HYPER-ELASTIC PARAMETER ESTIMATION OF HUMAN HEEL-PAD: A FINITE ELEMENT AND EVOLUTIONARY BASED ALGORITHM

2012 ◽  
Vol 12 (03) ◽  
pp. 1250034 ◽  
Author(s):  
M. M. KHANI ◽  
H. KATOOZIAN ◽  
K. AZMA ◽  
I. NASEH ◽  
A. H. SALIMI
Keyword(s):  
Experimental Data ◽  
Genetic Algorithm ◽  
Finite Element ◽  
Nonlinear Material ◽  
Elastic Behavior ◽  
Diabetic Patients ◽  
Initial Contact ◽  
Heel Pad ◽  
Hyper Elastic ◽  
The Impact

The heel-pad as a biological shock absorber has an important role in the initial contact phase of gait cycle dissipating the impact forces resulted in locomotion. An axisymmetric finite element model of human heel-pad has been generated and the heel-pad experimental data deduced from a published force-deflection graph of the same specimen (Iain R. Spears, Janice E. Miller-Young), Iterative identification task has been used to extract nonlinear material properties describing hyper-elastic behavior of heel-pad. The genetic algorithm was incorporated into estimation process using an interface program. Two parameters of hyper-elastic materials potential energy function represented by Mooney–Rivlin were determined by using the genetic algorithm technique to minimize the displacement error between the experimental data and the corresponding finite element results after a considerable number of iterations. The result can be used for design and construction of synthetic heel-pad and therapeutic foot wear as well as insoles, especially for diabetic patients.

scholarly journals The Role of Pre-Conditioning Frequency in the Experimental Characterization of Hyper-Elastic Materials as Models for Soft Tissue Applications

2016 ◽  
Vol 08 (05) ◽  
pp. 1650066 ◽  
Author(s):  
Serena de Gelidi ◽  
Gianluca Tozzi ◽  
Andrea Bucchi
Keyword(s):  
Experimental Data ◽  
Biological Tissues ◽  
Experimental Simulation ◽  
Elastic Behavior ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Elastic Materials ◽  
Hyper Elastic ◽  
The Impact

Rubber-like materials as many soft tissues can be described as incompressible and hyper-elastic materials. Their comparable elastic behavior, up to a certain extent, has been exploited to develop and test experimental methodologies to be then applied to soft biological tissues such as aortic wall. Hence, theoretical and experimental simulation of aortic tissue, and more generally blood vessel tissue, has been often conducted using rubbers. Despite all the efforts in characterizing such materials, a clear and comprehensive testing procedure is still missing. In particular, the influence of pre-conditioning in the mechanical response of hyper-elastic materials has been often neglected. In this paper, the importance of pre-conditioning is demonstrated by: (i) exploring the effect of stretching frequency applied before the uniaxial tensile test; (ii) recognizing the role of specimen geometry and strain amplitude; (iii) verifying the impact of experimental data acquisition on finite element predictions. It was found that stress–strain relationship shows a statistical difference between some frequencies of pre-conditioning and its absence. Only certain pre-conditioning frequencies were able to generate repeatable experimental data for strip or dumb-bell shapes. This feature corresponds to a consistent reduction in the scatter of critical pressures obtained by numerical simulations.

scholarly journals Finite Element Simulations of the ID Venous System to Treat Venous Compression Disorders: From Model Validation to Realistic Implant Prediction

2021 ◽  
Author(s):  
Alissa Zaccaria ◽  
Francesco Migliavacca ◽  
David Contassot ◽  
Frederic Heim ◽  
Nabil Chakfe ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Element Model ◽  
Venous System ◽  
Venous Compression ◽  
Risk Of Rupture ◽  
Model Reliability ◽  
The Impact ◽  
Force Displacement ◽  
Realistic Geometry

AbstractThe ID Venous System is an innovative device proposed by ID NEST MEDICAL to treat venous compression disorders that involve bifurcations, such as the May-Thurner syndrome. The system consists of two components, ID Cav and ID Branch, combined through a specific connection that prevents the migration acting locally on the pathological region, thereby preserving the surrounding healthy tissues. Preliminary trials are required to ensure the safety and efficacy of the device, including numerical simulations. In-silico models are intended to corroborate experimental data, providing additional local information not acquirable by other means. The present work outlines the finite element model implementation and illustrates a sequential validation process, involving seven tests of increasing complexity to assess the impact of each numerical uncertainty separately. Following the standard ASME V&V40, the computational results were compared with experimental data in terms of force-displacement curves and deformed configurations, testing the model reliability for the intended context of use (differences < 10%). The deployment in a realistic geometry confirmed the feasibility of the implant procedure, without risk of rupture or plasticity of the components, highlighting the potential of the present technology.

Impact Pressure Evaluation of Water Jet Peening on Typical Concave Surfaces: Theoretical and Finite Element Analysis

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Shusen Zhao ◽  
Zhanshu He ◽  
Yanmin Li
Keyword(s):  
Finite Element ◽  
Peak Pressure ◽  
Water Jet ◽  
Impact Pressure ◽  
Concave Surface ◽  
Opening Angle ◽  
Initial Contact ◽  
Groove Surface ◽  
Metal Parts ◽  
The Impact

Abstract Water jet peening (WJP), a surface modification technique, can use the impact pressure induced by shock waves to introduce compressive residual stress in the surface of metal parts, thereby improving the fatigue life of metal parts, especially has broad application prospects in strengthening the concave surface area of metal parts. The impact pressure of the concave surface is different compared with the flat surface due to the effects of geometrical factors on the shock wave released. In this work, a mathematical model for calculating the peak pressure in the initial contact area of the concave surface is developed, and the effects of geometric factors (opening angle of V surface α and spherical radius R) and WJP parameters (jet velocity v and jet diameter d) on the peak pressure are analyzed by using finite element simulation models of WJP on concave V-shaped surface, concave spherical surface, V-groove surface, spherical groove surface, and spherical groove surface established with the coupled Eulerian–Lagrangian (CEL) algorithm of abaqus. A mechanism of impact pressure evaluation of the concave surface is developed to explain the peak pressure results obtained from finite element models. The results show that the peak pressure is mainly determined by α and v, while d does not affect the peak pressure for a concave V-shaped or V-groove surface. The peak pressure is mainly determined by R, v, and d for a concave spherical or spherical groove surface.

Response of Dolos Concrete Armor Units to Impact Loads

1991 ◽  
Vol 113 (4) ◽  
pp. 286-291 ◽  
Author(s):  
J. W. Tedesco ◽  
P. B. McGill ◽  
W. G. McDougal
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Concrete Strength ◽  
Impact Resistance ◽  
Nonlinear Material ◽  
Impact Loads ◽  
Model Formulation ◽  
Element Analysis ◽  
The Impact

A finite element analysis is conducted to determine the critical impact velocities for concrete dolos. The model formulation includes deformations at the contact surface and nonlinear material properties. Two dolos orientations are considered: vertical fluke seaward and horizontal fluke seaward. In both cases, the larger units fail at lower angular impact velocities. It is also shown that doubling the concrete strength increases the impact resistance by approximately 40 percent.

scholarly journals Coupled Numerical Method for Modeling Propped Fracture Behavior

2021 ◽  
Vol 11 (20) ◽  
pp. 9681
Author(s):  
Tamás Lengyel ◽  
Attila Varga ◽  
Ferenc Safranyik ◽  
Anita Jobbik
Keyword(s):  
Fluid Dynamics ◽  
Finite Element Method ◽  
Finite Element ◽  
Fracture Behavior ◽  
Elastic Behavior ◽  
Hydraulic Fractures ◽  
Coupled Models ◽  
Fracture Conductivity ◽  
The Impact ◽  
Element Method

Hydraulic fracturing is a well-known production intensification technique in the petroleum industry that aims to enhance the productivity of a well drilled mostly in less permeable reservoirs. The process’s effectiveness depends on the achieved fracture conductivity, the product of fracture width, and the permeability of the proppant pack placed within the fracture. This article presents an innovative method developed by our research activity that incorporates the benefit of the Discrete—and Finite Element Method to describe the in situ behavior of hydraulic fractures with a particular emphasis on fracture conductivity. DEM (Discrete Element Method) provided the application of random particle generation and non-uniform proppant placement. We also used FEM (Finite Element Method) Static Structural module to simulate the elastic behavior of solid materials: proppant and formation, while CFD (Computational Fluid Dynamics) module was applied to represent fluid dynamics within the propped fracture. The results of our numerical model were compared to data of API RP-19D and API RP-61 laboratory measurements and findings gained by publishers dealing with propped fracture conductivity. The match of the outcomes verified the method and encouraged us to describe proppant deformation and embedment and their effect as precisely as possible. Based on the results, we performed sensitivity analysis which pointed out the impact of several factors affecting proppant embedment, deformation, and fracture conductivity and let one be aware of a reasonable interpretation of propped hydraulic fracture operation. However, DEM–CFD coupled models were introduced regarding fracturing before, to the best of our knowledge, the developed workflow of coupling DEM–FEM–CFD for modeling proppant-supported fracture behavior has not been applied yet, thus arising new perspectives for explorers and engineers.

scholarly journals A Three-Dimensional Inverse Finite Element Analysis of the Heel Pad

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Snehal Chokhandre ◽  
Jason P. Halloran ◽  
Antonie J. van den Bogert ◽  
Ahmet Erdemir
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Three Dimensional ◽  
Element Analysis ◽  
Heel Pad ◽  
Tool Force ◽  
Specific Material ◽  
Inverse Finite Element Analysis

Quantification of plantar tissue behavior of the heel pad is essential in developing computational models for predictive analysis of preventive treatment options such as footwear for patients with diabetes. Simulation based studies in the past have generally adopted heel pad properties from the literature, in return using heel-specific geometry with material properties of a different heel. In exceptional cases, patient-specific material characterization was performed with simplified two-dimensional models, without further evaluation of a heel-specific response under different loading conditions. The aim of this study was to conduct an inverse finite element analysis of the heel in order to calculate heel-specific material properties in situ. Multidimensional experimental data available from a previous cadaver study by Erdemir et al. (“An Elaborate Data Set Characterizing the Mechanical Response of the Foot,” ASME J. Biomech. Eng., 131(9), pp. 094502) was used for model development, optimization, and evaluation of material properties. A specimen-specific three-dimensional finite element representation was developed. Heel pad material properties were determined using inverse finite element analysis by fitting the model behavior to the experimental data. Compression dominant loading, applied using a spherical indenter, was used for optimization of the material properties. The optimized material properties were evaluated through simulations representative of a combined loading scenario (compression and anterior-posterior shear) with a spherical indenter and also of a compression dominant loading applied using an elevated platform. Optimized heel pad material coefficients were 0.001084 MPa (μ), 9.780 (α) (with an effective Poisson’s ratio (ν) of 0.475), for a first-order nearly incompressible Ogden material model. The model predicted structural response of the heel pad was in good agreement for both the optimization (<1.05% maximum tool force, 0.9% maximum tool displacement) and validation cases (6.5% maximum tool force, 15% maximum tool displacement). The inverse analysis successfully predicted the material properties for the given specimen-specific heel pad using the experimental data for the specimen. The modeling framework and results can be used for accurate predictions of the three-dimensional interaction of the heel pad with its surroundings.

scholarly journals Life Prediction of Rubber Automotive Components Using Finite Element Method

2011 ◽  
Vol 462-463 ◽  
pp. 535-540
Author(s):  
M.S.A. Samad ◽  
Aidy Ali ◽  
Mohd Khairol A. Arifin
Keyword(s):  
Finite Element ◽  
Life Prediction ◽  
Large Strain ◽  
Elastic Behavior ◽  
Element Analysis ◽  
Automotive Components ◽  
The Finite Element Analysis ◽  
Hyper Elastic ◽  
Engine Mount ◽  
Failure Location

The usage of rubbers has always been so important, especially in automotive industries. Rubbers have a hyper elastic behavior which is the ability to withstand very large strain without failure. The normal applications for rubbers are used for shock absorption, sound isolation and mounting. In this study, the predictions of fatigue life of an engine mount of rubber automotive components were presented. The finite element analysis was performed to predict the critical part and the strain output were incorporated into fatigue model for prediction. The predicted result shows agreement in term of failure location of rubber mount.

Restraint Systems in Tactical Vehicles: Uncertainty Study Involving Airbags, Seatbelts and Military Gear

2017 ◽  
Author(s):  
Dorin Drignei ◽  
Zissimos P. Mourelatos ◽  
Ervisa Zhamo ◽  
Jingwen Hu ◽  
Cong Chen ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Body Size ◽  
Injury Risk ◽  
Finite Element Models ◽  
Risk Distribution ◽  
Frontal Crashes ◽  
Safety Features ◽  
The Impact

Adding advanced safety features (e.g. airbags) to restraint systems in tactical vehicles could decrease the injury risk of their occupants. The impact of frontal crashes on the occupants has been assessed recently through experimental data and finite element models. However, the number of such experiments is relatively small due to high cost. In this paper, we conduct an uncertainty study to infer the advantage of including advanced safety features, if a larger number of experiments were possible. We introduce the concept of group injury risk distribution that allows us to quantify under uncertainty the injury risk associated with advanced safety features, while averaging out the effect of uncontrollable factors such as body size. Statistically, the group injury risk distribution is a mixture of individual injury risk distributions of design conditions in the group. We infer that advanced safety features reduce the injury risk by at least two thirds in frontal crashes.

Restraint Systems in Tactical Vehicles: Uncertainty Study Involving Airbags, Seatbelts, and Military Gear

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Dorin Drignei ◽  
Zissimos P. Mourelatos ◽  
Ervisa Zhamo ◽  
Jingwen Hu ◽  
Cong Chen ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Body Size ◽  
Injury Risk ◽  
Risk Distribution ◽  
Frontal Crashes ◽  
Safety Features ◽  
The Impact

Adding advanced safety features (e.g., airbags) to restraint systems in tactical vehicles could decrease the injury risk of their occupants. The impact of frontal crashes on the occupants has been assessed recently through experimental data and finite element (FE) models. However, the number of such experiments is relatively small due to high cost. In this paper, we conduct an uncertainty study to infer the advantage of including advanced safety features, if a larger number of experiments were possible. We introduce the concept of group injury risk distribution that allows us to quantify under uncertainty the injury risk associated with advanced safety features, while averaging out the effect of uncontrollable factors such as body size. Statistically, the group injury risk distribution is a mixture of individual injury risk distributions of design conditions in the group. We infer that advanced safety features have the potential to reduce substantially injury risk in frontal crashes.

COUPLED BOUNDARY ELEMENT-FINITE ELEMENT MODEL TO ESTIMATE HUMAN HEEL-PAD ELASTICITY MODULUS

2017 ◽  
Vol 29 (03) ◽  
pp. 1750018
Author(s):  
Amirhossein Salimi ◽  
Hamid-Reza Katouzian ◽  
Paniz Naraghi-Bagherpour ◽  
Mohammad-Mehdi Khani
Keyword(s):  
Finite Element ◽  
Boundary Element ◽  
Computational Cost ◽  
Element Model ◽  
Elastic Behavior ◽  
Fe Model ◽  
Heel Pad ◽  
Local Stresses ◽  
Indentation Experiment

The key role of heel-pad in protecting calcaneus bone against excessive local stresses during walking and running is well discussed in the literature. Aiming to obtain a more profound understanding of this soft collagenous load-bearing tissue, material characterization of heel-pad has attracted the attention of many researchers. One way of achieving this goal is to estimate the mechanical properties of heel-pad based on Finite Element (FE) simulation of the indentation experiment which has been conducted by various teams before. During this process, the soft tissue undergoes a relatively large deformation causing the elements in FE Model to be extremely distorted particularly near the vicinity of indenter-heel pad contact making the numerical modeling tedious and significantly increasing the computational cost. The main contribution of the current study is to develop a coupled Boundary Element–Finite Element (BE–FE) plane strain model to improve the deficiency of the conventional numerical methods as the three-node 1 degree-of-freedom BEs eliminate the distortion issue near the deformed heel-pad zone and effectively lower the computational costs which is vital for iterative processes of this kind. Later through iterative post-processing of data, the modulus of elasticity (E) describing the elastic behavior of heel-pad is extracted. E is determined by using the inverse technique to minimize the displacement error between the experimental data and the corresponding numerical results after a considerable number of iterations. Obtained results contribute in design and construction of state-of-the-art prosthetic feet and therapeutic foot wear.

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