top system and hence supporting structure, light weight and efficient generator, efficient wind to mechanical energy conversion and manufacturing simplicity at affordable cost and reliable performance. Present study focused on the innovative wind turbines that installed as an offshore and onshore technology. There are more than one hundred of different innovative wind turbine designs listed research papers, books, magazines and internet. In present paper, innovative design aspects of some of these turbines discussed with the technological challenges. Innovations are in the area of blade profile design, aerodynamic shape of the wind turbine, reduction of noise and vibrations, the material of the blade, mechanical and electronic instruments such as gearbox and electronic power circuit, suitability to the application, etc. The aims of these innovations are improvement in the efficiency of the wind turbine; increase in power output and to lower the overall cost. At the end of paper the technological challenges that these innovations overcome, innovative concept and feasibility of the concept are discussed. These innovations include spiral wind turbine, VAWT with accelerator, Windpax-Collapsible portable wind turbine, multi-rotor wind turbines, diffuser augmented wind turbines and floating wind turbines.

Topics: Wind turbines
Commentary by Dr. Valentin Fuster

Emerging Technologies: Engineering for Healthcare

2015;():V014T06A007. doi:10.1115/IMECE2015-52817.

Virtual Reality (VR) is one of the areas of knowledge that have taken advantage of the computer technological development and scientific visualization. It has been used in different applications such as engineering, medicine, education, entertainment, astronomy, archaeology and arts. A main issue of VR and computer assisted applications is the design and development of the virtual environment, which comprises the virtual objects. Thus, the process of designing virtual environment requires the modelling of the virtual scene and virtual objects, including their geometry and surface characteristics such as colours, textures, etc.

This research work presents a new methodology to develop low-cost and high quality virtual environments and scenarios for biomechanics, biomedical and engineering applications. The proposed methodology is based on open-source software. Four case studies corresponding to two applications in medicine and two applications in engineering are presented. The results show that the virtual environments developed for these applications are realistic and similar to the real environments. When comparing these virtual reality scenarios with pictures of the actual devices, it can be observed that the appearance of the virtual scenarios is very good. In particular the use of textures greatly helps in assessing specific features such as simulation of bone or metal. Thus, the usability of the proposed methodology for developing virtual reality applications in biomedical and engineering is proved. It is important to mention that the quality of the virtual environment will also depend on the 3D modelling skills of the VR designer.

Commentary by Dr. Valentin Fuster
2015;():V014T06A008. doi:10.1115/IMECE2015-53385.

Measurements of sequential Ground Reaction Force (GRF) can provide quite useful information for monitoring of gait abnormalities during activities in daily life. Measuring sequential GRF in conventional approach using force plates is difficult due to the limited number of force plates. Therefore, we developed a fully untethered GRF sensing system having the low height (12 mm) and the capability of sensing simultaneously shear and normal GRF. The biaxial force sensing shoe showed the excellent repeatability (0.6 %) under long-term periodic loading condition for two hours. Comparison experiments with commercially available film type force sensors, FSR (Interlink) and Flexiforce (Tekscan), were performed under walking condition for twenty minutes. Owing to the high repeatability of the proposed system, variabilities of swing time and stance time of user were investigated with two subjects, a healthy subject and a foot-drop patient. We suggested three diagnostic measures in consideration of conventional approaches — variability for gait symmetry, center of pressure distribution for balance, and ratio of shear and normal GRFs for foot pronation.

Commentary by Dr. Valentin Fuster
2015;():V014T06A009. doi:10.1115/IMECE2015-53420.

In this paper a reinforcement learning algorithm is applied to regulating the blood glucose level of Type I diabetic patients using insulin pump. In this approach the agent learns from its exploration and experiences to selects its actions. In the current reinforcement learning algorithm, body weight, A1C level, and physical activity define the state of a diabetic patient. For the agent, insulin dose levels constitute the actions. There are five alternative actions for the agent: (1) raising the insulin infusion rate during 24 hours, (2) keeping it the same, (3) decreasing insulin infusion rate, (4) adjusting basal rate two times during 24 hours, and (5) adjusting basal rate three times during 24 hours. As a result of a patient’s treatment, after each time step t, the reinforcement learning agent receives a numerical reward depending on the response of the patient’s health condition. At each stage the reward is calculated as a function of the deviation of the A1C from its target value. Since reinforcement learning algorithm can select actions that improve patient condition by taking into account delayed effects it has tremendous potential to control blood glucose level in diabetic patients. This research will utilize ten years of clinical data obtained from a hospital.

Commentary by Dr. Valentin Fuster

Emerging Technologies: Poster

2015;():V014T06A010. doi:10.1115/IMECE2015-52458.

Preventing catastrophic failures is the most important task of prognostics and health management approaches in industry where Remaining Useful Life (RUL) prediction plays a significant role to schedule required preventive actions. Regarding recent advances and trends in data analysis and in Big Data environment, industries with such foreseeing approach are able to maintain their fleet of assets more efficiently with higher assurance. To address this requirement, several physics-based and data-driven methods have been developed to predict the remaining useful life of various engineering systems. In current paper, we present a simple, yet accurate stochastic method for data-driven RUL prediction of complex engineering system. The approach is constructed based on selecting the most significant parameters from raw data by using the improved distance evaluation method as feature selection algorithms. Subsequently, the health value of units is assessed by logistic regression and the assessment output is used in a Monte Carlo simulation to estimate the remaining useful life of the desired system. During Monte Carlo iterations, several features are extracted to help filtering less accurate estimations and improve the overall prediction accuracy. The proposed algorithm is validated in two ways. First of all, the accuracy of RUL prediction is measured by applying the method to 2008 PHM data challenge gas-turbine dataset. Subsequently, gradual changes in RUL prediction of a particular test unit are measured to verify the behavior of the algorithm upon availability of additional historical data.

Commentary by Dr. Valentin Fuster

Safety Engineering and Risk Analysis: Failure and Forensic Analysis I: Consumer Products

2015;():V014T08A001. doi:10.1115/IMECE2015-51927.

According to estimates reported in the U.S. Consumer Product Safety Commission’s National Electronic Injury Surveillance System, there were greater than 10,000 stepladder related injuries treated in hospital emergency rooms nationwide per year in the period from 2009 through 2013. Research and experience have sought to correlate specific stepladder damage patterns to the causes of some injuries involving stepladders. Prior studies have associated a specific damage pattern — inward deformation of the stepladder’s front side rails — with impact loading of a user’s body onto the lower portion of a front side rail following a fall from the stepladder. Those prior studies were conducted using stepladders with metal knee braces and with the ladder cap simply supported during impact testing. Currently sold fiberglass stepladders often have plastic rather than metal knee braces. In our study, side rail impact testing was performed in order to evaluate how a design change from metal knee braces to plastic knee braces affects impact damage patterns in fiberglass stepladders. Biomechanics simulations were used to inform the selection of the weights used for impact testing and allowed the test results to be evaluated in the context of potential body contact scenarios that could produce equivalent loading of the side rail. Our study demonstrates that depending on the weight of the impacting body, fiberglass ladders with plastic knee braces show different dynamic responses to impact loading than do their metal counterparts. Additionally, the test methods in this study incorporate realistic dynamics in that the weight impacted the lower portion of the stepladder’s front side rail while the stepladder was actively tipping with only two of its feet in contact with the ground and with the top cap unsupported.

The results indicate that ladders with metal knee braces can permanently deform when impacted with loads less than that required to permanently deform the ladders tested with plastic knee braces. The absence of permanent side rail deformation in the plastic knee braced stepladders tested even after undergoing significant elastic deformation during testing gives rise to new questions about the potential for damage that is not observable based on a visual examination.

Commentary by Dr. Valentin Fuster
2015;():V014T08A002. doi:10.1115/IMECE2015-52404.

Overhead doors see widespread use, primarily in garage door and truck body applications. Although overhead door systems can appear benign to users, there are some types of door system failures that can expose users to potentially injurious hazards. This paper will present the design and operation of an overhead door system in widespread use, the potential hazards of the system, and the possible failure modes of the system. A methodology will be presented that was used to analyze a door system that malfunctioned and resulted in a serious injury to a user. A test matrix which was used to analyze and replicate this malfunction is also presented.

Commentary by Dr. Valentin Fuster
2015;():V014T08A003. doi:10.1115/IMECE2015-53225.

A closed-loop test of a 1974 Ford F-150 4WD truck equipped with super oversized off-road mud tires was conducted to demonstrate that steering was possible after a left front rapid air-out event. A rim was built with six remotely deployable orifices that activated simultaneously and caused the air pressure to decrease below 2.5 psi in less than one second. The truck was configured in OEM condition except for the tires and rims. The tires were 42–14X16 mounted to 8X16 rims with zero offset. The tires that were originally sold with the vehicle were probably 8.75–16.5. Three tests at increasing speed of 35 mph, 45 mph, and 55 mph were conducted on a large, remote, and closed parking lot in a two-lane travel way marked with surface paint. The truck, while monitored with a standard suite of instruments and video, was brought to speed in a straight-line. At a predetermined point, and while maintaining a straight path, the throttle was dropped and the left front tire air-out was remotely triggered. The driver, aware of the test conditions and with the benefit of experience, was instructed to steer the truck to maintain its position within the simulated traffic lanes. The truck was equipped with a four-speed manual transmission which remained in fourth gear throughout the response phase of the test. The clutch was depressed and brakes applied only after steering control had corrected the vehicle’s leftward motion. The post air-out path of the truck evidenced by printing from the left front tire in each test was measured, photographed and plotted. The truck never left the simulated roadway travel lanes, which represented one direction of a typical four-lane California state highway. The test data was recorded at 200 samples per second and was post-processed with a 6 HZ, 12-pole, phaseless digital filter. Test results were plotted and presented. The test results are of interest because they are a demonstration of the concept that even under extreme conditions, if a test driver knows what is going to happen and knows what to do, a controlled vehicle motion is the likely outcome. In the tests, as the driver gained experience and the speed increased, lateral motion decreased. These findings are consistent with conclusions in a NHTSA tread separation study including, “when drivers had prior knowledge of the imminent tread separation, they were significantly less likely to sustain loss of vehicle control following the tread separation.” And, “findings from test track studies in which test drivers were aware of an imminent tread separation may underestimate the extent to which tread separation occurring in the real world leads to instability and loss of vehicle control.”

Topics: Tires , Light trucks
Commentary by Dr. Valentin Fuster
2015;():V014T08A004. doi:10.1115/IMECE2015-53370.

Child poisoning has been dramatically reduced by the introduction of child resistant (CR) closures on some common home chemicals and pharmaceuticals. However, “child resistance” (often mischaracterized as “child proof”) is a mechanical design property that is neither well understood nor supported by a body of theory, nor that can be specified from engineering first principles. Instead, child resistance is an empirically developed and verified closure mechanical property derived from closure testing with child subjects, as specified by regulations under the Poison Prevention Packing Act (PPPA). The authors report their longitudinal study of a specific Type III CR closure over a period of decades made with materials from different suppliers over time and using different injection molding tools. The study examines if the property of “child resistance” persisted and if it correlated with the mechanical specifications of the closure actually measured and controlled in the closure manufacturing process. This data is combined with the authors’ mechanical measurements of closure performance. Child resistance, being a complex, empirically tested property, cannot be regularly tested in the normal manufacturing environment. Despite minor manufacturing process and specification changes, if the mechanical specifications are appropriate (e.g. not intended to produce changes in CR mechanical properties) and with adequate quality control, the property of child resistance persists.

Commentary by Dr. Valentin Fuster
2015;():V014T08A005. doi:10.1115/IMECE2015-53666.

Accident reconstruction involving consumer products and industrial equipment often requires biomechanical and/or human factors analyses to help determine the root cause of an accident scenario. A systematic method has been established which incorporates numerous components of the sciences of biomechanics and human factors and uses the scientific method as the framework for evaluating competing theories. Using this method, available data are gathered pertaining to the accident or incident and organized in a modified Haddon matrix, with categories for Man [person(s) involved in the accident], Product/Machine, and Environment. Information about the person(s) is separated further into injury and human factors components. The injuries are viewed as physical evidence, where each injury occurred as a result of being exposed to a specific combination of energy, force, motion/deflection, acceleration, etc. The injuries are evaluated with known injury research and categorized with a specific type, location, mechanism, and injury threshold. This injury evidence is then reconciled with the other physical evidence developed from the accident environment and product/machine categories. Human factors evaluations of body size, posture, capabilities, sensory perception, reaction time, and movements create similar information that is also reconciled with the rest of the evidence from an accidental circumstance. At the core of this method is developing scientific data or information that can be used to support or refute accident reconstruction conclusions. An accurate and complete accident reconstruction using the available data must be consistent with the laws of physics, and the physics of interaction between the man, product/machine, and environment.

Commentary by Dr. Valentin Fuster

Safety Engineering and Risk Analysis: General

2015;():V014T08A006. doi:10.1115/IMECE2015-50420.

Industry has been implementing condition monitoring for turbines to minimize losses and to improve productivity. Deficient conditions can be identified before losses occur by monitoring the equipment parameters. For any loss scenario, the effectiveness of monitoring depends on the stage of the loss scenario when the deficient condition is detected. A scenario-based semi-empirical methodology was developed to assess various types of condition monitoring techniques, by considering their effect on the risk associated with mechanical breakdown of steam turbines in the forest products (FP) industry. A list of typical turbine loss scenarios was first generated by reviewing loss data and leveraging expert domain knowledge. Subsequently, condition monitoring techniques that can mitigate the risk associated with each loss scenario were identified. For each loss scenario, an event tree analysis was used to quantitatively assess the variations in the outcomes due to condition monitoring, and resultant changes in the risk associated with turbine mechanical breakdown. An application was developed following the methodology to evaluate the effect of condition monitoring on turbine risk mitigation.

Commentary by Dr. Valentin Fuster
2015;():V014T08A007. doi:10.1115/IMECE2015-50848.

This paper focuses on the U-bolt pipe whip restraint in the industrial plants, which is used to protect the equipment and prevent chain destruction under the circumstance that the pipe whip phenomenon occurs. And to achieve better protection performance the deformation process and energy absorbing situations are studied through experiments. The experiments are able to simulate the whipping pipe impacting the U-bolt pipe whip restraint with different velocity and input energy. This study presents a novel experiment method using a rigid sled to impact the U-bolt pipe whip restraint. This horizontal impact experiment method allows to change the mass and the impact velocity of the sled easily, so it is more convenient to design and control the experiments than traditional vertical experiment method. Results of ten experiments are analyzed in this study, and some basic parameters are achieved. A significant conclusion is found that the process of the U-bolt pipe whip restraint deformation and energy absorbing has four obvious phases. Velocity effect and mass effect are also taken into account to find more details of this process. The deformation and energy absorbing law can also be used in engineering design.

Topics: Deformation , Pipes
Commentary by Dr. Valentin Fuster
2015;():V014T08A008. doi:10.1115/IMECE2015-52155.

What is an acceptable thickness of accumulated combustible dust in an industrial facility?

Combustible dusts present both flash fire and explosion hazards. Companies which generate, handle, process, store, or distribute combustible dusts need to cost-effectively manage these hazards. In the United States, the Occupational Health and Safety Administration (OSHA) has stepped up its enforcement activity and is conducting inspections at these locations to verify that the facility is being operated in accordance with recognized and generally accepted good engineering practices (RAGAGEP). The combustible dust safety standard from the National Fire Protection Association, NFPA 654 (1) is often cited as the RAGAGEP for combustible dust risk management. One aspect of combustible dust risk management is the monitoring and control of fugitive dust accumulation on horizontal surfaces. NFPA 654 gives specific guidance on how to determine an acceptable level of combustible dust accumulation using different risk scenarios. These acceptable levels or thresholds were only recently added as requirements in the 2013 edition of NFPA 654 and there is debate as to whether they are accurate. An examination of this guidance reveals that it is very conservative because it omits consideration of several distinct events necessary for a dust deflagration or flash fire to occur.

NFPA 654, 2013 edition presents four techniques to determine if a flash fire or explosion hazard exists in a building or enclosure. These are: the layer depth criterion, Mass Method A, Mass method B, and Risk Evaluation. The standard gives explicit directions on how to calculate critical layer thickness using the first three methods. The standard does not give guidance on how to conduct a risk evaluation. In this paper we present a risk evaluation based on the NFPA 654 layer depth criteria. We formulate the dust accumulation scenario as a sequence of distinct events, estimate probabilities for each event, and illustrate how the NFPA 654 guidelines generally skew the layer depth criteria towards lower values. It is argued that the NFPA 654 guidance may result in layer depth criteria that are too conservatively low for facilities that manage marginally combustible dusts. In those facilities a more quantitative risk analysis will likely yield better, i.e., more practical criteria.

Commentary by Dr. Valentin Fuster
2015;():V014T08A009. doi:10.1115/IMECE2015-52505.

In order to analyze the reliability of the new lock mechanism which is an important part of aircraft cabin door system, this paper studies the reliability and sensitivity for the lock mechanism based on surrogate models and variance methods respectively. Function hazard analysis (FHA) and failure mode effects analysis (FMEA) of lock mechanism is studied firstly. Then, based on dynamics simulation model, performance function and various random variables, the widely used surrogate models of lock mechanism is established and verified. Based on the most accurate metamodel which has been established, the unlocking reliability which is the most hazardous function is calculated. Finally, the variance-based sensitivity method is used for sensitivity analysis of influence factors, the result shows that the tension of lock-hook from lock-ring is the largest influence factor on the unlocking reliability, which could contribute to the analysis and further improvement of lock mechanism.

Commentary by Dr. Valentin Fuster
2015;():V014T08A010. doi:10.1115/IMECE2015-52603.

The DL150 CNC heavy duty lathes can fulfill multiple heavy duties with high precision, which is one type of fundament manufacturing equipment. They are now serving as indispensable equipment in the industries of energy, transportation, aerospace and defense. To achieve high availability and productivity, unit-specific condition monitoring and degradation analysis are carried out. The machining accuracy and lubrication debris are observed as performance indicators. Due to these two indicators are depended on each other and the working profile of these heavy duty lathes varied greatly from factories to factories, a method for bivariate degradation analysis under dynamic conditions is urgent. However, among traditional degradation analysis method, two types of assumptions are generally adopted for degradation analysis: single degradation indicator and constant external factors. These methods can hardly characterize the degradation of complex systems that are subjected to multiple performance indicators under dynamic conditions. Originated from reliability analysis of DL 150 heavy duty lathes, this paper introduces a bivariate degradation analysis method. It is aimed to mitigate these two general assumption by addressing two practical engineering-driven issues, including: (1) a new types of bivariate models is introduced to deal with bivariate degradation processes modeling, and (2) two types of dynamic covariates are incorporated and treated separately within the proposed model to cope with dynamic condition modeling. Finally, a numerical example drawn from a type of heavy machine tools is presented to demonstrate the application and performance of the proposed method.

Commentary by Dr. Valentin Fuster
2015;():V014T08A011. doi:10.1115/IMECE2015-52954.

A 3D mass evacuation simulation using precise kinematic digital human (KDH) models and an experimental study are discussed. The tidal wave associated with the large tsunami caused by the Great East Japan Earthquake was responsible for more than 90% of the disaster casualties. Unfortunately, it is expected that other huge tsunamis could occur in Japan coastal areas if an earthquake with magnitude greater than 8 occurred along the Nankai Trough. Therefore, recent disaster prevention plans should include evacuation to higher buildings, elevated ground, and construction of tsunami evacuation towers. In the evacuation simulation with 500 KDHs, the mass consists of several subgroups. It is shown that the possible evacuation path of each group should be carefully determined to minimize the evacuation time. Several properties such as evacuee motion characteristics of KDHs, number of evacuees, exit gates and, number of injured persons were carefully considered in the simulation. Evacuee motion was also experimentally investigated by building a test field that simulates the structure of an actual tsunami evacuation tower for accommodating approximately 120 evacuees. The experimental results suggest that an appropriately divided group population may effectively reduce the overall group evacuation time. The results also suggest that the fatigue due to walking during evacuation adversely affect the total evacuation time, especially the ascent of stairways. The experimental data can be used to obtain more accurate simulations of mass evacuation.

Commentary by Dr. Valentin Fuster
2015;():V014T08A012. doi:10.1115/IMECE2015-53056.

Currently in the United States, agencies responsible for regulations related to worker or public exposures to dust set rules based on a few general categories determined by gross particle size categories like PM10 (particles < 10 μm) and PM2.5 (particles < 2.5 μm) and the total mass of certain specific compounds (e.g., 3.5 mg/m3 of carbon black). Environmental health researchers however, have begun to focus on a new category of ultrafine particles (PM0.1; particles < 100 nm) as being more indicative of actual health risks in people. The emerging field of nanotoxicology meanwhile is providing new insights into how and why certain particles cause damage in the lungs by investigating the effects of exposure in animals to very well characterized engineered nanomaterials.

Based on this recent research the National Institute of Occupational Safety and Health (NIOSH) has issued new recommended exposure limits (RELs) for carbon nanotubes (CNTs) and titanium dioxide nanoparticles that are 2–3 orders of magnitude more stringent than RELs for larger particles of the same or similar substance. It remains unclear at present how stringent future regulations may be for engineered and inadvertently created nanoparticles or ultrafine dusts. Nor is it clear whether verification methods to demonstrate compliance with these rules could or should be devised to differentiate between engineered and inadvertently created nanoparticles.

This study presents a review of the history of dust regulation in the United States, how emerging data on the health risks of ultrafine particles and engineered nanoparticles is changing our understanding of the risks of inhaled dust, and how future rulemaking in regards to these and similar particulate materials may unfold.

This review shows the extent to which rules on dust have become more stringent over time specifically in the case of diesel emissions and silica exposure, and indicates that new rules on worker exposure to ultrafine dusts or engineered nanomaterials may be expected in the United States within 5–10 years based on past experience on the time delay in connecting research on new hazards to regulatory intervention. Current research suggests there will be several challenges to compliance with these rules depending on the structure of the final rule and the development of detection technologies. Although the research on ultrafine dust control technologies appears to indicate that once rulemaking begins there may be no serious feasibility limits to controlling these exposures. Based on ongoing exposure studies, those industries likely to be most affected by a new rule on ultrafine dusts not specific to engineered nanomaterials will include transportation, mining, paper and wood products, construction, and manufacturing.

Commentary by Dr. Valentin Fuster
2015;():V014T08A013. doi:10.1115/IMECE2015-53138.

The potential benefits of a safety program are generally, only realized after an incident has occurred. Resource allocation in an organization’s safety program has the imperative task of balancing costs and often unrealized benefits. Management can be wary to allocate additional resources to a safety program because it is difficult to estimate the return on investment, especially since the returns are a set of negative outcomes not manifested.

One way that safety professionals can provide an estimate of potential return on investment is to forecast how the organizations incident rate can be affected by implementing the different resource allocation strategies, and what the expectation for the incident rate would have been without intervention. Safety professionals often trend the performance of their organization’s safety program by benchmarking incident rates against other organizations. Previous studies have employed different statistical forecasting methods to predict how incident rates will react to changes in resource allocation.

This paper analyzes the performance of four statistical forecasting methods employed in previous resource allocation studies along another statistical forecasting method, never before used for incident rate prediction, to ascertain the method that provides the highest level of forecast accuracy. By identifying the most accurate forecasting method, the uncertainty of which method a safety professional should utilize for incident rate prediction is reduced. Incident data from the Mine Safety and Health Administration (MSHA) Part 50, was used to forecast both short and long term incident rates. The performance of each of these forecasting methods were evaluated against one another to determine which method has the highest level of accuracy, lowest bias, and best complexity-adjusted goodness-of-fit metrics.

Evaluation of the performance provides indications that the double exponential smoothing statistical forecasting method can provide the most accurate incident rate predictions. Analysis of forecast bias indicated that the error for the double exponential smoothing method is unbiased, within the acceptable range for tracking signal, and had a level of prediction accuracy above 70%. The results of this observational study indicate that the double exponential smoothing method should be the method to consider for incident rate prediction. Consistent use of the same forecasting methodology amongst safety professionals as part of their safety program’s resource allocation process, will allow for more consistent benchmarking of incident rate prediction.

Commentary by Dr. Valentin Fuster
2015;():V014T08A014. doi:10.1115/IMECE2015-53277.

In order to analyze the reason of failure and improve the reliability of the idler shaft, this paper studies the reliability and sensitivity for the idler shaft based on Kriging model and Variance Methods respectively. The finite element analysis (FEA) of idler shaft is studied in ABAQUS firstly. Then, combining the performance function and various random variables, the Kriging model of idler shaft is established and verified. Based on Kriging model which has been established, the relationship between random variables and the response value is studied, and the function reliability is calculated which explains why the failure of the idler shaft occurred frequently in service. Finally, the variance-based sensitivity method is used for sensitivity analysis of influence factors, the result shows that the reliability of idler shaft is sensitive to the inner diameter of body A and inner diameter of body B, which could contribute for the analysis and further improvement of idler shaft.

Commentary by Dr. Valentin Fuster
2015;():V014T08A015. doi:10.1115/IMECE2015-53585.

Go-karts are a common amusement park feature enjoyed by people of all ages. While intended for racing, contact between go-karts does occur. To investigate and quantify the accelerations and forces which result from contact, 44 low-speed impacts were conducted between a stationary (target) and a moving (bullet) go-kart. The occupant of the bullet go-kart was one of two human volunteers. The occupant of the target go-kart was a Hybrid III 50th percentile male anthropomorphic test device (ATD). Impact configurations consisted of rear-end impacts, frontal impacts, side impacts, and oblique impacts. Results demonstrated high repeatability for the vehicle performance and occupant response. Go-kart accelerations and velocity changes increased with increased impact speed. Impact duration and restitution generally decreased with increased impact speed. All ATD acceleration, force, and moment values increased with increased impact speed. Common injury metrics such as the Head Injury Criterion (HIC), Nij, and Nkm were calculated and were found to be fairly low. These results indicate that the potential for serious injury is low during low-speed go-kart impacts.

Topics: Vehicles
Commentary by Dr. Valentin Fuster

Safety Engineering and Risk Analysis: Reliability Methods

2015;():V014T08A016. doi:10.1115/IMECE2015-51289.

GO methodology is a success-oriented method for system reliability analysis. There are Multiple-Input, which contain control signal, oil provided and electrical signal et.al and MultiFunction Components (MIMFC) in some repairable systems, such as double-action variable displacement pump, multiple directional control valve, and hydraulic coupler etc. Because existing 17 basic GO operators in GO methodology can’t describe these MIMFCs accurately, it is a problem to adopt existing GO methodology to conduct the reliability analysis for these systems with MIMFC. In this paper, firstly a new GO operator combination, which is composed of a new function GO operator and a new auxiliary GO operator, is created to represent MIMFC. The new function GO operator named as Type 22 operator is created to represent MIMFC itself, and the auxiliary GO operator named as Type 15B operator is created to represent multi-conditions control signals of MIMFC. Then, quantitative calculation formulas of new GO operator combination are derived based on logical relationships among inputs, outputs, and component itself. Thirdly, this new GO operator combination is applied for the first time in steady availability analysis and qualitative analysis of the fan drive system of a Power-shift Steering Transmission. Finally, the results obtained by the method in this paper are compared with the result of Fault Tree Analysis (FTA) and result of Monte Carlo simulation, and the comparison results show that this new GO operator combination is usable and correct for reliability analysis of repairable system with MIMFC, and it has more advantageous in the aspects of building system model and quantitative analysis. Meantime, this paper provides guidance for reliability analysis of other repairable systems with MIMFC.

Commentary by Dr. Valentin Fuster
2015;():V014T08A017. doi:10.1115/IMECE2015-51307.

Fault Tree Analysis (FTA) is one of the most developed techniques in reliability studies; however static analysis is not able to encompass the dynamic behavior of complex systems. To overcome this problem, Dynamic Fault Tree (DFT) analysis is suggested in recent researches. The main motivation of this study is a comparative study on differences between Static Fault Tree (SFT) and DFT models of a typical mechanical system (case study of a wind turbine). Also, this paper is aimed to interpretation of the results and sufficiency analysis of SFT to model this system. This study, first presents a SFT analysis for a wind turbine system. Then, DFT is developed for the system. Monte Carlo simulation based method is applied for its analysis. The comparison showed that the DFT method presents more useful and realistic model of a wind turbine system. The proposed method improved the analysis through modification of dynamic gates.

Commentary by Dr. Valentin Fuster
2015;():V014T08A018. doi:10.1115/IMECE2015-52928.

The study on the optimization of system reliability allocation rarely involved the constraints on different functions of system. Some constraints only referred to the main function or one function in system. Owing to the requirement of mission and other factors, all system functions need to have different performance and reliability respectively. For this reason, we proposed a new method for optimization of reliability allocation in this paper. The constrains in the method focus on the discrepancy of reliability of different functions of system. The reliability of system function is defined as it whether to meet the requirement of mission capacity, and the reliability of all different system functions will be calculated by universal generating function, and the objective is to minimize system cost. At last, this method is applied in reliability optimization allocation of a Power-shift Steering Transmission with the improved genetic algorithm.

Commentary by Dr. Valentin Fuster
2015;():V014T08A019. doi:10.1115/IMECE2015-53366.

Degradation process directly impacts the system operational state. It is necessary to consider this effect on system failure for developing a precise model for system condition determination. Reliability prediction based on degradation modeling is an efficient method to determine life duration for some highly reliable components or systems under rare failure event occurrences. Sensors, (potentially high reliable components) are exposed to different environmental conditions accelerating their degradation rate. This study is aimed to evaluate the sensor reliability affecting the monitoring process. First, a sensor characteristic is selected through which the degradation process is affected. Then a degradation model is developed to calculate the sensor time to failure. For studying the sensor reliability effect on monitoring process, sensors are considered as system components. It is assumed that the failure of component will occur only when both the component and related sensor fail together. Considering this phenomena, sensors are added to the system in parallel form. Then, functional model of each scenario is developed. Cutsets of each scenario is extracted and the probability of top event is calculated. The scenario with less top event probability is selected as the optimal one.

Commentary by Dr. Valentin Fuster
2015;():V014T08A020. doi:10.1115/IMECE2015-53441.

Time-dependent system reliability is measured by the probability that the responses of a system do not exceed prescribed failure thresholds over a period of time. In this work, an efficient time-dependent reliability analysis method is developed for bivariate responses that are general functions of random variables and stochastic processes. The proposed method is based on single and joint upcrossing rates, which are calculated by the First Order Reliability Method (FORM). The method can efficiently produce accurate upcrossing rates for the systems with two responses. The upcrossing rates can then be used for system reliability predictions with two responses. As the general system reliability may be approximated with the results from reliability analyses for individual responses and bivariate responses, the proposed method can be extended to reliability analysis for general systems with more than two responses. Two examples, including a parallel system and a series system, are presented.

Commentary by Dr. Valentin Fuster
2015;():V014T08A021. doi:10.1115/IMECE2015-53452.

Using fundamentals of irreversible thermodynamics, with specific focus on entropy generation, this paper studies the structural integrity of degraded materials. All damage mechanisms share a common feature namely energy dissipation. Dissipation, as a fundamental measure for irreversibility in a thermodynamic treatment of non-equilibrium processes, is quantified by entropy generation. Based on the theoretical relationship between entropy generation and generalized thermodynamic forces and fluxes, the entropic damage is measured during a corrosion-fatigue degradation experiment. Life estimation of components, which were subject to complex corrosion-fatigue degradation mechanism, was then estimated through a proposed entropic-based prognostic framework. The performance of predictions was evaluated and compared with previous predictions in terms of the influence of additional features on components health assessment.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Fatigue and Fracture of Joining Methods for Lightweight Materials

2015;():V014T11A001. doi:10.1115/IMECE2015-50315.

The effect of loading condition on the stress intensity factor (SIF) solution for a metric threaded bolt with helix angle consideration is investigated. Available SIF solutions for a nut loaded bolt do not consider the effect of helix angle of thread. Various loading conditions such as: (i) far field loading, (ii) thread face loading without helix angle, (iii) thread face loading with helix angle and (iv) nut loading with helix angle are considered in the present study. 3-D contact analysis is carried out to observe the stress distribution between the bolt and nut interface. A crack was introduced at the first thread of the bolt so that the crack faces experience opening mode of fracture under nut loading condition. The SIF estimated by each loading condition was compared with the SIF values computed taking into consideration the nut loading with helix angle. SIF solutions obtained under far field loading condition are lower than those obtained under other loading conditions at short crack depths (a/d = 0.1); at deep crack depths (a/d = 0.5), SIF obtained under nut loading condition are lower than those obtained under other loading conditions. At deep crack depths (a/d = 0.5) the effect of loading condition on SIF is more pronounced for an elliptic crack (a/c = 0.2) than semi circular crack (a/c = 1). Due to the combined effect of mode II and mode III fracture which is caused by helix angle, non symmetric distribution of SIF was observed along the crack front. It is noted that, crack growth rate derived from SIF under nut loading condition is lower than published data at the middle region (P/P0 = 0).

Topics: Stress , Fasteners
Commentary by Dr. Valentin Fuster
2015;():V014T11A002. doi:10.1115/IMECE2015-51398.

The friction welding of AISI 52100 grade low chromium and high carbon steel joints are investigated in this work to evaluate the fatigue life of the joints by conducting the experiments using servo hydraulic fatigue testing machine at different stress levels. All the experiments are conducted under uniaxial tensile loading condition (stress ratio=0). Fatigue strength, fatigue notch factor (Kf) and notch sensitivity factor (q) are evaluated for the optimized joints and the relationship between tensile and fatigue properties of Fully Deformed None (FDZ) is established. Finally, the Characteristics of friction welded joint is investigated with the help of Scanning Electron Microscope and Optical Microscopy under optimized condition.

Commentary by Dr. Valentin Fuster
2015;():V014T11A003. doi:10.1115/IMECE2015-52307.

In this work, experiments were conducted to quantify the mechanical properties and microstructure of friction stir welded (FSW) 6061 aluminum alloy butt joints. In particular, strain-control experiments were carried out to characterize the low-cycle fatigue (LCF) performance of the FSW joint and a microstructure-sensitive fatigue model was used to elucidate structure-property relationships. Under fatigue testing, two distinct modes of failure were observed. In the first case, the fatigue cracks initiated and propagated though the heat affected zone, which is due to material softening as a result of the frictional heat generated by the FSW process. The second mode of failure observed was when the fatigue crack initiated and propagated through the stir zone, as a result of inappropriate material mixing. Additionally, results of this study show a strong dependence on the tool rotational rate, where the monotonic tensile and cyclic mechanical properties increased as the tool rate increased. However, experimental results showed that the increase in the mechanical properties were observed to level off or in some case decline as the tool rotational rate continued to increase. This behavior is due to several factors including welding defects and higher frictional heat. In order to further understand the effect of microstructure and welding defects on fatigue behavior, a multi-stage fatigue (MSF) model that incorporates incubation and crack growth regimes was implemented to capture the effect of variation in tool rotational speeds. The MSF model exhibited good correlation to the experimental results, suggesting that the multi-stage approach for modeling fatigue damage in FSW joints is a reasonable approach. Furthermore, the model appears to capture the underlining mechanisms associated with damage in this type of welded joint.

Commentary by Dr. Valentin Fuster
2015;():V014T11A004. doi:10.1115/IMECE2015-53258.

Stress Corrosion Cracking (SCC) is the initiation and slow growth of cracks under the influence of tensile stresses and aggressive corrosion environment. Al alloy 2014 T 651 was solution heat treated and stress-relieved. In the present work, Stress Corrosion Cracking (SCC) experimental arrangement has been used to test the severity of aluminium alloys under particular environmental conditions. Sound welds were obtained with Friction Stir Welding at rotational speed of 800 rpm and welding speed of 200 mm/min. Friction Stir Welds were cut into standard tensile specimens as per ASTM E8 standards. Time to failure of the welds were obtained using 3.5 wt% NaCl solution at pH 10 in 0.7 and 1.1 yields by Stress Corrosion Cracking. Vickers micro-hardness was taken along various regions of the weld. Optical micro-graphs and scanning electron fractographs were taken to analyse the fracture behavior and fracture morphology of Friction Stir Welded aluminium alloy specimens, subjected to Stress Corrosion Cracking.

Commentary by Dr. Valentin Fuster
2015;():V014T11A005. doi:10.1115/IMECE2015-53693.

This paper is concerned with the problem of prediction of the total life of an engineering structure based on the fatigue crack growth model. The life of an engineering component is generally modeled as a combination of the time required for a crack to initiate and then the time required for crack to propagate till the final fracture. Unfortunately the crack initiation size is a vaguely defined parameter. In order to overcome this ambiguity it is proposed to model the total life of an engineering structure by using the UniGrow fatigue crack growth model with assumption of the intrinsic material parameter ρ* as an initial crack size. The method to overcome the small crack problem in fatigue crack modeling is presented as well. The proposed model was successfully used to predict fatigue lives of misaligned cruciform welded joints under a constant amplitude loading. Results from the analysis and experiment are in a good agreement.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Genomics and Informatics for Mesoscale Mechanics of Materials

2015;():V014T11A006. doi:10.1115/IMECE2015-52113.

The structure-function relationship of biological filaments is greatly impacted by their mesoscale mechanics that involves twisting and bending deformations. For example, the mechanics of DNA looping is a key driver in gene regulation. The continuum-rod models have emerged as efficient tools for simulating the nonlinear dynamics of such deformations. However, there is no direct way to derive or measure the constitutive law of biological filaments for their continuum modeling. Therefore, it is an active area of research to develop inverse algorithms based on a continuum rod model that can estimate the constitutive law from the atomistic configurations of the filament. This paper presents a set of such algorithms that can use data from the dynamic states of deformation obtained from atomistic simulations or other sources. Depending on the kinematic quantities that are computed from the configuration data, the inverse algorithms differ in their steps to estimate the internal restoring moments and forces. The paper investigates and compares the robustness of these inverse algorithms accounting for the effect of noise in the data.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Innovations in Processing, Characterization and Applications of Bioengineered Materials

2015;():V014T11A007. doi:10.1115/IMECE2015-51748.

In this study, magnesium (Mg) disks were coated with β-tricalcium phosphate (β-TCP) doped with different mass percent of silver (Ag) (0 wt%, 1 wt%, 5 wt% and 10 wt%) in an effort to modulate the detrimental osteoimmunomodulatory properties and colonization of bacteria on Mg disk, due to the reported favorable osteoimmunomodulatory properties of β-TCP and antibacterial properties of Ag. This paper describes the growth, characterization and corrosion analyses of β-TCP doped with different compositions of Ag thin film coatings. The phase composition and microstructure analyses were performed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The SEM images showed that varying the percentage of Ag dopant affects the surface morphology of the β-TCP coatings. The corrosion protection behavior of the coated samples were evaluated using electrochemical measurement techniques, such as potentiodynamic polarization (PD) and electrochemical impedance spectroscopy (EIS). The corrosion tests were performed in Hank’s Balanced salt solution using a three-electrode electrochemical cell. The results showed that the β-TCP coating and β-TCP doped with Ag coatings on the Mg disks exhibit a much superior stability and lower corrosion rate compared to bare Mg. It was observed that increasing the mass of the Ag dopant increases the corrosion protection, but 10 wt% Ag doping in β-TCP reduces the corrosion protection behavior. The SEM images of the samples after corrosion show that the β-TCP and β-TCP doped with 10 wt% Ag suffered the most corrosion attack compare to β-TCP doped with 1 wt% and 5 wt% Ag. In conclusion, we have developed β-TCP and β-TCP doped with 1 wt%, 5 wt% and 10 wt% Ag coating with tunable corrosion protection efficiency above 88%.

Topics: Silver , Corrosion
Commentary by Dr. Valentin Fuster
2015;():V014T11A008. doi:10.1115/IMECE2015-51767.

In this study, Mg/SiO2 and MgO/SiO2 multilayer coatings with bilayer thicknesses (Λ) 10, 20, 40, 100, 200 and 1000 nm were deposited on glass substrates using DC and reactive pulsed DC magnetron sputtering processes. The aim of these coatings is to control the initial degradation and provide mechanical strength to magnesium implant during handling and installation. The initial thickness calibrations and deposition rates optimization were conducted using stylus profilometer. After deposition of the multilayer coatings, the values of their bilayer thicknesses (Λ) were obtained from X-ray reflectometery. The mechanical properties, surface morphology and roughness of multilayer coatings were studied using nanoindentation, SEM and AFM respectively. The nanoindentation results showed higher hardness of MgO/SiO2 multilayer coatings compared to single layer Mg. The roughness analyses showed improved roughness for bilayer thicknesses (Λ) less than 20 nm. It was observed from the SEM images that SiO2 coatings has pores. By adding Mg and/or MgO in the form of multilayers improves the pores significantly. The Mg/SiO2 multilayer coatings showed controlled degradation rate when immersed in saline solution compared to the monolithic SiO2 coating. In conclusion, conditions for depositing Mg/SiO2 and MgO/SiO2 multilayer coatings has been optimized. Alternating brittle SiO2 ceramic layers with soft and ductile Mg layers significantly improved the hardness of the Mg coating. Hardness of multilayer coatings can be fine-tuned by modifying bilayer thicknesses. Significant improvement in the corrosion and mechanical properties of the multilayer coatings can be used to protect surface of magnesium implant material during handling, storage and installation.

Commentary by Dr. Valentin Fuster
2015;():V014T11A009. doi:10.1115/IMECE2015-51920.

In recent years, magnesium (Mg) and its alloy are being studied for their potential use in orthopedic implants with the novel ability to biodegrade after the implant serves its therapeutic function. Pure Mg, by itself, would not be suitable for use in a load-bearing implant application, due to its high corrosion rate and poor tribological properties. However, through proper alloying, this degradable metal is capable of achieving good mechanical properties reasonably similar to bone, a retarded rate of corrosion and enhanced biocompatibility. Previous studies have shown that alloying Mg with aluminum, lithium, rare earth (RE), zinc (Zn), and calcium (Ca) result in lower corrosion rates and enhanced mechanical properties. Despite the growing popularity of Mg and it alloys, there is relatively little information in the literature on their wear performance. In this paper, we report on an investigation of the directional tribological properties of Mg and Mg-Zn-Ca-RE alloy fabricated via two different manufacturing processing routes: as-cast and hot-extruded after casting, with extrusion ratios of 10 and 50. Pure Mg was cast 350°C. After casting, Mg-Zn-Ca-RE alloy was heat-treated at 510°C. Another Mg-Zn-Ca-RE alloy was hot-extruded at 400°C. Dry sliding wear tests were performed on as-cast and hot-extruded pure Mg and Mg-Zn-Ca-RE alloys using a reciprocating test configuration. Wear rate, coefficient of friction and wear coefficient were measured under applied loads ranging from 0.5–2.5N at sliding frequency of 0.2 Hz for 120 cycles, using microtribometery. Wear properties of the extruded specimen were measured in cross-section and longitudinal section. In the longitudinal section studies, wear properties were investigated along the extrusion direction and the transverse direction. Hardness properties were evaluated using microindentation. Cross-section and longitudinal section were indented with a Vickers indenter under applied load of 2.94 N. Alloying and extrusion enhanced the mechanical properties significantly, increased hardness by 80% and wear resistance by 50% compared to pure Mg. Despite the low hardness in both Mg and the Mg alloy cross-sections, the cross-sections for both displayed higher wear resistance compared to the longitudinal section. In the longitudinal section, wear resistance was higher along the transverse direction of the longitudinal section for both Mg and the Mg alloy. The wear coefficient was used to evaluate how the wear behavior of the material varied with respect to alloying, fabrication process, and direction of wear. The wear coefficient of pure Mg decreased as the extrusion ratio increased, thus, increasing the specific wear rate. The opposite behavior was found in the Mg alloy: as the wear coefficient increases, the specific wear rate decreases. The active wear mechanisms observed on the worn surface of Mg were fatigue, abrasive, adhesive and delamination wear. The same wear mechanisms were observed in the Mg alloy except for fatigue wear. Surface microstructure and topographical characterization were conducted using optical microscopy, scanning electron microscopy mechanical stylus profilometry, and optical profilometry.

Commentary by Dr. Valentin Fuster
2015;():V014T11A010. doi:10.1115/IMECE2015-53082.

Bone has a remarkable ability to regenerate and heal itself when damaged. Most minor injuries heal naturally over time, but when the defects are larger, they require a substrate to support the cell growth and guide the repair process. Bone grafting is currently done by using either an autograft, where the substrate is harvested from a suitable donor site within the patient’s body; or an allograft, where the substrate is harvested from a cadaver. However, both techniques have significant drawbacks. In autografting, significant complications tend to arise from donor site morbidity. In allografting, the issues are the risk of disease transmission, and the logistical difficulties in the local or even global matching process for donor tissue. A third approach, employing tissue-engineered scaffold materials, provides superior performance by helping to restore bone tissue functions during regeneration and by subsequent resorption of the graft material as new bone tissue forms. These bioactive scaffolds are porous and made of natural materials that are capable of harboring growth factors, drugs, genes, or stem cells. The objectives of this research are to synthesize biofunctional composite scaffold materials, based on chitosan (CS) and magnesium (Mg), for use in bone regeneration and to measure their physiochemical properties. Scaffolds were fabricated from the aqueous dispersions of starting materials by subsequent freezing and phase separation by the lyophilization process. A CS solution was prepared by dissolving CS in 2 % (v/v) acetic acid solution, whereas carboxymethyl chitosan (CMC) was dissolved in deionized water. The concentrations of CS and CMC (in a constant 1:1 weight ratio) ranged between 2% and 5 %. Various dry weight percentages of Mg gluconate (MgG) were added to the scaffolds by dissolving the MgG solution in the CS/CMC. SEM imaging showed the scaffolds to possess uniform porosity with a pore size distribution range of 100–150 μm. Micro CT analysis showed that the pores were distributed throughout the scaffold’s entire volume and they were highly interconnected. Compressive strengths of up to 340 kPa and compressive moduli of up to 5 MPa were obtained for these fabricated scaffolds. When introduced into a cell culture medium, these scaffolds were found to remain intact, retaining their original three-dimensional frameworks and ordered porous structures maintaining sufficient mechanical strength. These observations provide a new effective approach for preparing scaffold materials suitable for bone tissue engineering.

Commentary by Dr. Valentin Fuster
2015;():V014T11A011. doi:10.1115/IMECE2015-53090.

Recent advances in developing composite nanofibers are of great interest for scientific community due to their wide range of potential applications in biomedical engineering such as drug delivery, wound healing, tissue engineering and implant coatings. Here, we present a fabrication of Mg incorporated polycaprolactone/low molecular weight chitosan (PCL/LMW-CS) composite nanofiber via an electrospinning technique. PCL, a synthetic polymer, has good mechanical properties, whereas, chitosan, a natural polymer, has good bio-functional properties and good cell adhesion properties. Furthermore, magnesium is the second most abundant intracellular cation in the body and is important to metabolism. These nanofibers were characterized by using Scanning Electron Microscopy (SEM), ImageJ, and Instron Universal Testing Machine.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Material Processing of Flexible Electronics, Sensors, and Devices

2015;():V014T11A012. doi:10.1115/IMECE2015-50308.

The market for wearable electronics has been gaining momentum in the recent years. For completely electronic wearable textiles with integrated sensors, actuators, computing units and communication circuitry, it is important that there is significant stretchability. This stretchability can be obtained by introducing periodic stretchable structures between the electronic circuits. In this work, we derive the equations and constraints governing the stretchability in horseshoe lateral spring structures. We have derived the optimum design and the parameters therein, to help develop the best spring structures for a given stretchability. We have also developed a figure of merit, called area efficiency of stretchability, to compare all two-dimensional stretchable systems. Finally, we experimentally verify the validity of our equations by fabricating a metal/polymer bilayer thin film based stretchable horseshoe lateral spring structures. We obtain a stretchability of 1.875 which is comparable to the theoretical maxima of 2.01 for the given parameters.

Topics: Design , Springs , Electronics
Commentary by Dr. Valentin Fuster
2015;():V014T11A013. doi:10.1115/IMECE2015-52587.

This paper presents the possibility of closed-loop regulation of position or force at features (posts) on an active composite membrane. Active composite membranes are multilayered membranes with different functions, actuation, sensing, interconnect, mechanical compliance tuning assigned to them. Here we demonstrate the ability to perform closed-loop control on an array of four posts on a membrane stamp designed for micro-transfer printing. The paper also assesses the positioning and force resolution obtaining from such membranes.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Materials Processing and Characterization

2015;():V014T11A014. doi:10.1115/IMECE2015-50113.

Aluminum based metal matrix composites offer greater potential for light weight, wear resistant and high temperature applications. Secondary processing like extrusion results in the improvement of strength and ductility of the as-cast composites. The objective of this research is to investigate the effect of reinforcement type and extrusion process on the microstructure and mechanical properties of the hot extruded Al2014 aluminum alloy. Two different composites were made by reinforcing the alloy with 10 wt.% SiC and 10 wt.% Si3N4 particles using stir casting method. The particles were electroless Ni coated to improve the wettability of reinforcement by the matrix alloy. The composite ingots were further extruded at 475 °C with an extrusion ratio of 8:1. The microstructures and the mechanical properties of the base alloy and the composites were examined systematically. The extruded composites show more homogenous microstructure with uniform distribution of particles in the matrix alloy. Both the Al/SiC and Al/Si3N4 composites exhibited improved hardness compared to the base alloy in both as-cast and extruded conditions. It was also found from tension tests that the both the composites show higher yield strength, ductility and ultimate tensile strength (UTS) than the base alloy in the extruded condition. The reason for improvement in strength in the extruded conditions is explained in detail. Fracture surface analysis revealed the transition from brittle fracture mode in the as cast composites to the ductile fracture in the extruded condition.

Commentary by Dr. Valentin Fuster
2015;():V014T11A015. doi:10.1115/IMECE2015-50972.

Microstructure of annealed plain carbon steels is examined using optical microscopy. When the inter-lamellar spacing in pearlite is small, optical microscope at 1000X is unable to resolve the ferrite and cementite lamellae. In hyper-eutectoid steels, cementite in pearlite appears as darker phase whereas the pro-eutectoid cementite appears as a lighter phase. Atomic force microscopy (AFM) of etched steels is able to resolve ferrite and cementite lamellae in pearlite at similar magnifications. Both cementite in pearlite as well as pro-eutectoid cementite appear as raised areas (hills) in AFM images. Interlamellar spacing in pearlite increases with increasing hardenability of steel.

Commentary by Dr. Valentin Fuster
2015;():V014T11A016. doi:10.1115/IMECE2015-51184.

Soft-lithography, or the printing of self-assembling molecular inks at micro or sub-micron scale holds the promise of large-scale surface patterning for a variety of applications. One key to the ultimate utility of this concept is continuous roll-to-roll printing on lost-cost flexible substrates. Accordingly, this paper discusses the basic processes involved in roll-to-roll printing of octadecylphosphonic acid (ODPA) on aluminum-coated PET substrates using novel cylindrical stamps cast from PDMS. In addition to printing, visualization of the pattern is achieved through controlled condensation of water vapor and by a post-printing acid etch. By using a roll-to-roll configuration, along with continuous stamps and measurements that can permit real-time online quality monitoring, this method represents a significant step forward in making soft lithography a commercially viable process.

Topics: Aluminum , Printing
Commentary by Dr. Valentin Fuster
2015;():V014T11A017. doi:10.1115/IMECE2015-51766.

Industries such as aerospace, automotive, oil and gas utilize various chemical, thermal, and mechanical techniques to improve the surface properties of engineering components. Deposition of metallic or nonmetallic materials on the surface of engineering components using different thermal spraying techniques is a common method to improve the mechanical properties of the surface of the components working at severe conditions. Thermal spraying techniques are capable of deposition of a coating layer with high corrosion, wear, erosion, and high temperature resistance. This technology can also be used for surface repair and treatment. Zirconia (ZrO2) based coatings are excellent candidates to serve at high temperature due to their tribological and insulation properties, and also high stiffness. ZrO2-based coatings are usually used in aircraft and gas-turbine engines as thermal barrier coatings. However, the relatively low wear and erosion resistance of Zirconia-based coatings limits their application. Among all coating materials, Tungsten Carbide (WC) based materials are commonly used to improve wear and corrosion resistance of the surface. It is speculated that combination of ZrO2 and WC follows by generating a coating with desirable thermal and mechanical properties, particularly at high temperature conditions. In the presented work, an innovative thermally sprayed coating material was proposed by depositing mixture of ZrO2-Y2O3 and WC-Ni (YPSZ/WC-Ni) powders on a low carbon steel substrate using Atmospheric Plasma Spraying (APS). As thermomechanical properties of coatings are under the influence of the microstructural features such as porosity, micro cracks, voids, and possible oxides, in this study microstructure and phase consistency of the resultant coating was briefly evaluated. To this end, Optical Microscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) were used. The results indicated that deposited coating was well-bonded to the substrate with minimum observed separation line. Porosity amount of APS deposited YPSZ/WC-Ni measured by image analysis of the cross-sectional area Moreover, mechanical properties including hardness and elastic modulus of the coating were evaluated. Since thermally sprayed coatings exhibit anisotropic behavior, the Knoop hardness in the longitudinal and transverse directions were analyzed in this study. Elastic modulus of the coating was also evaluated, based on the measurement of elastic recovery of Knoop indentation in both directions using Marshal analytical model. Wear resistance of the coating was also investigated by pin-on-disk method, at room temperature. The friction coefficient of the consecutive coating was calculated and had a value lower than that of reported for APS deposited YPSZ.

Commentary by Dr. Valentin Fuster
2015;():V014T11A018. doi:10.1115/IMECE2015-52368.

This study focuses on the fundamental of solidification of commercial grey cast iron as a function of the externally applied cooling rate. Grey cast iron powders were prepared using the drop-tube method, which is a good analogue for commercial production via high pressure gas atomization. The as-solidified droplets were collected and sieved into size ranges from > 850 μm to < 53 μm diameter, with estimated cooling rates of 500 K s−1 to 75,000 K s−1, with each sieve fraction being prepared for metallographic characterization. The microstructure and phase composition of the powders were analyzed using XRD, optical and scanning electron microscopy, with the results being compared against a control sample subject to slow cooling in the drop-tube crucible; which has typical grey cast iron microstructure with extensive flake graphite in a largely ferrite matrix. In contrast, flake graphite was absent in virtually all the drop-tube samples, even in those with the most modest cooling rates. Microstructural analysis revealed that as the cooling rate increased there was less fragmentation of the primary austenite/ferrite dendrites and the volume fraction of primary dendritic material increased. Hence, as the particle fractions get smaller (D < 106 μm) there is a distinct microstructural evidence of a martensite phase which is related to its better mechanical properties (microhardness) as the sample sizes decrease.

Topics: Cooling , Cast iron
Commentary by Dr. Valentin Fuster
2015;():V014T11A019. doi:10.1115/IMECE2015-52433.

Corrosion is the gradual deterioration of materials by chemical reaction with their environment, leading to the formation of less desirable material, which lacks in functionalities of the system. Corrosion resistant coatings have being an active subject of research since a while. Aiming at the replacement of toxic anti-corrosion pigments in organic coating industries, in the last two decades several environmentally friendly pigments have been studied, which involves passivating compounds such as molybdates, permanganates, vanadates, and tungstates. Cerium compounds are attaining more attention due to their potential as corrosion inhibitors. The present work aims at the experimental investigation on the effect of zirconium on corrosion resistance of ceria nanoparticles, in epoxy resins. Ceria and cerium zirconium mixed oxide nanoparticles was prepared by co-precipitation method. Ceria and cerium zirconium mixed oxide nanoparticles were dispersed in epoxy resin and the composites were spin coated on mild steel specimens. Surface studies was done using AFM and electrochemical studies were done one the coated surfaces using Zahnier IM6 modular electrochemical workstation. The Impedance spectra and surface structure studies showed highly improved corrosion resistance for ceria and cerium zirconium mixed oxide nanoparticles added epoxy primers as compared to unmodified epoxy resin primer. UV resistance of the coatings were found to be improved for ceria and cerium zirconium mixed oxide nanoparticles based coatings.

Commentary by Dr. Valentin Fuster
2015;():V014T11A020. doi:10.1115/IMECE2015-53307.

In the present work, the addition of ethanol to endothermic gas during the carburizing process of DIN 17NiCrMo7 steel gears was investigated with the objective of determining the impact on carbon surface concentration and microstructure. The materials were carburized at 870°C and 930°C, oil quenched, tempered and subsequently shot peened. Carburizing was carried out in a continuous industrial furnace for a total of 280 min. After quenching and tempering, the in-depth carbon concentrations were determined through quantitative chemical analysis and the resulting profiles were modeled in order to obtain carbon diffusivity constants. The amount of retained austenite and austenite grain size, determined by X-ray diffraction and optical microscopy, were found to increase with carburizing temperature. Residual stress profiles were also determined by X-ray diffraction before and after the shot-peening process. The microstructure of the specimens was further investigated by transmission electron microscopy, which revealed the presence of BCC martensite before and after shot-peening. The enrichment of the endothermic gas carrier with ethanol could be shown to be a viable option, allowing for surface concentrations of up to 0.8%C.

Commentary by Dr. Valentin Fuster
2015;():V014T11A021. doi:10.1115/IMECE2015-53435.

Samarium Cobalt (SmCo) magnets have been the magnet of choice for a variety of industries for many years due to their favorable magnetic properties. Their high coercivity, combined with a low temperature coefficient, make them the ideal permanent magnet for demanding high temperature applications. One of the biggest concerns with rare earth magnets is their brittleness. Samarium Cobalt magnets in particular are prone to fracturing during machining and assembly. In manufacturing, great care must be taken to avoid chipping or fracturing these magnets due to their brittle nature.

There are two main grades of Samarium Cobalt magnets, 1:5 and 2:17. These ratios define the nominal ratio of rare earth to transition metal content.

In this paper, an investigation is performed on the fracture toughness of permanent magnets based on the Samarium Cobalt 2:17 composition. Various techniques are used to characterize the microstructure of the material, and quantify the material properties.

Optical microscopy is used to characterize the grain structure of the material and quantify the porosity of the material after sintering. By comparing the average grain size and fracture toughness of several samples, grain size was shown to not affect fracture toughness in standard material. Latent cracks in defective material showed no preference to follow grain boundaries, oxides inclusions or voids.

River marks in fracture surfaces are seen through scanning electron microscopy, confirming the transgranular cracking pattern seen by Li et al [1]This suggests that the toughness of the material is an inherent property of the main phase, not of grain boundaries or contaminants.

Samarium Cobalt magnets exhibit both mechanical and magnetic anisotropy due to the alignment of their crystal structure in the manufacturing process.

Using Palmqvist indentation crack techniques, the magnetic orientation of the grains was seen to greatly influence the direction of crack propagation from the tip of the indenter. Measurements of fracture toughness using this technique produce highly scattered data due to this anisotropic nature of the material. Specimens loaded with the indenter axis parallel to the direction of orientation show normal Palmqvist cracks, while specimens loaded perpendicular to the direction of magnetization exhibit crack propagation initiating from the faces of the indenter.

To better quantify the material’s brittleness, fracture testing is performed on specially prepared samples to obtain an absolute measure of fracture toughness (K1c). Results show that SmCo is measurably weaker than other magnetic materials such as neodymium iron boron magnets[2]. Furthermore, neither relative concentration of Samarium nor source of raw material show notable effect on the fracture toughness of the material.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Modeling and Simulation of Material Failure

2015;():V014T11A022. doi:10.1115/IMECE2015-50223.

Due to its distinguished properties especially being isotropic, particulate reinforced composite is considered as one of the attractive material for wide range of applications, where the relatively low manufacturing cost is a desirable advantage. In the present analysis, deteriorated particles embedded in particulate reinforced composite have been investigated. The impact of the fractured particles is studied through the principles of fracture mechanics using finite element method. Mainly the stiffness variation of the composite due to the presence of the fractured particles is mainly predicted, since it is considered as an important factor especially from the view point of the damage-tolerant design of composite structures. A representative volume element (RVE) has been selected to represent the particulate composite with different particle volume fractions. It is important to point out that based on a previous investigation and comparison between two and three dimensional finite element analysis for a particulate reinforced composite, two-dimensional, plane strain finite element analysis is used to estimate the stresses and deformation that taken place. Uniaxial tensile stress perpendicular to the crack face of the fractured particle has been applied to the representative volume element. Due to symmetry of the studied geometries, quarter of the representative volume element is modeled via finite element method with a consistent mesh as possible to maintain reliable results. Linear elastic fracture mechanics (LEFM) is adopted through estimating stress intensity factor (SIF) of the cracked particles. Basically, the investigation covers the assessment of fractured particles with different crack lengths, where the particle’s stiffness is considered as a substantial parameter in the analysis in combination with others. Moreover, various particles volume fractions are taken into account to figure out their influence on the effective Young’s modulus of the representative volume element chosen for the studied cases. Multiple point constraints (MPC) technique is adopted in the finite element model to calculate the effective stiffness of the fractured particle. In general, it has been shown that there is a considerable influence of the deteriorated particles on increasing stress intensity factor levels at the crack tip as long as the crack length increases with respect to the particle size, and this basically depends on the stiffness ratio of the matrix/particle considered in the analysis. In the other hand, it has been noticed that a significant reduction in the effective stiffness of the particulate composite which is calculated based on the modeled representative volume element as a function of the crack length.

Commentary by Dr. Valentin Fuster
2015;():V014T11A023. doi:10.1115/IMECE2015-50486.

Composite materials have emerged as promising materials in applications where low weight and high strengths are desired. Aerospace industry has been using composite materials for past several decades exploiting their characteristics of high strength to weight ratio over conventional homogenous materials. To provide a wider selection of materials for design optimization, and to develop lighter and stronger vehicles, automobile industries have been exploring the use of composites for a variety of components, assemblies, and structures. Composite materials offer an attractive alternate to traditional metals as designers have greater flexibility to optimize material and structural shapes according to functional requirements. However, any automotive structure or part constructed from composite materials must meet or exceed crashworthiness standards such as Federal Motor Vehicle Safety Standard (FMVSS) 208. Therefore, for a composite structure designed to support the integrity of the automotive structure and provide impact protection, it is imperative to understand the energy absorption characteristics of the candidate composite structures. In the present study, a detailed finite element analysis is presented to evaluate the energy absorbing characteristics of a carbon fiber reinforced polymer composite lower rail, a critical impact mitigation component in automotive chassis. For purposes of comparison, the analysis is repeated with equivalent aluminum and steel lower rails. The study was conducted using ABAQUS CZone module, finite element analysis software. The rail had a cross-sectional dimension of 62 mm (for each side), length of 457.2 mm, and a wall thickness of 3.016 mm. These values were extracted from automobile chassis manufacturer’s catalog. The rail was impacted by a rigid plate of mass 1 tonne (to mimic a vehicle of 1000 Kg gross weight) with an impact velocity of 35 mph (15646.4 mm/s), which is 5 mph over the FMVSS 208 standard, along its axis. The simulation results show that the composite rail crushes in a continuous manner under impact load (in contrast to a folding collapse deformation mode in aluminum and steel rails) which generates force-displacement curve with invariable crushing reactive force for the most part of the crushing stroke. The energy curves obtained from reactive force-displacement graphs show that the composite rail absorbs 240% and 231% more energy per unit mass as compared to aluminum and steel rails. This shows a significant performance enhancement over equivalent traditional metal (aluminum and steel) structures and suggests that composite materials in conjunction with cellular materials/configurations have a tremendous potential to improve crashworthiness of automobiles while offering opportunities of substantial weight reductions.

Commentary by Dr. Valentin Fuster
2015;():V014T11A024. doi:10.1115/IMECE2015-50725.

As the unsprung components of vehicle, lightweight wheel plays a significance role for handling stability and riding comfort. Besides, the energy saving effect of lightweight design for wheel is 1.2 to 1.3 times as much as that of components without rotating. Therefore, the lightweight design of wheel is an inevitable development tendency in future. For the wheel composed by long-fiber reinforced composites through injection process, the difference of fiber distribution and orientation at various positions leads to anisotropy on the macro performance. This paper explores a new type of high-performance thermoplastic composites (LGFTs) material reinforced by long glass fiber for lightweight wheel design. The dynamic impact simulations on the LGFT wheel with isotropic properties and anisotropic properties are conducted according to the ISO procedure, using the software Moldflow, Digimat, and Abaqus. The comparison of the simulation results demonstrates that the anisotropic properties of material have a significant effect on the impact characteristics of the wheel. The research in this paper is beneficial to improve the accuracy of the impact simulation on LGFT wheel, and also provides foundation for further lightweight design of the wheel.

Commentary by Dr. Valentin Fuster
2015;():V014T11A025. doi:10.1115/IMECE2015-51005.

Predicting the damage progression behavior of fiber composites using finite element methods is an ongoing challenge in design of high performance structures. A common application of fiber composites is out-of-plane bending of a notched composite panel. This loading occurs, for example, in an aircraft fuselage near reinforcing members such as ribs or stringers. The material parameters used by the finite element package Abaqus that dictate damage progression behavior of fiber composites include 6 strength values which control when damage is initiated, and 4 energy parameters that control how damage propagates. The values of the initiation parameters (strengths) are often accurately known, however the values of the propagation parameters (energies) are often not accurately known. The consequences of these inaccuracies are not consistent. Current research indicates that accurate FEA results for out-of-plane bending always require accurate values for the material strengths. However the effect of inaccurate material propagation energy values can vary depending on composite laminate layup. Understanding how these effects vary and which values are important can help a designer select a material and/or determine which propagation energy values need to be accurately determined. This study uses the Abaqus implicit FEA solver to model center notched carbon fiber panels to explore the effect of ply orientation on the sensitivity of maximum load to values of matrix tensile propagation energy and matrix compressive propagation energy. Preliminary studies of this loading scenario showed that these values have significant effects on maximum load only for certain layups. Five different 20 ply layups were chosen for this study with varying number of plies oriented in the 90 degree direction. The 90 degree direction is defined as perpendicular to the bending stresses and parallel to the notch. For each layup, matrix compressive and tensile propagation energies were specified at ±20% from their nominal values to create two-level factorials. Each layup was also run using nominal values as a center point to assess linearity of the effects. Furthermore, damage propagation paths were compared to understand how damage propagation was being affected. This way, nonlinear effects of matrix propagation energy values on maximum load could be separated from any regime changes in damage propagation. The results of this study lend understanding to the finite element analyst on how layup affects the need for high-accuracy values of certain material properties. Accurate FEA results for some layups do not depend on accurate matrix propagation energy values. Having this in mind can save significant resources in the fiber composite design process by eliminating unnecessary destructive tests to determine material property values accurately.

Commentary by Dr. Valentin Fuster
2015;():V014T11A026. doi:10.1115/IMECE2015-52965.

The evolution of microstructure occurs in the deformation of metals via texture evolution. The effect of the microstructural evolution, i.e., anisotropy evolution, on the free end shear problem is investigated. An anisotropic ductile fracture model that takes into account the evolution of the orthotropic axes in the matrix is employed to perform the above task. With the model, a well-known experiment that provides the evidence of anisotropy evolution, the free end cyclic torsion test, is simulated. For the simulation of the free end cyclic torsion test, an explicit numerical scheme for the free end shear simulation is proposed and performed to reproduce the experimental result of the free end torsion test. The simulation result reveals the physics of the shear damage process, which is that porosity evolves in the shear deformation of (induced) anisotropic materials due to the evolution of anisotropy. A series of the free end shear simulations reveal the effect of the interaction among the matrix anisotropy, porosity and void shape onto the deformation pattern and the ductile damage process of porous materials.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Multifunctional Materials and Hybrid Materials: Modeling, Design, and Processing

2015;():V014T11A027. doi:10.1115/IMECE2015-52296.

Study of nanomaterials and their characteristics have added a new dimension to the rapid development of nanotechnology. Carbon-based nanomaterials are considered to be one of the key elements in nanotechnology since they are known to exhibit a variety of unusual properties which make them beneficial in the field of medicine and bioengineering. Nanoparticles, because of their size are capable of entering the human body by different modes and can spread to different parts by physical translocation or chemical clearance processes and hence requires a thorough understanding of their interaction with biological molecules, sub-cellular units, cells, tissues, and organs. Cytotoxicity of four types of carbon based nanomaterials — Carbon Nanowire (CNW), Carbon Nanotubes (CNTs), Graphene and Fullerene, on L929 mouse fibroblast cancerous cells is evaluated by MTT Assay. An analysis based on morphology, concentration and contact duration is discussed in this paper. Graphene was the most toxic material with an average toxicity of 52.24%, followed by CNTs, Fullerene and CNW. The differences in the toxicity levels has been attributed to different structural arrangements and aspect ratio. Lower concentration levels exhibited lower levels of cytotoxicity in three of the four nanomaterials but contact duration failed to show any fixed trend.

Topics: Nanoparticles , Carbon
Commentary by Dr. Valentin Fuster
2015;():V014T11A028. doi:10.1115/IMECE2015-52658.

Liquid crystalline polymers (LCPs) are among a high-performance class of materials, which derive unique mechanical, chemical, and electrical characteristics from their long-range molecular order. The evolution of anisotropic orientation in the LCP microstructure during processing, however, can adversely affect the macroscopic polymer behavior. Simulation of this anisotropy is crucial to the design of manufacturing processes producing the desired material properties, and the ability to quantify the polymer directionality is a necessary metric of the model. Using a Monte-Carlo approach introduced by Goldbeck-Wood et al., a practical method for simulating LCP orientation is used to model the polymer flow, and the directionality results are then used to calculate a quantitative molecular degree of order. This metric, known as the order parameter, is an ideal candidate for measuring the LCP orientation, ranging from zero to unity between the isotropic and perfectly aligned states, respectively, as it is sensitive to both the direction of the average molecular orientation, as well as to the distribution of crystals around the average orientation. The effects of varying process parameters in the directionality model on the order parameter are shown. Understanding of these relationships will ultimately drive the design of manufacturing processes for more isotropic materials.

Commentary by Dr. Valentin Fuster
2015;():V014T11A029. doi:10.1115/IMECE2015-52895.

Developing advanced energy absorption materials and structures is of both fundamental scientific interest and great technological importance. In this study, we investigate the energy absorption capability of a new composite material under impact loading by using ANSYS and LS-DYNA. This new composite is composed of polymeric matrix and Nanoporous Particle Suspended Liquid (NPSL) fillers. NPSL fillers are embedded in a polymeric matrix to form a composite protective layer on a rigid substrate. A numerical method based on the PLANE162 finite element scheme has been developed specifically to investigate the effects of the various material parameters on the energy absorption efficiency provided by the NPSL-based composite. Among these parameters, activation pressure is at the NPSL level, while filler diameter and spacing are at the composite level. All these parameters show pronounced effects on the mechanical properties of the composite, and they can be engineered by fine-tuning the processing techniques.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Nanoengineered, Hierarchical, and Multi-Scale Materials

2015;():V014T11A030. doi:10.1115/IMECE2015-53113.

Hexagonal boron nitride (h-BN) is well known for its unique properties, such as high thermal conductivity, excellent mechanical strength, high electrical insulating, and high chemical stability. This paper studies the effect of h-BN to the mechanical and electrochemical properties of cement concrete. Sodium cholate is used as an ionic surfactant to exfoliate h-BN and subsequently stabilize them in water solution. Different cement concrete samples with different doping levels of h-BN and different sizes of h-BN were prepared for comparisons. Also, steel fiber reinforced h-BN/cement concrete samples were also prepared. The results show that the addition of h-BN can improve the strength of cement composites, and the degree of reinforcement are influenced by the doping levels and feature size of h-BN. The corrosion resistance of h-BN/cement composites were also tested. Experiments results show that h-BN can enhance the corrosion resistance of cement composites.

Commentary by Dr. Valentin Fuster
2015;():V014T11A031. doi:10.1115/IMECE2015-53602.

Fiber/matrix interphase in composite materials plays an important role on its structural performance. However, structure and properties of this region are not completely known, due to lack of understanding of the processes occurring at atomic/molecular level during formation of interphase and comprehensive experimental methods for characterization of interphase. In addition, most of the currently used experimental techniques are available for micron size fibers and are not sufficient to characterize the nanofiber/matrix interphase. Recently, molecular dynamics simulations have shown promising results in obtaining the mechanical properties of fiber reinforced polymer composites. The objective of this study is to determine the mechanical properties of silane treated glass nanofibers and epoxy resin interphase using molecular dynamics simulations. To simulate the interphase (blend of sizing/coupling agent and matrix), atomistic models of blend of silane coupling agent (3-aminopropyl) triethoxysilane (APTES) and cross linked epoxy 862 resin system are developed. Mechanical properties of the interphase are predicted for different weight fractions of silane using molecular dynamics simulation.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Nanostructured Materials for Energy Applications

2015;():V014T11A032. doi:10.1115/IMECE2015-51982.

The synthesis and characterization of Polyaniline/Graphene/ Nanodiamond Nanocomposite is reported. The resulting materials were synthetized following a polymerization in situ scheme and characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TGA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Cyclic Voltammetry (CV). The effect of different loads of graphene and nanodiamond on the resulting nanocomposite was studied. Despite the presence of the host materials, the formation of Polyaniline polymer is successfully accomplished for all samples. The microstructure of the resulting materials is core-shell type with the additives being covered (core) by layers of the conjugated polymer (shell). The thermal stability of the nanocomposites is improved as confirmed by measuring an increase on the Temperature of Decomposition and the Cross-Linking Temperature compared to bare polymer. Electrochemical characterization reveals that the presence of the additives does not affect the electroactive behaviour of the matrix polymer allowing it to reversely shift from different oxidation stages. The effect of additive content on the charge transfer kinetics is discussed.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Posters

2015;():V014T11A033. doi:10.1115/IMECE2015-50539.

The objective of this paper is to numerically analyze the buckling of reinforced structures (stiffened plate) cracked under compressive stress by considering the evolution of cracks and its orientation. Numerical modeling and calculation by the finite element method, estimated the critical load for compression panel. The work presented in the article was inspired by several publications that related to this field. Brighenti have studied the behavior of elastic buckling of rectangular cracked thin plate for different boundaries conditions. Following these calculations, a calibration function was derived to estimate the load ratio Ψ to the compression function of the crack length and its inclination. We found that the variation of the critical stress is proportional to the crack dimensions. In buckling, a transverse crack is more stable than a longitudinal crack.

Topics: Buckling , Compression
Commentary by Dr. Valentin Fuster
2015;():V014T11A034. doi:10.1115/IMECE2015-52143.

The performance of a therapeutic drug can be optimized by controlling the rate and extent of its release in the body. Polymeric microparticles are ideal vehicles for many controlled release drug delivery applications. Poly(lactic-co-glycolic acid) (PLGA) is a biodegradable, biocompatible and FDA approved synthetic polymer. When PLGA based controlled release drug delivery devices are fabricated, the surface of PLGA is typically modified by other hydrophilic polymers. But some hydrophilic polymers, such as poly(ethylene glycol) (PEG) can negatively influence the therapeutic outcomes. The goal of the present study was to fabricate and investigate the PLGA/chitosan microparticles for controlled release of therapeutic drugs. Chitosan is a naturally occurring biodegradable polysaccharide. We hypothesized that chitosan could be used as a surface coating of PLGA to improve controlled release of therapeutic drugs. The double emulsion solvent evaporation technique was modified and utilized to fabricate the PLGA/chitosan microparticles. The microparticles were tested with respect to several physicochemical properties, such as morphology, size distribution, chemical structure, quantification of chitosan content and in vitro release study of model drug. Magnesium is an essential electrolyte in the human body. Magnesium oxide (MgO) is used for treatment of magnesium deficiency. MgO was encapsulated in the PLGA/chitosan microparticles as a model drug.

Commentary by Dr. Valentin Fuster
2015;():V014T11A035. doi:10.1115/IMECE2015-52790.

Magnesium (Mg) and its alloys are attractive orthopedic biomaterials because of their degradability and mechanical properties, which are similar to bone’s. Characterizing the mechanical changes and interactions of these promising degradable biomaterials and the host environment (bone) is essential to their success in orthopedic devices.

The objective of this study was to develop a protocol to evaluate in vivo biodegradable Mg-alloy screws and surrounding new and cancellous bone in rabbit femurs over time, using high resolution micro-computed tomography (micro-CT) images and the finite element method.

Micro-CT was used to visually evaluate bone remodeling and degradation of Mg-alloy screws that were implanted in rabbit femoral condyles for 2, 4, 12, 24, 36 and 52 weeks. Over time, the degradation product around the device and the remainder of the intact core was observed. Scans were segmented into bone, degradation/corrosion products and non-degraded device, then reconstructed into 3D volumes. These volumes were meshed and assigned material properties based on CT data. The meshed volumes were exported to finite element software and analyzed in a virtual environment.

Several foundational observations were made about animal modeling of in vivo degrading magnesium devices with a micro-CT to FEA protocol.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Processing, Characterization, and Applications of High Temperature Materials

2015;():V014T11A036. doi:10.1115/IMECE2015-53722.

High temperature mechanical properties of Ni-base superalloys are improved by the fine cuboidal γ’ (Ni3Al) precipitates orderly-dispersed in the γ matrix (Ni-rich matrix) because the dispersed texture in a grain inhibits dislocation motion. However, it is well known that directional coarsening of the γ’ precipitates perpendicular to a principal stress occurs not only during creep loading but also during cyclic loading and, the formation of the raft causes the decreasing of high temperature strength drastically. Therefore, it is very important to evaluate the damage of the alloys caused by creep and fatigue loading based on the change of their micro texture. In this study, the change of crystallinity of the Ni-base superalloys (CM247LC) under creep loading was analyzed by applying Electron Back-Scattered Diffraction (EBSD) method. The image quality (IQ) value obtained from the EBSD analysis was used for the quantitative evaluation of the crystallinity in the area where an electron beam of 10 nm in diameter was irradiated. The quality of the atomic alignment of both γ’ and γ phases was found to degrade with increasing creep damage. The degradation of crystallinity suggests that the ordered L12 structure of Ni3Al became disordered and the density of dislocations and vacancies increased. However, KAM (Kernel Average Misorientation) value did not change significantly with increasing creep damage. Therefore, the dominant factor of the creep damage of this alloy is the strain-induced diffusion of elements under loading, and the decrease of the crystallinity.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Processing, Structure and Property of Polymers, Soft Materials and Composites

2015;():V014T11A037. doi:10.1115/IMECE2015-51145.

In this study, a numerical representative volume element (RVE) model was used to predict the mechanical properties of a Rice Husk Particulate (RHP)-Epoxy composite for use as an alternative material in non-critical applications. Seven different analytical models Counto, Ishai-Cohen, Halpin-Tsai, Nielsen, Nicolais, Modified Nicolais and Pukanszky were used as comparison tools for the numerical model.

The mechanical properties estimated for 0%, 10% and 30% RHP-Epoxy composites using the numerical and analytical models are in general agreement with each other. Using the analytical models, it was calculated that an increase in volume percentage of RHP to 30% led to continual reduction in elastic Young’s modulus and ultimate tensile strength of the composite. The numerical RVE models also predicted a similar trend between filler volume percentage and material properties.

Overall, the results of this study suggest that RHP can be used to reduce the composite raw material costs by replacing the more expensive polymer content with agricultural waste products with limited compromise to the composite’s mechanical properties.

Commentary by Dr. Valentin Fuster
2015;():V014T11A038. doi:10.1115/IMECE2015-51391.

Composite materials are preferred in all engineering applications, because of their superior properties over the traditional materials. Among composite materials, Natural fiber reinforced polymer finds rapid development in industrial applications and many areas of research. In this paper, thermal properties of Sisal-Glass fiber reinforced epoxy composites are studied to assess the influence of different fiber orientation. Thermal properties of the composite are analyzed using Thermo Gravimetric Analysis (TGA) and Differential Thermal Analysis (DTA) to investigate the influence of change in fiber orientation.

Commentary by Dr. Valentin Fuster
2015;():V014T11A039. doi:10.1115/IMECE2015-51392.

Paper recycling is an effective way in reducing deforestation and energy consumption. Therefore recycling paper and paper products has been widely applied in many areas, such as packaging industry, film rolls, adhesive-tape industry, furniture decoration and temporary structures in building. They can be produced into various structure according to different requirement, such as paper tube, corrugated paperboard and normal paperboard. Paper-tubes gain more and more applications as a traditional structure due to their excellent mechanical property and environmentally friendly property. In order to meet various needs of paper-tube and produce high performance paper-tubes, designing for paper-tubes fabrication is needed. It is necessary to research the lateral compression strength of paper tube because various paper-tubes are used as packages, cores, poles and structure materials. To establish a relation of mechanical property between paperboards and paper-tubes is an important aspect. The current study is to investigate this relation. Paperboards are built from cellulose fibers jointed by hydrogen bonds and some additional elements like talc. The fibers are distributed randomly on the paperboards. However due to the tension action during fabrication process, more fibers are distributed in machine rolling direction which is defined as machine direction (MD, TD for transverse direction). The material expresses obvious anisotropic property. On the other hand, due to the laminated structure of paper materials, it is possible to generate interlaminar fracture in the usage process, especially in the construction made of paper such as paper tubes. The mechanical property of three kinds of paperboards used for paper-tubes fabrication was investigated included tension, compression and peeling combining with anisotropic property.

These three kinds of paperboards have different mechanical properties but same dimension for paper-tubes fabrications. By this method, the effects of different properties including tension, compression and peeling on mechanical property of paper-tube could be evaluated. A series of paper-tubes with different layers was fabricated and the lateral compression test was carried out and evaluated. The fracture form of paper-tubes and fracture position on paper-tube were discussed together with paperboards. The cause of delamination behavior of laminated paper was analysis based on the detailed observation. The optical observation were employed to evaluate the fracture properties of paper-tubes after lateral compression test. It was found that the initial fracture of paper-tubes occurred inside the paperboards rather than between layers and the peeling property of paperboard has a signification effects on lateral compression property of paper-tubes.

Commentary by Dr. Valentin Fuster
2015;():V014T11A040. doi:10.1115/IMECE2015-52576.

As the extraordinary thermal, electrical, and mechanical properties of carbon nanotubes (CNTs) have become better understood, they have found their way into a wide range of engineering applications. Used in conjunction with fiber-reinforced composite materials, CNTs provide enhanced thermal conductivity, interlaminar strength, and ballistic resistance of laminar composite materials. However, the direct application of the macro form of CNT sheet as a heating element for use in a thermal actuator has not been reported. In the present study, CNT sheets are used as a flexible, efficient, and fast-responding heating element that induces transverse motion in a multilayered functional polymer composite based on thermal expansion mismatch between layers. The CNT heating element is designed to have a specific cross-sectional area to length aspect ratio, giving it a specific resistance and power consumption characteristic. The heating element is bonded to a compliant silicone elastomer substrate and a stiff constraining polyimide thin film, forming a flap-like actuator. The robust design and simple operation of the actuator makes it a potential candidate for control surfaces on micro air vehicles and actuating elements in microscale fluid pumps. The heating response rate of the actuator is measured experimentally using an infrared thermal imager. The temperature change in the thermal actuator is measured as a function of input voltage. The edge deflection of the actuator is also measured as function of the applied voltage. Finally, finite element modeling of the thermal actuator, a parametric study of material selection, and deflection analysis are conducted to better understand the result of these experiments.

Commentary by Dr. Valentin Fuster
2015;():V014T11A041. doi:10.1115/IMECE2015-52598.

Many companies are currently researching VaRTM molding method for practical application in the composite material industry, such as in wind-powered power generating equipment, boats and ships, and aircrafts because it can produce moldings with complicated shapes or large sizes, does not require a large amount of business investments, and can make molding cost efficient. However, it is difficult discovering the optimal conditions for molding, as VaRTM molding requires perform manufacturing process which makes the fiber base material fit into a three-dimensional shape by applying pressure and heat. It is said that the accuracy of the preform affects the mechanical properties of the molding product. In recent years, despite continued investigations into the automated manufacturing of preforms, the majority of preforms are still manufactured by the hands of workers, causing the accuracy of the preform to be dependent on the ability of the worker. In this research, we made three subjects with varying number of years’ experience create preforms and produce a VaRTM molding. Conducting an interlaminar shear strength test on the molding products revealed that they had a higher intensity in order of the most years of experience to least. In order to identify the reason why the accuracy in creating a preform is dependent on the ability of the worker, we informed all of the subjects of the work process beforehand, made them use the same tools and fiber base materials, and investigated the differences in manufacturing method and manufacturing techniques caused by the workers’ number of years of experience. Differences were observed in the expert and non-experts from an overall image of the subjects when working, such as how they handled the tools (iron), their posture when layering, how they exerted strength into layering, etc. We also measured the subjects’ eye movements, focusing on where they were looking. Rather than analyzing the amount of time and the movements of their entire bodies in each work process, instead, we focused on the movements of their line of sight when working. Thus, we compared where each of the subjects was watching and the order in which they watched them. Furthermore, as well as the movement of their line of sight, we also focused on how they moved their hands when conducting the work and investigated the coordination of all of the subjects when working. Based on the fact that there were differences in the accuracy of the preforms, it is clear that manufacturing preforms is not a general concept in which the technique is handed down. While optimizing the creation of systems, work instruction manuals and tools which produce exactly the same accuracy, regardless of the worker manufacturing the preform, we will continue to conduct research that leads to the development of automated production technology.

Commentary by Dr. Valentin Fuster

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