Multiphase Poroelastic Finite Element Models for Soft Tissue Structures

1992 ◽  
Vol 45 (6) ◽  
pp. 191-218 ◽  
Author(s):  
Bruce R. Simon
Keyword(s):  
Finite Element ◽  
Soft Tissue ◽  
Material Behavior ◽  
Constitutive Law ◽  
Finite Strains ◽  
Finite Element Models ◽  
Tissue Fluid ◽  
Biomechanical Models ◽  
Highly Nonlinear ◽  
Tissue Structures

During the last two decades, biological structures with soft tissue components have been modeled using poroelastic or mixture-based constitutive laws, i.e., the material is viewed as a deformable (porous) solid matrix that is saturated by mobile tissue fluid. These structures exhibit a highly nonlinear, history-dependent material behavior; undergo finite strains; and may swell or shrink when tissue ionic concentrations are altered. Given the geometric and material complexity of soft tissue structures and that they are subjected to complicated initial and boundary conditions, finite element models (FEMs) have been very useful for quantitative structural analyses. This paper surveys recent applications of poroelastic and mixture-based theories and the associated FEMs for the study of the biomechanics of soft tissues, and indicates future directions for research in this area. Equivalent finite-strain poroelastic and mixture continuum biomechanical models are presented. Special attention is given to the identification of material properties using a porohyperelastic constitutive law and a total Lagrangian view for the formulation. The associated FEMs are then formulated to include this porohyperelastic material response and finite strains. Extensions of the theory are suggested in order to include inherent viscoelasticity, transport phenomena, and swelling in soft tissue structures. A number of biomechanical research areas are identified, and possible applications of the porohyperelastic and mixture-based FEMs are suggested.

Characterization of Material Behavior of the Fused Deposition Modeling Processed Parts

2017 ◽  
Author(s):  
Madhukar Somireddy ◽  
Aleksander Czekanski
Keyword(s):  
Finite Element ◽  
Elastic Moduli ◽  
Fused Deposition Modeling ◽  
Material Behavior ◽  
Constitutive Law ◽  
Finite Element Models ◽  
Strength Parameters ◽  
Fused Deposition ◽  
Deposition Modeling

In the present research, one of the additive manufacturing techniques, fused deposition modeling (FDM) fabricated parts are considered for investigation of their material behavior. The FDM process is a layer upon layer deposition of a material to build three dimensional parts and such parts behave as laminated composite structures. Each layer of the part acts as a unidirectional fiber reinforced lamina, which is treated as an orthotropic material. The mesostructure of a part fabricated via fused deposition modeling process is accounted for in the investigation of its mechanical behavior. The finite element (FE) procedure for characterization of a material constitutive law for the FDM processed parts is presented. In the analysis, the mesostructure of the part obtained via FDM process is replicated in the finite element models. Finite element models of tensile specimens are developed with mesostructure that would be obtained from FDM process, then uniaxial tensile test simulations are conducted. The elastic moduli of a lamina are calculated from the linear analysis and the strength parameters are obtained from the nonlinear finite element analysis. The present work provides a FE methodology to find elastic moduli and strength parameters of a FDM processed part by accounting its mesostructure in the analysis.

Viscoelastic characterization of soft tissue from dynamic finite element models

2008 ◽  
Vol 53 (22) ◽  
pp. 6569-6590 ◽  
Author(s):  
Hani Eskandari ◽  
Septimiu E Salcudean ◽  
Robert Rohling ◽  
Jacques Ohayon
Keyword(s):  
Finite Element ◽  
Soft Tissue ◽  
Finite Element Models ◽  
Dynamic Finite Element

scholarly journals Key considerations for finite element modelling of the residuum–prosthetic socket interface

2020 ◽  
pp. 030936462096778
Author(s):  
JW Steer ◽  
PR Worsley ◽  
M Browne ◽  
Alex Dickinson
Keyword(s):  
Finite Element ◽  
Soft Tissue ◽  
Finite Element Modelling ◽  
Soft Tissues ◽  
Shear Stresses ◽  
Material Models ◽  
Element Modelling ◽  
Prosthetic Socket ◽  
Highly Nonlinear ◽  
Socket Interface

Background: Finite element modelling has long been proposed to support prosthetic socket design. However, there is minimal detail in the literature to inform practice in developing and interpreting these complex, highly nonlinear models. Objectives: To identify best practice recommendations for finite element modelling of lower limb prosthetics, considering key modelling approaches and inputs. Study design: Computational modelling. Methods: This study developed a parametric finite element model using magnetic resonance imaging data from a person with transtibial amputation. Comparative analyses were performed considering socket loading methods, socket–residuum interface parameters and soft tissue material models from the literature, to quantify their effect on the residuum’s biomechanical response to a range of parameterised socket designs. Results: These variables had a marked impact on the finite element model’s predictions for limb–socket interface pressure and soft tissue shear distribution. Conclusions: All modelling decisions should be justified biomechanically and clinically. In order to represent the prosthetic loading scenario in silico, researchers should (1) consider the effects of donning and interface friction to capture the generated soft tissue shear stresses, (2) use representative stiffness hyperelastic material models for soft tissues when using strain to predict injury and (3) interrogate models comparatively, against a clinically-used control.

scholarly journals Biaxial estimation of biomechanical constitutive parameters of passive porcine sclera soft tissue

2021 ◽  
Author(s):  
Zwelihle Ndlovu ◽  
Dawood Desai ◽  
Thanyani Pandelani ◽  
Harry Ngwangwa ◽  
Fulufhelo Nemavhola
Keyword(s):  
Finite Element ◽  
Soft Tissue ◽  
Finite Element Model ◽  
Test Data ◽  
Element Model ◽  
Finite Element Models ◽  
Anisotropic Model ◽  
Material Models ◽  
Material Parameters ◽  
Constitutive Parameters

This study assesses the modelling capabilities of four constitutive hyperplastic material models to fit the experimental data of the porcine sclera soft tissue. It further estimates the material parameters and discusses their applicability to a finite element model by examining the statistical dispersion measured through the standard deviation. Fifteen sclera tissues were harvested from porcine’ slaughtered at an abattoir and were subjected to equi-biaxial testing. The results show that all the four material models yielded very good correlations at correlations above 96 %. The polynomial (anisotropic) model gave the best correlation of 98 %. However, the estimated material parameters varied widely from one test to another such that there would be needed to normalise the test data to avoid long optimisation processes after applying the average material parameters to finite element models. However, for application of the estimated material parameters to finite element models, there would be needed to consider normalising the test data to reduce the search region for the optimisation algorithms. Although the polynomial (anisotropic) model yielded the best correlation, it was found that the Choi-Vito had the least variation in the estimated material parameters thereby making it an easier option for application of its material parameters to a finite element model and also requiring minimum effort in the optimisation procedure. For the porcine sclera tissue, it was found that the anisotropy more influenced by the fiber-related properties than the background material matrix related properties.

scholarly journals Finite Element Software for Rubber Products Design

2018 ◽  
Vol 3 (1) ◽  
pp. 13-20
Author(s):  
Dávid Huri
Keyword(s):  
Finite Element ◽  
Complex Analysis ◽  
Large Deformations ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Material Models ◽  
Finite Element Software ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Different Types

Automotive rubber products are subjected to large deformations during working conditions, they often contact with other parts and they show highly nonlinear material behavior. Using finite element software for complex analysis of rubber parts can be a good way, although it has to contain special modules. Different types of rubber materials require the curve fitting possibility and the wide range choice of the material models. It is also important to be able to describe the viscoelastic property and the hysteresis. The remeshing possibility can be a useful tool for large deformation and the working circumstances require the contact and self contact ability as well. This article compares some types of the finite element software available on the market based on the above mentioned features.

Nonlinear Finite Element Analysis for Thermoplastic Pipes

1998 ◽  
Vol 1624 (1) ◽  
pp. 225-230 ◽  
Author(s):  
Chuntao Zhang ◽  
Ian D. Moore
Keyword(s):  
Finite Element ◽  
Geometrical Nonlinearity ◽  
Constitutive Models ◽  
Material Behavior ◽  
Pipe Material ◽  
Limit States ◽  
Element Analysis ◽  
Finite Element Program ◽  
Highly Nonlinear ◽  
Nonlinear Constitutive Models

Thermoplastic pipes are being used increasingly for water supply lines, storm sewers, and leachate collection systems in landfills. To facilitate limit states design for buried polymer pipes, nonlinear constitutive models have recently been developed to characterize the highly nonlinear and time-dependent material behavior of high-density polyethylene (HDPE). These models have been implemented in a finite element program to permit structural analysis for buried HDPE pipes and to provide information regarding performance limits of the structures. Predictions of HDPE pipe response under parallel plate loading and hoop compression in a soil cell are reported and compared with pipe response measured in laboratory tests. Effects on the structural performance of pipe material nonlinearity, geometrical nonlinearity, and backfill soil properties were investigated. Good correlations were found between the finite element predictions and the experimental measurements. The models can be used to predict pipe response under many different load histories (not just relaxation or creep). Work is ongoing to develop nonlinear constitutive models for polyvinylchloride and polypropylene to extend the predictive capability of the finite element model to these materials.

Initial Stress in Biomechanical Models of Atherosclerotic Plaques

2011 ◽  
Author(s):  
L. Speelman ◽  
A. C. Akyildiz ◽  
J. J. Wentzel ◽  
E. H. van Brummelen ◽  
J. Jukema ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Finite Element ◽  
Initial Stress ◽  
Atherosclerotic Plaque ◽  
Initial Stresses ◽  
Atherosclerotic Plaques ◽  
Finite Element Models ◽  
Biomechanical Models ◽  
Fibrous Cap ◽  
Stress Studies

Rupture of the cap of an atherosclerotic plaque is instigated when the stresses in the cap due to the blood pressure exceed the local cap strength. Image based computational finite element models of atherosclerotic plaques are widely used to compute stresses in the fibrous cap. These models are often based on pressurized geometries. The shape of the plaque is determined by the blood pressure at the time of imaging, and thus contains initial stresses (IS) and strains, which are generally ignored in plaque stress studies.

The Collagen Fiber Kinematics in the Anteroinferior Glenohumeral Capsule Are Not Affine-Predicted

2011 ◽  
Author(s):  
Carrie A. Voycheck ◽  
Patrick J. McMahon ◽  
Richard E. Debski
Keyword(s):  
Finite Element ◽  
Structural Model ◽  
Glenohumeral Joint ◽  
Structural Models ◽  
Clinical Problem ◽  
Collagen Fibers ◽  
Material Behavior ◽  
Finite Element Models ◽  
Glenohumeral Ligament ◽  
Glenohumeral Capsule

Glenohumeral dislocation is a significant clinical problem and often results in injury to the anteroinferior (anterior band of the inferior glenohumeral ligament (AB-IGHL) and axillary pouch) glenohumeral capsule. [1] However, clinical exams to diagnose capsular injuries are not reliable [2] and poor patient outcome still exists following repair procedures. [3] Validated finite element models of the glenohumeral capsule may be able to improve diagnostic and repair techniques; however, improving the accuracy of these models requires adequate constitutive models to describe capsule behavior. The collagen fibers in the anteroinferior capsule are randomly oriented [4], thus the material behavior of the glenohumeral capsule has been described using isotropic models. [5,6] A structural model consisting of an isotropic matrix embedded with randomly aligned collagen fibers proved to better predict the complex capsule behavior than an isotropic phenomenological model [7] indicating that structural models may improve the accuracy of finite element models of the glenohumeral joint. Many structural models make the affine assumption (local fiber kinematics follow global tissue deformation) however an approach to account for non-affine fiber kinematics in structural models has been recently developed [8]. Evaluating the affine assumption for the capsule would aid in developing an adequate constitutive model. Therefore, the objective of this work was to assess the affine assumption of fiber kinematics in the anteroinferior glenohumeral capsule by comparing experimentally measured preferred fiber directions to the affine-predicted fiber directions.

scholarly journals Finite element and deformation analyses predict pattern of bone failure in loaded zebrafish spines

2019 ◽  
Vol 16 (160) ◽  
pp. 20190430 ◽  
Author(s):  
Elis Newham ◽  
Erika Kague ◽  
Jessye A. Aggleton ◽  
Christianne Fernee ◽  
Kate Robson Brown ◽  
...  
Keyword(s):  
Finite Element ◽  
Disease Process ◽  
Intervertebral Discs ◽  
Vertebral Compression Fractures ◽  
Finite Element Models ◽  
Micro Computed Tomography ◽  
Spinal Motion ◽  
Biomechanical Models ◽  
Testing Stage ◽  
Ultimate Failure

The spine is the central skeletal support structure in vertebrates consisting of repeated units of bone, the vertebrae, separated by intervertebral discs (IVDs) that enable the movement of the spine. Spinal pathologies such as idiopathic back pain, vertebral compression fractures and IVD failure affect millions of people worldwide. Animal models can help us to understand the disease process, and zebrafish are increasingly used as they are highly genetically tractable, their spines are axially loaded like humans, and they show similar pathologies to humans during ageing. However, biomechanical models for the zebrafish are largely lacking. Here, we describe the results of loading intact zebrafish spinal motion segments on a material testing stage within a micro-computed tomography machine. We show that vertebrae and their arches show predictable patterns of deformation prior to their ultimate failure, in a pattern dependent on their position within the segment. We further show using geometric morphometrics which regions of the vertebra deform the most during loading, and that finite-element models of the trunk subjected reflect the real patterns of deformation and strain seen during loading and can therefore be used as a predictive model for biomechanical performance.

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