scholarly journals Automatic Generation of User Material Subroutines for Biomechanical Growth Analysis

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Jonathan M. Young ◽  
Jiang Yao ◽  
Ashok Ramasubramanian ◽  
Larry A. Taber ◽  
Renato Perucchio
Keyword(s):  
Code Generation ◽  
Growth Analysis ◽  
Soft Tissues ◽  
Constitutive Relations ◽  
Strain Energy Function ◽  
Automatic Generation ◽  
Passive Layer ◽  
Isotropic Layer ◽  
Element Analysis ◽  
Hyperelastic Materials

The analysis of the biomechanics of growth and remodeling in soft tissues requires the formulation of specialized pseudoelastic constitutive relations. The nonlinear finite element analysis package ABAQUS allows the user to implement such specialized material responses through the coding of a user material subroutine called UMAT. However, hand coding UMAT subroutines is a challenge even for simple pseudoelastic materials and requires substantial time to debug and test the code. To resolve this issue, we develop an automatic UMAT code generation procedure for pseudoelastic materials using the symbolic mathematics package MATHEMATICA and extend the UMAT generator to include continuum growth. The performance of the automatically coded UMAT is tested by simulating the stress-stretch response of a material defined by a Fung-orthotropic strain energy function, subject to uniaxial stretching, equibiaxial stretching, and simple shear in ABAQUS. The MATHEMATICA UMAT generator is then extended to include continuum growth by adding a growth subroutine to the automatically generated UMAT. The MATHEMATICA UMAT generator correctly derives the variables required in the UMAT code, quickly providing a ready-to-use UMAT. In turn, the UMAT accurately simulates the pseudoelastic response. In order to test the growth UMAT, we simulate the growth-based bending of a bilayered bar with differing fiber directions in a nongrowing passive layer. The anisotropic passive layer, being topologically tied to the growing isotropic layer, causes the bending bar to twist laterally. The results of simulations demonstrate the validity of the automatically coded UMAT, used in both standardized tests of hyperelastic materials and for a biomechanical growth analysis.

Finite Bending and Straightening of Hyperelastic Materials: Analytical Solution and FEM

2019 ◽  
Vol 11 (09) ◽  
pp. 1950084 ◽  
Author(s):  
Sara Sheikhi ◽  
Mohammad Shojaeifard ◽  
Mostafa Baghani
Keyword(s):  
Finite Element ◽  
Strain Energy ◽  
Strain Energy Function ◽  
Optimization Procedure ◽  
Element Analysis ◽  
Energy Functions ◽  
Hyperelastic Materials ◽  
Finite Bending ◽  
Strain Energy Functions ◽  
Analytical Approaches

In this research, an incompressible, isotropic, nonlinear elastic rectangular block and a circular cylindrical sector are studied under bending and straightening moments, respectively. Analytical approaches are presented on implementing of the left Cauchy–Green tensor and Cauchy stresses. In addition, finite element analysis of both problems is carried out using UHYPER user-defined subroutine in ABAQUS to verify the analytical methods. Four different invariant-based strain energy functions, including neo-Hookean, Mooney–Rivlin, Arruda–Boyce, and recently proposed polynomial Exp-Exp models, are examined, and the results are compared. Material parameters of silicon rubber for the strain energy functions are identified by applying an optimization procedure. Finite element method results confirmed the analytical approach with great compatibility. Results showed that the length of the unbent beam does not affect the stress. Likewise, the initial angle of curved structure does not affect the unbending moment and stresses. Moreover, the Exp-Exp model had a slightly different result rather than other strain energies, which means that this model is more conservative than its counterparts. Furthermore, the Exp-Exp strain energy function is calibrated for tissue-like phantom and is compared with experimental data.

A Finite Strain Analytical Solution for Stress-Softening of Hyperelastic Materials Under Cyclic Bending

2021 ◽  
Vol 13 (01) ◽  
pp. 2150014
Author(s):  
Jafar Pashazadeh ◽  
Arya Amiri ◽  
Ali Taheri ◽  
Mostafa Baghani
Keyword(s):  
Analytical Solution ◽  
Strain Energy Function ◽  
Geometrical Parameters ◽  
Element Analysis ◽  
Softening Function ◽  
Cyclic Bending ◽  
Hyperelastic Materials ◽  
Design And Optimization ◽  
Stress Softening ◽  
Finite Bending

In this paper, a new approach for stress-softening of an isotropic, incompressible, hyperelastic and rectangular beam that undergoes cyclic bending-unbending deformation, is presented. Employing an exponential softening function, damage response of the hyperelastic beam due to cyclic finite bending is investigated. The stress-softening phenomenon occurs in elastomeric materials when they deform for the first time. Under the same deformation, the stress required in reloading is smaller than the initial loading stage. This is known as the Mullins effect. To verify the accuracy of the proposed solution, finite element analysis of the same problem is carried out. In this study, a principal stretch-based strain energy function i.e., Ogden model and an invariant-based function such as a newly introduced Exp–Exp model are used for all bending, unbending and re-bending procedures. The proposed method needs a much shorter time compared to FEM simulations. Thus, in design and optimization of the structures under bending that requires a large number of analyses, the proposed semi-analytical solution can be considered as an efficient tool for studying the effects of different material and geometrical parameters.

scholarly journals A refined dynamic finite-strain shell theory for incompressible hyperelastic materials: equations and two-dimensional shell virtual work principle

2020 ◽  
Vol 476 (2237) ◽  
pp. 20200031 ◽  
Author(s):  
Xiang Yu ◽  
Yibin Fu ◽  
Hui-Hui Dai
Keyword(s):  
Shell Theory ◽  
Finite Strain ◽  
Virtual Work ◽  
Constitutive Relations ◽  
Strain Energy Function ◽  
Two Dimensional ◽  
Weak Formulation ◽  
Virtual Work Principle ◽  
Hyperelastic Materials ◽  
Shell Equations

Based on previous work for the static problem, in this paper, we first derive one form of dynamic finite-strain shell equations for incompressible hyperelastic materials that involve three shell constitutive relations. In order to single out the bending effect as well as to reduce the number of shell constitutive relations, a further refinement is performed, which leads to a refined dynamic finite-strain shell theory with only two shell constitutive relations (deducible from the given three-dimensional (3D) strain energy function) and some new insights are also deduced. By using the weak formulation of the shell equations and the variation of the 3D Lagrange functional, boundary conditions and the two-dimensional shell virtual work principle are derived. As a benchmark problem, we consider the extension and inflation of an arterial segment. The good agreement between the asymptotic solution based on the shell equations and that from the 3D exact one gives verification of the former. The refined shell theory is also applied to study the plane-strain vibrations of a pressurized artery, and the effects of the axial pre-stretch, pressure and fibre angle on the vibration frequencies are investigated in detail.

scholarly journals Automatic modelling of human musculoskeletal ligaments – Framework overview and model quality evaluation

2021 ◽  
pp. 1-14
Author(s):  
Noura Hamze ◽  
Lukas Nocker ◽  
Nikolaus Rauch ◽  
Markus Walzthöni ◽  
Matthias Harders ◽  
...  
Keyword(s):  
Statistical Model ◽  
Soft Tissues ◽  
Automatic Generation ◽  
Cadaveric Study ◽  
Patient Specific ◽  
Mean Square ◽  
Shape Modelling ◽  
Morphological Studies ◽  
Insertion Sites ◽  
Mean Square Errors

BACKGROUND: Accurate segmentation of connective soft tissues in medical images is very challenging, hampering the generation of geometric models for bio-mechanical computations. Alternatively, one could predict ligament insertion sites and then approximate the shapes, based on anatomical knowledge and morphological studies. OBJECTIVE: In this work, we describe an integrated framework for automatic modelling of human musculoskeletal ligaments. METHOD: We combine statistical shape modelling with geometric algorithms to automatically identify insertion sites, based on which geometric surface/volume meshes are created. As clinical use case, the framework has been applied to generate models of the forearm interosseous membrane. Ligament insertion sites in the statistical model were defined according to anatomical predictions following a published approach. RESULTS: For evaluation we compared the generated sites, as well as the ligament shapes, to data obtained from a cadaveric study, involving five forearms with 15 ligaments. Our framework permitted the creation of models approximating ligaments’ shapes with good fidelity. However, we found that the statistical model trained with the state-of-the-art prediction of the insertion sites was not always reliable. Average mean square errors as well as Hausdorff distances of the meshes could increase by an order of magnitude, as compared to employing known insertion locations of the cadaveric study. Using those, an average mean square error of 0.59 mm and an average Hausdorff distance of less than 7 mm resulted, for all ligaments. CONCLUSIONS: The presented approach for automatic generation of ligament shapes from insertion points appears to be feasible but the detection of the insertion sites with a SSM is too inaccurate, thus making a patient-specific approach necessary.

Enterprise WAE: A Lightweight UML Extension for the Characterization of the Presentation Tier of Enterprise Applications with MDD-Based Mockup Generation

2017 ◽  
Vol 27 (08) ◽  
pp. 1291-1331
Author(s):  
Humberto Cortés ◽  
Antonio Navarro
Keyword(s):  
Code Generation ◽  
Web Application ◽  
Service Oriented Architecture ◽  
Low Cost ◽  
Unified Modeling Language ◽  
Automatic Generation ◽  
Role Based Access Control ◽  
Enterprise Applications ◽  
Uml Extension ◽  
Automatic Code

Nowadays, the Unified Modeling Language (UML) is the most successful notation for the design of object-oriented applications. However, plain UML is not enough to characterize the web presentation tier of enterprise applications, including the navigational, structural and role-based access control (RBAC) features present in these applications. In this paper, we present Enterprise Web Application Extension (E-WAE), a lightweight UML extension for the modeling of these elements, which permits the inclusion of multitier, Service-Oriented Architecture (SOA) and security design-level patterns in the models. Our approach follows a Model-Driven Development (MDD) approach, which enables the automatic generation of intermediate platform-specific models and automatic code generation for JavaServer Faces (JSF) and Active Server Pages.NET Model-View-Controller (ASP.NET MVC) frameworks. In addition, this generated code can be used as a low-cost mockup for early client validation of the navigational, structural and RBAC features of enterprise applications. E-WAE has been used with different applications. In this paper, we refer to the checkout process in the Amazon website, the delete resources use case in OdAJ2EE, an educational application developed by us, and the US Library of Congress Online Catalog search facility as examples of its applicability.

Analysis of Passive Filling With Fibrotic Myocardial Infarction

2015 ◽  
Author(s):  
Fulufhelo Masithulela
Keyword(s):  
Myocardial Infarction ◽  
Structural Changes ◽  
Strain Energy Function ◽  
Transversely Isotropic ◽  
Magnetic Resonance Images ◽  
Cardiac Contraction ◽  
Diastolic Filling ◽  
Element Analysis ◽  
Infarcted Heart ◽  
Longitudinal Strains

Cardiovascular diseases account for one third of all deaths worldwide, more than 33% of which are related to ischemic heart disease, involving a myocardial infarction (MI). Following myocardial infarction, the injured region and ventricle undergo structural changes which are thought to be caused by elevated stresses and reduction of strains in the infarcted wall. The fibrotic phase is defined as the period when the amount of new collagen and number of fibroblasts rapidly increase in the infarcted tissue. We studied through finite element analysis the mechanics of the infarcted and remodeling rat heart during diastolic filling. Biventricular geometries of healthy and infarcted rat hearts reconstructed from magnetic resonance images were imported in Abaqus©. The passive myocardium was modelled as a nearly incompressible, hyperelastic, transversely isotropic material represented by the strain energy function W = ½C(eQ − 1) with Q = bfE112 + bt(E222 + E332 + E322) + bfs(E122 + E212 + E132 + E312). Material parameters were obtained from literature [1]. As boundary conditions, the circumferential and longitudinal displacements at the base were set to zero. The radial displacements at the base were left free. A linearly increasing pressure from 0 to 3.80 kPa and 0.86 kPa, respectively, was applied to the endocardial surfaces of left and right ventricle. Average radial, circumferential and longitudinal strains during passive filling were −0.331, 0.135, 0.042 and −0.250, −0.078 and 0.046 for the healthy heart and the infarcted heart, respectively. The average radial, circumferential and longitudinal stresses were −1.196 kPa, 3.87 kPa in the healthy heart and 0.424 kPa and −1.90 kPa, 8.74 kPa and 1.69 kPa in the infarcted heart. The strains were considerable lower in the infarcted heart compared to the health heart whereas stresses were higher in the presence of an infarct compared to the healthy case. The results of this study indicate the feasibility of the models developed for a more comprehensive assessment of mechanics of the infarcted ventricle including extension to account for cardiac contraction.

scholarly journals GERADOR DE CÓDIGOS PARA O DESENVOLVIMENTO DE APLICAÇÕES WEB A PARTIR DA MODELAGEM ENTIDADE-RELACIONAMENTO

e-xacta ◽  
2016 ◽  
Vol 9 (1) ◽  
pp. 37
Author(s):  
Cristiano Martins Monteiro ◽  
Flavianne Braga Campos de Lima ◽  
Carlos Renato Storck
Keyword(s):  
Programming Languages ◽  
Code Generation ◽  
Design Pattern ◽  
Design Patterns ◽  
Source Code ◽  
Automatic Generation ◽  
Code Generator ◽  
Routine Tasks ◽  
Entity Relationship ◽  
Web Systems

<p>A geração automática de código-fonte é uma prática adotada no desenvolvimento de softwares para agilizar, facilitar e padronizar a implementação dos projetos. Embora seja uma prática comum nas fábricas de software, não se conhece uma ferramenta que permita escolher o padrão de projeto a ser usado. O objetivo principal deste trabalho é apresentar um gerador de códigos para o desenvolvimento de sistemas Web a partir de uma modelagem entidade-relacionamento, uma linguagem de programação e um padrão de projeto determinados pelo usuário. Os objetivos específicos são propor uma arquitetura do sistema capaz de adequar e reaproveitar diferentes padrões de projeto, linguagens de programação e projetos cadastrados; permitir que o usuário cadastre, altere, exclua, importe e exporte um projeto; e gerar automaticamente o seu código-fonte e scripts de banco de dados. Este trabalho se justifica pela importância de reduzir erros de codificação; e evitar perca tempo ao realizar atividades rotineiras de implementação de padrões de projeto. Possibilitando assim, maior dedicação no planejamento das regras de negócios e redução de custos. A ferramenta proposta (GCER) foi desenvolvida em linguagem Java com o uso banco de dados Oracle 11g, e seguindo os padrões DAO e MVC. Os resultados foram avaliados através da geração e compilação de códigos de um projeto para cadastro de veículos. A geração com êxito evidencia a viabilidade da ferramenta proposta para a geração automática de códigos no processo de desenvolvimento de software.</p><p>Abstract</p><p>The automatic generation of source code is a practice adopted in the development of software to streamline, facilitate and standardize the implementation of projects. Although it be a common practice in software factories, it is not known a tool able to choose the design pattern to be used. The main objective of this paper is to present a code generator for the development of Web systems from an entity-relationship modeling, a programming language and a design pattern determined by the user. The specific objectives are to propose a system architecture able to suit and reuse different design patterns, programming languages and saved projects; allow the user to insert, update, delete, import and export a project; and automatically generate the source code and database scripts. This work is justified by the importance to reduce errors of coding; and to avoid waste of time in the development of Web systems performing routine tasks. Allowing, then, a greater dedication in the planning of business rules and the reduction of costs. The tool proposed (GCER) was developed in Java with the database using Oracle 11g, and following the DAO and MVC patterns. The results were evaluated by generating and compiling codes of a project for vehicle registration. The successful code generation demonstrate the feasibility of the proposed tool for the automatic generation of code in the software development process.</p>

Hyperelastic Muscle Simulation

2007 ◽  
Vol 345-346 ◽  
pp. 1241-1244 ◽  
Author(s):  
Mohd. Zahid Ansari ◽  
Sang Kyo Lee ◽  
Chong Du Cho
Keyword(s):  
Skeletal Muscle ◽  
Silicone Rubber ◽  
Soft Tissues ◽  
Material Model ◽  
Incompressible Material ◽  
Material Behavior ◽  
Rubber Tube ◽  
Stress Strain ◽  
Element Analysis ◽  
Strain Behavior

Biological soft tissues like muscles and cartilages are anisotropic, inhomogeneous, and nearly incompressible. The incompressible material behavior may lead to some difficulties in numerical simulation, such as volumetric locking and solution divergence. Mixed u-P formulations can be used to overcome incompressible material problems. The hyperelastic materials can be used to describe the biological skeletal muscle behavior. In this study, experiments are conducted to obtain the stress-strain behavior of a solid silicone rubber tube. It is used to emulate the skeletal muscle tensile behavior. The stress-strain behavior of silicone is compared with that of muscles. A commercial finite element analysis package ABAQUS is used to simulate the stress-strain behavior of silicone rubber. Results show that mixed u-P formulations with hyperelastic material model can be used to successfully simulate the muscle material behavior. Such an analysis can be used to simulate and analyze other soft tissues that show similar behavior.

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