scholarly journals Lamb wave based approach to the determination of elastic and viscoelastic material parameters

2021 ◽  
Vol 88 (s1) ◽  
pp. s28-s33
Author(s):  
Sarah Johannesmann ◽  
Leander Claes ◽  
Bernd Henning
Keyword(s):  
Viscoelastic Material ◽  
Lamb Waves ◽  
Measurement Data ◽  
Material Model ◽  
Measurement Procedure ◽  
Ultrasonic Waves ◽  
Thermoelastic Effect ◽  
Material Parameters ◽  
Yield Information

Abstract In this paper a measurement procedure is presented to identify both elastic and viscoelastic material parameters of plate-like samples using broadband ultrasonic waves. These Lamb waves are excited via the thermoelastic effect using laser radiation and detected by a piezoelectric transducer. The resulting measurement data is transformed to yield information about multiple propagating Lamb waves as well as their attenuation. These results are compared to simulation results in an inverse procedure to identify the parameters of an elastic and a viscoelastic material model.

Material Identification On Thin Shells Using the Virtual Fields Method, Demonstrated On the Human Eardrum

2021 ◽  
Author(s):  
Felipe Pires ◽  
Stephane Avril ◽  
Pieter Livens ◽  
Julio A. Cordioli ◽  
Joris Dirckx
Keyword(s):  
Experimental Data ◽  
Outer Surface ◽  
Plate Theory ◽  
Measurement Data ◽  
Total Strain ◽  
Virtual Fields Method ◽  
Material Parameters ◽  
Membrane Strain

Abstract Characterization of material parameters from experimental data remains challenging, especially on biological structures. One of such techniques allowing for the inverse determination of material parameters from measurement data is the Virtual Fields Method (VFM). However, application of the VFM on general structures of complicated shape has not yet been extensively investigated. In this paper, we extend the framework of the VFM method to thin curved solids in 3D, commonly denoted shells. Our method is then used to estimate theYoung's modulus and hysteretic damping of the human eardrum. By utilizing Kirchhoff plate theory, we assume that the behavior of the shell varies linearly through the thickness. The total strain of the shell can then be separated in a bending and membrane strain. This in turn allowed for an application of the VFM based only on data of the outer surface of the shell. We validated our method on simulated and experimental data of a human eardrum made to vibrate at certain frequencies. It was shown that the identified material properties were accurately determined based only on data from the outer surface and are in agreement with literature. Additionally, we observed that neither the bending nor the membrane strain in an human eardrum can be neglected and both contribute significantly to the total strain found experimentally.

Experimental Characterization and Constitutive Modeling of the Mechanical Properties of Uncured Rubber

2010 ◽  
Vol 83 (1) ◽  
pp. 1-15 ◽  
Author(s):  
M. Kaliske ◽  
C. Zopf ◽  
C. Brüggemann
Keyword(s):  
Viscoelastic Material ◽  
Test Procedure ◽  
Fem Simulation ◽  
Optimization Procedure ◽  
Material Model ◽  
Experimental Characterization ◽  
Material Parameters ◽  
Analysis Strategy ◽  
Material Formulation ◽  
The Mean

Abstract The properties of uncured rubber are characterized by a viscoelastic material formulation in order to develop a finite element method (FEM) to predict the deformation behavior of this material during processing. As material formulation, a viscoelastic material model is considered, which consists of a nonlinear Hooke spring connected in parallel to a finite number of Maxwell elements. To identify the material parameters, various tests have to be conducted. The chosen test procedure and data analysis strategy are presented. An evolutionary optimization procedure is used to fit the material parameters to the measurements by minimizing the mean square error of the approximation. At the end, the suitability of the chosen material model and the identified material parameters is shown. Finally, the result of a molding test is compared to the corresponding FEM simulation.

Inverse Finite Element Analysis of the Indentation Response of Human Cervical Tissue

2013 ◽  
Author(s):  
Kristin Myers ◽  
Wang Yao ◽  
Kyoko Yoshida ◽  
Joy Vink ◽  
Noelia Zork ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Viscoelastic Material ◽  
Material Model ◽  
Spherical Indentation ◽  
Cervical Tissue ◽  
Tissue Slices ◽  
Element Analysis ◽  
Material Parameters ◽  
Inverse Finite Element Analysis

The mechanical function of the cervix is crucial during pregnancy when it is required to resist the compressive and tensile forces generated from the growing fetus. Pathologies of the cervical extracellular matrix (ECM), premature cervical remodeling, and alterations of cervical material properties have been implicated in placing women at high-risk for preterm birth (PTB). To understand the mechanical role of the cervix during pregnancy and to potentially identify etiologies for PTB, the overall goal of our group is to quantify ECM-material property relationships in normal and diseased human cervical tissue. In this study we present an inverse finite element analysis (IFEA) that optimizes material parameters of a viscoelastic material model to fit the stress-relaxation response of excised tissue slices to spherical indentation. Here we detail our IFEA methodology, report viscoelastic material parameters for cervical tissue slices from nonpregnant (NP) and pregnant (PG) hysterectomy patients, and report slice-by-slice data for whole cervical tissue specimens.

scholarly journals Inverse Analysis of Cellulose by Using the Energy-Based Method and a Rotational Rheometer

2018 ◽  
Vol 8 (8) ◽  
pp. 1354 ◽  
Author(s):  
Bilen Abali
Keyword(s):  
Nonlinear Response ◽  
Material Model ◽  
Nonlinear Material ◽  
Strain Response ◽  
Representation Theorems ◽  
Material Parameters ◽  
Highly Nonlinear ◽  
Material Equation ◽  
Material Equations

Biological and polymer-type materials usually show a complicated deformation behavior. This behavior can be modeled by using a nonlinear material equation; however, the determination of coefficients in such a material equation is challenging. We exploit representation theorems in continuum mechanics and construct nonlinear material equations for cellulose in an oscillatory rheometer experiment. The material parameters are obtained by using the energy-based method that generates a linear regression fit even in the case of a highly nonlinear material equation. This method allows us to test different nonlinear material equations and choose the simplest material model capable of representing the nonlinear response over a broad range of frequencies and amplitudes. We present the strategy, determine the parameters for cellulose, discuss the complicated stress-strain response and make the algorithm publicly available to encourage its further use.

Lifetime Prediction of Tires with Regard to Oxidative Aging5

2008 ◽  
Vol 36 (1) ◽  
pp. 63-79 ◽  
Author(s):  
L. Nasdala ◽  
Y. Wei ◽  
H. Rothert ◽  
M. Kaliske
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Temperature Distribution ◽  
Superposition Principle ◽  
Accelerated Aging ◽  
Material Model ◽  
Aging Behavior ◽  
Element Analysis ◽  
Material Parameters ◽  
Reaction Processes

Abstract It is a challenging task in the design of automobile tires to predict lifetime and performance on the basis of numerical simulations. Several factors have to be taken into account to correctly estimate the aging behavior. This paper focuses on oxygen reaction processes which, apart from mechanical and thermal aspects, effect the tire durability. The material parameters needed to describe the temperature-dependent oxygen diffusion and reaction processes are derived by means of the time–temperature–superposition principle from modulus profiling tests. These experiments are designed to examine the diffusion-limited oxidation (DLO) effect which occurs when accelerated aging tests are performed. For the cord-reinforced rubber composites, homogenization techniques are adopted to obtain effective material parameters (diffusivities and reaction constants). The selection and arrangement of rubber components influence the temperature distribution and the oxygen penetration depth which impact tire durability. The goal of this paper is to establish a finite element analysis based criterion to predict lifetime with respect to oxidative aging. The finite element analysis is carried out in three stages. First the heat generation rate distribution is calculated using a viscoelastic material model. Then the temperature distribution can be determined. In the third step we evaluate the oxygen distribution or rather the oxygen consumption rate, which is a measure for the tire lifetime. Thus, the aging behavior of different kinds of tires can be compared. Numerical examples show how diffusivities, reaction coefficients, and temperature influence the durability of different tire parts. It is found that due to the DLO effect, some interior parts may age slower even if the temperature is increased.

Determination of a Rubber-Like Material Model as an Inverse Problem

2011 ◽  
Vol 70 ◽  
pp. 225-230 ◽  
Author(s):  
Agnieszka Derewonko ◽  
Andrzej Kiczko
Keyword(s):  
Selection Process ◽  
Axial Stress ◽  
Constitutive Models ◽  
Material Model ◽  
Polyester Fabric ◽  
Point Of View ◽  
Air Cushion ◽  
Ill Conditioning ◽  
Stress States

The purpose of this paper is to describe the selection process of a rubber-like material model useful for simulation behaviour of an inflatable air cushion under multi-axial stress states. The air cushion is a part of a single segment of a pontoon bridge. The air cushion is constructed of a polyester fabric reinforced membrane such as Hypalon®. From a numerical point of view such a composite type poses a challenge since numerical ill-conditioning can occur due to stiffness differences between rubber and fabric. Due to the analysis of the large deformation dynamic response of the structure, the LS-Dyna code is used. Since LS-Dyna contains more than two-hundred constitutive models the inverse method is used to determine parameters characterizing the material on the base of results of the experimental test.

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