bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of Blood Flow Computations Using Analytical, In Vitro, and In Vivo Methods
Authors: Taylor Charles A. , Draney Mary T.
Published: January 2022

Computational investigations of blood flow require validation using analytical solutions and in vitro and in vivo experimental methods. Analytical solutions to the Navier-Stokes equations are possible in only a few select cases with very special geometry and boundary conditions. Fortunately, a canonical solution for pulsatile flow does exist: the Womersley solution for fully developed pulsatile flow in a straight circular cylinder. This analytical solution is essential in assessing the accuracy of numerical methods and examining such important issues as spatial and temporal discretization errors. In vitro experimental investigations can be used to validate computational solutions for blood flow in rigid and deformable models of complex geometries. Detailed information on velocity fields can be obtained using Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV). Although analytical and in vitro experimental methods are extremely important tools for validating numerical solutions, ultimately in vivo measurements, utilizing ultrasound or magnetic resonance imaging, must be utilized for validating predictions made with numerical methods.

Computational solutions for blood flow in a straight cylindrical vessels are validated using Womersley’s analytic solution. Computational solutions for flow in a model of an end-to-side anastomosis are validated by comparing predicted velocity profiles with those obtained by Loth (1993) using LDA. Magnetic resonance imaging of blood flow in the aorta was performed during dynamic exercise conditions to investigate whether numerically predicted changes in infrarenal blood flow are observed in vivo.
Flow in a Model of a Ventricular Assist Device: Numerical and Experimental Results
Authors: König C. S. , Clark C. , Mokhtarzadeh-Dehghan M. R.
Published: January 2022

The flow in a ventricular assist device (VAD) is unsteady and three-dimensional, and is characterised by a moving boundary. An experimental model of a VAD was designed specifically to allow validation of numerical results. Qualitative comparisons between the experimental and numerical results were conducted based on the flow patterns of particle paths, obtained from flow visualisation, and of velocity vectors from the simulation. Quantitative comparisons have been conducted based on velocity data using a laser Doppler anemometer (LDA). Validation is being extended in the areas of pressure and wall shear stress distributions, and particle residence times.
An Experimental Model of Interfacial Mechanics in Pulmonary Gas Embolism
Authors: Eckmann David M. , Cavanagh Daniel P.
Published: January 2022

A model of pulmonary gas embolism consists of air bubbles in steady water flow in an inclined rigid acrylic or glass tube. Pressure-flow relationships are measured as a function of tube inclination angle and bubble volume. Flow resistance increases with steeper tube angles and increasing bubble volume. Critical flow rates for bubble detachment and displacement in the upstream and downstream directions are determined. Critical flow rates depend on bubble size, tube material and inclination angle.
A Computational Study of the Flow in Bifurcating Channels and Tubes: Exhalation
Authors: Hassan Amgad A. , Evrensel Cahit A.
Published: January 2022

Researchers have used both the rectangular geometry (Evrensel, et al., 1996, King et al., 1985) and the circular geometry (Kim et al., 1986) to study the effect of the shear stress on the mucus clearance in pulmonary airways. Since the circular geometry makes it practically impossible to keep the mucus layer constant, rectangular geometry is preferable. The main goal of this study is to investigate the differences and similarities between the turbulent flows through bifurcating 2-D rectangular channel and a 3-D circular tube. The geometry studied is similar to the one used in our previous work (Hassan and Evrensel, 1996), but the flow direction is reversed to study the exhalation case. The results indicate a flow separation in downstream of the main branch in both cases and a region of a relatively strong secondary flow for the bifurcating tube. Also, the distribution of the shear stress is shown to be similar in both geometries, although the magnitude of the maximum shear is larger for the circular case.
Effects of Boundary Conditions for the CFD Modelling of Respiratory Flow in an Asymmetric Bifurcation
Authors: Kurujareon Jutarat , Holdø Arne Erik , Calay Rajnish K.
Published: January 2022

Modelling airflow in the conducting airways of the human lungs is important to predict particle deposition of both contaminants and pharmaceuticals. In order to achieve good predictions of deposition the airflow has to be modelled correctly.

Because of the complexity of the bronchial tree structure, the using of the small airways and highly asymmetric of the structure, in vivo studies are difficult for obtaining the global airways effects and the detail of small airways downstream. While the experimental studies are crucial to obtain a somewhat satisfied detail by utilising physiologically scaled up model to study airflow in the lungs. However, those experimental studies are limited up to the 3rd generations of bifurcation and the smaller airways deep within the lungs are inaccessible to most experimental technique even in the scaled up model. CFD studies through the solutions of Navier-Stoke equations seem to be a better way to access the smaller airways and easy to show a large number of data in three dimensional physiologically realistic airway geometries.

In both experimental and CFD simulations the control and choice of boundary conditions are essential. A particular problem is the control of boundary conditions, since the complete lung models cannot be modelled and the experiment in vivo data are not available. The only data available is the flow rate at the mouth as a function of time. Because of the complexity of the airway geometries and the limitation of the present day computer power a truncated lung model has to be used to study in airflow dynamics in the lungs at the first stage. This results in a need to control the flow rates in each airway which causes a problem in the numerical boundary condition.

Thus in the current investigation aims to carry out the appropriate numerical boundary condition for controlling the flow rates in each airway. A two dimensional CFD model of an asymmetric single bifurcation has been used as a test case. This numerical airway model is an anatomic approximation based on Horsfield’s data [Horsfield et al., 1971]. The radii of curvature in the transition zone from the parent branch to daughter branches and a curved shape of carinal ridge have been taken into account on this model. Different flow boundary conditions have been used for respiratory flow. The most realistic result has been obtained by using numerical pistons attached into the end of most downstream airways. Each piston has been enlarged/contracted to generate the required oscillatory flow rate of air through the single bifurcation of the system. The two dimensional CFD model of the airways with numerical pistons along with finite-element mesh model has been shown in figure 1. These results are compared with the published CFD results using standard boundary conditions [Wilquem & Degrez, 1997].
Nonlinear Oscillations in a Collapsible-Tube Model
Authors: Mawasha P. Ruby , Gross Richard , Conway Ted
Published: January 2022

In the present study, a nonlinear analysis is performed for a collapsible tube system consisting of a reservoir with inlet and outlet flow conditions. The forced downstream pressure is modeled as a cubic function similar to the van der Pol equation for a relaxation oscillator. Features that give rise to sustained relaxation oscillations exhibited in the van der Pol oscillator manifest here as inertia due to fluid flow, capacitance due to compressible volume inside the reservoir, and an energy source from the work done by the downstream pressure. Mechanisms that give rise to relaxation oscillations in a collapsible tube system are examined based on numerical results. Also, the effects of compressible volume, length of the channel on pressure and mass flow rate oscillation are investigated.
Thromboresistance of Electrostatically Seeded Endothelial Cells on 4 mm I.D. e-PTFE Using a Canine Femoral Arterial Model
Authors: Bowlin Gary L. , Rittgers Stanley E. , Bulgrin Jeffrey , Sims Rick
Published: January 2022

Recently, an electrostatic technique has been described which enhances EC adhesion and retention upon physiologic shear stress [1–2]. The results of the in vitro evaluation indicated that the optimum electrostatic seeding using human umbilical vein endothelial cells (HUVEC) was obtained at +1.0 Volt applied for a 16 minute seeding time. The optimum conditions resulted in an average EC seeding density of 73,540 HUVEC/cm2 with an average viable surface coverage of 97.4%. The average morphological maturation ranking represented all flattened HUVECs with an average damage ranking corresponding to minimal cellular membrane damage. The HUVEC retention study (in vitro) showed that the optimally electrostatic seeded grafts experienced no significant (α = 0.05) loss of HUVECs upon physiologic shear stress exposure (15 dynes/cm2). The biochemical assay results showed no significant (α = 0.05) production of prostacyclin or thromboxane A2 by either the gravitationally or electrostatically seeded HUVECs [2].
Tools and Techniques for Visualizing Three-Dimensional Medical Datasets
Authors: Tombropoulos Rhea Z. , Huffman John
Published: January 2022

Imaging techniques such as computed tomography (CT) and magnetic resonance (MR) enable physicians to view a patient’s internal anatomy and the relative location of structures within the anatomy. Although, to date, these techniques have been used primarily for diagnosis, three-dimensional medical imaging is beginning to emerge as a powerful tool for training physicians, aiding in presurgical planning, providing intraoperative surgical guidance, and enabling the performance of surgeries remotely. Such new applications demand real-time visualization of medical data in three dimensions, as well as effective methods for interacting with these data.
Use of Daily Activity Data to Assess Injury Potential in Low-Speed Motor Vehicle Crashes
Authors: Paver Jacqueline G. , Khadilkar Anil V. , Ward Carley C.
Published: January 2022

Human tolerance testing has established criteria for the risk of serious-to-fatal injury to specific body regions. Using these criteria, injury potential in motor vehicle crashes has been assessed in sled and full-scale car-crash tests using volunteers, anthropomorphic dummies, and cadavers. Based on these criteria, vehicle compliance testing is aimed to protect occupants from serious-to-fatal injury. However, there exists no threshold or minimum crash severity (e.g., delta V) that establishes a “no injury” v. “injury” condition. This study addresses efforts to establish such a condition and identifies confounding factors, the most confused of which may be injury pattern, severity, and symptom duration. Volunteer data was compiled from measurements made during non-injurious daily activities and compared to loading experienced by similarly-instrumented volunteers in low-speed sideswipe, angled-side, broadside, rear-end, and front-end impacts. These results support the use of daily activity data for comparisons of loading and provide additional data to establish non-injurious crash severities in low-speed motor vehicle accidents. However, for different types of impacts, additional work is still required to establish accepted thresholds above which “injury” is probable.
Biomechanical Analysis of Restraint Receptacles
Authors: Sances Anthony
Published: January 2022

Various designs of automotive restraint receptacles (buckles) are currently in use which can release inertially. A substantial number of patents exist for designs of receptacles that protect against inertial unlatching. Furthermore, a number of currently manufactured receptacles are of anti-inertial unlatching design. This study was conducted to evaluate various receptacles which are susceptible to inertial unlatching to determine the impact speed, the applied force and acceleration with a laboratory pendulum using various interface materials. The receptacles without anti-inertial design opened at speeds of 2.2 to 3.4 meters/second with forces in the region of 220N to 440N at accelerations to 100 G’s at the time of unlatching. In contrast, the anti-inertial designed receptacles did not open at speeds up to 5.4 meters/second with corresponding higher impact force and acceleration.
Directional Properties of Gray and White Brain Tissue Undergoing Large Deformation
Authors: Prange Michael T. , Meaney David F. , Margulies Susan S.
Published: January 2022

Biomechanical analyses of diffuse axonal injury (DAI) suggest a link between brain material response (stress or strain) and white matter injury (Margulies et al., 1990; Meaney et al., 1994; Mendis et al., 1995; Lee et al., 1987; Zhou et al., 1994). Material properties of the brain tissue, including a description of their inhomogeneity, are important to predict intracranial deformations from the applied inertial loads. It is essential that these properties are defined separately for the gray and white matter, and account for the potential nonlinear viscoelasticity at finite strains.
Microstructural Kinematics During Elongation of Central Nervous System Tissue: Implications for Traumatic Axonal Injury
Authors: Bain Allison C. , Meaney David F.
Published: January 2022

Diffuse axonal injury (DAI) is the most common form of closed head injury and is responsible for over a third of all head injury deaths. Axons are the primary constituent of the white matter in the brain, and frequently form aligned tracts in the brain. Research has indicated that traumatic axonal injury occurs when these axons experience tensile strains above a critical level. Our laboratory is currently working toward identifying injurious strain levels for axons using the optic nerve stretch model. The optic nerve is an isolated bundle of aligned central nervous system (CNS) axons, thus, dynamic elongation of the optic nerve is an in vivo approximation of the process by which axons are injured in the brain.
Parametric Tests of the Human Pelvis: The Influence of Load Rate and Boundary Condition on Peak Stress Location During Simulated Side Impact
Authors: Plummer Jason W. , Eberhardt Alan W. , Alonso Jorge , Mann Kenneth A.
Published: January 2022

Pelvic fractures occur in 8% to 14% of near-side automobile collisions (Cesari et al., 1980). The type of fracture varies widely and includes pubic rami, pubic symphysis, acetabuli, sacro-iliac joint, and iliac wing fractures. In the laboratory environment, fractures of the pubic rami have been reproduced in both full cadaver (Cavanaugh et al., 1990) and isolated pelvis studies (Guillemot et al., 1997). Recently, Molz and co-workers (1997) found acetabular fractures in their isolated pelvic experiments. However, the loading history and mechanical boundary conditions for the two experiments varied widely.
Intervertebral Disc Pressure Changes During Low Back Treatment Procedures
Authors: Gudavalli Maruti R. , Cox James M. , Cramer Gregory D. , Baker James A. , Patwardhan Avinash G.
Published: January 2022

Some of the treatments for low back pain use different motions to the spine. One such treatment protocol used by chiropractic physicians in the treatment of low back pain is the Cox flexion-distraction procedure (1). The Cox procedure consists of placing the patient in a prone position on a flexion-distraction table and then creating distraction, flexion, extension, lateral flexion, and circumduction motions at the joint of interest. Gudavalli et al. (2) reported decreases in intradiscal pressures during the combined motions of flexion-distraction motions. However, no data exist during other motions of the table. The purpose of the present study was to measure the changes in the intradiscal pressures during all the maneuvers of the treatment protocols.
A Multi-Body Optical Measurement System for the Study of Human Joint Motion
Authors: DiAngelo Denis J. , Vossel Keith A. , Jansen Thomas H.
Published: January 2022

Human joint systems exhibit complex, coupled movement patterns. Various measurement devices have been developed to study human joint behavior. They include electromechanical, electromagnetic, and electro-optical systems; and radiographic techniques [Lim et al., 1997; Milne et al., 1996; Moeini et al., 1996]. When measuring global joint motion, accuracy of the system must be considered. Measures of “relative” joint motion depend on system resolution and repeatability. An improved three-dimensional (3-D) non-contact measurement system was develop to study human joint motion. System calibration for two-dimensional (2-D) analysis was performed. Application to the cervical spine is presented.
Biomechanical Study on C4-C7 Cervical Spine
Authors: Natarajan R. N. , Chen B. H. , An H. S. , Andersson G. B. J.
Published: January 2022

It is known that surgery performed at one level in the spine affects the biomechanical characteristics of adjacent levels. Study of biomechanical response such as change in flexibility at the level of surgery as well as change in motions at the adjacent levels to applied multiplaner loadings will help to understand effects of surgery and rehabilitation requirements in these tissues. Experimental studies on the effect of large number of different surgeries on the stability of cervical spine are very expensive and time consuming if not impossible. Finite element modeling can be effectively used under these circumstances. Recent developments in this area have produced 2 segment (C4-C6) finite element models (Yoganandan et al., 1996). Three-motion segment model becomes necessary to understand the unconstrained effect of different surgical procedures performed at the middle level. The present study focuses on the biomechanical characteristics of a three motion segment model (C4-C7) so that it is possible to study the effect of surgery at the C5-C6 level without any interference from either the applied loading or the boundary conditions. The three-motion segment finite element model was validated under pure flexion and torsion moment loadings.
Geriatric Cervical Spine Biomechanics: Effect of Degeneration Severity on Biomechanical Response
Authors: Kumaresan Srirangam , Yoganandan Narayan , Pintar Frank A. , Maiman Dennis J.
Published: January 2022

Biomechanical responses of the geriatric cervical spine with varying degrees of degeneration were studied using an anatomically accurate three-dimensional nonlinear detailed finite model of the human lower cervical spine. The geometrical details of the bony structure of the cervical spine model were obtained from the computed tomography images and the soft tissue details from cryomicrotome anatomic sections. The finite element model was validated under physiologic compression, flexion, extension and eccentric complex loading modes in terms of the angular stiffness, and the localized strain in the vertebral body and bilateral facet masses. Different levels of degenerated conditions in the cervical spine model were simulated by altering the material properties of the intervertebral nucleus pulposus, fiber content in the annulus fibrosus and decrease in the height of the disc. The external stiffness and internal stress responses of geriatric degenerated spines were compared with the adult normal spine. The overall stiffness of the geriatric spine increased with increasing severity of degeneration. Similarly, the stress magnitudes in the vertebral body increased with increasing levels of degeneration.
Stress Distribution in Osteoarthritic and Normal Glenohumeral Joints: A Finite Element Analysis
Authors: Ramaniraka N. , Farron A. , Iannotti J. P. , Rakotomanana L. , Terrier A. , Courvoisier D. , Leyvraz P.-F.
Published: January 2022

Many studies have been conducted to evaluate the pattern of glenoid erosion from CT scans e.g. (Mullaji et al., 1994). The basic postulate was that the knowledge of the eroded geometry compared to the normal ones enabled the choice of the most appropriate design a fixation of glenoid component in presence of osteoarthrisis. The presence of mechanical loadings in soft tissues and bones probably requires the additional knowledge of the stresses within the bones. All these data are then expected to allow the surgery to be planned to obtain the most secure fixation in the available bone. Different complex shoulder models have been introduced in the literature combining the rigid body motion e.g. (Engin and Turner, 1989) — or beam modelling for bones — with the passive and active truss elements for modelling ligaments and muscles e.g. (Van der Helm et al., 1992). Although providing very useful information on forces and kinematics, most of these models are not interested in the bone stresses particularly at the epiphysis and at the articular surfaces.
Cement Fixation of the Acetabular Cup in Total Hip Replacement: Are 10 mm-Depth Anchorage Holes Required?
Authors: Mootanah Rajshree , Ingle Paul , Watkinson Brian V. , Cheah Kevin , Dowell John
Published: January 2022

Long-term studies have shown that failure of the acetabular component in a total hip replacement increases exponentially ten years following surgery (Morscher, 1992). During the cemented fixation of the acetabular cup in a total hip replacement, anchorage holes are drilled in the acetabulum in order to increase the torsional resistance of cement bonding. So far, there seems to be no definite number, size, shape, location and depth of the anchorage holes. Usually, the depth is 10mm, the edge is 90°, while the number and size of holes are interrelated; the smaller the diameter of the hole, the larger the number of holes are drilled and vice versa.
A Mixed Finite Element Formulation of Triphasic Theory and its Application to Free Swelling Problem
Authors: Sun D. N. , Guo X. E. , Lai W. M. , Mow V. C. , Gu W. Y.
Published: January 2022

It has been shown that the triphasic theory [1] is capable of describing many mechano-electrochemical phenomena observed in charged hydrated soft tissues or cells, such as free-swelling, stress-relaxation, streaming potential, diffusion potential, and electro-osmosis [e.g., 1–3]. The theory is useful for the study of signal transduction mechanisms at both tissue and cellular levels. This is important to understanding tissue physiology and pathology. To facilitate applications of the triphasic theory to many practical problems, it is necessary to develop a numerical method for quantitatively investigating tissue behaviors. Thus, the objective of this study is to develop a finite element formulation for the triphasic theory. A free-swelling problem was studied using this finite element method to investigate effects of inhomogeneity of fixed charge density (FCD) on ion concentration, tissue deformation, fluid flow and streaming potential etc.
A Generalized Self-Consistent Method for Osteonal Cortical Bone Modeling
Authors: Guo X. Edward , Dong X. Neil , Huang Y. Young
Published: January 2022

Morphologically, cortical bone resembles a fiber-matrix composite material such that an osteon is analogous to the fiber while the interstitial bone to the matrix. For example, there have been several studies addressing the mechanical properties of cortical bone based on this point of view (Hogan 1992, Aoubiza et al. 1996). Our interest in cortical bone mechanics stems from the characterization and mechanisms of microdamage such as microcracks in cortical bone. The exponential increase of microdamage in cortical bone tissue has been implicated in increased bone fragility with aging (Schaffler et al. 1995). None of these above mentioned techniques can be conveniently used for our long term study on cortical bone damage mechanics. Recently, significant advances have been made in the mechanics of composite materials. For example, a generalized self-consistent formulation for effective mechanical properties of composites have been developed such that it can apply to the case where the volume fraction of fibers is as high as 80–90% (Huang et al. 1994). In addition, microcracks can be easily included for damage mechanics or fracture mechanics analysis. The objective of this paper is to develop a general scheme for a cortical bone composite model based on the generalized self-consistent method for calculation of effective elastic properties.
Minimizing Stress Shielding in Hip Implant by Mechanical Design
Authors: Cunningham Robert A.
Published: January 2022

Today’s technology of hip prosthesis implants, where the implant stem is fixed to the internal surface of the femur by bonding, bone growth or press fit, results in “stress shielding” of that portion of the implanted femur. Subsequent bone atrophy often requires remedial work and/or replacement of the hip prosthesis. A new design is presented in which the manner of the load transfer from the prosthesis to the bone greatly reduces stress shielding. The reduction of the stress shielding is so dramatic that a once-in-a-lifetime installation, without remedial work is a strong possibility.
A Hand Model for the Development and Validation of a Fuzzy Controlled Orthosis
Authors: Petroff Neil B. , Mason Paul A. C. , Reisinger Kim D.
Published: January 2022

Restoring hand control to upper extremity paralysis victims will enable them the perform daily tasks and lead independent lifestyles. This study was undertaken to develop a fuzzy controlled hand orthosis that will be unobtrusive, user friendly and aesthetically pleasing. A simplified hand orthosis model, consisting of four fingers and a thumb, is derived for the purpose of planning appropriate grasp trajectories (fingertip pinch, lateral pinch and cylindrical grasp) and validating a fuzzy logic control architecture. The controller is hierarchical in design, consisting of a supervisory controller that uses the intended motion to coordinate individual finger motions and, a lower level controller for each finger that produces the required joint angles for the specific grasp. Preliminary results indicate that the hand orthosis model is capable of achieving the required grasps, and that fuzzy logic can be used as the controller.
Design Issues in the Development of an Externally-Powered Partial Hand Prosthesis
Authors: Weir Richard F. ff.
Published: January 2022

We are planning to build an externally-powered prosthesis for persons with partial-hand amputations of all digits. Currently, there are no commercially available externally-powered partial-hand prostheses that are functional yet cosmetic. This paper sets out some of the design constraints and issues that must be considered before such a hand can be built. We feel that preservation of the wrist motion for positioning of the terminal device is of paramount importance to achieving maximum function and cosmesis. In a partial hand prosthesis the only space for any mechanisms is in the digits. The challenge is to be able to fit all the requisite mechanisms and electronics in this highly confined volume and still have reasonable performance. The availability of small motors (MicroMo MM1016) operating in synergy (Childress, 1972) makes such a device possible.
The Utilization of Ambient-Stored Pre-Preg Carbon Composite Material With a New Fabrication Technique for the Development of Ankle-Foot Braces
Authors: Fite Richard , Polliack Adrian A. , Landsberger Samuel , McNeal Donald R. , Vargas Vicente
Published: January 2022

A novel, room temperature-stored carbon-graphite cloth has been utilized to produce a variety of ankle-foot orthoses (AFO). It was discovered that the curing process of the composite could be altered, and the AFO could be partially cured under vacuum. After removal of the composite AFO from the mold, the material maintains its shape and allows the orthotist to hand-modify it further. Following this, the brace is returned to the oven for final curing. This advance in the fabrication process may allow for the manufacture and distribution of modular AFOs in the partially cured state without need of refrigeration. They could then be custom-shaped by hand to fit the patient. This material is post-formable by heat with no delamination.

Mechanical testing of the carbon cloth is in progress along with evaluation of the brace by able-bodied subjects. Failure mode investigation is also underway and attention is now directed to safety issues. Results of some of these findings are presented.
Experimental Study of a Stress Change in Ankle-Foot Orthoses due to a Weight Change
Authors: Chu Tai-Ming
Published: January 2022

An Ankle-Foot Orthosis (AFO) is a device that prescribed to assist patient during recovering of lost functions, and at the same time, to protect the ankle-foot from further injuries when patients are in motion. Currently, polypropylene is the most popular thermoplastic for all kinds of custom-made orthoses. It has the characteristics of low weight, high strength, high fatigue resistance and excellent molding capabilities. However, there are too many pre-manufacturing parameters such as the thickness and curvatures required that makes the quality control impossible. Supan and Hovorka (1995) studied the thermoplastic Ankle-Foot Orthoses adjustments/replacements in young cerebral palsy and spina bifida patients. Six types of thermoplastic AFOs were tested. They found that neuromusculoskeletal functional status appears to determine the AFO design and its replacement. Chu, et al., (1997) developed an experimental method that studied the stress changes in the AFO due to AFO geometry changes. The goal of this project is to quantify the stress changes associated with a series of body weights and motion change; thus, to determine if the resulting stresses are of such magnitude as to potentially result in fractures and destruction of the AFOs.
Biaxial Fiber Kinematics and Structural Constitutive Modeling of Small Intestinal Submucosa
Authors: Gloeckner D. Claire , Sacks Michael S.
Published: January 2022

Small intestinal submucosa (SIS) has been studied as a potential biomaterial for use in tissue engineering applications. Extracted from the mammalian small bowel, it consists of two collagen fiber populations at ∼±30° from the longitudinal axis. We have previously investigated the biaxial mechanical properties of SIS (Sacks and Gloeckner, 1998), which were comparable to other bioprosthetic biomaterials. Our long-term goal is to develop structural constitutive models of implantable biomaterials made from SIS and other acellular materials. These models can aid in determining how well a biomaterial will perform in the virgin and remodeled states. Structural models require quantitative morphologic information, especially fiber structure and kinematics. In this study, we examined the change in the fiber kinematics at different states of biaxial stretch and developed an initial structural constitutive model for SIS.
Long-Term Mechanical Fatigue Response of Porcine Bioprosthetic Heart Valves
Authors: Billiar Kristen L. , Sacks Michael S.
Published: January 2022

Porcine bioprosthetic heart valves (PBHVs) have excellent short-term durability, but have generally poor long-term performance. Although the exact mechanism is still unknown, it is almost certain that mechanical factors play a significant role in PBHV failure. Aortic valve cusps are highly anisotropic with a complex, non-uniform structure (Fig. 1, top). It is therefore understandable that to date there have been no quantitative studies to determine how mechanical behavior is altered by mechanical fatigue. In this study we performed biaxial mechanical tests and uniaxial failure tests on cusps harvested from 4mmHg glutaraldehyde treated PBHVs loaded intact up to 300 × 106 cycles.
Prediction of Effects of Mechanical Stress and Estrogen on Bony Structure Using Fuzzy Logic Control
Authors: Luo Zong-Ping , An Kai-Nan , Turner Russell T.
Published: January 2022

A theoretical model has been developed based on fuzzy logic control to predict bony response to mechanical load and estrogen. The results show good agreement with the experimental findings, which suggests that bone may be regulated by simple remodeling rules, similar to those used in the fuzzy logic control.
Comparing Standing Characteristics of Prosthesis Users and Normal Subjects Using a Tracking Model
Authors: Chan Richmond B. , Childress Dudley S. , Jhoun Janet H.
Published: January 2022

A model for standing based on a “human tracking” model is presented. The model suggests that the velocity of the center of pressure is proportional to the acceleration of the center of mass, with a time delay. Standing characteristics of seven normal and three bilateral above-knee prosthesis users were studied. There was agreement between the experimental data and prediction of the model. Results support the potential capability of this model to characterize standing behavior.
Non-Invasive Estimation of Wall Stress Distribution in Abdominal Aortic Aneurysm
Authors: Raghavan Madhavan Lakshmi , Federle Michel P. , Webster Marshall W. , Vorp David Alan
Published: January 2022

In the clinical management of abdominal aortic aneurysm (AAA) patients, it is desirable to determine when, during the course of this disease, the risk of aneurysm rupture justifies surgical intervention and its related complications. Presently, there is no reliable criterion to predict the risk of rupture of AAA and hence make a sound surgical decision. We believe that principles in mechanics may be used to predict the propensity of rupture for AAA. With the development of an aneurysm, the stress on the aortic wall increases progressively (Vorp et al., 1998) until it reaches its gradually decreasing failure strength (Raghavan et al., 1996). Therefore, knowledge of AAA wall stress distribution could be used as a reliable indicator of rupture. Previous stress analyses of AAA by other researchers (e.g., Stringfellow et al., 1987, Elger et al., 1996) were performed using hypothetical, idealized. 2D geometries of AAA and/or simplified mathematical models with the primary goal of understanding the mechanics of the problem. In this work, we demonstrate a methodology to determine more reliable estimates of the in-vivo wall stresses for actual AAA on a patient to patient basis. The ultimate goal of this work is to develop a clinically usable computational tool that may be used for individualized non-invasive assessment of AAA patients.
Integrated Design and Control of Media Advance System for Thermal Inkjet Printers
Authors: Chen Cheng-Yi , Chiu George T.-C. , Cheng Chi-Cheng
Published: January 2022

Inkjet printer offers an attractive feature set that fits well to the consumer’s needs at the low-end color hardcopy market. Better performance at the lower cost is and will always be the driving force for the future product development. In this paper, we presented an integrated approach to the design and control of the media advance system in thermal inkjet printers. Using H∞ analysis and synthesis approach, the effects of design tolerance and system disturbance on the achievable performance is characterized. We will use the media advance system of thermal inkjet printers to illustrate the effectiveness of the proposed approach. The benefit of using an integrated design and control approach will also be discussed.
The Depletion and Retention Characteristics of PFPE Lubricants and X1P on Magnetic Media
Authors: Jiaa Chi L. , Liu Youmin
Published: January 2022

The depletion and retention characteristics of magnetic thin film rigid disks coated with PFPE lubricants and X1P additive were investigated in this study. The tribological performance was evaluated by a drag test with a waffle head sliding against the disk that was designed to mechanically wear out the lubricant layer. An IR beam was aligned on the test track to directly measure the amount of PFPE lubricants and X1P left on the media surfaces for determining the depletion and retention characteristics of the lubricants. The test results show that under ambient and hot/wet (60°C/80%RH) conditions the media coated with AM3001 have higher retention ratio on the test track than those coated with ZDOL2000. After the head sliding for 100 hours, about 40% AM3001 still remains on the test track, while almost no ZDOL2000 left. However, the X1P was observed to strongly anchor on the surface and not wear out as PFPE lubricants did. The retention characteristics of X1P are independent of lube combination, either AM or ZDOL lubricants. The data indicate that more than 60% of the original X1P remains on the test track under all test conditions. The remaining X1P is quite stable and does not decrease as the drag test time increases during the latter test stage. It is demonstrated that X1P exhibits a good antiwear property and excellent retention performance.
A Flexibility-Based Inverse Algorithm for Identification of Substructural and Joint Properties
Authors: Park K. C. , Felippa Carlos A.
Published: January 2022

This paper presents an inverse problem methodology for the identification of structural joint characteristics. The underlying theory employs a substructural flexibility method that allows statistical uncertainties in joints and interfaces. The method partitions structures into continuum and localized joint/interface substructural regions. The former are modeled by continuum finite elements and built up with the standard direct-stiffness method. Joint and interface regions are constructed from continuum and/or special elements. The novel aspect of the method is that the coupling of substructures is effected in terms of node-collocated Lagrange multipliers, which leads naturally to a boundary-flexibility formulation. Coupling through interaction forces addresses the concern that delicate localized effects are not masked out in the overall structural model. This heightened sensitivity is significant for inverse problems in which localized properties and uncertainties are deduced indirectly, through a hierarchical “peeling off” process. The method is applied to identify joint flexibilities in a model engine mount, which demonstrates key features of the method and its high-fidelity capability.
Identification Problems for Vibrating Composite Plates
Authors: Abrate Serge , Perry Marcus
Published: January 2022

This paper addresses an inverse vibration problem for cantilever composite plates. A two-step procedure is proposed to estimate the elastic properties of the material. First, simple formulas are used to provide an initial estimate given experimentally determined natural frequencies. A very accurate Rayleigh-Ritz model is then used to refine these estimates and obtain good agreement between predictions and experimental values. Imperfect support conditions at the root affect the dynamics of the plate significantly. Neglecting this effect leads to unrealistic estimates of the material properties. A procedure to identify the stiffness of the supports is presented and demonstrated on several examples.
Fatigue Crack Propagation Under Variable-Amplitude Load: Part II — A Stochastic Model
Authors: Ray Asok , Patankar Ravindra
Published: January 2022

This paper is the second part in a two-part sequence and presents a stochastic model of fatigue crack propagation in metallic materials that are commonly encountered in mechanical structures and machine components of complex systems (e.g., aircraft, spacecraft, ships and submarines, and power plants). The stochastic model is built upon the deterministic state-space model of fatigue crack growth under variable-amplitude load presented in the first part. Predictions of the stochastic model are in agreement with the experimental data for specimens made of 2024-T3 and 7075-T6 aluminum alloys and Ti-6A1-4V alloy. The (non-stationary) statistics of the crack growth process under (tensile) variable-amplitude load can be obtained in a closed form without solving stochastic differential equations in the Wiener or Itô setting. The crack propagation model thus allows real-time execution of decision algorithms for risk assessment and life prediction on inexpensive platforms such as a Pentium processor.
Model-Based Selection of Accelerometer Locations for Helicopter Gearbox Monitoring
Authors: Wang Keming , Yang Dongzhe , Danai Kourosh , Lewicki David G.
Published: January 2022

A novel method is introduced to quantify based on the structure of the gearbox the monitoring effectiveness of accelerometer locations on the housing. In this method, monitoring effectiveness of sets of accelerometer locations is defined in terms of two indices: the coverage index and the overlap index. The coverage index is obtained from an influence matrix defining the level of effect of component faults on accelerometer readings. The overlap index denotes the level of overlap between pairs of accelerometers in coverage of components. The effectiveness of the proposed method is verified experimentally based on measurement-fault data obtained from an OH-58A main rotor gearbox. The estimated rankings of various sets of accelerometer locations based on the estimated values of their monitoring effectiveness agree closely with those obtained empirically.
Collocation Algorithm for Solving Equations of Motion of Multibody Mechanical Systems
Authors: Pasic Hajrudin , Williams Robert L. , Hui Chunwu , Moody Russell
Published: January 2022

A collocation algorithm is applied to solve index three differential-algebraic equations (DAEs) of multibody dynamics. The algorithm is based on the approximation of solutions with polynomials of different degrees. The resultant system of algebraic equations, with the coefficients of the polynomials as the unknown variables, is solved with the Newton-Raphson method. The results show the potential of the collocation algorithm as a general approach for the solutions to initial value problems of higher index, nonlinear, stiff DAEs.
Nonlinear System Identification by Automatic Localized Modeling
Authors: Li C. James , Huang Tung-Yung
Published: January 2022

This paper describes two automated methods to identify binary and continuous systems from their operating data. Both methods employ data clustering and localized modeling. For binary functions, the Karnaugh map is employed to transform an arbitrarily high dimensional distribution into a two-dimensional one where an elliptical clustering algorithm can be performed to identify a set of local neural net models to approximate the data. For real continuous functions, the input space is partitioned into regions that are small enough that a simple neural network can approximate the data well in each region. The partitioning method is inspired by an automatic mesh generation algorithm for Finite Element Method (FEM). A 7-bit Exclusive-OR (XOR), a Van der Pol oscillator, and a pendulum, respectively, are used to test the two proposed algorithms, and they are found to be satisfactory in generating models that can simulate the systems well.
Human Assisted Walking Robot
Authors: Neuhaus Peter D. , Kazerooni H.
Published: January 2022

The design goal was to invent a machine that could successfully maneuver heavy loads in isolated areas for extended periods of time. The motivation was to reduce the complexity of autonomous walking robots by involving the human in the operation of the machine. By taking advantage of the intelligence of the operator, the complexity of bipedal locomotion was reduced to tractable problem. The result of this research is that a two-legged, single actuated degree of freedom, walking machine was designed, built, and tested. The robot successfully navigated terrain including steep inclines and stairs. Additionally, a mechatronic control system was added to provide for smooth speed control and regulation. The leg driving architecture, the double four-bar linkage, designed for this machine can be extended to produce simplified four- and six-legged walking machines. The preliminary results can be used to extend this concept to a machine with an actuated balance assist system based on the human operator’s interaction with the machine.
Perception and Control of Finger Forces
Authors: Jones Lynette A.
Published: January 2022

The focus of this research is on the perception and control of forces produced by the hand. It is known that the change in force that subjects can reliably discriminate is approximately 6%, and that subjects are able to match forces generated by two corresponding muscle groups with an accuracy of approximately 15%. The present study was concerned with measuring the ability to control finger force using only haptic feedback and both haptic and visual feedback. It was found that subjects were surprising good at controlling forces for up to 120 s using only haptic feedback with mean absolute errors of less than 0.3 N over a force range of 2–6 N. The variation in force averaged 10.5% when haptic feedback was available and decreased to 6% when visual feedback was also provided. These results provide a framework for specifying the characteristics of force-reflecting haptic interfaces that should optimize human perception.
Tactile After-Images From Static Contact
Authors: Singh U. , Fearing R. S.
Published: January 2022

It is well known that human skin is a viscoelastic material, and the mechanical and electrophysiological responses to transient indentation have been studied and modelled. For tactile display system design, it is also important to determine the perceptual effects, if any, of skin viscoelasticity. The spatial characteristics and sinusoidal steady state response of the sense of touch have been comparatively well studied. This paper describes initial work in quantifying tactile “after-images” resulting from large loads applied over several seconds to the finger tip. We first measured finger tip relaxation responses. We then ran psychophysical experiments on human subjects to determine if viscoelastic memory affects tactile perception. To reduce sensitivity to fine surface detail and since most teletaction systems will include an elastic layer as an anti-aliasing filter, our tests were carried out with a layer of elastic material on the finger. We found a statistically significant correlation between mechanical memory and perception “after-images” from large loads presented to the subjects. We offer a possible explanation for the results based on simplified mechanical models of the skin.
Dextrous Haptic Interface for JACK™
Authors: Popescu Viorel G. , Burdea Grigore C.
Published: January 2022

This paper presents a simulation system which integrates a real-time hand sensing and force-feedback interface (the Rutgers Master II) with a full body modeling software (JACK™). The RM-II system and the Polhemus Fastrak™ 3D magnetic tracker were initially integrated with “JACK” full-body simulation software. The system performance (graphics update rates, sensorreading updates) is evaluated on two graphic workstations (SGI High Impact and SGI Infinite Reality). Next we propose the concept of a Virtual Human Agent enhanced with haptic feedback. This concept is illustrated by a simulation developed using the RM-II system, JACK software library and a speech recognition engine.
Design and Characteristic Analysis of 7 DOF Hybrid Master Arm With Human Arm Kinematics
Authors: Choi Jonghyun , Kim Jungtae , Kim Dongshin , Lee Chongwon , Park Jong-Oh , Park Jang-Hyun
Published: January 2022

There are already various types of master arm for teleoperation. But the viewpoint of human arm characteristic requires higher adaptability of master device to human arm. Several characteristics of human arm required for design of new master arm are as follows: hybrid kinematics of human arm (serial and parallel in consideration of kinematics and actuator configuration), distributed muscle. New concept of master arm with human arm characteristics was generated. It has 7 DOF hybrid kinematics and distributed form. Modeling and kinematic analysis was done. Master arm construction and teleoperation system were developed and related control routine was explained. This new master arm shows several improvements in light weight even with worn-type and higher adaptability to distributed human muscles.