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.

Application of a Unified Constitutive Theory to the Nonproportional Multiaxial Strain Deformation of 1045 Steel

1992 ◽  
Vol 114 (2) ◽  
pp. 147-155 ◽  
Author(s):  
J. A. Sherwood ◽  
E. M. Fay
Keyword(s):  
Inelastic Strain ◽  
Material Model ◽  
Flow Equation ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Unified Theory ◽  
Strain Plasticity ◽  
Dependent Strain ◽  
1045 Steel

An automated procedure for the determination of the material constants in a constitutive equation which is used to model the multiaxial nonlinear material behavior of isotropic materials is discussed. The material model used in this research is a unified theory where the time-dependent strain (creep) and time-independent strain (plasticity) are treated as one (unified) inelastic strain. The flow equation considers the inelastic rate of strain and it is assumed that inelastic strain is present at all levels of stress. Application of the model to proportional and nonproportional biaxial loadings is presented.

scholarly journals The influence of Material Nonlinearity and Microstructural Damage on the Inplane Shear response of Carbon/Epoxy Composites

1992 ◽  
Vol 1 (1) ◽  
pp. 096369359200100 ◽  
Author(s):  
K Gipple ◽  
E T Camponeschi
Keyword(s):  
Finite Element Analysis ◽  
Nonlinear Response ◽  
Epoxy Composites ◽  
Nonlinear Material ◽  
Strain Response ◽  
Element Analysis ◽  
Material Models ◽  
Microstructural Damage ◽  
Failure Theory ◽  
Measured Response

Accurate nonlinear material models must include both material and damage related nonlinearities. Even at the specimen level macromechanical boundary conditions and specimen geometry can significantly affect the measured response. In this study two experimental techniques for determining shear stress strain response are compared and a micromechanical finite element analysis is used to determine the effect of failure theory on predicted nonlinear response.

scholarly journals A Study of Speed of the Boundary Element Method as applied to the Realtime Computational Simulation of Biological Organs

2014 ◽  
Vol 12 (2) ◽  
Author(s):  
Kirana Kumara P
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Computational Simulation ◽  
Material Model ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Processing Unit ◽  
Material Models ◽  
Highly Nonlinear ◽  
Element Method

In this work, possibility of simulating biological organs in realtime using the Boundary Element Method (BEM) is investigated. Biological organs are assumed to follow linear elastostatic material behavior, and constant boundary element is the element type used.  First, a Graphics Processing Unit (GPU) is used to speed up the BEM computations to achieve the realtime performance. Next, instead of the GPU, a computer cluster is used.  Results indicate that BEM is fast enough to provide for realtime graphics if biological organs are assumed to follow linear elastostatic material behavior. Although the present work does not conduct any simulation using nonlinear material models, results from using the linear elastostatic material model imply that it would be difficult to obtain realtime performance if highly nonlinear material models that properly characterize biological organs are used. Although the use of BEM for the simulation of biological organs is not new, the results presented in the present study are not found elsewhere in the literature.

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.

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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