bluuebunny/crossref_metadata_2025 huggingface dataset:
Techniques to Evaluate Heavy Truck Dynamics Using Multi-Body Simulation
Authors: Gunter David D. , Bylsma Wesley W. , Letherwood Michael D.
Published: December 2021

This paper will describe the use of simulation at the US Army Tank-automotive and Armaments Command – Research, Development and Engineering Center (TARDEC) to investigate the vehicle stability, handling, yaw stability and ride quality of large military trucks. The multi-body modeling methodology used to create the vehicle models as well as the characteristic data used to define the models and their subsystems will be described. The criteria used to evaluate the dynamic stability characteristics, and the truck yaw stability / handling performance are identified. Also, the “virtual” tests performed in simulation to evaluate these performance characteristics are discussed. Efforts to improve the vehicle’s performance through an iterative modify-simulate-evaluate procedure, and experiments using the computer models designed to identify parameter modifications that have the greatest impact the vehicle’s yaw stability performance are also described. Design parameter trade-offs between lateral stability and yaw stability influences are identified as well as efforts to balance these trade-offs to arrive at an optimum configuration.
Effects of Heavy Vehicle Speeds on the Structure and Vibration of Bridges
Authors: Sammartino Giuseppe , Amirouche Farid , Chen Zhen L. , Wang Ming L.
Published: December 2021

Heavy Vehicles speeds and dynamic loads are critical factors to bridge’s structure fatigue and rapid deterioration. The proposed paper addresses the modeling and simulation of dynamic loads of heavy vehicles, such as trucks and buses, on bridges and the effects of their speed on frequency response. In light of the above analysis, this paper proposes a method on how to minimize the structural vibrational of the combined vehicle and bridge system using semi-active suspension control. The vehicle dynamic load is minimized through an optimization scheme to yield an impact force with negligible bridge lateral deflection. The dynamic coupling between the vehicle and bridge are studied by examining the modes that are most likely to be excited by the vehicle speed and the roughness of the bridge surface.

The models consist of a bridge and a heavy vehicle. The bridge is modeled as continuos, lightly damped beam with different supports defined by the boundary conditions. The vehicle is a multi-degree of freedom (MDOF) system undergoing motion in one plane.

The methods of solution consist of a simple supported beam that closely simulates the first three beam modes of the Kishwaukee Bridge in Rockford, Illinois. The surface of the bridge generates some random excitation that serves as input to the vehicle, this is commonly known as the roughness of the bridge surface. The heavy vehicle is moving from left to right of the simply supported beam. The system is analyzed and optimized by semi-active control algorithms.

Close form numerical solution is obtained by a set of second order differential equations for the bridge-vehicle system. Experimental data obtained from the vibration testing of Kishwaukee Bridge (Illinois) were collected and validated with a FEM model. Only the first three beam modes were used due to the experimental limitations and the actual structural condition of the bridge. Using MATLAB a simulation is obtained by inputting the linear time-variant equations and optimizing the system.

Simulations of bridge vertical motion under different dynamic load conditions were examined and the results of bridge structure response were analyzed by comparing the effects of passive versus semi-active suspension controls. The method shows effectively how we can reduce the dynamic load force magnitude and its frequency of impact. The latter is usually associated with structural damage caused to the bridge.
Dynamics of a Three Wheeled Vehicle Driven by DC-Motors
Authors: Bestaoui Yasmina
Published: December 2021

This paper presents dynamics models of a conventionally driven tricycle. The derivation of dynamics models uses Lagrangian approach, introducing electro-mechanichal equations of the motors. If the inductance L cannot be ignored then combining motor equations with vehicle dynamics leads to a set of third order differential equations. Then analysis of these models is performed, generalizing some well-known properties of kinematics models.
Planar Dynamics and Control of a Two-Wheeled Single-Axle Vehicle
Authors: Abbott Michael S. , Soper R. Randall , Grove Donald E. , Reinholtz Charles F.
Published: December 2021

A two-wheeled, uniaxial, differentially driven vehicle possesses many salient advantages when compared to traditional vehicle designs. In particular, high traction factor, zero turn radius, and inherent stability are characteristics of this configuration. Drive torque is provided via a swinging reaction mass hanging below the axle. While mechanically simple, the resulting nonlinear vehicle dynamics can be quite complex. This work develops a planar dynamic model for the two-wheeled vehicle using traditional Hamiltonian techniques. Numerical simulations of the system step response demonstrate behavioral bifurcation and other nonlinear characteristics. However, the simple linear proportional-derivative control designed herein provides robust performance over steady slopes.
Orientation-Regulated Platforms for Use in Biplanar Bicycles
Authors: Grove Donald E. , Soper R. Randall , Abbott Michael , Reinholtz Charles F.
Published: December 2021

This work develops an active feedback control law that provides robust regulation for a pendulating platform attached to a new class of land vehicle. The biplanar bicycle is a novel two-wheeled single-axle differentially driven vehicle. The vehicle generates locomotive torques by driving against a reaction mass (comprised of the main chassis, motors, etc.), which is free to rotate. The lack of a fixed-orientation mount for peripheral and excitation-sensitive equipment may be a major disadvantage of this new vehicle class. However, active feedback control using a second reaction or proof mass to stabilize a platform fills this need. Here, the procedure for modeling and control of such a structure is demonstrated through the example of a camera spar for an autonomous biplanar bicycle. The dynamics of the example are developed using Lagrangian techniques. The application of optimal control theory to a linearized approximation of the plant is shown to provide robust regulation, with respect to perturbations and external disturbances, of the fully nonlinear system.
Design of a Tibio-Talar Joint Replacement Wear Test Machine
Authors: Suggs Jeremy F. , Petrella Anthony J. , Smolinski Patrick J. , Miller Mark C. , Conti Stephen F.
Published: December 2021

Application of an ankle joint replacement has become more effective with new developments in surgical technique and biomaterials. Although clinical trials are proving successful, little literature is available concerning long-term wear characteristics. To address the issue of wear, a prototypical machine has been designed to model the force and displacement profile that the ankle undergoes during a normal walking cycle. Load application and joint rotation are both accomplished through the use of cams operating at 1 Hertz. With continuous operation, ten years worth of wear can be attained in about six months.

Component alignment and replication of the kinetic environment of the tibio-talar joint are the major issues in the design of the wear tester. Improper alignment of the components can lead to misleading results in both the wear pattern and magnitude. Incorrectly modeled ankle kinematics or load application can lead to similarly confounding results.
Capsulorrhexis Instrument Design for Use in Cataract Surgery
Authors: Turner Benjamin , Sulaiman Shamsul , Pidaparti R. M. , Valluri S.
Published: December 2021

A cataract develops when the lens of the eye becomes opaque, clouding one’s vision. This can be corrected by cataract surgery, where the opaque lens is removed and replaced with an artificial lens. During this surgery, it is necessary after entering the eye to cut the membrane covering the anterior capsule (Fig. 1) to allow access to the cataractous lens. The cutting of this membrane is known as capsulorrhexis.
An Assistive Device to Aid the Visually Impaired to Play Basketball
Authors: Murnyack Roberta , Viktoriany Khristi , Sediqe Ajmal , Chong Waiseng , Hefzy Mohamed Samir
Published: December 2021

The purpose of this project is to allow a visually impaired person to enjoy playing the sport of basketball in his/her driveway or yard. The project required adapting a portable basketball goal system so that a visually impaired person can experience this sport. The assistive technology developed consisted of instrumenting the pole with a custom built beacon to allow the person to know where the portable system is located, thus determining in which direction to shoot the basketball. The beacon, mounted on the pole, emits a continuous distinct beeping sound. Also, the hoop was instrumented with a sensor that allows the person to know if he/she makes a basket. A sound is triggered to signal when the basketball passes though the hoop successfully. Furthermore, the hoop was custom sized to increase the odds of making a basket.
Using Finite Element Analysis to Evaluate Countermeasures to Bone Demineralization During Long Duration Space Flight
Authors: Murphy Benjamin M. , Shackelford Linda C. , Todd Beth A. , Cuttino James F.
Published: December 2021

During long duration space flight, astronauts must exercise to prevent bone demineralization. Exercises are used as countermeasures to the bone mineral loss. The effectiveness of the countermeasures is closely related to the mechanical stress developed during the exercises. A finite element model of the human femur was developed to determine the stress distribution during weight bearing. The model was developed using serial, transverse magnetic resonance images. The finite element analysis performed on the femur model showed an area of high stress in the femoral neck of approximately 1,200 psi. The highest stress seen in the model was approximately 2,000 psi. This information will then be used to evaluate the proposed exercises to be used as countermeasures.
Evaluation of the Viscoelastic Properties of the Intact Medial Collateral Ligament in a Goat Model
Authors: Clineff Theodore D. , Debski Richard E. , Scheffler Sven U. , Withrow John D. , Woo Savio L.-Y.
Published: December 2021

The time and history dependent viscoelastic properties have been determined for the normal medial collateral ligament (MCL) of canine (Woo, 1981), porcine anterior cruciate ligament (Kwan, 1993), and human patellar tendon in a cadaver model (Johnson, 1994). The objective of this study was to use a combined experimental and analytical approach to quantify the viscoelastic properties of the intact MCL in a goat model. A thorough understanding of the viscoelastic properties at low strain levels is necessary to future studies of the healing MCL. The quasi-linear viscoelastic theory (QLV) (Fung, 1972) was used to characterize the properties of the MCL during stress relaxation.
Dependence of Yield Strain on Anatomic Site for Human Trabecular Bone
Authors: Morgan Elise F. , Arramon Yves P. , Kopperdahl David L. , Keaveny Tony M.
Published: December 2021

The yield strain behavior of trabecular bone has gained increased importance as evidence accumulates that remodeling and failure criteria can be expressed as a function of strain alone (Turner et al., 1997; Silva et al., 1998). These findings rely on the results of previous studies in which yield strains were found to be isotropic and generally independent of volume fraction (Turner, 1989; Kopperdahl and Keaveny, 1998; Chang et al., 1999), although relatively little work has been done to substantiate these results for human trabecular bone. Thorough consideration of the dependence of yield strain on volume fraction should include analyses of trabecular bone from different anatomic sites since site-dependent differences in trabecular architecture have been well-correlated with mechanical properties (Goulet et al., 1994). However, differences in testing protocols and in definitions of modulus and yield point (Linde, 1994) have led to discrepancies in reported yield strain values in the literature (Kopperdahl and Keaveny, 1998). This prevents inter-study comparisons of the yield strain behavior of human trabecular bone across different anatomic sites, and yet characterizing this behavior is a fundamental step both. In the validation of uniform strain adaptation models and in the development of failure criteria.
A New Method for Determination of the Tensile Modulus of Articular Cartilage In Situ in a Free-Swelling Configuration
Authors: Narmoneva Daria A. , Wang Jean Y. , Setton Lori A.
Published: December 2021

Studies of cartilage swelling have been used to demonstrate the effects of collagen network damage associated with osteoarthritis (OA) [1,7]. Elevated swelling, or increased hydration, is generally observed in fibrillated and degenerated cartilage where the integrity of the collagen network is insufficient to restrain the interstitial swelling pressure [8]. We recently developed an experimental method to quantify these swelling effects as components of a swelling-induced strain tensor in free-swelling tests of cartilage in situ [9]. Using this method, we were able to detect changes in swelling strains with cartilage degeneration in the meniscectomy model of OA [10]. In this study, we propose to quantify the material properties of canine and human cartilage studied in the free-swelling test and to compare them with site-matched values measured in uniaxial tensile testing. A triphasic constitutive model [6] was used to predict the components of strain in the free-swelling test for comparison with experimentally measured values. Values for the tensile modulus were found to compare well using the free-swelling and uniaxial testing methods. These findings demonstrate the potential of this new methodology for quantifying cartilage properties in small cartilage samples, such as in small animal models of OA.
Does the Load Carrying Capacity of Third Bodies Affect Contact Conditions in Total Knee Replacement (TKR)?
Authors: Wimmer Markus A.
Published: December 2021

Third-body wear is a frequently reported phenomenon in TKR, however, little attention has been paid to the load carrying capacity of third bodies. It may be possible that these particles accumulate to a quantity, sufficient to separate the articulating surfaces of the bearing. To address this question, the particle number for a complete separation was theoretically determined and compared to realistic values. Based on the results, a total separation of the artificial knee articulation appears likely and should be considered when interpreting surface wear based on common stress analyses. This seems to be reflected by clinical observation that flat tibial components do not wear faster than dished ones.
Etiological Expression of Heat Shock Protein 70 (HSP70) in Human Endothelial Cells With Hemodynamic Shear Stress
Authors: Chang Jun Keun , Han Dong Chul
Published: December 2021

The expression of heat shock protein 70 (hsp70) and the polymerization of the actin cytoskeleton of human umbilical vein endothelial cells (HUVECs) were investigated with the endothelial cell-extracellular matrix system and the laminar flow chamber appratus. Shear stress-induced polymerization of the actin cytoskeleton of HUVEC was summarized with the formation of the ‘dense peripheral band’ after 5 min exposure of flow, shear-induced focal contact formation at the proximal periphery, and the aligned actin microfilament formation to the direction of flow. In contrast to the intranucleous expression of hsp70 with the conventioanl heat shock, perinuclear expression of hsp70 was detected with the laser scanning confocal microscope and the western blotting of HUVECs exposed to 15 dyne/cm2 shear stress for 1 hour. Expression of hsp70 in perinuclear region increased with proportional to the magnitude of shear stress. The polymerization of cytoplasmic actin cytoskeleton and the cytoplasmic expression of hsp70 may prevent the cellular damage from the pathophysiological stimulus that initiate vascular cell disease, such as the atherosclerosis. Consequently, three-dimensional intracellular expression and the localization of protein and organelles play an important role in the signal transduction generated by the mechanical cue, such as fluid shear stress.
The Effect of Branching on the Interaction of Airflow With a Viscoelastic Layer in a Channel
Authors: Hassan Amgad A. , Evrensel Cahit A.
Published: December 2021

The interaction of airflow with a viscoelastic layer, Locust Bean Gum (LBG)/ Borax solution, in a branching channel is studied experimentally. The intent is to investigate, qualitatively, the effect of increased wall shear due to branching on the wave formation and clearance of mucus in pulmonary airways. The onset air velocity for wave initiation is compared to the previously published results for a straight channel without branching. Our preliminary investigation for the branch angle of 30° does not suggest any appreciable effect of the resulting locally increased shear on the wave initiation.
Research Contribution of Prosthetic Valve Manufacturers Interfacing Academic-Industry Research Efforts
Authors: Gong Xiao , Woo Yi-Ren , Yoganathan Ajit P. , Anayiotos Andreas
Published: December 2021

Prosthetic heart valve is one of the most successful implantable medical devices. However, introducing better performing and longer lasting prosthetic mechanical heart valves (MHV) into clinical use has been slow because predicting the long term performance of a new valve design is difficult.

Although significant progresses in many scientific fronts relevant to prosthetic heart valve development have been achieved, we still have an imperfect understanding of host responses to an implantable medical device and incomplete knowledge in associating hemodynamic characteristics of a valve design to clinical performance. Valve designers, frequently need to over design the valve components to ensure structural safety and thus, sacrifice the opportunity to optimize performance. Complications such as infection, thrombus formation, thromboembolic incidents, and hemorrhage associated to the use of prosthetic valves are still reported and valve designers are working hard to eliminate them.

Further advancing scientific knowledge in designing and evaluating prosthetic heart valves is of great interest to many Valve designers and manufacturers. Interfacing Industry and Academic research efforts has been thwarted due to predominantly proprietary issues. Considering the benefits of a better performing MHV to the patients, this industry session will bring researchers from various MHV companies and academic institutions to discuss how to share the results of scientific studies more effectively. This will help accelerate new MHV development without compromising the confidentiality of key valve design information. The issue of standardized MHV testing will also be addressed.
Intimal Hyperplasia — Development and Regression in Response to Fluid Shear
Authors: Berceli Scott A. , Clowes Alexander W.
Published: December 2021

The long-term success of autogenous and prosthetic bypass grafts is dictated by the development and subsequent progression of intimal hyperplasia. While recent advances in vascular biology continue to improve our understanding of the mechanisms which control this process, available clinical therapies which treat or slow its progression have yet to be identified. Among the factors which influence the development of intimal hyperplasia are the physical forces exposed to bypass conduits. As initially described by Glagov et al. (1988) and confirmed by multiple other investigators, the biology of the hyperplastic response is modulated by the imposed fluid shearing forces While our ability to modulate the local hemodynamics of bypass conduits is limited, an understanding of how these forces govern the healing response can serve as a basis for future pharmacological therapies. In our laboratory we have employed a primate model to understand the influence of shear stress on the development of intimal hyperplasia in PTFE grafts.
Artery as a Pressure Vessel: Correlation Between Stress Concentration and Pathology
Authors: Thubrikar Mano J. , Robicsek Francis
Published: December 2021

Arterial disease most often can be classified in one of two categories — aneurysm and atherosclerosis. Interestingly enough these diseases affect the artery only at certain locations rather than the whole organ, i.e., the diseases have predilection for certain sites. Furthermore, some of the sites are common to both the diseases and at some sites, not so infrequently, the diseases occur together one preceding the other.
Computational Modeling of Platelet Aggregation
Authors: Fogelson Aaron , Yu Haoyu
Published: December 2021

Platelet aggregation is an essential component of normal hemostasis and pathological thrombosis. It involves complex, dynamic, often competitive, mechanical and chemical interactions among platelets, fluid, and vessel wall, the balance among which determines whether and to what extent aggregate growth occurs and persists. It is very difficult in a laboratory setting to measure more than a few quantities of interest, and usually only at a few spatial locations or a few times. From such measurements, it is very hard to piece together a coherent picture of the dynamics. Further it is very difficult to control more than a couple of the players involved. Mathematics, by contrast, is well suited for studying the evolution of a complex system, and for precisely controlling the inputs into the system. It can provide a wealth of temporal and spatial detail about the interactions taking place. It allows for extraction of ‘essential’ elements of the complex system, and through study of the behavior of the simplified system can provide insight into the workings of the true biological system. It thus complements more traditional experimental approaches. But the mathematical study of platelet aggregation presents its own substantial challenges, among them how to handle the mechanical interactions between fluid and platelets, platelets and other platelets, and platelets and vessels walls. This talk is addressed at ways to meet these challenges.
Acoustically Modulated Speckle Imaging of Soft Tissue
Authors: Kirkpatrick Sean J. , Jacques Steven L.
Published: December 2021

Previous research has demonstrated the usefulness of employing laser speckle and dynamic optical coherence measurements in medical imaging. For example, Briers (1993) discussed speckle fluctuations to detect movement within tissue and Zimnyakov et al., (1997) described a camera system that uses speckle fluctuations to monitor tissue structure. Speckle metrology has been used to evaluate displacements and strains in biological hard tissues, such as bone, particularly in the vicinity of implants (Shelton and Kate, 1991). Kirkpatrick and Brooks (1998) demonstrated a speckle technique for directly evaluating strain rates in cortical bone.
Thermal Modification of Collagen
Authors: Torzilli Peter A. , Wall Michael S. , Deng Xiang-Hua , O’Brien Stephen J. , Warren Russell F.
Published: December 2021

Shoulder capsular (collagen) shrinkage has recently been advocated as a therapeutic modality in a select group of patients with multidirectional instability. Tissue shrinkage is a function of temperature and time. This relationship was studied and two models were derived to describe the relationship mathematically for shrinkage and mechanical properties.
Isotonic Biaxial Loading: An Economic, Versatile Method for the Study of Fibroblast-Populated Collagen Gels
Authors: Holmes Jeffrey W. , Borg Thomas K.
Published: December 2021

Studies of collagen gel contraction by embedded fibroblasts have characterized the response of free (unloaded) or isometric (maximally loaded) gels but not the response to intermediate loads. An inexpensive, simple system was devised to isotonically load fibroblast-populated collagen gels using freely hanging weights. This system provided excellent repeatability. Maximal contraction force was estimated at 1 mN per million cells in neonatal rat cardiac fibroblasts, a value that agreed well with reported isometric experiments in fibroblasts from other tissues. The ability to load uniaxially or biaxially and with variable loads will facilitate exploration of the regulation of fibroblast mechanics and biology by stress.
Contractility Affects Stress Fiber Remodeling and Reorientation of the Endothelial Cells in Response to Mechanical Stretching
Authors: Wang James H.-C. , Yin Frank C.-P.
Published: December 2021

Actin cytoskeletal stress fibers are thought to be the major cellular constituents responsible for cell shape and locomotion. As such, stress fiber remodeling likely plays a major role in the cell reorientation responses to mechanical stimuli (Iba and Sumpio, 1991). The assembly and dis-assembly of stress fibers in non-muscle cells are mediated by contractility via the interaction of actin and myosin (Chrzanowska-Wodnicka and Burridge, 1996). Reactive oxygen species (ROS) also play an important role in organization of stress fibers (Hinshaw et al., 1991). Since cyclic stretching can enhance production of certain ROS, including H2O2 (Howard et al., 1997) and H2O2 stimulates, in a time- and dose-dependent manner, myosin light chain (MLC) phosphorylation (Zhao and Davis, 1998), stress fiber remodeling and cell reorientation in response to cyclic stretching should be affected by changes in contractility — including changes in ROS. The roles of these factors have not been carefully examined.
Protein Conformational Changes Under Applied Forces
Authors: Xu Yangqing , Bao Gang
Published: December 2021

Recent studies confirm that stresses, including that due to gravity, tension, compression, pressure, and shear influence cell growth, differentiation, secretion, movement, signal transduction, and gene expression. Yet, little is known about how cells sense the mechanical stresses or deformations, and convert these mechanical signals into biological or biochemical responses. A possible mechno-chemical coupling mechanism involves protein conformational changes under mechanical forces. Our hypothesis is that mechanical forces can cause large changes of the conformation of proteins, which in turn can influence receptor-ligand binding. To test this hypothesis, molecular dynamics simulations and biochemical assays are performed.
The Effect of Motion Path on the Wear Rate of UHMWPE for Orthopaedic Implants
Authors: Sprague Jeff A. , Sauer Willard L.
Published: December 2021

The effect of adding a second axis of motion was investigated for pin-on-disk wear testing of ultra-high-molecular-weight polyethylene (UHMWPE) for orthopaedic implant applications. In addition to linear reciprocation of the UHMWPE or metal disk, axial rotation of the metal or UHMWPE pin was conducted. The added rotation reproduces the cross-shear on the UHMWPE surface that is generated in clinically relevant wear simulator tests and in vivo. The wear rates that result from the multi-axis pin-on-disk tests are significantly higher (one to two orders of magnitude) than those seen in the linear-only tests. This supports the findings of other researchers (Bragdon et al., 1996; McKellop, 1995; Walker et al., 1996; Wang et al. 1997) in that the application of nonlinear motion increases the wear of UHMWPE substantially. This is further validated by the comparison of a hip simulator wear test conducted with three axes of motion — rotation, flexion, and abduction — to a test conducted with two axes of motion — rotation and flexion. The absence of the abduction eliminated a significant degree of nonlinear motion (cross-shear) and, consequently, the wear rate was significantly lower than that seen in the test with abduction.
Effect of Wear on Kinematics of a TKR: A Simulator Comparison of Molded and Machined UHMWPE Tibial Plateaus
Authors: Benson Lisa C. , DesJardins John D. , Schroeder David W. , LaBerge Martine
Published: December 2021

The wear and mechanical performance of identically designed total knee replacement (TKR) tibial bearing surfaces, which differed only in manufacturing process, were evaluated using a Stanmore KC Four Station Knee Joint Simulator. The first group utilized Co-Cr-Mo alloy femoral components with ultra-high molecular weight polyethylene (UHMWPE) tibial bearings processed by direct compression molding. The second group was identical to the first, except that the UHMWPE components were machined from a compression molded sheet. The implant alignment and testing conditions were identical for both series, with a 1 Hz standardized force-controlled walking cycle being employed for a duration of 3 million cycles. Gravimetric wear and surface roughness of the UHMWPE components were quantified every 1 million cycles. Measures of implant mechanics and kinematics were quantified every 0.1 million cycles. Results show that molded UHMWPE exhibited less wear (12 mg/million cycles) and no changes in kinematics. Moreover, the higher rate of wear (18 mg/million cycles) in the machined components was correlated with a statistically significant change in implant kinematics.
Three-Dimensional Lubrication Model of an Artificial Hip Joint With Gait Analysis
Authors: Meyer Donna M. , Tichy John A.
Published: December 2021

The development of the hip prosthesis is a result of extensive collaboration between the medical and engineering fields. Although the technology to replace ailing human joints with artificial replicas is quite advanced, these remarkable advances require additional attention. In particular, extending the service life of a hip prosthesis is a primary consideration. An artificial hip joint may require revision surgery due to a number of contributions, one of which is extensive wear. Within the first few years following hip implantation, high amounts of wear particles form due to the contact of the articulating surfaces. The amounts of wear debris generated is a function of the material combinations of the rubbing surfaces of the joint, the amount of lubrication present in the joint during activity and the types and levels of activity.
Mechanical Degradation of Retrieved UHMWPE Tibial Components Characterized by the Small Punch Test
Authors: Kurtz S. M. , Jewett C. W. , Kalinowski A. , Rimnac C. M. , Edidin A. A.
Published: December 2021

Miniature specimen testing techniques are necessary to characterize the mechanical behavior of UHMWPE components for total joint replacement after sterilization, shelf aging, and implantation. The small punch test has been shown to reproducibly characterize virgin and in vitro aged UHMWPE. The first goal of this study was to demonstrate the feasibility of applying this technology to UHMWPE components after retrieval from the human body. Six short-term retrievals of the same tibial design were characterized with the intent of comparing the mechanical behavior of conventional and enhanced UHMWPE having an extended chain crystalline morphology. Statistically significant relationships were observed between damage scores and the small punch test metrics of initial load, ultimate load, and work to failure. The results of this study support the hypothesis that the in vivo performance of tibial bearings is related to the large deformation mechanical behavior of UHMWPE.
Rotational Stiffness Adjustability of a Prototype Foot/Ankle Prosthesis
Authors: Quesada Peter M. , Hays John A. , Pitkin Mark R. , Colvin James M.
Published: December 2021

Mechanical testing was conducted for a prototype prosthetic foot/ankle component to assess the potential for being able to adjust dynamic rotational stiffness of the prototype in a simple but quantitative manner. The tested prototype has been dubbed the rolling joint ankle (RJA) prosthesis. The RJA prototype design is based on a concept in which rotational stiffness is lower with the ankle position closer to neutral, and increases as ankle rotation moves away from neutral. Adjustment of the RJA prototype’s stiffness involved systematic tightening and loosening of two set screws. Two sets of mechanical testing were conducted at each of three different loading rates to evaluate repeatability of rotational stiffness and to examine the effects of loading rate on RJA stiffness.
Effects of Mechanical Loading and Interstitial Fluid Pressure on Bone Remodeling
Authors: Turner Charles H.
Published: December 2021

Mechanical loading clearly affects bone remodeling (by remodeling, I refer to the process of removal and replacement of bone tissue rather than bone shape changes). Bone remodeling is minimal under normal physiological conditions, but becomes elevated under disuse or extreme overuse (Figure 1). In each case, the mechanism for elevated remodeling is probably quite different. Elevated bone remodeling in overuse is probably caused by microdamage accumulation in the bone tissue. Microdamage causes site-directed bone remodeling [1,2], preceded by osteocyte apoptosis [3]. Conversely, elevated bone remodeling in disuse is not due to tissue microdamage but probably diminished tissue perfusion. In bone subject to disuse, osteocytes show signs of hypoxia within three days and remodeling becomes elevated a few days later [4]. Therefore elevated bone remodeling is preceded by osteocyte distress regardless of whether it is caused by disuse or overuse, suggesting that osteocytes play an important role in the signal cascade leading to elevated bone remodeling. Osteocytes form a highly interconnected network within the bone matrix which has signal processing capabilities, yet is unclear how osteocytes process information, e.g., microdamage. In this paper some effects of disuse and overuse on bone remodeling are discussed with the goal of outlining the key mechanical parameters important for bone remodeling.
Strain Amplification in the Bone Mechanosensory System
Authors: You Lidan , Cowin Stephen C. , Weinbaum Sheldon
Published: December 2021

In this work we suggest a mechanism whereby the bone deformation driven flow of bone fluid through the glycocalyx surrounding an osteocytic cell process in its canaliculus will lead to strains in the cell process membrane which are many times those in the whole bone. We shall describe a mechanism whereby the low magnitude of the strain applied to the whole bone (0.1% to 0.3%) is amplified by nearly two orders of magnitude at the membrane of the cell process. The possibility of this strain amplification depends upon the values of the certain physical and biological parameters. These parameters include the elastic constants of the cell membrane, the elastic constants of the fibers that constitute the glycocalyx. the pre-tension in the fibers and cell membrane, the permeability of bone fluid through the glycocalyx, the physical dimensions of the cell process, the canaliculus, the fibers and fiber spacing of the glycocalyx.

The model employed is an interactive micro-macro mechanical model. It was analyzed numerically. The micro model is a detailed model of the structure and contents of a canaliculus and the macro model is poroelasticity. A mechanical loading range from 1 MPa to 20 MPa at different frequencies, 1Hz to 20Hz, were considered. We calculated the ratio of the drag force on the fibers to the shear force on the osteocyte membrane in a canaliculus and found that the drag force is at least 50 times larger than the shear on the cell membrane. We also calculated the strain al the membrane, as well as the strain amplification ratio, and found that the strain amplification ratio reached a maximum value of 65 for this loading range. Thus the proposed mechanism amplifies the strain applied to the whole bone when it is experienced at the osteocyte process membrane.
The Dependence of the Elastic Constants of Cancellous Bone Upon Volume Fraction
Authors: Yang Guoyu , Cowin Stephen C. , Kabel Jesper , Odgaard Anders , van Rietbergen Bert , Huiskes Rik
Published: December 2021

A simple and explicit representation for the anisotropic elastic constants of human cancellous bone was determined using a new method of analysis on a data base consisting of 141 human cancellous bone specimens. The method of analysis shows that human cancellous bone has orthotropic elastic symmetry at the 95% confidence level and it also provides expressions for all the orthotropic elastic constants as functions of the volume fraction of solid only; no stereological measures of trabecular architecture are involved. This result should be employed to improve the in vivo evaluation of cancellous bone stiffness and strength from a standard clinical test.
Kinematic and Kinetic Analyses in Full-Body Asymmetric Lifting
Authors: Li Yi-Chun , Lavender Steven A. , Natarajan Raghu N. , Andersson Gunnar B. J. , Amirouche Faird M. L.
Published: December 2021

Biomechanical models had been used to conduct a series of lifting related experiments which were performed to understand different parameters such as asymmetry, lifting speed, load magnitude, lifting techniques, fatigue, etc. These studies were performed either in Bottom-Up or Top-Down models to predict kinematic or kinetic data in each inter-segment joint. Bureau of Labor Statistics (1995) [1] reported that in 1994, 367,424 injuries due to overexertion in lifting had 65% affected the back; 93,325 injuries due to overexertion in pushing or pulling, 52% affected the back; 68,992 injuries due to overexertion in holding, carrying, or truning, 58% affected the back; and totaled across these three categories, 47,861 disorders affected the shoulder [2]. Since lifting activities are whole body motion and each inter-segment joint cannot be treated as individual, the synchronization of all body joints should be considered during lifting tasks. Therefore the whole-body posture, kinematic, and kinetic analyses were included in this study. The whole-body posture analysis included lift duration, peak box velocity and acceleration, and the orientation of the trunk and pelvis segment; the whole-body kinematic analysis contained angular displacement, velocity, and acceleration of all body joints; and the whole-body kinetic analysis consisted of the inertial forces and inertial moment of each body segment, and the local forces and moments of each inter-segment joint.
Biomechancial Stability of an Artificial Cervical Joint
Authors: DiAngelo Denis J. , Davis Champ , Robertson James T.
Published: December 2021

Anterior cervical discectomy with or without fusion is an acceptable surgical method for the treatment of cervical spondylosis or other spinal disc diseases. A spinal device may be used to immobilize the operated/injured region to promote bony fusion. Clinical studies have shown that motion at spinal segments adjacent to a fused region increases over time and may cause adjacent segment problems [Chow et al., 1996; Lee et al., 1988]. Multiple factors have been implicated, including the number of levels fused, health condition, post-operative alignment, and rigid fixation. An alternative approach to fusion surgery of the cervical spine is to restore the motion to the diseased joint using a movable artificial cervical joint (MACJ). The objective of the study was to determine the biomechanical stability of the harvested and instrumented cervical spine tested under physiologic flexion/extension and lateral bending loading mechanics. The instrumented spine consisted of a single level discectomy with subsequent disc replacement using a prototype artificial intervertebral disc implant by the Sofamor Danek Group, Memphis, TN.
Coupled Rigid-Deformable Body Formulation for Analysis of Joint Stress and Deformation During Gait
Authors: Hovey Chad B. , Heegaard Jean H.
Published: December 2021

Analysis of human gait often uses rigid body dynamics to predict joint motions and forces [Andriacchi, et al., 1997]. While these approaches can help identify healthy and pathological human movement, the rigid body assumption does not allow determination of stress and deformation within the joint. This information is desirable not only to help understand the etiology of joint disease, but also for determining how joint replacements will perform once implanted. Finite element analysis, used to determine joint stress and deformation, employs boundary conditions which are intended to simulate physiological conditions [Maxian, et al, 1996]. Because these boundary conditions are defined a priori, it remains unclear as to how well these applied tractions and displacements match what is truly occurring during human motion.
Dynamic Response Analyses of Rabbit Knee Joint
Authors: Kasra M. , Grynpas M. D. , Shirazi-Adl A.
Published: December 2021

The knee joint is a complex nonlinear dynamic system. It is generally known that mechanical factors play an important role in the etiology of knee injuries and diseases such as osteoarthritis. While performing daily activities such as walking, running, and climbing as well as during occupational operations, the joint is exposed to vibrations and multiple impacts. During these activities, according to an individual’s condition (e.g., age, fitness, weight), the joint load and stiffness may reach critical limits initiating or accelerating different knee disorders. This is the case in athletes or workers during occupational activities (1). Therefore, understanding the dynamic characteristics of the knee joint is essential in prediction and prevention of knee disorders as well as in subsequent joint replacement and rehabilitation procedures. There have been very few reported experimental studies investigating the dynamic behavior of the whole knee joint as a dynamic system (2). The objective of this study was to investigate the changes in mechanical properties of the rabbit knee joint under different compressive dynamic loading conditions. Rabbit has frequently been used as an osteoarthritic knee model (3). The data obtained in this study, hence, will also be beneficial in our future studies of osteoarthritic rabbit models.
Medial Placement of the Patellar Button Improves Contact Pressure Distribution Following Total Knee Arthroplasty
Authors: Petrella Anthony J. , Karmas Alexandros , Miller Mark C. , Berger Richard A. , Rubash Harry E.
Published: December 2021

Total knee arthroplasty is now a common and successful means of treating osteoarthritis and other degenerative conditions in the knee joint. Historically, mechanical failures (e.g. button loosening or separation from the metal backing) and chronic subluxation have been among the most common complications associated with the patello-femoral joint. Advances in fixation, implant design, and surgical technique have lead to a decrease in the incidence of mechanical failures, but restoration of stable function to the distal extensor mechanism remains challenging. The center of pressure (COP) on the patellar implant is an indication of the distribution of contact forces on the device and of the stability of patellar tracking. An eccentric COP suggests the possibility of subluxation, high contact stresses, and increased patellar wear. The main objective of this study was to determine the affect of medial-lateral patellar placement on the COP of the patellar implant. It was hypothesized that medial-lateral placement of the patella would have a significant effect on the COP.
A Triphasic Analysis of Indentation on Articular Cartilage
Authors: Sun D. N. , Guo X. E. , Lai W. M. , Mow V. C.
Published: December 2021

The indentation experiment is one of the most frequently used methods for studying biomechanical properties of articular cartilage. This experimental configuration is attractive because it does not require special specimen preparation [1,2]. Indentation can be performed on an articulating surface with the cartilage attached on the bone, a condition resembling closer to the physiologic and anatomic condition than compression of osteochondral plugs excised from the joint surface. It provides a non-destructive method to determine the variation of cartilage properties over the joint surface and has a potential for in vivo applications of determining mechanical and electrochemical properties of articular cartilage. Numerous theoretical and numerical analyses of indentation on articular cartilage have been performed and used to calculate the in situ mechanical material constants (Ha, k, v) of the tissue [e.g., 1–3].
A Large Strain Hyperelastic Constitutive Model for Intraluminal Thrombus From Abdominal Aortic Aneurysm
Authors: Wang David H. J. , Makaroun Michel S. , Webster Marshall W. , Vorp David A.
Published: December 2021

Rupture of abdominal aortic aneurysm (AAA) occurs when the wall stress acting on the dilated aortic wall exceeds the strength of the tissue. Therefore, accurate estimation of the wall stress distribution in AAA may be a clinically useful tool to predict their rupture. A majority of AAA contains a laminated, stationary, intraluminal thrombus (ILT) (Harter et al., 1982). Previous investigations have shown that ILT may significantly alter the wall stress acting on AAA (Inzoli et al., 1993; Mower et al., 1997; Stringfellow et al., 1987; Vorp et al., 1998; Di Martino et al., 1998). However, all of those studies used a simplified linear elastic model for ILT. This is inappropriate and can lead to inaccuracies since both AAA wall and contained ILT undergo large deformation during the cardiac cycle (Vorp et al., 1996). Therefore, to accomplish accurate stress analysis of AAA, appropriate constitutive models for both the wall and ILT are necessary. Our group has previously proposed a finite strain constitutive model for the AAA wall (Raghavan et al., in press). The purpose of this work was to derive a more suitable constitutive model and the associated mechanical properties for the ILT within AAA.
Equivalent Mixed “PHETS” and “MPHETS” Poroelasttc-Transport-Swelling Finite Element Models for Soft Biological Tissues
Authors: Simon B. R. , Williams S. K. , Liu J. , Nichol J. W. , Rigby P. H. , Kaufmann M. V.
Published: December 2021

A soft hydrated tissue structure can be viewed as a “PETS” (poroelastic-transport-swelling) model, i.e., as a continuum composed of an incompressible porous solid (fibrous matrix with fixed charge density, FCD) that is saturated by a mobile incompressible fluid (water) containing mobile positively (p) and negatively (m) charged species. Previously, we described two PETS models — a “semi-mixed” porohyperelastic PHETS model (Simon et al. 1998) and a “fully mixed” MPHETS model (Simon et al. 1999) using FEMs (finite element models) that included geometric and material nonlinearity and coupled electrical/chemical/mechanical transport of the fluid and charged species. Here, we demonstrate the equivalence of the PHETS and MPHETS formulations that are useful when the solid and fluid materials are incompressible and the electrical-chemical potential and mechanical-osmotic pressure fields are discontinuous at material interfaces.
A Novel Technique for Measuring Regional Deformation With High Spatial Resolution in the Beating Heart
Authors: Gaudette Glenn R. , Chiang Fu-Pen , Todaro Joseph , Krukenkamp Irvin B.
Published: December 2021

Many diseases result in a heterogeneous distribution of regional function. This results in the need for a technique that can accurately measure deformation with high spatial resolution. We have developed computer aided speckle interferometry (CASI) to accomplish this task. Instead of tracking individual particles, CASI tracks clusters of particles. In the isolated beating rabbit heart, CASI was used to determine the simultaneous displacement of 625 points located in a region approximately 5.5 × 5.5 mm. These displacements were plotted as a function of the left ventricular pressure to generate a regional work loop, which has conventionally been used to determine regional function in the myocardium. In summary, we have developed a technique to measure regional function with high spatial resolution and applied it to the beating heart.