bluuebunny/crossref_metadata_2025 huggingface dataset:
Capability and Variability of Trunk Performance During Upright Isometric Pure and Combined Exertions
Authors: Sheikhzadeh Ali , Nordin Margareta , Parnianpour Mohamad
Published: December 2021

High physically demanding tasks during daily living activities and industrial tasks are best represented by a with combination of the sagittal and lateral or transverse torque. Based on the results of this study, the combination of sagittal and transverse torque present higher risk of spinal injury compared to pure exertions, all muscles presenting higher activity. The capability and controllability of the generated torques are significantly lowered during combined exertions. These results suggest that the trunk muscles will be taxed at a higher relative load while performing combined loading tasks, increasing the probability of muscle fatigue and low back injury.
On an Idealized Wrapping Loading of the Human Spine
Authors: Shirazi-Adl A. , Parnianpour M.
Published: December 2021

The kinetic redundancy of the complex human spinal system presents a rather insurmountable obstacle in estimating the activation patterns and passive-active load sharing. A plausible hypothesis is that the spinal posture, at a given task and load level, is so adjusted as to maintain equilibrium and a sufficient margin of safety against instability while minimizing the need for muscle exertion. Our recent in vivo and model studies support the importance of the pelvic tilt and lumbar curvature in mechanics of the human spine (Shirazi-Adl and Parnianpour, 1996, 1999). In view of very low compression load-carrying capacity (i.e., stability) of the passive ligamentous spine, attempts have been made to investigate optimal path of applied compression loading that could both stabilize the passive system and result in lower stresses and higher margin of safety against tissue failure (Aspeden, 1989; Gracovetsky et al., 1989). Recent in vitro experimental and model studies on the lumbar spine has demonstrated that the passive ligamentous lumbar spine with no musculature is stable under compression loads that remain perpendicular to disc mid-height planes (i.e., wrapping or continuous follower loads) (Patwardhan et al., 1998; Shirazi-Adl and Parnianpour, 1998). In this work, the response of the lumbar and thoracolumbar spine under wrapping compression loads is investigated in order to study the stabilizing effect of this idealized loading configuration as well as its effect on internal tissue-level stress/strain values.
Biomechanics of Human Cervical Spinal Column Under Physiologic Loads
Authors: Hollowell James P. , Kumaresan Srirangam , Yoganandan Narayan , Pintar Frank A.
Published: December 2021

The determination of the biomechanics of the human cervical spinal column under physiologic loads was a focus of the present study. The effects of pre-load on the load carrying capacity of spine were investigated. Structural morphology was divided into young, representing normal/non-degenerated, and old, representing abnormal/degenerated spines. Intact human cadaver cervical spinal columns were carefully isolated by maintaining the integrity of the ligamentous soft tissues. Fat and surrounding musculature were dissected. Radiographs of the specimens were obtained before the test. At each level of the cervical column, retroreflective targets were inserted into the bony articulations. Kinematic information was obtained from these targets. Principles of continuous motion analysis were used to determine the kinematics of the cervical column. A six-axis load cell was attached at the inferior end of the specimen. Flexion, extension, axial rotation, and lateral bending moments were applied. The specimens were tested with and without pre-load conditions. Results are presented with regard to variations in angular stiffness values as function of applied moment, pre-load, and spine condition. This study emphasizes the differing roles contributed by the load vector and specimen morphology on cervical spine biomechanics.
Equilibrium Point and Knee Joint Modeling
Authors: Li Li
Published: December 2021

Human running behavior has been modeled as bouncing ball. In this regard, mass-spring model has been employed to study the mechanical characteristics of lower extremity during running. The mechanical adaptation of the lower extremity to the environment during running presents significant considerations in the understanding of the mechanism that governing the mass-spring system. A mass-spring model with a changing equilibrium point is developed in this study. The model predicts that the knee joint will experience three different stages during running stance phase. Each stage (phase) is associated with different joint stiffness, which is constant with in the each phase. The model further suggests that this unique stiffness could be estimated by using kinematics of knee joint only without kinetic measures. This model provides information that improves our understanding of knee joint mechanical behavior and neuromuscular control mechanism. It also has important clinical applications.
Nondestructive Evaluation of Fiberglass Reinforced Plastic Subjected to Combined Localized Heat Damage and Fatigue Damage Using Acoustic Emission
Authors: Nayeb-Hashemi H. , Kasomino P. , Saniei Nader
Published: December 2021

The effect of fatigue damage to unidirectional fiberglass composite specimens with prior contact heat damage was investigated. After damaging the specimens by contacting them to a hot tip at 360 °C, the specimens were subjected to fatigue loading at cyclic stress amplitude corresponding to 65% of the specimens’ ultimate tensile strength. The fatigue experiments was halted after 3000 cycles. The specimens were then subjected to tensile tests while monitoring their Acoustic Emission activity. In addition, acoustic emission activities of undamaged and contact heat damaged specimens were monitored during tensile tests for comparison with specimens with combined fatigue and heat damage. AE activities of all specimens can be categorized into three regions: an early rise in activity, a relatively dormant period in activity and a high exponential activity before failure. The early rise in activity did not appear on the specimens with combined contact heat and fatigue damage. For undamaged and contact heat damaged specimens, the period of the dormant activity was independent of the contact heat duration of less than 15 minutes. However, the period was a function of the contact heat duration for combined contact heat and fatigue damaged specimens. Analyzing event duration distribution identified micro-mechanisms of the damage growth upon tensile loading.

AE-stress delay concept was used to predict the state of the damage in the composite. A correlation between stress delay parameter and damage parameter was obtained for all of the specimens.

Fatigue life of contact heat damaged specimen was also studied. It was found that localized heat damage reduced the fatigue life significantly. Loss of matrix to transfer the load to the fibers uniformly was believed to be responsible for the reduction in the fatigue life.
Experimental Investigation of Compressive Overloads on Delamination Growth Behavior in Fatigued Composites
Authors: Pelegri Assimina A. , Valentine Charles
Published: December 2021

The behavior of laminated graphite/epoxy composites under variable amplitude compressive loading is studied. Laminate composites in aerospace applications undergo both compressive and tensile fatigue stresses as well as spectrum loading. These materials are particularly susceptible to compressive loads and overloads, which cause the growth of any small pre-existing delaminations. Such delamination growth, and the resulting sublaminate buckling, are major causes of fatigue failure. This experimental program investigates the effects of overloads on laminate composite specimens in which small delaminations are introduced during fabrication. The delamination growth is monitored in real time during fatigue tests. Different variable amplitude load spectra are applied, and the delamination position through the depth of the specimens is varied. Up to now, research has focused on constant amplitude fatigue testing or simple two block testing. Some variable amplitude studies have been done but attention has mostly been given to the reduction in residual strength or stiffness of the specimen. Much of the prior work is done in tension instead of compression. This investigation will provide data specifically on the growth behavior of pre-existing delaminations in composites under compressive overloads.
Durability and Damage Development in Woven Ceramic Matrix Composites Under Tensile and Fatigue Loading at Room and Elevated Temperatures
Authors: Haque Anwarul , Rahman Md. M. , Mohamed Hisham T. , Mahfuz Hassan , Vaidya Uday K. , Jeelani Shaik
Published: December 2021

This paper investigates the damage development in SiC/SiNC woven composites under tensile and cyclic loading both at room and elevated temperatures. The ultimate strength, failure strain, proportional limit and modulus data at a temperature range of 23°C–1380°C are generated. The tensile strength and the modulus of SiC/SiNC woven composites have been observed to decrease insignificantly with increased temperatures beyond the linear portion of the stress/strain plot. The stress/strain plot shows a pseudo-yield point at 25% of the failure strain (εf) which indicates damage initiation in the form of matrix cracking. The evolution of damage beyond 0.25 εf both at room and elevated temperature comprises of multiple matrix cracking, interfacial debonding and fiber pullout. Although the nature of the stress/strain plot shows damage-tolerant behavior under static loading both at room and elevated temperature, the life expectancy of SiC/SiNC composites degrades significantly under cyclic loading at elevated temperature. This is mostly due to the interactions of fatigue damage caused by the mechanically induced plastic strain and the damage developed by the creep strain. The in situ damage evolutions are monitored by acoustic event parameters, ultrasonic C-scan and stiffness degradation.
Energy Analysis of Piezoelectric-Actuated Structures Driven by Linear Amplifiers
Authors: Leo Donald J.
Published: December 2021

Energy expressions for a piezoelectric actuator coupled to a resonant mechanical load are analyzed for the purpose of determining the energy requirements of controlled structures. The analysis illustrates that the energy dissipated within the linear amplifier is a function of four parameters: the driving frequency, the piezoelectric coupling coefficient, the relative stiffness of the actuator and load, and the amplifier supply voltage. The piezoelectric actuator and the mechanical load are assumed to be lossless to highlight the relationship between energy dissipated within the amplifier and the energy stored in the actuator. For a specific frequency, the minimum energy dissipation within the amplifier is equal to twice the stored electrical energy in the piezoelectric when the amplifier voltage is equal to the driving voltage of the actuator. Additional energy is dissipated within the amplifier when the supply voltage is greater than the driving voltage. In the case when the actuator displacement is constant as a function of frequency, the energy dissipation in the amplifier decreases near the resonance of the coupled electromechanical system and reaches a minimum when the piezoelectric charge due to the applied voltage is equal and opposite to the charge induced by the load. The steady-state amplitude of the charge, and hence the actuator current, is equal to zero at this frequency. The results illustrate that energy dissipation is minimized when the actuator is operated at near the resonance or antiresonance of the coupled electromechanical system.
A General Method for a Piezothermoelastic Plate of Crystal Class 6mm Subjected to Axisymmetric Loading
Authors: Wang Xiangqing , Agrawal Om Prakash
Published: December 2021

Applications of piezoelectric materials for the development of “intelligent” structural and mechanical systems through sensing, actuation, and control have received considerable recent interest. In this document, we present a general solution method for piezothermoelasticity for hexagonal piezoelectric solids of class 6 mm. In the formulation presented, potential functions are introduced to represent the coupled thermal, elastic, and mechanical fields, which satisfy the thermal, mechanical, and electrical equilibrium and prescribed boundary conditions. The formulation is similar to those presented by Ashida, Tauchert, and Noda (1993, 1994), however, it is simpler and direct, and it eliminates the need to discuss special cases. To demonstrate applications of the technique, a piezothermoelasticity problem subjected to axisymmetric thermal, electrical and mechanical loads on a plate is considered. Numerical calculations for the stresses and the electrical potential are carried out for a cadmium selenide body exhibiting class 6mm symmetry. Results of these calculations are presented graphically.
Mechanics of Electrostrictive Materials With Periodic Microstructure
Authors: Somphone T. , Yu N.
Published: December 2021

The effective properties as well as local elastic and electric fields in smart electrostrictive composite materials with periodic microstructure are estimated by using the Fourier series technique (Nemat-Nasser et al., 1993) and the equivalent inclusion method (Eshelby, 1957). The developed model involves many microstructural parameters and can provide guidelines for the design of flexible, nonlinear electrostrictive transducers.
Mechanical Characterization of Shape Memory Alloy Composites for Designing Smart Structures
Authors: Bruck Hugh A. , Moore Charles L.
Published: December 2021

Actuators with large displacement ranges are being designed for smart structures by utilizing the unconventional mechanical behavior of Shape Memory Alloys (SMAs). This behavior is characterized by deformation recovery through thermally activated phase transformations. However, because of this deformation mechanism, conventional constitutive models cannot be employed to predict the mechanical behavior of SMAs. Appropriate constitutive models have been proposed, but their application can be computationally intensive. In this investigation, SMA wire-reinforced fiberglass composites are fabricated to determine the relationship between the mechanical response of the composite and the composition of SMA wire reinforcement. A modified linear Rule-of-Mixtures (ROM) formulation is proposed for predicting the mechanical behavior of the SMA composites. This simple, uniaxial constitutive model provides a reasonable prediction of SMA composite mechanical behavior, and is computationally efficient enough to use with Finite Element Analyses for designing smart structures that contain heterogeneous compositions.
Efficient Actuation Utilizing Fuel Cell Power Sources
Authors: Leo Donald J.
Published: December 2021

The performance of a fuel cell-powered piezoceramic actuator is investigated analytically and experimentally. Fuel cells are electrochemical engines that are comparable to batteries in specific energy density and can be instantly ‘recharged’ with the addition of fuel. This study focuses on the use of a methanol-powered alkaline fuel cell as a DC power source for a piezoceramic actuator exciting a thin beam. The fuel cell consists of a non precious metal cathode, a platinum anode, and a potassium hydroxide (KOH) electrolyte. The performance of the fuel cell is investigated by determining the voltage and power output as a function of the load current. A peak power of 30 mW is obtained with a 1M KOH electrolyte and 47 mW is obtained with a 4M concentration. A power analysis of constant-amplitude piezoceramic actuator demonstrates that low-power, efficient actuation is achieved by driving the actuator near an antiresonance of the coupled electromechanical systems. The antiresonance frequencies are determined from an admittance analysis of the coupled actuator and structure. Experimental results demonstrate that the power required for actuation in the kilohertz range is reduced from 4.5 to 1 mW by exciting the actuator at a known antiresonance, thus reducing the load on the fuel cell and increasing the effective lifetime of the actuator.
Passive and Active Control of Solar Array Vibrations Induced by the Change of Thermal Input
Authors: Tabacchi L. , Natori M. C.
Published: December 2021

The behaviour of large and flexible space structures, if compared with compact and rigid ones, is largely influenced by thermal loads in orbit. In this paper, the control of a spacecraft attitude disturbance, induced by cyclic temperature variations in the solar array substructures, is investigated. Both passive and active control techniques have been considered to reduce the vibration amplitude. A new version of tension mechansim powered by constant force springs is compared with a previous mechanism from the point of view of induced disturbances in the satellite attitude. A new algorithm for closed-loop pole placement of a symmetric, second order dynamical system is presented, and results of closed-loop numerical simulations are shown. Finally, experimental investigations are discussed and the relative results are presented.
Experiments in Robust Active Vibration Control Design for Slewing Flexible Structures
Authors: Wilson D. G. , Starr G. P. , Parker G. G. , Robinett R. D.
Published: December 2021

In this paper we present a hybrid Sliding Mode Control (SMC) and Constant Amplitude Feedback Control (CAFC) architecture for slewing flexible structures. The SMC controller is used to servo the flexible structure and the CAFC is used to suppress residual vibrations of the flexible structure. A single-axis encoder/DC motor/harmonic drive assembly is used for large angle slewing. A graphite/epoxy composite structure with embedded strain sensors/actuators is used for active vibration suppression. The results of this study include the analytical dynamic and control system development with experimental verification. The hybrid control algorithm uses the output sensor data from the encoder and strain sensor along with filters to derive velocity information to compute the control effort for the motor and strain actuators. Near-minimum time maneuvers based on an equivalent rigid structure are used to slew the flexible active structure. The tip mass was varied to evaluate control system robustness. Experimental slewing studies were performed to compare the benefits of using active rather than passive structures. For the active case the experimental results showed a reduction in residual vibration and settling time.
Effect of the SAR Distribution of a Radio Frequency (RF) Coil on the Temperature Field Within a Human Leg: Numerical Studies
Authors: Ling J. X. , Hand Jeffrey W. , Young Ian R.
Published: December 2021

This paper presents a three dimensional Finite Element Model for studying the effect of the specific absorption rate (SAR) distribution of a RF coil on the temperature distribution within a human leg due to the energy deposit. The model consists of fat, muscle, and bone, and has 21,158 uniform elements. The 3-D leg model was derived from the tissue maps that are obtained from the 79 sequential MR images of a volunteer’s leg. The specific absorption rate (SAR) data are from the solution to the fundamental Maxwell’s electromagnetic equations of the leg with RF coil in place using finite difference time domain (FDTD) method. The blood perfusion term, which is a function of the local tissue temperature, along with the metabolic heat as well as the SAR term, are treated as one heat source term in the classical bio-heat transfer equation. A commercial FEA code, ANSYS, was used to solve the 3-D heat conduction equation with an additional iteration method to deal with the temperature dependent source term. The 3-D temperature fields without and with the SAR term were computed, as well as the changes in temperature. They predict that the maximum temperature change occurs in approximately the same location as the maximum local SAR. The map of the temperature change clearly shows how the presence of the RF coil affect the temperature distribution within the leg. With 2 watts absorbed in the leg, about 8.8 w/kg of peak SAR value, the maximum change in temperature of the leg is about 1.74° C.
Temperature Dependent Tissue Properties and Ultrasonic Lesion Formation
Authors: Kolios Michael C. , Sherar Michael D. , Hunt John W.
Published: December 2021

High intensity focused ultrasound has considerable potential for the noninvasive treatment of localised disease. A detailed understanding of the kinetics of tissue coagulation is required to optimise ultrasonic parameters. In this presentation a theoretical model was used to examine the effects of temperature dependent ultrasonic attenuation and absorption on the transient tissue temperature distributions and lesion dimensions. A finite difference algorithm was used to solve numerically the nonlinear form of the bioheat transfer equation in cylindrical coordinates. The lesion dimensions were calculated based on the time-temperature distributions in tissue by using a thermal dose threshold to define the lesion boundaries. The results were compared to published experimental data in which the the location of maximal energy deposition during short duration high intensity focused ultrasound irradiation of in vitro tissue was examined. It was found that the theoretical model did not predict the size and shape of the experimental lesions. To correctly predict lesion size and shape much higher values of attenuation and absorption were required than can be accounted for by thermal coagulation of the tissue alone. The values used suggest that for intensities greater than 3030 W/cm2 the effective local attenuation/absorption in the focal region increased by a factor of 10–20. It is finally shown that temperature dependent tissue changes should be incorporated in thermal models to avoid underestimation of the induced temperature distributions during high intensity focused ultrasound therapy.
Temperature Feedback Control for Hyperthermia of Chest Wall Volumes With Dual-Frequency Ultrasound
Authors: Moros Eduardo G. , Straube William L. , Myerson Robert J.
Published: December 2021

Therapeutic temperature distributions during hyperthermia treatments are very difficult to maintain (e.g., 41.5 to 43°C for 45 to 60 min.) due to many heat removal/loss mechanisms. Thermoregulatory responses of the human body are efficacious in preserving and re-establishing normothermic conditions, and are considered to be the main cause of temperature non-uniformities through effected changes in blood perfusion and blood flow in large vessels. From the very beginning of hyperthermia technology development temperature feedback control systems (temperature controllers) have been proposed as a way to counterbalance thermoregulation and improve thermal doses. Only a few controllers, however, have been thoroughly tested numerically, experimentally, and most importantly, clinically. In this paper the proportional-integral-derivative bang-bang (PIDBB) controller of Lin et al. (1990), originally designed for a scanned focused ultrasound system for deep localized hyperthermia, was applied numerically to a scanned dual-frequency planar ultrasound system for chest wall hyperthermia. It was found that PIDBB controller with the optimal parameter values as determined by Lin et al. (1990) performed satisfactorily in controlling temperatures in superficial chest wall volumes.
Skin Heating Effects of Millimeter Waves: Inter-Species Variability
Authors: Nelson D. A. , Walters T. J. , Ryan K. L. , Johnson L. R.
Published: December 2021

The increasing use of radiofrequency signals in the millimeter wave (MMW) band in both defense and civilian applications necessitates a better understanding of the bioeffects of electromagnetic energy within this frequency range (30 GHz – 300 GHz). Because MMW irradiation penetrates less than 1 mm below the skin surface, the primary bioeffect is skin heating (1). Thus the use of the specific absorption rate (SAR) to establish safe exposure levels is not appropriate in this frequency band (2).

The use of animal models for evaluation of skin heating effects from MMW irradiation makes problematic the extrapolation of results to humans. Differences in tissue composition, skin blood flow, and surface cooling mechanisms (sweating) may complicate the interpretation of results obtained from animals and their application to humans.

This paper presents the results of series of experiments in rats, rhesus monkeys and humans to determine the rate of surface temperature increase resulting from exposure to MMW.
Numerical Results of an Integral Formulation of Transient Radiative Transfer
Authors: Tan Z.-M. , Hsu P.-F.
Published: December 2021

Numerical computations are performed for the transient radiative transfer equation within the one-dimensional parallel plate geometry using an integral formulation obtained in a prior work. The medium under consideration is absorbing and isotropically scattering. One boundary is a black emitting surface or a transparent surface subjected to the collimated incident radiation. The incident intensity is applied at the start of the transient. The other boundary is a cold and black or specularly reflecting surface. The spatial and temporal incident radiation and radiative flux distributions are presented for different boundary conditions and for uniform and nonuniform property distribution. The transient results at large time step are compared with steady-state solutions by the finite volume and quadrature methods and show excellent agreement. The solutions of reflecting boundary condition exhibit distinctive behavior from that of the non-reflecting boundary. The integral formulation is extended to handle the transient transfer within the nonhomogeneous participating media. The integral formulation has several advantages over the differential treatment of the hyperbolic wave of the radiative transport; among others: (1) The avoidance of using a high order upwind difference scheme in resolving the wave front; (2) Providing a sound basis for physical interpretation as the radiative transfer is a volumetric process; and (3) Many integral equation numerical methods that have previously been developed for the steady state integral formulation can be re-applied to treat the transient problem.
In Vivo Measurement of Microvessel Permeability and Tissue Diffusion Coefficient in Frog Mesentery by Confocal Microscopy
Authors: Fu Bingmei M. , Adamson Roger H. , Curry Fitz-Roy E.
Published: December 2021

Our early studies showed that tissue diffusion coefficient (Dt) of small solute sodium fluorescein (0.45 nm radius) in frog mesentery is 30% of its free diffusion coefficient (Dfree) in aqueous solution. We test here the hypothesis that because of its size-limiting structure the interstitium would provide larger resistance to larger solute α-lactalbumin (2.0 nm radius). We extended our previous method by using laser-scanning confocal microscopy to measure both solute capillary permeability (P) and solute tissue diffusion coefficients (Dt) from the rate of tissue solute accumulation and the radial concentration gradients around individually perfused microvessels in frog mesentery. pα-lactalbumin was 1.7 ± 0.7 (SD) × 10−6 cm/s (n = 6). Dt/Dfree was 27% ± 5% (SD) (n = 6). This value is comparable to that for small solute sodium fluorescein. Our results indicate that frog mesenteric interstitium is less selective to larger solute α-lactalbumin than the microvessel wall.
Diffusion-Limited Cell Dehydration: Analytical and Numerical Solutions for a Planar Model
Authors: Kasharin Alexander V. , Karlsson Jens O. M.
Published: December 2021

The process of diffusion-limited cell dehydration is modeled for a planar system by writing the one-dimensional diffusion-equation for a cell with moving, semipermeable boundaries. For the simplifying case of isothermal dehydration with constant diffusivity, an approximate analytical solution is obtained by linearizing the governing partial differential equations. The general problem must be solved numerically. The Forward Time Center Space (FTCS) and Crank-Nicholson differencing schemes are implemented, and evaluated by comparison with the analytical solution. Putative stability criteria for the two algorithms are proposed based on numerical experiments, and the Crank-Nicholson method is shown to be accurate for a mesh with as few as six nodes.
Enhanced Thermal Management Using Encapsulated Phase Change Materials: An Overview
Authors: Colvin David P.
Published: December 2021

Since 1983, investigators at Triangle Research and Development Corporation have pioneered the research and development of encapsulated phase change materials through 25 Small Business Innovation Research (SBIR) programs for NASA, DOD (USAF, NAVY, USMC, SDIO and SOCOM), NSF, USDA and HHS (NIOSH). Additional programs by licensees have also shown how these novel particles can produce superior apparel and coolant products. For pumped systems, two-component coolant slurries have demonstrated up to 40X (4,000%) improvement in the fluid’s effective thermal capacitance with up to 3X (300%) increase in the Nusselt Number within isothermal coolant loops for NASA, USAF and NAVY. MicroPCM machining coolants have also demonstrated enhanced heat transport along with significant reductions in tool wear, thermal distortions and coolant emissions for NSF and NIOSH.

For un-pumped passive systems, microPCM powders have been added to textile fibers, and apparel foams for 10X enhancement in thermal storage. MicroPCM coatings are being developed for numerous agricultural applications for NSF and the USDA. PCMs are also being macroencapsulated for garments in high heat stress applications with the USMC. Numerous products are now being introduced to global markets using this advanced technology. This paper will address the above applications in an overview that will also provide an introduction to the other papers in this session.
Damage Study in Notched Particulate Composite Specimens Under Non-Uniform Strain Loading
Authors: Kwon Y. W. , Liu C. T.
Published: December 2021

This paper studied crack initiation in a hard particle reinforced composite with a soft rubber-like matrix material using a numerical technique. The numerical specimen considered had a semi-circular notch with a linearly varying length. The initial crack size occurring at the notch tip was modeled and predicted using a micro/macro-approach along with a damage model. A criterion to predict the initial crack size was proposed based on the size of a localized unstable material zone. Different notch sizes were compared to their initial crack sizes.
Dynamic Stability of Multi-Tool Machining
Authors: Kushnir E. , Raj B. R.
Published: December 2021

The proposed numerical model of machine tool dynamic structure is constructed as a single-loop system consisting of two multi-dimensional links. This approach offers the advantage of considering all the working processes of the machine tool equally and simultaneously by placing them into a single multi-dimensional link. Employing matrix methods of analysis farther enhances the simplicity and universality of this methodology so that modern computer could be used for determining the dynamic qualities of the machine tools. The proposed methodology was validated by tests. The results of these tests are compared with data obtained from proposed computational approach.
A Multiple Term Viscoelastic Constitutive Model Implemented and Applied for Plastic
Authors: Verderber Rudy R. , Feng William W.
Published: December 2021

This paper discusses implementation and application of a multiple term viscoelastic constitutive model suitable for plastic materials. The constitutive model uses Feng’s recursive formula where the stress updates depend only on the stress terms in the prior state. The multiple term creep equations are accurate over longer periods of time. A tensile test simulation shows that the model provides reasonable results. Then a press fit example shows the holding force depends on time according to viscoelasticity.
MEMS Curriculum Development in Mechanical Engineering at the University of Michigan
Authors: Lin Liwei
Published: December 2021

MEMS curriculum development in Mechanical Engineering at the University of Michigan is presented. A course curriculum structure that integrates both mechanical and electrical engineering courses is proposed for mechanical engineering students who are interested in MEMS research. The proposed curriculum starts from undergraduate study and finishes at the Ph.D. level. Two new graduate-level MEMS courses are proposed. They are “Introduction to MEMS” for senior and entry-level, graduate students and “Advanced MEMS” for graduate students. The first course has been experimentally taught at the University of Michigan for the past three years and the class assessments are summarized and analyzed in this paper. It is clear from the student responses that for more advanced MEMS courses should be offered. The vision of the future MEMS curriculum development has also been discussed with the suggestion of the development a new undergraduate-level MEMS course in the college of engineering.
Assessing UV Exposure Limits for Surgical Luminaires
Authors: Fisher Kenneth J.
Published: December 2021

Research conducted at the University of Genoa has suggested that ultraviolet (UV) energy levels generated by Tungsten Halogen lamps may produce skin cancer. Similar threshold limit values for exposure to UV radiation have been reported by the American Conference of Governmental Industrial Hygienists (ACGIH) covering the spectral region of tungsten halogen emissions.

Such information has led to safety concerns by users of surgical lighting systems. It was deemed necessary to conduct an investigation regarding the possible effects of long term exposure to UV emitted by surgical luminaires.

The investigation included a review of materials used in the optical design of surgical luminaires related to the degree of filtration of UV transmission posed by the design and a measurement of UV radiation levels for a worst case exposure scenario.

The results of the investigation indicate that UV exposure levels from surgical lighting systems are within the levels of safe usage per guidelines established by ADGIH. It is concluded that surgical luminaires sufficiently reduce UV exposure to preclude the potential of adverse health effects.
Codes and Practice of Fatigue Design for Welded Structures
Authors: Sakamoto Haruo
Published: December 2021

This paper describes the codes and practice for designing welded structures such as railroad truck frames. For designing the first configuration, rather simple criteria are desired, although most codes such as AWS. AISC, etc. are complex. They consist of a variety of welded joint categories, which make a designer feel uncomfortable when deciding the first configuration. Therefore, such codes are considered to be mainly used for the evaluation of designed and constructed structures, and not to be used for deciding the first configuration. The JIS (Japanese Industrial Standard) for a railroad truck frame is explained as an example of a simple code, and is compared with some fatigue data. This standard is thought to be useful for a designer. However, the result of this investigation suggests a modification of the JIS for obtaining more reasonable criteria.

Desirable criteria should be simple for a designer and sufficiently safe for structures. Additional investigations on fatigue data of welded joints, a statistical study for desirable non-fracture probability, and methods of structural stress analysis are to be conducted in the future. A practical fatigue testing method is also needed for investigating the strength in a high cycle region such as 108.
An Accurate Approximation of the Orowan Rolling Force Equation for Homogeneous Compression of Metals in Cold Rolling
Authors: Urso André C.
Published: December 2021

The theory of rolling metals has been adequately developed since the mid 1940’s. Of the popular theories, the complex formulations are accurate over a large range of rolling conditions, and the approximate formulations tend to be accurate only on a narrow range. This paper covers the development of an approximate formulation of the Orowan (1943) rolling theory that is applicable over a relatively large range of reductions, material strengths, and strip tensions.
A New Approach to Mechanical Structure Approximation Analysis With Global Characteristics
Authors: Xiao Shide , Lu Jingui , Chen Jim X. , Gao Dayong
Published: December 2021

In this paper it has been theoretically proved that a three layer neural network can be applied to implementing exactly the function between the stresses and displacements and the design variables of any mechanical elastic structure based on Kolmogorov’s mapping neural network existence theorem. A new approach to the mechanical structure approximation analysis with the global characteristics based on artificial neural networks is presented. It has been verified by computer simulation experiments that the new approach is effective.
Decomposition and Reconstitution Based Fixturing Planning Automation
Authors: Huang K. , Rong Y.
Published: December 2021

Fixturing planning has become a focus in concurrent engineering which is required for efficient and effective product design, process planning and fixture design. In the context of DFM in concurrent engineering, a new Decomposition and Reconstitution (D&R) Based Fixture Planning Automation is developed as a top-down approach for fixture design automation. Decomposition and reconstitution problems are discussed for building a prototype fixture planning system. Finally a practical example is given to show its application process and effectiveness.
Improving the Economics of Machining PMMCs
Authors: El-Gallab Mariam S. , Sklad Mateusz P.
Published: December 2021

It is the purpose of this paper to present a mathematical model for the prediction of surface finish during turning 20%SiC/Al particulate metal matrix composites (PMMCs). The surface finish relation to the cutting parameters (tool material, tool geometry, speed, feed rate and depth of cut) is further employed in a general form for tool life in order to arrive at optimum cutting parameters that would cost the least and yet meet the surface roughness requirements. A simple C++ program has been developed to find the optimum cutting conditions iteratively. The mathematical models quantify the results of an extensive experimental work on oblique turning of the SiC/Al PMMCs. The results of the experimental work reveal that increasing the feed rate up to 0.55 mm/rev. improves the tool wear rate. This is attributed to the reduced area of contact between the tool surface and the abrading SiC particles. Further increases in the feed rate results in tool failure by edge chipping. The optimum cutting conditions arrived at by the mathematical model yield 21–37% cost reduction when compared to the currently employed cutting parameters.
Modeling of Gear Hobbing: Part I — Cutting Simulation and Tool Wear Prediction Models
Authors: Bouzakis Konstantinos D. , Kombogiannis Spiros , Antoniadis Aristomenis , Vidakis Nectarios
Published: December 2021

Gear hobbing is the most common method to manufacture high quality and performance toothed wheels. The gear hobbing kinematics induces complicated chip formation and is characterized by convoluted wear mechanisms of the cutting tool. The variant cutting contribution of each cutting tooth is responsible for the uneven wear distribution on the successive hob teeth and the poor utilization of the entire cutting tool. Moreover, the gear width influences the chip geometry in the tool entry and exit regions into the workpiece, and sets a mathematical wear description even more complicated. To study quantitatively the tool wear progress in gear hobbing, experimental-analytical methods have been established. Gear hobbing experiments and advanced mathematical models are hired to correlate the undeformed chip geometry and other cutting parameters with the anticipated wear. With the aid of such procedures and of appropriate constants, essential for the description of the wear development in the individual gear gaps generating positions, an optimization of the hobbing process can be achieved. Hence, among others, appropriate tangential shifts of the hobbing tool may be predicted.
Modeling of Gear Hobbing: Part II — A Computer Supported Experimental-Analytical Determination of the Wear Progress to Optimize the Tool Life Time
Authors: Bouzakis Konstantinos D. , Kombogiannis Spiros , Antoniadis Aristomenis , Vidakis Nectarios
Published: December 2021

Tool wear prediction models for gear hobbing were presented in the first part of this paper. To determine the constants of the equations used in these models, fly hobbing experiments with uncoated and coated HSS tools were conducted. Hereby, it was necessary to modify the fly hobbing kinematics from continuous tangential feed to continuous axial feed. The experimental data were evaluated, and correlated to the analytical ones, elaborated through the described digital simulation of the cutting process. The determined constants of the wear laws for the investigated tools were used in a further developed user friendly software, enabling the prediction of the tool wear accomplishment in gear hobbing. On that account the wear development can be precisely foreseen and the tangential shift of the tool is optimized. The open and modular structure of the developed code enables the continuous enrichment of its database with other type of coating and workpiece materials. With the aid of the aforementioned techniques, the superiority of coated HSS tools in comparison to uncoated ones is also quantitatively exhibited.
Generalized Modeling of Milling Mechanics and Dynamics: Part I — Helical End Mills
Authors: Engin Serafettin , Altintas Yusuf
Published: December 2021

Variety of helical end mill geometry is used in industry. Helical cylindrical, helical ball, taper helical ball, bull nosed and special purpose end mills are widely used in aerospace, automotive and die machining industry. While the geometry of each cutter may be different, the mechanics and dynamics of the milling process at each cutting edge point are common. This paper presents a generalized mathematical model of most helical end mills used in industry. The end mill geometry is modeled by helical flutes wrapped around a parametric envelope. The coordinates of a cutting edge point along the parametric helical flute are mathematically expressed. The chip thickness at each cutting point is evaluated by using the true kinematics of milling including the structural vibrations of both cutter and workpiece. By integrating the process along each cutting edge, which is in contact with the workpiece, the cutting forces, vibrations, dimensional surface finish and chatter stability lobes for an arbitrary end mill can be predicted. The predicted and measured cutting forces, surface roughness and stability lobes for ball, helical tapered ball, and bull nosed end mills are provided to illustrate the viability of the proposed generalized end mill analysis.
On the Dynamic Stability of Nonlinear Chatter Machining
Authors: Fofana M. S.
Published: December 2021

This paper is concerned with the dynamic stability of nonlinear chatter leading to instability machining at a Hopf bifurcation point. Regions of stable and unstable chatter machining are identified in an infinite-dimensional space for a reasonable and fixed time delay between successive cuts. The influence of nonlinear cutting force as a function of the chip thickness and feed rate, and parametric excitations on machining dynamics have been characterized.
Experimental Study of Superfinishing
Authors: Chang Shih-Hsiang , Farris Thomas N. , Chandrasekar Srinivasan
Published: December 2021

An experimental study has been made of the superfinishing process. A force measurement system, developed for external cylindrical superfinishing, has been used to directly measure the forces acting on the abrasive stone. A systematic parametric study of material removal rate, force ratio, specific energy and surface finish is detailed. The force ratio and specific energy are found to be sensitive indicators of the cutting action of the stone. This indicates that the force ratio could be used to monitor the process, online in industrial applications. The two regimes of rough finishing and fine finishing have been characterized. A sharp transition from fine to rough finishing occurs at a stone oscillation frequency of about 1600 cpm. This characteristic frequency is mostly independent of stone-work contact pressure. The experimental data is used to construct a superfinishing process map, analogous to the wear-regime map, to depict the various regimes in which different modes of superfinishing dominate.
High Speed Grinding of Silicon Nitride With Electroplated Diamond Wheels: I — Wear and Wheel Life
Authors: Hwang T. W. , Evans C. J. , Whitenton E. P. , Malkin S.
Published: December 2021

An investigation is reported on high speed grinding of silicon nitride using electroplated single-layered diamond wheels. The present paper is concerned with wheel wear and wheel life, and a second paper (Hwang et al., in press) with wheel topography and grinding mechanisms. It has been suggested that grinding performance may be enhanced at higher wheel speeds due to a reduction in the undeformed chip thickness. Grinding experiments were conducted at wheel speeds of 85 m/s and 149 m/s with the same removal rate. Contrary to expectations, the faster wheel speed gave no improvements in surface finish, grinding ratio, or wheel life. Microscopic observations of the wheel surface revealed dulling of the abrasive grains by attritious wear, thereby causing a progressive increase in the forces and energy until the end of the useful wheel life. For all grinding conditions, a single-valued relationship was found between the wheel wear and the accumulated sliding length between the abrasive grains and the workpiece. A longer wheel life and improved grinding performance can be obtained when the operating parameters are selected so as to reduce the abrasive sliding length per unit volume of material removal.
Solidification Modeling and Porosity Control in Aluminum Alloy Castings
Authors: Shenefelt Jeffrey R. , Luck Rogelio , Berry John T. , Taylor Robert P.
Published: December 2021

Commercial software packages enable the thermal environment of shaped castings to be determined provided the boundary conditions are well understood. Criteria functions (CF’s) based on the thermal environment provide a means for estimating shrinkage porosity within a casting. However, the CF’s do not account for gas driven porosity forming within the casting. This paper reviews the CF’s and additional approaches to account for hydrogen evolution in aluminum-copper and aluminum-silicon alloys.
Contract Manufacturing at Work: How to Avoid the Pitfalls of Outsourcing in a Global Economy
Authors: Shina Sammy G.
Published: December 2021

The increase in outsourcing and global contract manufacturing has led to significant impacts on the development of new products and their manufacturing operations conducted around the world. This paper outlines some of the outcomes of this trend in terms of changes to the product development process, manufacturing strategy, and human, financial, legal and business issues in global outsourcing. A strategy for new product realization and its manufacturing with the supply chain is then presented to select, manage and negotiate with suppliers in order to minimize adverse consequences of contract manufacturing.