scholarly journals Effects of volumetric boundary conditions on the compressive mechanics and modeling of passive skeletal muscle

2020 ◽  
Author(s):  
Anurag Vaidya ◽  
Benjamin Wheatley
Keyword(s):  
Skeletal Muscle ◽  
Finite Element ◽  
Boundary Conditions ◽  
Human Body ◽  
Material Properties ◽  
Computational Models ◽  
Compressive Behavior ◽  
Confined Compression ◽  
In Vivo Loading

For over two decades, computational models of human body—such as the Toyota THUMS model— have been used in automobilesafety. These models rely on accurate material properties for eachtissue. However, the compressive behavior of skeletal muscle is notfully understood, particularly regarding the differences in muscleresponse to in vivo loading conditions. It is likely that in vivo muscleexperiences a variation between confined and unconfined volumetricboundary conditions, but nearly all previous studies investigatingpassively compressed tissue have focused on muscle in unconfinedcompression (UC). One study has investigated muscle underanisotropic semi-confined compression, however none have studiedmuscle in fully confined compression (CC). Thus, we have investigatedthe effects of volumetric boundary conditions (UC and CC) on the stressrelaxation of skeletal muscle. Moreover, a finite element modelsimultaneously characterizing muscle behavior in both boundaryconditions is explored.

scholarly journals Novel Volumetric Compression Relaxation Testing of Skeletal Muscles

2020 ◽  
Author(s):  
Anurag Vaidya ◽  
Benjamin Wheatley
Keyword(s):  
Skeletal Muscle ◽  
Stress Relaxation ◽  
Human Body ◽  
Material Properties ◽  
Skeletal Muscles ◽  
Computational Models ◽  
Surrounding Tissue ◽  
Unconfined Compression ◽  
Compressive Behavior

Computational models of the human body – such as those that simulate automotive impact – rely onaccurate material properties for bodily tissues. However, the compressive behavior of skeletal muscle is not fullyunderstood, particularly with regards to compression under confinement by surrounding tissue. For example, itis likely that in vivo muscle experiences a variation between confined and unconfined volumetric boundaryconditions, but nearly all previous studies have focused on muscle in unconfined compression (UC) or fullyconfined compression (CC). Thus, we have developed novel instrumentation to investigate the effects ofvolumetric boundary conditions (SC and CC) on stress relaxation of skeletal muscles.

scholarly journals An experimental and computational investigation of the effects of volumetric boundary conditions on the compressive mechanics of passive skeletal muscle

2019 ◽  
Author(s):  
Benjamin Wheatley
Keyword(s):  
Skeletal Muscle ◽  
Finite Element ◽  
Root Mean Square Error ◽  
Mean Square Error ◽  
Material Properties ◽  
Mean Square ◽  
Unconfined Compression ◽  
Confined Compression ◽  
Passive Muscle

Computational modeling, such as finite element analysis, is employed in a range of biomechanics specialties, including impact biomechanics and surgical planning. These models rely on accurate material properties for skeletal muscle, which comprises roughly 40% of the human body. Due to surrounding tissues, compressed skeletal muscle in vivo likely experiences a semi-confined state. Nearly all previous studies investigating passively compressed muscle at the tissue level have focused on muscle in unconfined compression. The goals of this study were to (1) examine the stiffness and time-dependent material properties of skeletal muscle subjected to both confined and unconfined compression (2) develop a model that captures passive muscle mechanics under both conditions and (3) determine the extent to which different assumptions of volumetric behavior affect model results. Muscle in confined compression exhibited stiffer behavior, agreeing with previous assumptions of near-incompressibility. Stress relaxation was found to be faster under unconfined compression, suggesting there may be different mechanisms that support load these two conditions. Finite element calibration was achieved through nonlinear optimization (normalized root mean square error <6%) and model validation was strong (normalized root mean square error <17%). Comparisons to commonly employed assumptions of bulk behavior showed that a simple one parameter approach does not accurately simulate confined compression. We thus recommend the use of a properly calibrated, nonlinear bulk constitutive model for modeling of skeletal muscle in vivo. Future work to determine mechanisms of passive muscle stiffness would enhance the efforts presented here.

scholarly journals Development and implementation of volumetric compression relaxation testing of skeletal muscle

2020 ◽  
Author(s):  
Anurag Vaidya ◽  
Benjamin Wheatley
Keyword(s):  
Skeletal Muscle ◽  
Boundary Conditions ◽  
Skeletal Muscles ◽  
Computational Models ◽  
Viscoelastic Model ◽  
Confined Compression ◽  
Automobile Safety ◽  
Body Tissues ◽  
Fluid Properties

Computational models of human body— such as the Toyota THUMS model— are frequently used in the automobile safety industry. Such models rely on accurate material properties for body tissues. However, the compressive behavior of skeletal muscle is not fully understood yet, particularly regarding the differences in muscle response to various in vivo loading conditions. It is likely that in vivo muscle experiences a variation between confined and unconfined volumetric boundary conditions, but nearly all previous studies investigating passively compressed tissue have focused on muscle in unconfined compression (UC) or fully confined compression (CC). One study has investigated muscle under anisotropic semi-confined compression (SC). However, the apparatus used by Bol et al. (2016) does not allow testing the effect of interstitial fluid properties on the mechanics of skeletal muscles. Thus, we have developed novel instrumentation that can help to investigate the effects of volumetric boundary conditions (SC and CC) on stress relaxation of skeletal muscles. We also present a viscoelastic model that shows how relaxation behavior differs from boundary conditions.

Dependence of Mechanical Behavior of the Murine Tail Disc on Regional Material Properties: A Parametric Finite Element Study

2005 ◽  
Vol 127 (7) ◽  
pp. 1158-1167 ◽  
Author(s):  
Adam H. Hsieh ◽  
Diane R. Wagner ◽  
Louis Y. Cheng ◽  
Jeffrey C. Lotz
Keyword(s):  
Finite Element ◽  
Mechanical Behavior ◽  
Nucleus Pulposus ◽  
Material Properties ◽  
Mechanical Response ◽  
Swelling Pressure ◽  
Transient Behavior ◽  
Sensitivity Analyses ◽  
Intact Mouse

In vivo rodent tail models are becoming more widely used for exploring the role of mechanical loading on the initiation and progression of intervertebral disc degeneration. Historically, finite element models (FEMs) have been useful for predicting disc mechanics in humans. However, differences in geometry and tissue properties may limit the predictive utility of these models for rodent discs. Clearly, models that are specific for rodent tail discs and accurately simulate the disc’s transient mechanical behavior would serve as important tools for clarifying disc mechanics in these animal models. An FEM was developed based on the structure, geometry, and scale of the mouse tail disc. Importantly, two sources of time-dependent mechanical behavior were incorporated: viscoelasticity of the matrix, and fluid permeation. In addition, a novel strain-dependent swelling pressure was implemented through the introduction of a dilatational stress in nuclear elements. The model was then validated against data from quasi-static tension-compression and compressive creep experiments performed previously using mouse tail discs. Finally, sensitivity analyses were performed in which material parameters of each disc subregion were individually varied. During disc compression, matrix consolidation was observed to occur preferentially at the periphery of the nucleus pulposus. Sensitivity analyses revealed that disc mechanics was greatly influenced by changes in nucleus pulposus material properties, but rather insensitive to variations in any of the endplate properties. Moreover, three key features of the model—nuclear swelling pressure, lamellar collagen viscoelasticity, and interstitial fluid permeation—were found to be critical for accurate simulation of disc mechanics. In particular, collagen viscoelasticity dominated the transient behavior of the disc during the initial 2200s of creep loading, while fluid permeation governed disc deformation thereafter. The FEM developed in this study exhibited excellent agreement with transient creep behavior of intact mouse tail motion segments. Notably, the model was able to produce spatial variations in nucleus pulposus matrix consolidation that are consistent with previous observations in nuclear cell morphology made in mouse discs using confocal microscopy. Results of this study emphasize the need for including nucleus swelling pressure, collagen viscoelasticity, and fluid permeation when simulating transient changes in matrix and fluid stress/strain. Sensitivity analyses suggest that further characterization of nucleus pulposus material properties should be pursued, due to its significance in steady-state and transient disc mechanical response.

Numerical Study of the Effect of Geometry and Boundary Conditions on the Collapse Behaviour of Stocky Stiffened Panels

2012 ◽  
Vol 154 (A2) ◽  
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Ultimate Strength ◽  
Material Properties ◽  
Finite Element Modelling ◽  
Numerical Study ◽  
Fe Analysis ◽  
Stiffened Panels ◽  
Element Modelling ◽  
Geometric Configurations

This study aims at studying different configurations of the stiffened panels in order to identify robust configurations that would not be much sensitive to the imprecision in boundary conditions that can exist in experimental set ups. A numerical study is conducted to analyze the influence of the stiffener’s geometry and boundary conditions on the ultimate strength of stiffened panels under uniaxial compression. The stiffened panels with different combinations of mechanical material properties and geometric configurations are considered. The four types of stiffened panels analysed are made of mild or high tensile steel and have bar, ‘L’ and ‘U’ stiffeners. To understand the effect of finite element modelling on the ultimate strength of the stiffened panels, four types of FE models are investigated in FE analysis including 3 bays, 1/2+1+1/2 bays, 1+1 bays and 1 bay with different boundary conditions.

Age Dependent and Anisotropic Material Properties of Immature Porcine Sclera

2013 ◽  
Author(s):  
Jami M. Saffioti ◽  
Brittany Coats
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Anisotropic Material ◽  
Computational Models ◽  
Fe Model ◽  
Ocular Tissues ◽  
Load Bearing ◽  
Anisotropic Properties ◽  
Age Dependent ◽  
Testing Protocols

Current finite element (FE) models of the pediatric eye are based on adult material properties [2,3]. To date, there are no data characterizing the age dependent material properties of ocular tissues. The sclera is a major load bearing tissue and an essential component to most computational models of the eye. In preparation for the development of a pediatric FE model, age-dependent and anisotropic properties of sclera were evaluated in newborn (3–5 days) and toddler (4 weeks) pigs. Data from this study will guide future testing protocols for human pediatric specimens.

A Comparative Study of the Human Body Finite Element Model Under Blast Loadings

2012 ◽  
Author(s):  
X. G. Tan ◽  
R. Kannan ◽  
Andrzej J. Przekwas
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Human Body ◽  
Material Properties ◽  
Complex Geometry ◽  
Blast Loading ◽  
Element Model ◽  
Stress Wave Propagation ◽  
Brain Response ◽  
Time Step

Until today the modeling of human body biomechanics poses many great challenges because of the complex geometry and the substantial heterogeneity of human body. We developed a detailed human body finite element model in which the human body is represented realistically in both the geometry and the material properties. The model includes the detailed head (face, skull, brain, and spinal cord), the skeleton, and air cavities (including the lung). Hence it can be used to accurately acquire the stress wave propagation in the human body under various loading conditions. The blast loading on the human surface was generated from the simulated C4 blast explosions, via a novel combination of 1-D and 3-D numerical formulations. We used the explicit finite element solver in the multi-physics code CoBi for the human body biomechanics. This is capable of solving the resulting large system containing millions of unknowns in an extremely scalable fashion. The meshes generated for these simulations are of good quality. This enables us to employ relatively large time step sizes, without resorting to the artificial time scaling treatment. In order to study the human body dynamic response under the blast loading, we also developed an interface to apply the blast pressure loading on the external human body surface. These newly developed models were used to conduct parametric simulations to find out the brain biomechanical response when the blasts impact the human body. Under the same blast loading we also show the differences of brain response when having different material properties for the skeleton, the existence of other body parts such as torso.

Finite Element Modeling of Repair Cartilage Beneath a Protective Layer

2003 ◽  
Author(s):  
John R. Owen ◽  
Jennifer S. Wayne
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Critical Role ◽  
Axial Deformation ◽  
Element Analysis ◽  
Direction Parallel ◽  
Preferred Direction ◽  
Articulating Surface ◽  
Line Direction

Significant efforts are being devoted to the creation of replacement tissue for repair of defects in articular surfaces. Some success has been realized; yet, the normal zonal characterstics of articular cartilage throughout its thickness and normal material properties have not been reproduced in vitro in scaffolds nor in vivo in repairing defects. The fate of such transplanted scaffolds in vivo may be doomed mechanically from the outset if material properties of sufficient quality are not developed. The superficial tangential zone (STZ) has been shown to play a critical role in supporting axial loads and retaining fluids (Glazer and Putz, 2002, Torzilli, et al, 1983, Torzilli, 1993). Previous models have demonstrated excessive axial deformation of repair cartilage without the STZ (Smith, et al 2001, Wayne, et al, 1991) Additionally, modeling the STZ of normal cartilage as transversely isotropic has yielded better agreement with indentation experimental results than isotropic models (Korhonen, et al, 2002, Mow, et al, 2000, Cohen, et al, 1993). This study uses finite element analysis to model the STZ with a preferred direction parallel to the articulating surface, thereby simulating a “split-line” direction. The in-plane directions are modeled normal to the “split-line” direction and the articulating surface. Normal and repairing defects are modeled with the importance of the STZ emphasized.

DEVELOPMENT AND BIOFIDELITY EVALUATION OF AN OCCUPANT BIOMECHANICAL MODEL OF A CHINESE 50TH PERCENTILE MALE FOR SIDE IMPACT

2017 ◽  
Vol 17 (07) ◽  
pp. 1740039 ◽  
Author(s):  
ZHENGWEI MA ◽  
LELE JING ◽  
FENGCHONG LAN ◽  
JINLUN WANG ◽  
JIQING CHEN
Keyword(s):  
Finite Element ◽  
Human Body ◽  
Computational Models ◽  
Rating Scale ◽  
Element Model ◽  
Side Impact ◽  
Body Parts ◽  
Lateral Impact ◽  
Human Body Model ◽  
Body Model

Finite element modeling has played a significant role in the study of human body biomechanical responses and injury mechanisms during vehicle impacts. However, there are very few reports on similar studies conducted in China for the Chinese population. In this study, a high-precision human body finite element model of the Chinese 50th percentile male was developed. The anatomical structures and mechanical characteristics of real human body were replicated as precise as possible. In order to analyze the model’s biofidelity in side-impact injury prediction, a global technical standard, ISO/TR 9790, was used that specifically assesses the lateral impact biofidelity of anthropomorphic test devices (ATDs) and computational models. A series of model simulations, focusing on different body parts, were carried out against the tests outlined in ISO/TR 9790. Then, the biofidelity ratings of the full human body model and different body parts were evaluated using the ISO/TR 9790 rating method. In a 0–10 rating scale, the resulting rating for the full human body model developed is 8.57, which means a good biofidelity. As to different body parts, the biofidelity ratings of the head and shoulder are excellent, while those of the neck, thorax, abdomen and pelvis are good. The resulting ratings indicate that the human body model developed in this study is capable of investigating the side-impact responses of and injuries to occupants’ different body parts. In addition, the rating of the model was compared with those of the other human body finite element models and several side-impact dummy models. This allows us to assess the robustness of our model and to identify necessary improvements.

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