Nonlinear Viscoelastic Material Property Estimation of Lower Extremity Residual Limb Tissues

2004 ◽  
Vol 126 (2) ◽  
pp. 289-300 ◽  
Author(s):  
Ergin To¨nu¨k ◽  
M. Barbara Silver-Thorn
Keyword(s):  
Finite Element ◽  
Viscoelastic Material ◽  
Soft Tissues ◽  
Residual Limb ◽  
Element Analysis ◽  
Nonlinear Viscoelastic Material ◽  
Nonlinear Viscoelastic ◽  
Force Relaxation ◽  
Material Formulation

Axisymmetric nonlinear finite-element analysis was used to simulate force-relaxation and creep data obtained during in vivo indentation of the residual limb soft tissues of six individuals with trans-tibial amputation [1]. The finite-element models facilitated estimation of an appropriate set of nonlinear viscoelastic material coefficients of extended James-Green-Simpson material formulation for bulk soft tissue at discrete, clinically relevant test locations. The results indicate that over 90% of the experimental data can be simulated using the two-term viscoelastic Prony series extension of James-Green-Simpson material formulation. This phenomenological material formulation could not, however, predict the creep response from relaxation experiments, nor the relaxation response from creep experiments [2–5]. The estimated material coefficients varied with test location and subject indicating that these coefficients cannot be readily extrapolated to other sites or individuals.

scholarly journals Combining Freehand Ultrasound-Based Indentation and Inverse Finite Element Modeling for the Identification of Hyperelastic Material Properties of Thigh Soft Tissues

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Nolwenn Fougeron ◽  
Pierre-Yves Rohan ◽  
Diane Haering ◽  
Jean-Loïc Rose ◽  
Xavier Bonnet ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Material Properties ◽  
Soft Tissues ◽  
Force Sensor ◽  
Element Analysis ◽  
Element Modeling ◽  
The Mean ◽  
Constitutive Parameters

Abstract Finite element analysis (FEA) is a numerical modeling tool vastly employed in research facilities to analyze and predict load transmission between the human body and a medical device, such as a prosthesis or an exoskeleton. Yet, the use of finite element modeling (FEM) in a framework compatible with clinical constraints is hindered by, among others, heavy and time-consuming assessments of material properties. Ultrasound (U.S.) imaging opens new and unique opportunities for the assessment of in vivo material properties of soft tissues. Confident of these advances, a method combining a freehand U.S. probe and a force sensor was developed in order to compute the hyperelastic constitutive parameters of the soft tissues of the thigh in both relaxed (R) and contracted (C) muscles' configurations. Seven asymptomatic subjects were included for the experiment. Two operators in each configuration performed the acquisitions. Inverse FEM allowed for the optimization of an Ogden's hyperelastic constitutive model of soft tissues of the thigh in large displacement. The mean shear modulus identified for configurations R and C was, respectively, 3.2 ± 1.3 kPa and 13.7 ± 6.5 kPa. The mean alpha parameter identified for configurations R and C was, respectively, 10 ± 1 and 9 ± 4. An analysis of variance showed that the configuration had an effect on constitutive parameters but not on the operator.

Nonlinear Viscoelastic Finite Element Analysis of Adhesive Joints

1988 ◽  
Vol 16 (3) ◽  
pp. 146-170 ◽  
Author(s):  
S. Roy ◽  
J. N. Reddy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Viscoelastic Behavior ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Element Analysis ◽  
Adhesively Bonded Joints ◽  
Nonlinear Viscoelastic ◽  
Structural Failures ◽  
Updated Lagrangian

Abstract A good understanding of the process of adhesion from the mechanics viewpoint and the predictive capability for structural failures associated with adhesively bonded joints require a realistic modeling (both constitutive and kinematic) of the constituent materials. The present investigation deals with the development of an Updated Lagrangian formulation and the associated finite element analysis of adhesively bonded joints. The formulation accounts for the geometric nonlinearity of the adherends and the nonlinear viscoelastic behavior of the adhesive. Sample numerical problems are presented to show the stress and strain distributions in bonded joints.

Development and Verification of a Dynamic TKR Model

2002 ◽  
Author(s):  
Jason P. Halloran ◽  
Anthony J. Petrella ◽  
Paul J. Rullkoetter
Keyword(s):  
Finite Element ◽  
Contact Mechanics ◽  
Dynamic Loading ◽  
Soft Tissues ◽  
Dynamic Models ◽  
Total Joint Replacement ◽  
Fe Model ◽  
Loading Conditions ◽  
Dynamic Loading Conditions

The success of current total knee replacement (TKR) devices is contingent on the kinematics and contact mechanics during in vivo activity. Indicators of potential clinical performance of total joint replacement devices include contact stress and area due to articulations, and tibio-femoral and patello-femoral kinematics. An effective way of evaluating these parameters during the design phase or before clinical use is via computationally efficient computer models. Previous finite element (FE) knee models have generally been used to determine contact stresses and/or areas during static or quasi-static loading conditions. The majority of knee models intended to predict relative kinematics have not been able to determine contact mechanics simultaneously. Recently, however, explicit dynamic finite element methods have been used to develop dynamic models of TKR able to efficiently determine joint and contact mechanics during dynamic loading conditions [1,2]. The objective of this research was to develop and validate an explicit FE model of a TKR which includes tibio-femoral and patello-femoral articulations and surrounding soft tissues. The six degree-of-freedom kinematics, kinetics and polyethylene contact mechanics during dynamic loading conditions were then predicted during gait simulation.

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