Modified Bilston Nonlinear Viscoelastic Model for Finite Element Head Injury Studies

2006 ◽  
Vol 128 (5) ◽  
pp. 797-801 ◽  
Author(s):  
F. Shen ◽  
T. E. Tay ◽  
J. Z. Li ◽  
S. Nigen ◽  
P. V. S. Lee ◽  
...  
Keyword(s):  
Finite Element ◽  
Head Injury ◽  
Brain Tissue ◽  
Loss Modulus ◽  
Viscoelastic Model ◽  
Constitutive Law ◽  
Critical Parameters ◽  
Test Results ◽  
High Frequencies ◽  
Nonlinear Viscoelastic

This paper proposes a modified nonlinear viscoelastic Bilston model (Bilston et al., 2001, Biorheol., 38, pp. 335–345). for the modeling of brain tissue constitutive properties. The modified model can be readily implemented in a commercial explicit finite element (FE) code, PamCrash. Critical parameters of the model have been determined through a series of rheological tests on porcine brain tissue samples and the time-temperature superposition (TTS) principle has been used to extend the frequency to a high region. Simulations by using PamCrash are compared with the test results. Through the use of the TTS principle, the mechanical and rheological behavior at high frequencies up to 104rad∕s may be obtained. This is important because the properties of the brain tissue at high frequencies and impact rates are especially relevant to studies of traumatic head injury. The averaged dynamic modulus ranges from 130Pato1500Pa and loss modulus ranges from 35Pato800Pa in the frequency regime studied (0.01rad∕sto3700rad∕s). The errors between theoretical predictions and averaged relaxation test results are within 20% for strains up to 20%. The FEM simulation results are in good agreement with experimental results. The proposed model will be especially useful for application to FE analysis of the head under impact loads. More realistic analysis of head injury can be carried out by incorporating the nonlinear viscoelastic constitutive law for brain tissue into a commercial FE code.

scholarly journals Investigation of the Compressive Viscoelastic Properties of Brain Tissue Under Time and Frequency Dependent Loading Conditions

2021 ◽  
Author(s):  
Weiqi Li ◽  
Duncan E. T. Shepherd ◽  
Daniel M. Espino
Keyword(s):  
Finite Element ◽  
Brain Tissue ◽  
Time Domain ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Series Representation ◽  
Experimental Tests ◽  
Finite Element Models ◽  
Frequency Dependent

AbstractThe mechanical characterization of brain tissue has been generally analyzed in the frequency and time domain. It is crucial to understand the mechanics of the brain under realistic, dynamic conditions and convert it to enable mathematical modelling in a time domain. In this study, the compressive viscoelastic properties of brain tissue were investigated under time and frequency domains with the same physical conditions and the theory of viscoelasticity was applied to estimate the prediction of viscoelastic response in the time domain based on frequency-dependent mechanical moduli through Finite Element models. Storage and loss modulus were obtained from white and grey matter, of bovine brains, using dynamic mechanical analysis and time domain material functions were derived based on a Prony series representation. The material models were evaluated using brain testing data from stress relaxation and hysteresis in the time dependent analysis. The Finite Element models were able to represent the trend of viscoelastic characterization of brain tissue under both testing domains. The outcomes of this study contribute to a better understanding of brain tissue mechanical behaviour and demonstrate the feasibility of deriving time-domain viscoelastic parameters from frequency-dependent compressive data for biological tissue, as validated by comparing experimental tests with computational simulations.

Microindentation on Gelatin Films with a Spherical Indenter -- A Viscoelastic Analysis

1993 ◽  
Vol 308 ◽  
Author(s):  
Beta Y. Ni ◽  
Gary R. Bisson ◽  
Andy H. Tsou
Keyword(s):  
Viscoelastic Model ◽  
Tensile Modulus ◽  
Polymeric Materials ◽  
Element Model ◽  
Gelatin Film ◽  
Spherical Indenter ◽  
Constitutive Law ◽  
Viscoelastic Analysis ◽  
Nonlinear Viscoelastic ◽  
Gelatin Films

ABSTRACTA finite element model was employed to analyze the microindentation test with a spherical indenter on gelatin films. The deficiency of using elastic-plastic constitutive law to describe indentation response of gelatin film was recognized and a viscoelastic model was proposed for the first time to analyze indentation experiments on polymeric materials. Based on viscoelastic analysis, it was found that gelatin is nonlinear viscoelastic. In addition, modulus in the thickness direction of a gelatin film was determined to be 2.5–2.9 GPa as compared with its tensile modulus of 4.6 GPa in the transverse direction.

Verification of Mechanical Properties of A V-4Cr-4Ti Alloy Using Finite Element Method

2005 ◽  
Vol 297-300 ◽  
pp. 1013-1018
Author(s):  
Choon Yeol Lee ◽  
E.G. Donahue ◽  
G.R. Odette
Keyword(s):  
Finite Element ◽  
Experimental Studies ◽  
Mechanical Tests ◽  
Constitutive Law ◽  
Fracture Mechanisms ◽  
Test Results ◽  
Element Analysis ◽  
Vanadium Alloys ◽  
Fracture Specimens

Vanadium alloys in the composition range around V-4Cr-4Ti have been proposed as candidate materials for fusion reactor applications and structures. These applications will require detailed characterization of constitutive and fracture properties. This study is aimed at understanding the basic constitutive and fracture mechanisms in vanadium alloys. Understanding of the basic constitutive and fracture mechanisms is achieved through a series of mechanical tests. These test results are combined with quantitative models of the underlying macro- and micromechanics. In addition to these experimental studies, finite element analysis (FEA) techniques are used to determine stress and strain fields to verify the constitutive law used in the fracture specimens.

A Nonlinear Viscoelastic Model for Adipose Tissue Representing Tissue Response at a Wide Range of Strain Rates and High Strain Levels

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Hosein Naseri ◽  
Håkan Johansson ◽  
Karin Brolin
Keyword(s):  
Finite Element ◽  
Adipose Tissue ◽  
Human Body ◽  
Viscoelastic Model ◽  
Tissue Response ◽  
Strain Rates ◽  
Nonlinear Viscoelastic ◽  
Wide Range ◽  
Human Body Models ◽  
Nonlinear Viscoelastic Model

Finite element human body models (FEHBMs) are nowadays commonly used to simulate pre- and in-crash occupant response in order to develop advanced safety systems. In this study, a biofidelic model for adipose tissue is developed for this application. It is a nonlinear viscoelastic model based on the Reese et al.'s formulation. The model is formulated in a large strain framework and applied for finite element (FE) simulation of two types of experiments: rheological experiments and ramped-displacement experiments. The adipose tissue behavior in both experiments is represented well by this model. It indicates the capability of the model to be used in large deformation and wide range of strain rates for application in human body models.

Comparison Between a Quasilinear and a Nonlinear Viscoelastic Model for Brain Tissue

2000 ◽  
Author(s):  
Kurosh K. Darvish ◽  
Jeff R. Crandall
Keyword(s):  
Brain Tissue ◽  
Viscoelastic Model ◽  
Constitutive Models ◽  
Viscoelastic Behavior ◽  
Bovine Brain ◽  
Integral Model ◽  
Nonlinear Viscoelastic ◽  
Hereditary Integral ◽  
Nonlinear Constitutive Models ◽  
Nonlinear Viscoelastic Model

Abstract The nonlinearity of the viscoelastic behavior of brain tissue was studied. Two nonlinear constitutive models were developed using the experimental results of forced vibrations on bovine brain samples, namely a quasilinear viscoelastic model and a multiple hereditary integral model. The latter was found to be superior especially at higher frequencies (above 27 Hz).

A Constituent-Based Model for the Nonlinear Viscoelastic Behavior of Ligaments

2005 ◽  
Vol 128 (3) ◽  
pp. 449-457 ◽  
Author(s):  
P. Vena ◽  
D. Gastaldi ◽  
R. Contro
Keyword(s):  
Stress Relaxation ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Biological Tissues ◽  
Relaxation Behavior ◽  
Constitutive Law ◽  
Time Dependent ◽  
Nonlinear Viscoelastic ◽  
Nonlinear Viscoelastic Behavior ◽  
Constitutive Parameters

This paper presents a constitutive model for predicting the nonlinear viscoelastic behavior of soft biological tissues and in particular of ligaments. The constitutive law is a generalization of the well-known quasi-linear viscoelastic theory (QLV) in which the elastic response of the tissue and the time-dependent properties are independently modeled and combined into a convolution time integral. The elastic behavior, based on the definition of anisotropic strain energy function, is extended to the time-dependent regime by means of a suitably developed time discretization scheme. The time-dependent constitutive law is based on the postulate that a constituent-based relaxation behavior may be defined through two different stress relaxation functions: one for the isotropic matrix and one for the reinforcing (collagen) fibers. The constitutive parameters of the viscoelastic model have been estimated by curve fitting the stress relaxation experiments conducted on medial collateral ligaments (MCLs) taken from the literature, whereas the predictive capability of the model was assessed by simulating experimental tests different from those used for the parameter estimation. In particular, creep tests at different maximum stresses have been successfully simulated. The proposed nonlinear viscoelastic model is able to predict the time-dependent response of ligaments described in experimental works (Bonifasi-Lista et al., 2005, J. Orthopaed. Res., 23, pp. 67–76;Hingorani et al., 2004, Ann. Biomed. Eng., 32, pp. 306–312;Provenzano et al., 2001, Ann. Biomed. Eng., 29, pp. 908–214;Weiss et al., 2002, J. Biomech., 35, pp. 943–950). In particular, the nonlinear viscoelastic response which implies different relaxation rates for different applied strains, as well as different creep rates for different applied stresses and direction-dependent relaxation behavior, can be described.

Constitutive Equations and Finite Element Implementation of Isochronous Nonlinear Viscoelastic Behavior

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Hossein Sepiani ◽  
Maria Anna Polak ◽  
Alexander Penlidis
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Constitutive Relations ◽  
Viscoelastic Behavior ◽  
Material Behavior ◽  
Constitutive Law ◽  
Nonlinear Viscoelastic ◽  
Nonlinear Viscoelastic Behavior ◽  
Stress Dependent

We present a phenomenological three-dimensional (3D) nonlinear viscoelastic constitutive model for time-dependent analysis. Based on Schapery's single integral constitutive law, a solution procedure has been provided to solve nonlinear viscoelastic behavior. This procedure is applicable to 3D problems and uses time- and stress-dependent material properties to characterize the nonlinear behavior of material. The equations describing material behavior are chosen based on the measured material properties in a short test time frame. This estimation process uses the Prony series material parameters, and the constitutive relations are based on the nonseparable form of equations. Material properties are then modified to include the long-term response of material. The presented model is suitable for the development of a unified computer code that can handle both linear and nonlinear viscoelastic material behavior. The proposed viscoelastic model is implemented in a user-defined material algorithm in abaqus (UMAT), and the model validity is assessed by comparison with experimental observations on polyethylene for three uniaxial loading cases, namely short-term loading, long-term loading, and step loading. A part of the experimental results have been conducted by (Liu, 2007, “Material Modelling for Structural Analysis of Polyethylene,” M.Sc. thesis, University of Waterloo, Waterloo, ON Canada), while the rest are provided by an industrial partner. The research shows that the proposed finite element model can reproduce the experimental strain–time curves accurately and concludes that with proper material properties to reflect the deformation involved in the mechanical tests, the deformation behavior observed experimentally can be accurately predicted using the finite element simulation.

scholarly journals Comparison of Rheological Behaviour of Bio-Based and Synthetic Epoxy Resins for Making Ecocomposites

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 38
Author(s):  
Samireh Vahid ◽  
Valentino Burattini ◽  
Saeed Afshinjavid ◽  
Arash Dashtkar
Keyword(s):  
Phase Angle ◽  
Epoxy Resins ◽  
Loss Modulus ◽  
Rheological Behaviour ◽  
General Tendency ◽  
Test Results ◽  
High Frequencies ◽  
Oscillatory Rheology ◽  
Linear Viscoelastic ◽  
Typical Behaviour

In this paper, the rheological behaviour of a petroleum-based epoxy (EL2 laminating epoxy) was compared with the Super Sap CLR clear bio-resin epoxy. The focus of the work was on the viscous and viscoelastic performance of these epoxy resins. Rheological tests were carried out at 15, 30, and 60 min after the mixing of the pure epoxies and the hardeners at a constant temperature of 25 °C. The results obtained from the rheometer tests showed that the viscosity of both epoxy systems decreased with increasing shear rate, which is typical behaviour of a shear thinning fluid. Regarding the oscillatory rheology tests, the viscoelastic properties of both epoxy resins were studied within their linear viscoelastic region (LVER) by amplitude sweep test, which was also carried out 15, 30, and 60 min after mixing the epoxies with the hardeners. It was noticed that the petroleum-based epoxy possessed a more significant LVER relative to the bio-based resin. Finally, the storage modulus (G′), the loss modulus (G″), and the phase angle were extracted, and these parameters were investigated over low and high frequencies. From the test results, we observed that both epoxy resins showed a liquid-like viscoelastic behaviour due to their phase angle values, which were always between 45° and 90°, and by the general tendency of the G″ predominance over G′ at low and high frequencies.

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