bluuebunny/crossref_metadata_2025 huggingface dataset:
VRHose — Virtual Hydraulic Hose Routing Design
Authors: Chipperfield Kurt A. , Vance Judy M.
Published: December 2021

Hydraulic hoses, which are used to transport high pressure hydraulic fluid, are key components in many large industrial vehicles. In the design of an industrial vehicle, designers must allow sufficient space for hydraulic hoses to pass through the vehicle. Because these hoses are typically stiff and do not bend easily, planning the routing of the hoses around components in the vehicle is challenging. Currently designers use CAD programs to design vehicles and rely on past experience to plan hose routes and allow sufficient space for the hoses in a new vehicle. Later, during the prototype build, the actual hoses are fit and cut to length to determine exact specifications. This paper describes the program VRHose which provides the designer with a three-dimensional interface to aid in planning hose paths. VRHose allows designers to lay out hose routes through the vehicle by defining points in space which constrain the hose path. Virtual reality (VR) is used as the human-computer interface to provide three-dimensional viewing and interaction with the digital models. The initial development of VRHose has concentrated on providing the user with a three-dimensional input and evaluation tool to lay out hose routings. Future versions of VRHose will include hose material properties which will constrain the hose paths to those which are feasible.
Design and Utilization of Virtual Machines and Processes
Authors: Bzymek Zbigniew M.
Published: December 2021

Virtual Models (VMd), Virtual Machines (VMn) and Virtual Processes (VP) are becoming more and more useful tools in manufacturing design, research and development of products. They give possibility to investigate manufacturing and production problems prior to building a physical model or prototype of the machine. Virtual Machines and Virtual Processes are technologies used in the design of machining equipment and in looking at production processes. They consist of a group of recently developed techniques and approaches that allow the construction of machine computer models and the simulation of the fabrication process. What makes this group of manufacturing technologies special is that they allow the checking of machining and production parameters before actual prototypes and their specific tooling are manufactured. The possibility of using these virtual manufacturing techniques could result in great savings of both time and money. In general, virtual manufacturing promises shorter design cycles with more design iterations, leading to an optimal design and better use of resources. The end goal of any virtual manufacturing is to produce a virtual model of a machine that will virtually make the part from its database file containing the geometrical description of a physical object in terms of pre-defined geometric entities. The actual manufacturing hardware provides the physical means to machine the part, which Virtual Machining allows making the as a computer model. Special software is employed to bridge the gap between the CAD data and the virtual manufacturing system. Such software should control various parameters such as the rate at which the positioning system proceeds, the tool path, the thickness of the layer of the material for removal and/or length of the path, the slice length, and others. Virtual manufacturing provides a means of motion control and easy manipulation of various manufacturing hardware.

The methods and software described in this paper allow the creation of different kinds of milling and grinding machines which are later compared with the actual existing machines and the parts produced by them. Three virtual systems are presented in this paper. One system was compared to the actual system operating in the CAD&CAM and Expert Systems Laboratory, and another was designed for stereoscopic view experiment. The third is a new machine that is in the design process. Also some examples of workpiece finish produced by virtual machining are described.

The work presents an effort to extend virtual manufacturing techniques in design, testing demonstration and manufacturing equipment and processes as well as the teaching of design and manufacturing. The work was conducted at the University of Connecticut using Silicon Graphics systems equipped with inventor, GL library and C compilers.
Hybrid Least Squares Finite Element Methods for Reissner-Mindlin Plates
Authors: Thompson Lonny L. , Tong Yuhuan
Published: December 2021

An assumed-stress hybrid 4-node plate element is developed based on the Hellinger-Reissner variational principle modified with a generalized least-squares operator for accurate vibration and wave propagation response of Reissner-Mindlin plates. The least-squares operator is proportional to a weighted integral of a differential operator acting on the residual of the steady-state equations of motion for Reissner-Mindlin plates. Through judicious selection of the design parameters inherent in the least-squares modification, this formulation provides a consistent framework for enhancing the accuracy of mixed Reissner-Mindlin plate elements that have no shear locking or spurious modes. Improved methods are designed such that the complex wave-number finite element dispersion relations closely match the analytical relations for all wave angle directions. For uniform meshes, optimal methods are designed to achieve zero dispersion error along given wave directions. Comparisons of finite element dispersion relations demonstrate the superiority of the new hybrid least-squares plate element over the underlying hybrid element, and standard Galerkin elements based on selectively reduced integration. Numerical experiments validate these conclusions.
Correlation Between Register Pressure Drop and Noise
Authors: Humbad Niranjan G. , Chudzinski Andy
Published: December 2021

During the register design for automotive applications, airflow pressure drop and noise generation have to be considered. Testing different register design concepts for flow and noise can not be easily performed in the vehicles. Therefore, a simple measurement method was devised to evaluate the register as a component for flow and noise. The register to be evaluated was mounted on one face of a 35 × 35 × 35 cm box and flow was provided from the opposite face of the box. Pressure drop was measured in the box at various airflow rates. Noise measurements were carried out in semi-anechoic room. The noise and flow measurement data on 9 registers showed a large spread in flow pressure drops and noise levels at a given airflow (suggesting a large variation in register to register designs). The measured data is compared with theory to predict A-weighted sound pressure levels. This prediction model can be used in predicting sound pressure levels from measured or calculated flow pressure drop values.
Visualization of Sound Radiation From a Bowling Ball
Authors: Leach Kesho , Wu Sean F.
Published: December 2021

This paper presents results of an investigation on visualization of sound radiation from a bowling ball via the Helmholtz Equation Least Squares (HELS) method [Wang and Wu, 1997; Wu and Wang, 1998; Wu and Yu, 1998]. In conducting the tests, the bowling ball was excited by a vibration shaker using a random signal. The radiated acoustic pressures were measured over both conformal and planer surfaces at certain distances away from the source. The measured data were taken as the input to a computer model based on the HELS formulation. The reconstructed acoustic pressures on the surface and in the field were compared with the measured data at the same locations. Also shown are comparisons of the reconstructed and measured acoustic pressure spectra at various locations on the bowling ball surface. Results demonstrate that the accuracy of reconstruction based on measurements over a conformal surface is much higher than that over a planar surface. This is because a planar surface often extends beyond the near-field region, thus making the accuracy of measurements inconsistent. Nevertheless, satisfactory visualization of acoustic pressure distribution over the entire bowling ball surface can still be obtained, at least in the low-to-mid frequency regime, based on the measurements over a finite, planar surface on one side of the source. Such a capability is unique to the HELS method. However, the efficiency of numerical computations of the HELS method is expected to deteriorate at high frequencies, a difficulty inherent in all expansion theories.
Combined Transducer and Nonlinear Tissue Propagation Simulations
Authors: Wojcik Gregory L. , Mould John C. , Carcione Laura M.
Published: December 2021

Ultrasonic imaging system evaluation is often based on models of the transducer as a distribution of baffled piston sources, and of the tissue as a homogeneous, linear acoustic medium, e.g., Jensen’s Field code. In reality, these are fairly gross idealizations, since the transducer exhibits more complicated response modes and real tissue is inhomogeneous and nonlinear. Greater model fidelity would be useful, especially in the context of transducer design qualification, second harmonic imaging, and acoustic power indices. To this end we combine 2D finite element models of transducer dynamics with highly accurate 2D finite difference propagation models in the large-scale inhomogeneous tissue cross-sections. Transducer models employ the time-domain code, PZFlex, and tissue models utilize a new pseudospectral solver to be included in PZFlex. The pseudospectral algorithm solves the inhomogeneous acoustic wave equation using FFTs for high order approximation of the spatial differential operator and a fourth-order, explicit time integrator. Second-order (B/A) nonlinearity and frequency-accurate, causal absorption are included. We describe the algorithmic and modeling issues, and present a suite of simulations in lossy, nonlinear abdominal cross sections and tissue showing coupling of the 1D medical array to the tissue model and scattering from deeper inhomogeneities and back to the transducer. In contrast to paraxial schemes, like the KZK method, details of the field transmitted from the transducer and all backscatter within the model are included. However, models are currently limited to 2D (plane or axisymmetric) on readily available hardware.
Edge Flutter
Authors: Chang Young B. , Cho Chang H. , Moretti Peter M.
Published: December 2021

During manufacturing processes of thin materials (called webs) such as papers, photographic films, and magnetic films, the free edges of a web can vibrate violently due to the airflow in the cross direction. A traveling-wave analysis was done based on linear potential flow theory, and the critical flow velocity, wave velocity, wavelength and flutter frequency were predicted. Experimental verification was done in a wind tunnel built around a web-translating machine. Two laser-Doppler vibrometers were used for non-contact measurement of wave characteristics. For flexible webs, the theory and test results show good agreement. Test results for stiff webs, however, deviate from the prediction.
Force Distribution Dependence of Sound Radiation From a Doubly Rib-Stiffened Plate
Authors: Feit David , DiPerna Daniel
Published: December 2021

Analytical formulae for both the velocity spectrum and the acoustic far-field radiated sound pressure for a doubly rib-stiffened (small frames and bulkheads) fluid-loaded elastic plate, excited by several different force distributions, are derived. The force distributions are (1) a line-force applied at a single point and (2) two Gaussian distributed force intensities whose effective width either spans the small rib spacing or the large rib spacing. The far-field sound pressure as a function of frequency is calculated. The concentrated line force case shows evidence of frame interference effects (sometimes referred to as Bloch waves) in the radiated pressure fields. These arise from coherent interaction of the pressure fields emanating from the frame reaction forces and the applied force pressure field. The frequencies at which these coherence effects are manifest depend on the stiffeners’ spacing as compared to the fluid-loaded flexural wavelength. The Gaussian force distribution eliminates these interaction effects depending on whether or not the effective force width is greater or less than the respective rib spacing.
Micro-Stereolithography of 3D Complex Ceramic Microstructures and PZT Thick Films on Si Substrate
Authors: Jiang X. N. , Sun C. , Zhang X.
Published: December 2021

Microstereolithography of ceramics is investigated in this paper. Ceramic line width and lateral dimension control experiments are carried out and on the basis of these, three-dimensional alumina microstructures and PZT thick films on Si substrate are fabricated and characterized. A minimum line width of 5.7 μm (with the layer thickness of 10 μm) has been achieved. Three-dimensional ceramic microstructures with feature sizes ranging from 50 μm to 1mm are fabricated from alumina suspensions (50%∼59.5% Vol.). PZT thick films (50∼130 μm thick) have been successfully patterned on silicon substrate. The piezoelectric coefficients of the fabricated PZT thick films are measured as d33 of 100 pC/N and g33 of 59.5 × 10−3 Vm/N, which are more promising for applications compared with those of PZT films fabricated by other methods.
PIV Analysis of Instantaneous Flow Structures in an Inkjet Printhead
Authors: Zhang Hongsheng , Meinhart Carl D.
Published: December 2021

This paper presents experimental measurements and observations of instantaneous flow structures inside an inkjet printhead, using a micron-resolution Particle Image Velocimetry (PIV) system to record visualized flows and calculate velocity fields. The PIV technique uses 700 nm diameter fluorescent flow-tracing particles, a pulsed Nd:YAG laser, an epi-fluorescent microscope and an interline-transfer CCD camera to record images of a flow at two successive instances in time. By measuring how far a set of particles move during a specified duration of time, an estimate of the local fluid velocity can be obtained.

An electronic timing strategy has been developed to synchronize the PIV lasers, the CCD camera and the drop ejection system. An overall flow pattern during a 500 μs ejection cycle has been observed by phase-averaging hundreds of instantaneous velocity fields, which were recorded at 2–5 μs intervals throughout the cycle. A velocity field with spatial resolution of approximately 10 μm was obtained near the inkjet nozzle. Meniscus and nodes inside the printhead were also observed and recorded.
Design, Fabrication and Characterization of Micromirror Array for Display Application
Authors: Shin H. , Ko H. , Yoon Y. , Choi B.
Published: December 2021

A new design of micromachined mirror array for display purpose from Samsung Electronics is presented. Integrating multiple functions into a component and extensive use of photolithography make this design of mirror to be simple as well as easy to make.

The prototype is fabricated in an array of 50 × 50 micromirrors. The size of mirror plate is 50 × 50μm2 and the gap between them is 3μm. The mirror plate is tilted by the electrostatic force, and the angle is designed to be 10°.

Driving voltage for the finished micromirrors is 28v and the tilt angle is measured as 8.9°. The response time from the rest to full tilt and back to rest position takes about 20μs when it is driven at the natural frequency of 24.7kHz.

In the reliability point of view, the importance of anti-stiction coating can not be over stressed. Without one, most of the mirrors couldn’t survive a few contacts with the substrate. However, when proper anti-stiction coating is applied and atmosphere is controlled to eliminate the humidity, 94.6% of micromirrors were still rocking after 1.15 × 1010 cycles.

In a series of experiments, it was possible to show this new design of micromirror array could be used as a display device, when they are driven at a certain combination of addressing and bias signals. A variable character generation and PWM-type brightness control is successfully demonstrated.
An Electrochemically Actuated Micro Dosing System With Improved Dosing Control
Authors: Böhm Sebastian , Olthuis Wouter , Bergveld Piet
Published: December 2021

In this contribution a micromachined electrochemically-actuated micro dosing system is presented, which accurately can manipulate fluids in microsystems in the nanoliter range. The driving force to actively dispense liquids is provided by the electrochemical generation of gas bubbles (hydrogen and oxygen) by the electrolysis of an electrolyte. As these bubbles expand, they indirectly drive liquid out of a liquid filled reservoir, which is in hydraulic contact with the electrolyte in the bubble reservoir. The dosing system consists basically of a micromachined channel/reservoir structure in silicon, realized by dry reactive ion etching (DRIE). On top of this silicon fluidic board, a Pyrex® cover is bonded on which a set of electrodes is structured. These electrodes are applied for the generation of gas bubbles and at the same time, to measure the impedance of the gas/electrolyte mixture that is formed after bubble generation. It will be shown that this measured impedance reflects the gas bubble fraction in the bubble reservoir and that this parameter can be applied in determining the dosed amount of fluid. Besides the integrated sensor/actuator electrodes, measures have been taken to reduce the catalytic back reaction from the hydrogen oxygen gas mixture to water, as have been observed in the past.
Fabrication of a Free Floating Silicon Gate Valve
Authors: Papavasiliou Alexandros P. , Liepmann Dorian , Pisano Albert P.
Published: December 2021

This paper introduces an active planar microvalve with free floating moving pieces and a novel process for fabricating that valve. The valve presented has all of its moving pieces and actuation in the plane of the wafer in which it is microfabricated. The valve can be moved up to 100 μm using thermally generated vapor bubbles to provide actuation. The fabrication process involves bonding a thin (∼100μm) wafer to a handle wafer with epoxy. The moving pieces are then defined with DRIE etching and released from the epoxy bond with an oxygen plasma. The theoretical performance of the valve is presented as well as experimental results.
DSMC Simulation of Microfilter Elements
Authors: Aktas Ozgur , Aluru N. R. , Ravaioli Umberto
Published: December 2021

Direct Simulation Monte Carlo (DSMC) analysis of micro-filter elements for collection of airborne particles is considered in this paper. Three filter elements with different dimensions were simulated. Boundary conditions were chosen to simulate an array of filters. Our results indicate that, as the filter gets smaller, the slip flow will be critical in determining flow characteristics. The change in the flow rate and the characteristics of the flow in different dimensions are investigated.
Modeling and Prediction of Sub-Micrometer Heat Transfer During Thermomechanical Data Storage
Authors: King William P. , Santiago Juan G. , Kenny Thomas W. , Goodson Kenneth E.
Published: December 2021

Heat transfer governs the bit size and writing rate during sub-micrometer thermomechanical data storage with Atomic Force Microscope (AFM) cantilevers. The present work predicts the temperature distribution and rates of heat flow in the AFM tip and the substrate as functions of the peak cantilever temperature, the diameter of the tip-substrate contact, and the thickness of the deforming polymer coating on the silicon substrate. The calculations consider increased phonon scattering, radiation losses, and gas conduction losses at the silicon tip boundaries. Nearly ballistic phonon transport in the tip augments the dependence of the heat rate into the polymer on the tip-polymer contact diameter. For a cantilever heater temperature of 700 K and a polymer layer thickness of 80 nm, the temperature at the tip-polymer interface is predicted for contact diameters from 4 nm to 50 nm. This work models the deformation of the polymer layer during data writing and predicts data bit size as a function of tip temperature and writing time. These simulations will help optimize the design of the cantilever and the polymer data layer, with the goal of increasing the spatial density and rate of bit formation.
Global Approximation: Performance Comparison of Different Methods, With an Application to Road Vehicle System Engineering
Authors: Gobbi Massimiliano , Mastinu Giampiero
Published: December 2021

Optimisation of complex mechanical systems has often to be performed by resorting to global approximation. In usual global approximation practice, the original mathematical model is substituted by another mathematical model which gives approximately the same relationships between design variables and performance indexes. This is made to ensure much faster simulations which are of crucial importance to find optimal solutions. In this paper the performances of four global approximation methods (Neural Networks, Kriging, Quadratic Approximation, Linear Interpolation) are compared, with reference to an actual optimal design problem. The performances of a road vehicle suspension system are optimised by varying the system’s design variables. The Pareto-optimal set is derived symbolically. The performances of the different approximation methods taken into consideration are assessed by comparing the numerical- and the analytical-Pareto-optimal results. It is found that Neural Networks obtain the best accuracy.
Virtual Reality Assisted Visual Feedback of Cervical Spine Kinematics for Improved Control of Active Range-of-Motion Maneuvers
Authors: Sakai Jonathan L. , Gilbertson Lars G. , DeFrate Louis E. , Donaldson William F. , Kang James D. , Woo Savio L.-Y.
Published: December 2021

The current study investigated the efficacy of virtual reality (VR) assisted visual feedback for improving control of voluntary movements of the cervical spine during performance of active range-of-motion maneuvers. Active range-of-motion was assessed in 10 asymptomatic volunteers, both without and with VR-assisted visual feedback of overall cervical spine rotations. 8 of the 12 secondary rotations were significantly lower (p < 0.01) with VR feedback than the corresponding secondary rotations without VR feedback. No statistically significant differences were found between the primary rotations attained without VR and with VR feedback. These results support the use of VR-based visual feedback for enabling control of in-vivo cervical spine kinematics.
PIV Measurements of Flow Distal to Polyurethane Heart Valve Prosthesis Under Steady and Pulsatile Flow Conditions
Authors: Kim Jung Kyung , Sung Jaeyong , Yoo Jung Yul , Chang Jun Keun , Min Byoung Goo
Published: December 2021

Hemodynamic performance of a polyurethane heart valve prosthesis was evaluated in comparison with that of Björk-Shiley Monostrut mechanical valve in steady and pulsatile flow. Pressure losses through the valves were obtained from the streamwise pressure distributions downstream of the valves under steady flow condition. Unsteady and turbulent flow through the heart valve prostheses were investigated using PIV in conjunction with the opening behaviors of valve leaflets. Direct measurements of the wall shear stress by hot-film anemometry (HFA) were compared with the PIV data. By examining the velocity field downstream of the polyurethane heart valve, it is known that high shear stress regions exist at the interface between strong axial jet flows along the wall and vortical flows in the central area. In addition, there are large recirculation regions near the valve, where thrombus formation can be induced by accumulation of damaged blood cells. A correlation between the flow pattern downstream of the valve and the corresponding opening posture of the polyurethane valve leaflet gives useful data necessary for improved design of the superstructure and leaflet geometry of the valve.
Advances in 3-D Vascular Ultrasound Imaging
Authors: Fenster Aaron
Published: December 2021

In spite of the progress in the understanding of atherosclerotic disease made in the past two decades, neither the triggering mechanisms for carotid plaque haemorrhage and disruption, or the importance of plaque ulceration are well understood. Controversies exist because the mechanisms are complex and agreement on definitions (e.g., ulceration) is lacking. Advances in imaging techniques are helping to diagnose and quantify plaque morphology, composition, extent and ulceration (Steifler et al. 1994). In this paper we report on our work focusing on the development of improved non-invasive imaging tools, which will improve the accuracy and reduce the variability of the carotid exam and allow better serial monitoring. These will help elucidate the mechanisms contributing to the last phase of atherosclerosis — plaque disruption and haemorrhage.
Thermomechanical Characterization of Collagen Crosslinking in Developing Cardiovascular Tissues
Authors: Wells Sarah M. , Naimark Wendy A. , Lee J. Michael
Published: December 2021

We have used hydrothermal isometric tension (HIT) tests to assess developmental changes in collagen crosslinking in the ovine thoracic aorta and pericardium. Tissue strips were loaded under isometric tension and heated to 90°C for 3 hrs. Load relaxation at this temperature is associated with collagen hydrolysis and chain slip-page, the half-time of load decay (t1/2) being an indicator of collagen crosslinking. t1/2 was computed before and after tissues were treated with NaBH4 which stabilizes immature crosslinks. The t1/2 of untreated tissue increased from the lamb to the adult, indicating that collagen crosslinking increased postnatally. Furthermore, the t1/2 of NaBH4-treated lamb tissue (3d pericardium and 21d aorta) was similar to that of untreated adult tissue, suggesting that much immature crosslinking in the lamb is stabilized postnatally. These observations suggest (i) increased crosslinking occurs postnatally, (ii) this increase is largely due to the conversion of immature crosslinks into their mature, heat stable form (Naimark et al., 1998, Wells et al., 1999).
Mechanical Strength of PhotoFix® and Glutaraldehyde Treated Porcine Aortic Valve Wall Tissue
Authors: Talman Eric , Poehlmann Jeffery
Published: December 2021

The use of prosthetic heart valves manufactured from porcine aortic valves is commonplace. The standard design incorporates a valve mounted on a plastic or metal stent to facilitate implantation. More recently stentless valves have gained favor. These valves include the intact aortic root or a composite design. Composite valves are assembled using tissue from different valves cut axially along the aorta between valve leaflets. Composite designs are used to eliminate the right coronary leaflet substantially reducing the associated muscle shelf which has been the cause of high re-operation rates in the past (1). We are developing a tri-composite, PhotoFix® stentless valve, combining three non-coronary leaflets and it is the goal of this study to examine the mechanical strength of the associated aortic tissue. This is being done to ensure adequate strength of the material to withstand physiological loading. The strength will be compared to estimated in vivo loading conditions as well as to the strength of tissue from a commercially available glutaraldehyde fixed product.
3-D Stress Analysis in Cultured Endothelial Cells Exposed to Fluid Shear Stress
Authors: Ohashi T. , Sugawara H. , Ishii Y. , Sato M.
Published: December 2021

Under fluid shear stress, applied both in vivo and in vitro, vascular endothelial cells show morphological changes. After applying shear stress, cultured endothelial cells showed elongation and orientation to the flow direction (Kataoka et al., 1998). Moreover, statistical image analysis showed that intercellular F-actin distributions were confirmed to change depending on the shear stress and the flow direction. Thus, the endothelial cell morphology relates closely with the cytoskeletal structures. Intercellular stress distributions in the cells may be also accompanied by the reorganization of cytoskeletal structures. The use of both atomic force microscopy measurements (AFM) of endothelial cell surface topography and computational fluid dynamics of shear stress distributions acting on the cell surface, it has revealed that the surface geometry defined the detailed distribution of shear stress (Davies et al., 1995).
Shape Memory Alloy Actuated Robot Protheses: Initial Prototypes
Authors: Pfeiffer Charles , Mavroidis Constantinos , DeLaurentis Kathryn , Mosley Mike
Published: December 2021

This paper describes the goals and current accomplishments of this research. The main thrust of this effort is to design artificial limbs that are lightweight, compact and dexterous, that mimic human anatomy and maintain a high lifting capability. The key to satisfying these objectives is the use of Shape Memory Alloy (SMA) artificial muscles as actuators. A general methodology to find the placement of SMA wires to achieve desired ranges of motion is presented. Three experimental prototypes, emulating human skeletal structures that are actuated by SMA artificial muscles are described in detail.

It is expected that upper extremity amputees will greatly benefit from the commercialization of the novel robot prosthetic devices that will be developed in this research. These lightweight prostheses with high lifting capabilities, force-reflective characteristics and multi-degree of freedom dexterity will tremendously improve the capabilities of amputees and therefore will attract their interest. In addition, our SMA actuated robotic devices can find other commercial applications. Of special interest to our team are two other commercial applications: space robotic systems and robot toys.
QCT Cortical Shell Thickness as a Predictor of Vertebral Body Strength for Cynomolgus Monkeys
Authors: Dickerson Clark R. , Saha Subrata , Hotchkiss Charlotte
Published: December 2021

Many studies have investigated the ability of vertebral trabecular BMC measurements to predict overall vertebral strength. Far fewer investigations, however, have examined the use of cortical shell data to predict maximum strength. In this study, we are investigating the load-carrying characteristics of the cortical region of vertebral bodies Lumbar vertebrae from macaca fascicularis were examined by QCT and mechanically tested in compression. Our results show that cortical thickness, as determined by QCT, is a significant predictor of vertebral maximum stress (R = 0.62, p < 1 E−5). This relationship is improved when the cortical thickness is compared to load (R = 0.77, p < 5 E−10). This information reveals that the cortical shell plays a major role in determining the load carrying capacity of lumbar vertebrae, and that examination of cortical thickness will give an approximation of maximum vertebral stress and load.
Evaluation of the Revised NIOSH Lifting Equation (1991): On the Asymmetric Multiplier
Authors: Li Yi-Chun , Lavender Steven A. , Natarajan Raghu N. , Andersson Gunnar B. J. , Amirouche Faird M. L.
Published: December 2021

The NIOSH 1981 lifting equation (NIOSH, 1981) [1] is based on biomechanical, physiological, psychophysical, and epidemiological criteria in order to identify the risk of low back injuries in bi-manual lifting. The 1991 revised lifting equation [2] expands the application scope of the 1981 equation for evaluating asymmetrical lifting tasks, lifts of objects with less than optimal hand-container couplings, and a larger range of work duration and lifting frequencies; also, the load constant is reduced from 40 kg to 23 kg; the Lifting Index (LI) and the Recommended Weight Limit (RWL) replace the Maximal Permissible Limit (MPL) and Action Limit to indicate the potential risk. LI is an actual lifted weight and uses RWL as its unit. If LI < 1, it assumes that more than 99% of males and 75% of females are capable of performing the lifting task and the risk of causing low back injury is nominal. If LI < 3, it assumes that less than 25% of males and 1% of females are capable of performing the lifting task, and a greater percentage of manual materials handling workers is likely to be at risk of developing low back pain.

Waters et al. (1993) [3] noted that although the 1991 equation has not been fully validated, the recommended weight limits derived from the revised equation are consistent with or lower than those generally reported in the literature. Hidalgo et al. (1995) [4] showed that the results of cross-validation of the NIOSH limits for psychophysical criterion confirmed the validity of assumptions made in the 1991 NIOSH revised lifting equation and for the biomechanical and physiological criteria which were not in total agreement. This validation was based on the psychophysical, biomechanical and physiological data recently published in the subject literature (Genaidy et al. 1990, Snook and Ciriello 1991, Genaidy et al. 1993, Asfour et al. 1991) [2]. Most of the validation limit in the sagittal plane lifting and 3.4 KN compressive force on the spine is the standard line in biomechanical criteria.

The 1991 revised NIOSH lifting equation recommended that the allowable weight of lift be reduced by about 30% for lifts involving asymmetric twists of 90 degrees (Water et al., 1993), which considers asymmetric multiplier in the sagittal lifts as 1 and 90 degrees lifts as 0.7, and linearly reduced between the sagittal lifts and 90 degrees lifts. This maximum acceptable lifting capacity is applied not only in the heavier loads but also in the lighter loads. The hypothesis in evaluating NIOSH lifting equation on the asymmetric multiplier is that asymmetric multiplier may be appropriate adopted in the heavier loads (LI = 3) but will be improper applied in the lighter loads (LI = 1). Several types of data, static and dynamic data of the L5/S1 forces, moments, and compressive forces, are observed.
Direct Hydraulic Permeability Measurements of Agarose Hydrogels Used as Cell Scaffolds
Authors: Soltz Michael A. , Stankiewicz Anna , Ateshian Gerard , Mauck Robert L. , Hung Clark T.
Published: December 2021

The objective of this study was to determine the intrinsic hydraulic permeability of 2% agarose hydrogels. Two-percent agarose was chosen because it is a concentration typically used for encapsulation of chondrocytes in suspension cultures [3–5], Hydraulic permeability is a measure of the relative ease by which fluid can pass through a material. Importantly, it governs the level of interstitial fluid flow as well as the interstitial fluid pressurization that is generated in a material during loading. Fluid pressurization is the source of the unique load-bearing and lubrication properties of articular cartilage [1,17] and represents a major component of the in vivo chondrocyte environment. We have previously reported that 2% agarose hydrogels can support fluid pressurization, albeit to a significantly lesser degree than articular cartilage [18]. Interstitial fluid flow gives rise to convective transport of nutrients and ions [6,7] and matrix compaction [9] which may serve as important stimuli to chondrocytes. We report for the first time the strain-dependent hydraulic permeability of 2% agarose hydrogels.
Biomechanics of Cervical Spine Ligaments
Authors: Yoganandan Narayan , Kumaresan Srirangam , Pintar Frank A.
Published: December 2021

The purpose of the present study was to determine the geometrical and biomechanical properties of human cervical spine ligaments from the axis to the first thoracic level. A total of 33 human cadavers were used. Geometrical data included the length and cross-sectional area measurements. Biomechanical properties included force, deflection, stiffness, energy, stress, strain, and Young’s modulus of elasticity. These data were obtained for the anterior longitudinal ligament, posterior longitudinal ligament, joint capsules, ligamentum flavum, and interspinous ligament. Geometrical characteristics were determined using cryomicrotomy techniques and biomechanical properties were obtained using in situ failure tensile testing. Force-deformation responses of each ligament type and at each spinal level were normalized. The joint capsules and ligamentum flavum exhibited the highest area of cross-section (p < 0.005). The longitudinal ligaments responded with the highest length measurements. The strain parameters were higher for the ligaments of the posterior complex, i.e., interspinous ligament, joint capsules, and ligamentum flavum, than for the ligaments of the anterior complex, i.e., the anterior and posterior longitudinal ligaments. In contrast, the failure stress and Young’s modulus of elasticity were higher for the anterior and posterior longitudinal ligaments compared to the ligaments of the posterior complex. These findings delineate the relative contribution of the anterior and posterior ligaments in the human cervical spine.
Electromyographic Activity of Trunk Muscles During Flexion-Distraction Treatment of Low Back Patients
Authors: Gudavalli Maruti R. , Backman Jerrilyn A. , Kirstukas Steven J. , Kadiyala Anant V. , Patwardhan Avinash G. , Ghanayem Alexander J.
Published: December 2021

The objective of this study was to determine the electromyographic (EMG) activity of the superficial muscles during the treatment of low back patients during a conservative procedure known as the Cox flexion-distraction procedure. A total of 33 low back pain patients were recruited for this study from chiropractic and allopathic orthopedic clinics. EMG signals were collected while the patient was in a prone relaxed position, during the treatment using the flexion-distraction procedure, and during maximum voluntary exertions in the three planes (flexion, extension, left and right lateral bending, and left and right twisting). The mean values of the Root Mean Square (RMS) values of EMG ratios during treatment versus resting indicate that the muscles are active during the treatment. This activity is more than the activity at rest. However the mean values of the RMS EMG ratios (during treatment versus maximum voluntary contraction) are small indicating that the muscle activity during treatment may not influence the treatment loads. The left and right muscles in all muscle groups were similarly active. During the treatment, erector spinae muscles were the most active, followed by the external oblique, and the rectus abdominus muscles. The results from this study provide quantitative data for the muscle activity during the flexion-distraction treatment. This information can be incorporated into computer models to estimate the loads generated during the flexion-distraction treatment due to the muscle activity compared to the loads generated by the chiropractic physician.
Effect of Pelvic Tilt and Lordosis on Passive-Active Synergy in Lumbar Spine Under Axial Compression
Authors: Shirazi-Adl A. , Sadouk S. , Parnianpour M.
Published: December 2021

The coupled load sharing-posture response of the human lumbar spine under relatively large compression loads with and without sagittal rotations remains yet to be adequately understood. Such investigations should account for the observed changes in the pelvic tilt and lumbar lordosis and influences thereof on the passive-active equilibrium and stability of the human spine. In pursuit of these goals, the objectives of the current work, using a nonlinear finite element model of the lumbosacral spine, are set as follows: - Study of the synergy of the active-passive lumbar spine under an axial compression load of 2800 N in quasi-neutral position; - Development of an optimal posture accounting for the postural adaptation of the spine in order to withstand the applied 2800 N load in quasi-neutral posture; and - Evaluation of local lumbar muscle forces in order to maintain the equilibrium of the system in such optimal posture.
Temperature Effect on Damage in S2 Glass/Toughened Epoxy Composites
Authors: Cheung C. K. , Long X. , Liaw B. M. , Delale F. , Walser A. D. , Raju B. B.
Published: December 2021

Composites made of S2 glass fibers and toughened epoxy with various lay-up configurations ([0°]24, [0°2/90°2]3S, [45°2/−45°2]35, and [0°3/45°3/90°3/−45°3]S) were tested under uniaxial tension at various temperatures from −60 to 125°C. The stress-strain curves are distinctly nonlinear, which can be attributed to various types of damage progression. Fiber breaks, fiber-matrix debonding, and fiber pull-out characterized damage in the [0°] and [0°/90°] specimens, which have stress-strain relations resembling those for quasi-brittle materials. Shear failure and delamination were dominant in the [±45°] specimens and resulted in stress-strain curves similar to those of quasi-ductile materials. The tensile behavior of the [0°/45°/90°/−45°] specimens, as expected, laid in between the two extremes. In addition to stacking sequence, temperature also exerted great influence on the stress-strain behaviors of these composites. In general, specimens tested at lower temperatures behaved more stiff and brittle than those tested at higher temperatures. Finally, micromechanics-based finite element analyses were conducted to verify the afore-mentioned various failure modes.
Mechanical Properties and Damage Growth of Notched Polymeric Composites Subjected to Adverse Environmental Conditions Under Sustained Loads
Authors: Buck Stephanie E. , Lischer David W. , Nemat-Nasser Sia
Published: December 2021

Structural composite materials are being investigated for use in applications which will require long-term durability in various environments under external loads. Flaws may be created in these composite materials during manufacturing, machining, or use. Adverse use conditions in the presence of seemingly minor flaws may result in significantly reduced mechanical properties and changes in the microstructure and damage mechanisms of composites. E-glass/vinyl ester composite coupons with a single edge notch have been conditioned in water for periods of up to 7,800 hours at room temperature and at an elevated temperature, mostly under a sustained tensile load, to determine the changes in the mechanical properties and damage mechanisms which occur due to the presence of the flaw. The tensile strength has been found to decrease by at least fifteen percent for notched samples when compared with unnotched samples subjected to the same environmental and load conditions. During conditioning, the dominant damage mechanisms have been found to change from transverse matrix microcracking, fiber cracking, and occasional edge delaminations for unnotched specimens to the growth of a significant matrix crack from the notch tip and local tow debonding for notched specimens. Nondestructive techniques have been used to observe the damage in the vicinity of the notch tip.
Fatigue Modulus Concept and Life Prediction of Thick-Section S2-Glass/Vinylester Composites Under Flexural Loading
Authors: Mahfuz Hassan , Zaman Kamruz , Haque Anwarul , Vaidya Uday , Mohamed Hisham , Jeelani Shaik
Published: December 2021

Fatigue life prediction of thick-section S2-Glass fiber reinforced Vinylester composites has been studied analytically using fatigue modulus concept. Flexural fatigue tests were conducted under three point bend configuration. A stress ratio of R = 0.1 and a frequency of 3 Hz has been used for the fatigue tests. Fatigue data have been generated at five load levels; 85%, 80%, 70%, 60% and 55% of the ultimate flexural strength. Using these fatigue data, S-N diagram has been generated. Fatigue modulus has been determined by the slope of the line drawn on a plot of applied stress vs. resultant strain at specific loading cycle. Since fatigue modulus degrades with cycle number, it was assumed that the degradation rate follows a power function of fatigue cycle. Using this concept, a practical and applicable equation for predicting fatigue life is established.

The Fatigue Life Prediction method used in this investigation requires two distinct parameters, namely applied stress level and two material constants. These material constants have been determined from the fatigue test data. A comparison has been made between the analytical prediction and the experimentally obtained S-N curve. The correlation between the two has been observed to be excellent. Flexural failure modes have also been identified as extensive delamination, fiber fracture and fiber kinking. Microscopic observation shows that all failures are predominantly on the tensile side with slight fiber kinking and matrix crushing on the compression side.
A Constitutive Model for Distributed Microcracking in Titanium Matrix Composite Laminae
Authors: Ball D. L. , Chan W. S.
Published: December 2021

The ply constitutive relations of an energy-based model for distributed microcracking in continuous fiber reinforced metal matrix composites are presented. Simple models for damage progression are used in conjunction with these damage dependent constitutive relations to allow the prediction of fatigue life under constant amplitude, isothermal conditions. The microcracking model is discussed in the context of fatigue analysis of unnotched titanium matrix composite laminates. Analytical results generated by using this model in a unidirectional laminate analysis algorithm are presented and compared with experimental results.
Detecting Delamination Damage in Tapered Rotorcraft Flexbeams Using the Direct Field Response
Authors: Purekar Ashish S. , Pines Darryll J.
Published: December 2021

Flexbeams in hingeless rotors have non-uniform geometries to form virtual hinges for the lead-lag and flap motions of blades. For bearingless rotors, the flexbeams also contain a virtual hinge for the pitch of the blades. Commonly, flexbeams are damaged through high cyclic and vibratory loadings. Damage in the form of delamination for composite beams degrade performance and can potentially cause catastrophic failure. In a beam of uniform cross section, the transverse dynamics of a beam can be characterized by four wavetypes. By tracking the progression of the waves along the beam and back again, the wavetypes can be used to infer damage. While this process has worked well for uniform beams with cracks, tapered beams are difficult to model. To avoid high fidelity spectral finite element modeling of tapered flexbeams, this paper introduces a concept involving the use of the dereverberated transfer function response to infer delamination damage. A “virtual control” is introduced to obtain the dereverberated transfer function with and without damage. Analytical and experimental results suggest that this approach can be used to qualitatively infer damage in flexbeams with tapered geometries. Preliminary experimental results are displayed for flexbeams with varying thickness and width tapers.
Measured Constitutive Behavior of Several Compositions of PZT
Authors: Lynch Christopher S. , Davis Brandon
Published: December 2021

PZT is often used as an actuator material. The actuation properties are dependent on several factors including composition, grain size, and processing; as well as on loading and load history. The effect of grain size and composition on the hysteresis behavior of PZT was experimentally characterized. The results show the effects of preload stress and temperature on the actuation capability of this class of materials.