bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of Nonlinear Aeroelastic Systems
Authors: Namachchivaya N. Sri , Lee A.
Published: March 2022

This paper investigates the effects of nonlinearities on the dynamics of flat panels in supersonic flow and presents new bifurcation results for a fairly general nonlinear aeroelastic system. In order to obtain these results we use the method of normal forms, global bifurcation techniques, and various other dynamical systems tools. The first part of this paper deals with modeling unsteady aerodynamic forces and moments acting on flat panels undergoing arbitrary motion in supersonic flow. This modeling also considers the structural nonlinearities inherent in panels. While deriving the equations of motion, many in the past have neglected some nonlinear aerodynamic terms as insignificant from the modeling point of view. However, inclusion of these terms in the analysis may completely change the bifurcation behavior. In aeroelastic systems it is the nonlinear dissipative terms that can change the behavior, and it is essential to carefully model these terms in the physical problems. In the absence of dissipative terms the nonlinear system is reversible, which provides the governing equations with near integrable structure. Thus certain analytical methods are used to study the bifurcation behavior of the system near critical points. For general nonlinear fiat panels in supersonic flow, we present these effects as various bifurcation results due to symmetry-breaking imperfections. For aeroelastic systems, the reversible symmetry is broken by the addition of unsteady aerodynamic terms.
Two- and Three-Dimensional Analyses of Flow Around Airfoils Subjected to Forced Oscillation
Authors: Yokono Yasuyuki
Published: March 2022

This paper describes extensive computer-based analytical studies on the details of unsteady flow behavior around oscillating airfoils in turbomachinery. To consider the time-dependent motions of airfoils, a complete Navier-Stokes solver incorporating a moving mesh was applied, and the drag and lift coefficients for the cases of stationary airfoils and airfoils subjected to forced oscillation were examined. In order to clarify the interaction between the airfoil structure and the flow induced force, the exact fluctuation of the drag and lift coefficients with time needed to be determined. Although two-dimensional analyses have been performed for two-dimensional airfoils, it has suggested to be difficult to obtain the true separation vortex in such analyses because the vortex structure is essentially three-dimensional. Therefore, in the present study, a comparison was made between the two- and three-dimensional analyses for NACA0012 airfoils, and the separation vortex structure was examined in detail.

From the numerical results, it was found that the separation vortex consisted of large-scale rolls with axes in the span direction, and rib substructures with axes in the stream direction. The three-dimensional analysis could simulate these rolls and ribs, but the two-dimensional analysis was inadequate to realize this vortex structure. This is the main difference between the two- and three-dimensional analyses. In addition, the formation of ribs was found to be affected by the forced oscillation, and the transformation of rolls increased and the vortex structure became more fine as the oscillation frequency increased.
Design and Analysis of a Precision Multi-DOF Placement Device
Authors: Bahrami Hassan , Tzou H. S.
Published: March 2022

Piezoelectrics are increasingly being used in a large number of research explorations and engineering applications. In industry, piezoelectrics are widely being accepted as sensors, giving engineers more leverage to add new features to their products. In recent years, for example, distributed piezoelectric sensors and actuators are widely used in active vibration control of structures or precision mechatronic and structronic systems. In this paper, a piezoelectric quad-morph based multiple degrees of freedom (DOF) end-effector is designed and its multi-DOF precision placement operation is analyzed. This new multi-DOF cantilever beam design consists of multiple piezoelectric rectangular rods glued together, which provides a way to accurately position the end in space. Detailed analysis of this advanced composite structure is carried out by the finite element method incorporating the piezoelectric actuations.
Formulation and Solution of Equations of Motion of Structures With Elastic and Viscoelastic Components
Authors: Escobedo-Torres Javier , Ricles James M.
Published: March 2022

The equations of motion of structures with elastic and viscoelastic materials in the time domain are derived. The development is consistent with finite element formulations and leads to systems of equations where the matrices are symmetric, real, and composed of constant coefficients. Four-parameter fractional derivative models are used to model the frequency dependence of the linear viscoelastic materials since experimental data can be fitted successfully over wide frequency ranges. The resulting equations of motion are known as the elastic-viscoelastic equations of motion. Numerical procedures for solving the elastic-viscoelastic equations of motion in the time domain are developed. The closed-form, steady state solution of a single degree of freedom system is obtained in the frequency domain and is used to validate the results obtained by using the numerical procedures. The dynamic response of a multi-degree of freedom structure is obtained by using the numerical procedures.
Maximizing the Power Output of Air-Acoustic Actuator Arrays
Authors: Leo Donald J. , Paine Jeffrey S. N.
Published: March 2022

Maximizing the acoustic power output of air-acoustic actuator arrays is studied. The problem is shown to reduce to a generalized eigenvalue problem for the case of a planar structure radiating in an infinite baffle. The matrices of the eigenvalue problem are a function of the material and geometric properties of the plate, the location of the actuators in the array, and a nondimensional wavenumber. A simply-supported plate driven by an array of point force actuators is used as a representative example. The numerical study illustrates that the maximum sound power output of the array increases as the number of actuators increases, but the mass-normalized power efficiency of the array is not always maximized when the number of actuators in the array is increased.
Dynamics for Large Deflections of Laminated Composite Plates Including Piezoelectric Effect
Authors: Yu Y. Y.
Published: March 2022

Laminated composite plates have been treated systematically in our recent book (Yu 1996). In one of the chapters, classical and refined modelings for large deflections of laminates are formulated on the basis of nonlinear elasticity. In a separate chapter, similar modelings for large deflections of piezoelectric plates are dealt with on the basis of both nonlinear elasticity and piezoelectricity. In this paper we carry out a combined treatment of large deflections of laminated composite plates including the piezoelectric effect, through the use of constitutive relations.
Control of Distributed Actuators Without Electrodes
Authors: Main John A.
Published: March 2022

Presented in this paper is a new method for application of control signals to piezoelectric material patches that eliminates the need for both distributed electrodes and wire leads. The aim of this new method is to provide a design solution for smart structural applications that require a very high spatial resolution over a relatively large area. In such applications smart material patches with distributed electrodes are often an impractical choice because the number of separate electrodes and wire leads is driven extremely high.

This paper presents a smart material control concept that eliminates the need for separate electrodes and leads by using an electron gun to deposit control charges directly on the surface of the piezoelectric material. Since piezoelectric materials are dielectrics a surface charge accumulates due to the incident electron beam. Both positive and negative electric displacements can be applied by controlling the energy of the incident electrons. Also, charge can be applied over an area a few microns wide or centimeters wide by controlling the divergence of the electron beam with electron optics. The impact of these characteristics of electron gun control on the design of smart structural systems is discussed.

The general concept of the electron beam controlled adaptive plate is presented in this paper along with an engineering analysis that focuses on the materials, system, and control aspects of this new smart structures paradigm.
Simultaneous Optimum Design of Structure and H∞ Control System
Authors: Kawamura Shozo , Yasutake Toshio , Iwatsubo Takuzo
Published: March 2022

In this paper, some approaches for simultaneous optimum design of the structure and H∞ control system have been proposed. It was first shown that the selection of the frequency weighting functions influences on the control performance and the robust performance. Next, an approach for simultaneous optimum design has been proposed. In the approach, the frequency weighting function is optimized in the simultaneous optimum design. The results show that the values of the objective functions of individual and simultaneous optimum design are same. A new selection method of the objective function was then proposed. In the new method, every objective function is normalized in order to make the available range for all objective functions uniform. Numerical results show that using the proposed objective functions the simultaneous optimum design can be attained with a better design than the individual optimum design.
Advances in Adaptive System Applications at Daimler-Benz Research Labs
Authors: Martin Willi , Jänker Peter , Siegling Hans-Friedrich , Voggenreiter Heinz , Wang Ping , Trutzel Michael , Ahrendt Heinz , Klöppel Valentin
Published: March 2022

Within the past years the Daimler-Benz Research & Technology Department has initiated work to explore the benefits of adaptive materials and structures technologies for use in a broad range of modern transportation systems in the aerospace, automotive and railway industries.

This paper presents recent research activities focusing on two aerospace guidance concepts where the application of adaptive systems will play a major role: the “Adaptive Wing” and the “Adaptive Rotor Systems”.

The “Adaptive Wing” will incorporate “smart” technologies to control wing geometry to adapt to actual lift and load requirements. Various concepts for airfoil shape adaptivity are currently under investigation. The “Adaptive Rotor Systems” include an innovative type of individual blade control (IBC) with piezo-driven servo flaps built into the outer trailing edge of the rotor blades.

The presented research activities cover the field of multifunctional sensor and actuator systems based on adaptive materials and include basic material research, e.g. new approaches to fast reacting, high strain actuator materials, as well as innovative concepts for deformable “adaptive” structures up to proof-of-concept demonstrators at laboratory level.
Vibration Control via Active-Passive Hybrid Piezoelectric Network With Variable Resistance
Authors: Morgan Ronald A. , Wang K. W.
Published: March 2022

Active-passive hybrid piezoelectric networks (APPN) have been shown to be effective devices for vibration suppression. It has also been recognized that the resistor element in these devices, which is necessary to provide passive damping, can reduce the authority of the active control action. One possible method to improve upon this situation is to use a variable resistor in the RL shunt and on-line adjust the resistance based on feedback. However, the concurrent design method previously synthesized for APPN systems becomes difficult to implement when such a state-dependent and time-varying resistor is used. In this research, an effective and simple control law is developed for an APPN system with variable resistor. It is shown that by proper on-line adjustment of the variable resistor, the efficiency of the APPN system can be significantly increased.
Optimal Static Control of Statically Determinate Discrete Parameter Adaptive Truss Structures With t Linear Functions of Observed Response Components
Authors: Baltimore Craig V. , Utku Senol
Published: March 2022

Given a statically determinate truss adaptive system with q number of strain inducing actuators (one actuator per truss element) and t attributes (expressed in the form of linear functions of p observed nodal displacement components), such that t ≤ p ≤ q, this paper describes the optimal placement and selection of actuators. The placement and selection optimization is based on a minimization of a norm of the actuator induced strains, Δu. The minimization is performed using the largest magnitude of the tth order minor of the Jacobean of the attributes with respect to bar elongations. The relationship for determining the actuation, Δu, is also examined.
Experimental Validation of a Four Components Mixture Theory for Swelling Porous Media
Authors: Frijns Arjan J. H. , Huyghe Jacques M. , Janssen Jan D.
Published: March 2022

Biological tissues exhibit swelling or shrinking behaviour. This behaviour is caused by water binding. Biological tissues are able to bind water because of the fixed charges of the solid skeleton. These electrical charges are responsible for a variety of physical phenomena such as streaming potentials, diffusion potentials, electro-osmosis, electrophoresis and swelling.
Biological Gradient Regulated Predictive Model of Long Bone Growth
Authors: Taboas Juan M. , Lerner Amy L.
Published: March 2022

Morphogenesis is regulated by a complex interaction of factors that are intrinsic and extrinsic to the cells composing the organism (e.g. genetic programming, cytokine gradients, and applied mechanical/electrical forces). Mechanical stimulation has been shown to affect bone growth, but the interaction of mechanical forces with biological factors during the development of a cartilage anlage into adult form is not clear. During skeletal development, chondrocytes produce cartilage through differential cell growth, cell volume changes, and extracellular matrix secretion. Cartilage cells at the growth front undergo significant hypertrophy and later their surrounding matrix becomes mineralized. In turn, the mineral is resorbed by osteoclasts and new bone tissue is deposited by osteoblasts. During later stages of prenatal development, contraction of developing muscles applies significant loads to the skeleton which in turn affects the bone growth. This research attempts to elucidate how these processes are controlled by biologic factors in the absence of mechanical factors using a finite element (FE) model of the proximal tibia from a paralyzed chick embryo.
A High Accuracy Three-Dimensional Coordinate Digitizing System for Reconstructing the Geometry of Diarthrodial Joints
Authors: Haut Tammy L. , Hull Maury L. , Howell Stephen M.
Published: March 2022

Finite element modeling (FEM) in orthopaedic biomechanics requires a measurement technique to obtain accurate, three-dimensional (3-D) representations of diarthrodial joints [5], Accurate representations of joints, including soft tissue, articular cartilage, and bone are needed for FEM to be useful in the study of joint behavior and orthopaedic implants. Based on measuring the thickness of articular cartilage, the accuracy requirement for the measurement technique is 20 μm for a relative error of 1 percent.
Strain Environment Effects on Bone Regeneration and Tissue Differentiation During Distraction
Authors: Richards Mark , Goulet James A. , Goldstein Steven A.
Published: March 2022

Numerous clinical conditions continue to drive the need to understand, both quantitatively and mechanistically, the relationship between physical forces and bone formation and adaptation. The global objective of this research was to investigate the influence of strain environment on patterns of tissue differentiation. To test hypotheses related to this overall objective, experimental animal models which take advantage of the large volume of bone formed during distraction osteogenesis (DO) were used to show how physical forces and strains influence bone regeneration at different stages of the repair process. The approach taken was: 1) to manipulate the mechanical environment within the mesenchymal gap tissue in vivo in a known fashion; 2) to predict the resulting changes in stresses and strains by computational and analytic means; and 3) to assess the effects of these changes on patterns of tissue differentiation. Correlations between strain environment and tissue response were then sought to gain insight into the relationship between these two entities. This abstract summarizes work done to accomplish these objectives in two different areas. First, both the time-dependent and large-deformation behavior of the mesenchymal distraction gap tissue were evaluated. Second, the strain environment was manipulated in three specific ways, and the effects of these changes on patterns of new bone formation and precursor tissue differentiation were assessed.
On the Features and Assumptions of Bone Remodelling Theories: Part II — Density-Property Correlation and Influence of Remodelling Rate Function
Authors: Ben Souda Karima , Breton Pierre , Misra Aran K. , Ahmed Abdul M.
Published: March 2022

Application of theories simulating the bone remodelling process (BRP) requires a knowledge of the correlation between the density of bone and its mechanical properties. The correlations that have been used so far are based on the pooled results of measurements using both human and bovine specimens [1]. It has been shown, however, that pooling of such results from different species is inappropriate [2]. In view of this, the first objective of Part II of this study, is to establish the density-property correlations based exclusively on the experimental results from human bone specimens and to investigate the influence of the nature of the correlations on the stability of the simulated BRP.
Numerical Analysis of Oscillatory Flow and Gas Transport Through a Bifurcating Airway Model
Authors: Fujioka Hideki , Oka Kotaro , Tanishita Kazuo
Published: March 2022

The axial dispersion in the High-frequency oscillatory Ventilation (HFO) occurs due to the interaction between radial mixing and radially-nonuniform axial velocity profile. Since an aspect of the geometry of pulmonary airway is characterized by the curved portion in the pulmonary branch, the secondary flow in the airway plays the important role. Pedley and Kamm (1988) identified the significant effect of curvature on the gas dispersion, and discovered the convective resonance phenomena which gives a highly-peaked local maximum of axial gas transport when the calculating circulation time of secondary flow becomes identical to the cycle period. Subsequently Sharp et.al. (1991) experimentally confirmed the presence of convective resonance in a fully developed oscillatory flow in a curved tube. However, the curved portion of pulmonary branch is not long enough to generate the fully developed flow. This leads to the necessity of study about gas dispersion through a single bifurcating airway model. In the present study, oscillatory flow and gas transport of an incompressible, Newtonian fluid through a bifurcating airway model was numerically analyzed by solving the 3-dimensional Navier-Stokes equations. The employed model was based on Pedley’s report (1977), which comprises the curvature ratio to be 1/8 and the angel formed between the two daughter tubes to be 70 degree, whose radius is taken to be 0.78 times of the parent tube. The purpose of this study is to get the basic knowledge of the secondary flow generation for various Reynolds number, the velocity field and the axial gas transport in sinusoidal oscillatory flow through the bifurcation.
In Vitro-In Vivo Comparison of Prosthetic Heart Valve Performance
Authors: Hirt Felix , Botnar René , Baldwin Tim , Zhang Zhengji , Kepner Jeff , Boesiger Peter
Published: March 2022

The present investigation is focused on the significance of pulsatile in vitro flow measurements in the vicinity of prosthetic bileaflet heart valves at the aortic position. With the help of a pulse duplicator system and of optical LDA-technique, mean flow data were collected first. Then the blood flow patterns downstream of the same valve type was visualized in vivo by using a novel MRI-procedure. The application of both techniques under pulsatile flow conditions made the in vitro - in vivo comparison possible for the first time.
Measurement of Micro Flow Field Over Model Endothelial Cells
Authors: Fukushima Shuichiro , Inagi Kenichiro , Oka Kotaro , Tanishita Kazuo
Published: March 2022

Shear stress induced by blood flow on the arterial wall affect morphology and physiology of endothelial cells. The specific mechanisms alternating shapes and functions have not been identified in endothelial cells, because of the lack of a detailed description of the flow near the cell surface. Although the velocity profiles were numerically calculated (Barbee et al., 1995, Satcher et al., 1992, Yamamoto et al., 1996), experimental verification has not been accomplished.
Effect of Shear Stress on Mitochondrial Membrane Potential of Cultured Endothelial Cells
Authors: Kudo Susumu , Morigaki Ryoma , Ikeda Mariko , Oka Kotaro , Tanishita Kazuo
Published: March 2022

Endothelial cells line on the inner surface of the vascular is continuously exposed to shear stress by a blood flow in vivo. It is known that shear stress influences energy-dependent physical (Dewey et al., 1981, Levesque et al., 1985) and biochemical characteristics of endothelial cells (Arisaka et al., 1995). We, therefore, evaluated mitochondrial ATP synthesis activity by a confocal laser scanning microscope (CLSM) and a mitochondrial membrane potential probe, 5.5’, 6.6’-tetrachloro-1.1’,3,3’-tetrathylbenzimidazolocarbocyananine iodide (JC-1), when shear stress was loaded over cultured endothelial cells.
Intra-Uterine Fluid Motion Due to Myometrial Contractions: A Mechanism for Embryo Transport
Authors: Eytan Osnat , Elad David , Hartoov Joseph , Jaffa Ariel J.
Published: March 2022

The initial phase of a successful pregnancy is composed of a set of transport phenomena. The detached ovum is transported to the ampulla of the fallopian tube, where fertilization may occurs. If fertilization occurred, the embryo enters the uterine cavity within three to four days of ovulation after it has grown to a ball of cells of about 100 μm in diameter. In the uterus, the embryo is conveyed with the uterine fluid for another three to four days to a successful implantation site at the fundus, which is at the upper part of the uterus. The embryo does not have a self propelling mechanism, and thus, it is passively transported with the intra-uterine fluid, which is a highly viscous liquid. Fluid movements within the uterine cavity may be induced by myometrial contractions, which have been observed in non-pregnant uteri via in vivo measurements of intra-uterine pressures and high-speed replaying ultrasound images.
Probabilistic Modeling of Formation and Breakage of Cell Aggregates in a Shear Field
Authors: Long Mian , Goldsmith Harry L. , Zhu Cheng
Published: March 2022

Previously, we employed the probabilistic formulation of McQuarrie [1] to model the no-load adhesion kinetics of cell-cell adhesion [2] and the steady state detachment of cells from surfaces [3]. Here we extend our model to describe the shear-induced formation and breakage of doublets of red cells [4] and latex spheres cross-linked by ligands [5]. We solved the probabilities of having adhesive bonds linking two spheres from the master equations [1], enabling us to calculate various statistical aspects of the experimental data, including the mean and variance of formation and breakage of doublets. This is in contrast to the Monte Carlo approach which computes these statistics from a simulated ensemble of realizations [4,5].
Sensitivity of the Flow Field in the Rabbit Abdominal Aorta to Various Flow Parameters
Authors: Cheer Angela Y. , Dwyer Harry A. , Barakat Abdul I. , Bice Michael , Sy Eugene
Published: March 2022

Atherosclerotic disease of the coronary arteries and the large vessels is the leading cause of death in industrialized countries. Early atherosclerotic lesions are more frequently found in regions of arterial branching and curvature where the flow field is “disturbed” [1]. This has long motivated the notion that arterial fluid mechanics may act as a localizing factor for early atherosclerotic lesions [2]. Despite intense study over the past three decades, the precise role of hemodynamics in atherogenesis remains to be elucidated. Furthermore, the sensitivity of arterial flow fields to changes in specific flow and geometric parameters remains incompletely understood. The objective of the current study is to investigate the impact of a range of physiologically-relevant fluid mechanical parameters on the flow field within the rabbit abdominal aorta in the vicinity of the celiac artery. This is accomplished using experimentally-validated finite volume numerical techniques. The rabbit was selected because we have previously studied both the flow field in the rabbit aorta [3,4] and the topography of sites of enhanced permeability thought to play a role in atherogenesis [5].
Vulnerable Points of Rupture of an Intracranial Aneurysm
Authors: Danturthi Ramalinga S. , Partridge Lloyd D. , Turitto Vincent T.
Published: March 2022

Clinical trials indicate that an intracranial aneurysm is most likely to rupture on the dome area where the wall is weak (1-3). Even though several factors contribute, the cause for rupture is still unclear; hemodynamic forces are believed to significantly effect the growth, development and rupture of an aneurysm. The entrance length or the ostium width, the shape and size of the aneurysm, the Reynolds number of the flow and the shape of the parent artery, all can contribute toward the rupture of an aneurysm (4, 7). A neck area, if present, can substantially influence the flow into the aneurysmal volume resulting in higher hemodynamic forces on the aneurysmal wall. The objective of this study is to investigate the effects of hemodynamic forces for suggesting vulnerable regions or points of rupture of an aneurysm considering the shape and size of the aneurysm, its ostium width and the Reynolds number (Re) of the flow. The research was done in two parts — theoretical computations with a CFD software Fluent were performed on 2D models of aneurysms and experimental determinations of the in-vitro velocity vector field with 2-D particle image velocimetry (PIV) were made with glass models of aneurysms.
Elastodynamics of Intracranial Saccular Aneurysms
Authors: Shah A. D. , Dimas A. , Humphrey J. D.
Published: March 2022

Intracranial saccular aneurysms are focal dilatations of the arterial wall that occur in and near the circle of Willis. These lesions are typically thin-walled and sphere-like in shape, and they exhibit a nonlinear, pseudoelastic behavior over finite strains; in addition it appears that unruptured lesions have negligible bending stiffness. Together, these observations suggest that one may employ a nonlinear membrane theory to study the associated mechanics.
Comparing the Influence of Graft Angle on Peri-Anastomotic Wall and Fluid Mechanics
Authors: Ballyk Peter D. , Ojha Matadial , Walsh Colin
Published: March 2022

Distal anastomotic intimal hyperplasia (DAIH) can lead to outflow stenosis of vascular bypass grafts. In end-to-side graft-artery anastomoses, two separate regions of DAIH have been identified: (i) the suture line and (ii) the floor of the anastomosis across from the suture line (Bassiouny et al., 1992). Suture-line intimal thickening seems to be associated with post-surgical healing and influenced by graft-artery compliance mismatch (Trubel et al., 1994), while floor hyperplasia appears to be linked to fluid mechanical phenomena, such as temporal variations in wall shear stress (Ojha, 1994).
Unsteady Coupled Fluid Flow and Elastic Wall Calculations for the Aorta
Authors: Rutaganira Thomas , Dwyer Harry A. , Cheer Angela , Barakat Abdul
Published: March 2022

It has been a goal for many decades to develop a detailed model of the aortic artery that includes a couple fluid/wall interaction that is time dependent and three-dimensional. Simple models of the large arteries have yielded valuable information, but the complications of coupled time dependencies, three dimensionality, and wall elasticity are needed to compare with actual diseased states. Our paper presents some of the first results for the full unsteady and three-dimensional Navier-Stokes numerical calculations which are coupled to an elastic model for the geometry of the thoracic aorta. The numerical models we have developed have the capability to include with increasing fidelity a detailed description of a large part of the aortic flow system.
Effects of Large Dynamic Curvature Changes on Flow in the Coronary Arteries
Authors: Santamarina Aland , Siegel John M. , Moore James E.
Published: March 2022

The localized nature of atherosclerosis has led to extensive study of blood flow patterns and their possible involvement in atherogenesis. Vessel geometry has always been considered a primary factor in determining blood flow patterns. In the coronary arteries, the geometry varies dynamically due to myocardial contraction. The effects of physiologic axial (Moore et al., 1994) and lateral (Delfino et al., 1994) vessel movement on coronary blood flow patterns have been shown to be important in producing oscillations in wall shear stress. Those studies were limited to straight vessels that translated in one direction only. Previous studies of flow in curved tubes with time-varying curvature showed relatively small (4% or less) changes in the mean inner wall shear rate near the tube entry (relative to the static, non-moving tube) when the curvature change was 10% or 30% of the mean radius of curvature (Santamarina et al., 1996). Angiographic data show that curvature changes may be as much as 85% of the mean radius of curvature (Pao et al., 1985). This study extends the analysis of Santamarina et al. (1996) to account for larger changes in curvature (50%), as well as different levels of mean curvature.
Modelling and Analysis of the Mechanical Properties of Trabecular Bone
Authors: Colombi Pierluigi , Contro Roberto , Pini Monica
Published: March 2022

The mechanical properties of both cortical and trabecular bone material are important in understanding the deformation and failure behaviour of bones. Substantial researches have been conducted to measure the mechanical properties of trabecular bone. In this paper we present experimental results on the mechanical behaviour of trabecular bone under uniaxial and cyclic loading. Moreover we propose a continuum damage model to predict the progressive degradation of mechanical properties under monotonic tensile loading.
On the Features and Assumptions of Bone Remodelling Theories: Part I — Stability Analysis and Selection of Remodelling Stimulus
Authors: Ben Souda Karima , Breton Pierre , Misra Arun K. , Ahmed Abdul M.
Published: March 2022

Evidence of adverse bone adaptation after arthroplasty has led to an increasing interest in the study of the bone remodelling process (BRP). A number of theories have been developed to simulate the process [1,2,3], with the objective of computing the effect of a change in the mechanical environment on bone geometry (i.e., external bone remodelling) or bone material properties (i.e., internal bone remodelling). However, the application of the theories continues to demand critical evaluation of a number of their features and assumptions. Part I of this presentation deals with the analysis of the stability characteristics of the simulated BRP, and with the selection of the mechanical stimulus assumed to drive the process.
Quantification of Femoral Surface Strain After Cementless Stem Implantation by Computer Analysis of the Photoelastic Method
Authors: Morris Randal P. , Grecula Michael J. , Buford William L. , Patterson Rita M.
Published: March 2022

Cementless femoral stems have been associated with surface strain changes and stress shielding after total hip arthroplasty. The changes may lead to post-operative bone resorption, micromotion, microfracture or implant failure. Therefore, detailed analysis of femoral surface strain before and after implantation can be useful in determining the features of implant designs that promote strain changes. The purpose of this research is to determine to what affect different cementless stem designs have on the surface strains of the femur. This protocol will follow a technique developed in a pilot study that uses the photoelastic method to resolve the fringe patterns on the femur, commercially available computer software to image these patterns, and original software programs to analyze the surface strains and provide comparative data.
A New Model Predicting In Vivo Finger Flexor Tendon Force
Authors: Dennerlein Jack Tigh , Mote C. D. , Diao Ed , Rempel David M.
Published: March 2022

Existing isometric force models can be used to predict tension in the finger flexor tendon, however, they have not been validated by experimental observations. In a previous study (Dennerlein 1997) the authors measured and reported in vivo tendon force of human flexor digitorum superficialis (FDS) of eight subjects during isometric pinch tasks. The estimated ratios of tendon force to fingertip force were larger than predicted by the theoretical models of Chao (1989) Harding, (1993) and Weightman & Amis (1982). Furthermore, FDS tendon tensions of pulp pinch postures (4 subjects) were significantly higher than for tip pinch postures. Models in the literature do not predict this difference. Our goal is to implement a 2-D tendon force model and to develop a new model better representing the causes of the observed differences.
A Mathematical Model of the Thumb Carpometacarpal Joint
Authors: Xu L. , Blankevoort L. , Ateshian G. A. , Cohen N. P. , Strauch R. J. , Rosenwasser M. P. , Mow V. C.
Published: March 2022

Osteoarthritis (OA) of the thumb carpometacarpal (CMC) joint is a common and disabling condition. Controversies surround the etiology of CMC OA because the internal mechanics of the joint is poorly understood. Several studies have been reported where mathematical modeling was used to study the biomechanical behavior of the CMC joint. Cooney et al (1977) developed a 3D static thumb model. An et al (1985) modified this model to simulate abnormal conditions of the thumb such as tendon laceration. Esteki (1995) developed a dynamic model to study neuromuscular stimulation of the hand. However, these previous studies have mostly employed idealized kinematic representations of the CMC joint (e.g., as a universal joint), and their results have focused primarily on the calculation of joint reactions forces. The biomechanical parameters which are believed to play key roles in CMC joint degeneration, such as contact area patterns of articular surfaces and complex higher pair kinematics, cannot be predicted by these models. Moreover, Imaeda et al (1994) demonstrated that the CMC joint may not be adequately modeled as a universal joint, emphasizing the need for employing the actual geometry of CMC articular surfaces for kinematic analyses.

The objective of this study is to develop a mathematical model of the thumb CMC joint which accounts for the complex topography of its articular surfaces as well as the capsular ligaments spanning the joint. This mathematical model can be employed to study complex 3D joint kinematics, contact forces and articular contact areas. When using accurate geometric and material data, this model can be used to elucidate the internal biomechanics of the CMC joint and to parametrically simulate processes which are hypothesized to play a role in the etiopathogenesis of CMC joint OA, such as capsular laxity and articular incongruence.
A Micromachined Device to Measure Subcellular Traction Forces
Authors: Galbraith Catherine G. , Sheetz Michael P.
Published: March 2022

Cell migration is an essential part of embryogenesis, wound healing and immuno-logical responses. As cells migrate forward, they exert forces against their extracellular matrices through matrix ligands such as integrins. The forces depend upon the cell-substratum adhesion strength [1] and the ability of integrins to bind to the cytoskeleton. The forces also vary according to cell speed; faster moving cells exert less force than slower moving cells [2]. Determining the traction forces exerted by cells and how these forces can be modified has important implications in tissue engineering where enhanced migration speed and traction induced reorganization of the extracellular matrix can have a profound effect on cell invasion.
Implementation of a Pharmocokinetic Approach to a Baculovirus System for Analytic Solutions to Virus and Cell Interactions
Authors: LeDuc Philip R. , Betenbaugh Michael J.
Published: March 2022

The baculovirus, Autographa californica multiple nuclear polyhedrosis virus (AcMNPV), expression system can be employed for a variety of different cellular applications. In recent years, this baculovirus system has been manipulated to serve as a recombinant system for the expression of heterologous proteins and as a possible retrovirus for gene therapy. A quantitative understanding of the cellular mechanics of virus trafficking would be useful in developing viral expression systems, understanding gene therapy and maximizing recombinant protein production. An analytic solution is presented which incorporates a pharmocokinetic system in order to analyze this problem of viral and cellular mechanics. The multiple stages of viral infection systems, specifically for the baculovirus system, include attachment, internalization, endosomal fusion, cytosol transportation, and nuclear accumulation. The effects of the rate parameters are investigated to determine the parameter sensitivity of the viral infection model in relation to accumulation of surface virus, internalized virus and nuclear virus. The concepts from this model can be used to design infection regimens for various cell lines and to analyze the inherent inefficiency of current baculovirus infecting systems. This approach can also be used to determine the effects of the rate-limiting behaviors exhibited by these types of cellular mechanics and can be further implemented to examine other types of infection applications including viral gene therapy [1].
Electrical Characterisation of Normal and Pathological Synovial Fluid in Arthritis
Authors: Pal S. , Kundu B. , Ghosh M. S.
Published: March 2022

Arthritis is a very painful and crippling disease, affecting almost 12–13% of the World population alone in the age group of 40 to 60 years, resulting out of the degeneration of the active lubricant synovial fluid (S.F.)[1]. The motivation of the present study is to investigate the electrical behaviours of synovial fluid in normal and different forms of arthritis; elaborate work has already been carried out on the rheological and biochemical properties of synovia but relatively very little has been reflected upon its electrical behaviour. It is believed that the rheological deterioration could show some changes in the electrical characteristics of this polar biofluid too.
Analysis of One-Dimensional Confined Swelling of Charged-Hydrated Soft Tissues
Authors: Liu Z. P. , Gu W. Y. , Lai W. M. , Mow V. C.
Published: March 2022

Charged hydrated soft tissues such as articular cartilage and the intervertebral disc have a strong tendency to swell in a hypotonic bath because of the high fixed charge density (FCD) within the tissue [e.g., 1–4]. For an excised tissue without externally applied loads, the tissue volume will change in response to changes in a bathing solution (free swelling) until the osmotic pressure is balanced by the elastic stresses on the solid matrix. A mechanical stress is needed to prevent the tissue from swelling from a given reference state (e.g., 0.15M NaCl). This stress may be called the swelling pressure relative to this reference state. The kinetic response of the swelling pressure to changes in bathing solution is associated with tissue material properties, such as the FCD, hydraulic permeability, ion diffusivity and stiffness of the solid matrix. In this study, we report our analysis on the one-dimensional confined swelling experiment of a charged hydrated soft tissue using the mechano-electrochemical theory developed in [3].
Nonlinear Viscoelastic Properties of the Inferior Glenohumeral Ligament
Authors: Huang Chun-Yuh , Wang Vincent M. , Cohen Nathaniel P. , Bucchieri John S. , Pawluk Robert J. , Pollock Roger G. , Mow Van C.
Published: March 2022

The inferior glenohumeral ligament (IGHL) of the shoulder has been recognized as an important static restraint with the arm in a position of clinical instability [6,10]. Recent studies [1,7,9] have reported different nonlinear viscoelastic behavior among the three anatomical regions of the IGHL (superior band, anterior axillary pouch and posterior axillary pouch) [10] as well as its response to repetitive loading.
The Effect of Graded Facetectomies on the Stiffness of the Lumbar Spine
Authors: Natarajan R. N. , Paruchuri S. , Andersson G. B. J. , Lavender S. A. , Patwardhan A. G.
Published: March 2022

Each year, there are 375,000 spine operations performed in the U.S. including a significant number that involve fusion. This is required to compensate for the loss in mechanical stiffness due to facetectomy. Although limited experimental studies have been done to analyze the mechanical effect of facetectomies, a finite element model allows for a sequential and complete study of the mechanical consequences of this surgical procedure. The purpose of this research is to quantify the loss in motion segment stiffness resulting from partial or total facetectomy through use of an analytical model of a lumbar spinal motion segment. These data will assist clinicians in determining when spinal fusion is necessary.
Sensitivity of Cervical Spine Finite Element Model to Material Property Variations
Authors: Kumaresan Srirangam , Yoganandan Narayan , Pintar Frank A.
Published: March 2022

The sensitivity of the human lower cervical spine finite element model to material property variations under physiologic loading vectors was determined. An anatomically accurate three-dimensional finite element model of the C4-C6 structure was exercised by independently varying the material property of its components under flexion, extension, lateral bending and axial torsion load vectors. Results indicated that the material properties of the soft tissue structures affect the external angular rotation response and the internal stresses in the spine more than the changes in the material properties of the hard tissues.
Positively and Negatively-Charged Ion Exchange Resins: Disparate Effects on Hard Tissue Repair
Authors: Simmons D. J. , Krukowski M. , Bi L. X. , Mainous E.
Published: March 2022

Bioelectrical investigations have long shown that surfaces of bone formation and resorption are negatively and positively charged respectively. We also know that in a number of experimental situations [1], implants of negatively-charged ion exchange resin (NCR= Sephadex, CM)are osteotropic, and that implants of positively-charged resin (PCR= Sephadex DEAE) strongly inhibit bone formation [2]. While the cellular mechanism of action for NCR is thought to involve the local production of transforming growth factor beta [3], the mechanics of PCR action is an unknown. Our laboratory has shown that PCR stunts the in vitro growth of medullary osteoprogenitor cells, normal and transformed osteoblasts, and a number of tumor cell lines [4], PCR was also able to strongly inhibit hamster pancreatic cell engraftment and the growth of established pancreatic cell tumors.
Cervical Spine Buckling: The Effects of Vertebral Mass and Loading Rate
Authors: Nightingale Roger W. , Armstrong Andrew J. , Camacho Daniel L. , Myers Barry S.
Published: March 2022

The importance of buckling during compressive loading of the cervical spine was suggested by Torg (1985) and has been subsequently demonstrated both quasi-statically2 and dynamically3. The complex deformations resulting from first and second order cervical spine buckling may explain the difficulty in producing repeatable injuries in impact experiments4,5,6. The purpose of this computational study is to test the hypothesis that during compressive impact loading of the cervical spine, the inertial properties of the vertebral bodies play a significant role in determining the buckling behavior. Further, it is hypothesized that these inertial effects provide the necessary constraints for the expression of higher order buckling modes7.
Implementation of Optimal Feedback Control to Model the Seated Postural Stability of Healthy and Spinal Cord-Injured Subjects
Authors: Kamper Derek G. , Parnianpour Mohamad , Barin Kamran , Weed Herman R.
Published: March 2022

Postural control may be severely compromised in individuals with spinal cord injury (SCI). Disturbance moments such as the ones experienced during normal driving may overwhelm the compensatory mechanisms in this population. Possible instability raises concerns about both comfort and, especially, safety for both passengers and drivers [1,2]. The goal of this research was to generate a computer model which could be used to investigate the effects of sustained disturbances on seated balance.
A Parametric Study on Virtual Tumor Detection Within Soft Tissue
Authors: Langrana Noshir A. , Fan Wen-Chung , Ladeji Jumoke
Published: March 2022

Palpation can aid physicians in the detection of tumors. Liver palpation during surgery, breast self-examination and clinical breast examination are some examples. There is a need for realistic palpation training tools for medical personnel (Campbell et al, 1991). Virtual reality provides an environment where a trainee can repeat the same scenario over a period of time. This provides an opportunity to expose the user to otherwise rare conditions.
Biomedical Imaging Analysis and Mesh Generation for Three-Dimensional Finite Element Models
Authors: Ehnes Dale L. , Stone James J.-S. , An Kai-Nan
Published: March 2022

The methodological procedure for generating three-dimensional (3-D) finite element analysis (FEA) geometry models from CT or MRI medical imaging scan data was developed in this study. Medical images of a human scapula and a fifth proximal phalangeal bone were used to demonstrate the techniques of image processing and generation of 3-D FEA models. The biomedical imaging quality and its effects on the outcome of the FEA geometry model was also studied.