scholarly journals Nonlinear viscoelastic constitutive model for bovine liver tissue

2020 ◽  
Vol 19 (5) ◽  
pp. 1641-1662 ◽  
Author(s):  
Adela Capilnasiu ◽  
Lynne Bilston ◽  
Ralph Sinkus ◽  
David Nordsletten
Keyword(s):  
Constitutive Equation ◽  
Liver Tissue ◽  
Motor Vehicle ◽  
Bovine Liver ◽  
Disease Diagnosis ◽  
Tissue Response ◽  
Viscoelastic Behaviour ◽  
Biomechanical Models ◽  
Nonlinear Viscoelastic ◽  
Viscoelastic Constitutive Model

Abstract Soft tissue mechanical characterisation is important in many areas of medical research. Examples span from surgery training, device design and testing, sudden injury and disease diagnosis. The liver is of particular interest, as it is the most commonly injured organ in frontal and side motor vehicle crashes, and also assessed for inflammation and fibrosis in chronic liver diseases. Hence, an extensive rheological characterisation of liver tissue would contribute to advancements in these areas, which are dependent upon underlying biomechanical models. The aim of this paper is to define a liver constitutive equation that is able to characterise the nonlinear viscoelastic behaviour of liver tissue under a range of deformations and frequencies. The tissue response to large amplitude oscillatory shear (1–50%) under varying preloads (1–20%) and frequencies (0.5–2 Hz) is modelled using viscoelastic-adapted forms of the Mooney–Rivlin, Ogden and exponential models. These models are fit to the data using classical or modified objective norms. The results show that all three models are suitable for capturing the initial nonlinear regime, with the latter two being capable of capturing, simultaneously, the whole deformation range tested. The work presented here provides a comprehensive analysis across several material models and norms, leading to an identifiable constitutive equation that describes the nonlinear viscoelastic behaviour of the liver.

Viscohyperelastic Material Modeling of Liver Tissue

2007 ◽  
Author(s):  
Kumar Vemaganti ◽  
Esra Roan
Keyword(s):  
Soft Tissue ◽  
Liver Tissue ◽  
Critical Role ◽  
Experimental Studies ◽  
Strain Energy Function ◽  
Bovine Liver ◽  
Disease Diagnosis ◽  
Strain Rates ◽  
The Continuum

Mechanical characterization of soft tissue plays a critical role in applications such as automated surgery, disease diagnosis and tissue engineering. Soft tissue is often modeled as an isotropic incompressible and hyperelastic material. However, it is well known that viscoelasticity plays an important role in determining the response of soft tissue to mechanical loads [1]. This work is concerned with the development of hyperviscoelastic models of soft tissue in general and liver tissue in particular. Experimental studies in uniaxial compression are conducted on bovine liver tissue at strain rates between 0.001 s−1 and 0.04 s−1. The response of liver tissue is modeled using the continuum mechanics framework using an exponential form of the strain energy function.

On the Nonlinear Viscoelastic Behaviour of the PVC-Coated Fabric

2010 ◽  
Vol 160-162 ◽  
pp. 1476-1481 ◽  
Author(s):  
Wu Lian Zhang ◽  
Xin Ding ◽  
Xu Dong Yang
Keyword(s):  
Viscoelastic Model ◽  
Constitutive Relationship ◽  
Viscoelastic Behaviour ◽  
Viscoelastic Response ◽  
Nonlinear Parameters ◽  
Creep And Recovery ◽  
Nonlinear Viscoelastic ◽  
Coated Fabric ◽  
Nonlinear Viscoelastic Model

The nonlinear viscoelastic response of a PVC-Coated Fabric has been studied. For the needs of the present study, creep and recovery tests in tension of both the warp and the weft directions at the different stress levels were executed while measurements were made of the creep and recovery strain response of the system. For the description of the viscoelastic behaviour of the material, Schapery’s nonlinear viscoelastic model was used. For the description of the nonlinear viscoelastic response and the determination of the nonlinear parameters, a method by using a combination of analytical formulations and numerical procedures based on a modified version of Schapery’s constitutive relationship where an instantaneous plastic and a transient plastic terms were added, has been developed. The method has been successfully applied to the current tests.

Constitutive modeling of strain-dependent bond breaking and healing kinetics of chemical polyampholyte (PA) gel

Soft Matter ◽  
2021 ◽  
Vol 17 (15) ◽  
pp. 4161-4169
Author(s):  
Sairam Pamulaparthi Venkata ◽  
Kunpeng Cui ◽  
Jingyi Guo ◽  
Alan T. Zehnder ◽  
Jian Ping Gong ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Uniaxial Tension ◽  
Constitutive Modeling ◽  
Finite Strain ◽  
Bond Breaking ◽  
Nonlinear Viscoelastic ◽  
Viscoelastic Constitutive Model ◽  
Kinetics Of ◽  
Strain Dependent

A finite strain nonlinear viscoelastic constitutive model is used to study the uniaxial tension behaviour of a chemical polyampholyte (PA) gel.

Some Implications of a Nonlinear Viscoelastic Constitutive Theory Regarding Interrelationships Between Creep and Strength Behavior of Ice at Failure

1989 ◽  
Vol 111 (2) ◽  
pp. 144-148 ◽  
Author(s):  
B. D. Harper
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Nonlinear Viscoelastic ◽  
Uniaxial Creep ◽  
Strength Behavior ◽  
Minimum Strain Rate ◽  
Strength Constant ◽  
Viscoelastic Constitutive Model ◽  
Stress And Strain Rate ◽  
Special Case

This study explores several possibilities for a correspondence in the behavior of ice at failure during uniaxial creep (constant stress) and strength (constant strain rate) experiments. The usual notion of failure in ice is employed (i.e., the occurrence of a minimum strain rate during a creep test and a peak or maximum stress during a strength test), and the behavior at failure is discussed in terms of a recently proposed nonlinear viscoelastic constitutive model for ice. It is demonstrated that no correspondence between creep and strength data can be expected in general; however, several approximate interrelationships do occur for the experimentally motivated special case of a constant (independent of stress and strain rate) failure strain.

scholarly journals Determination of the optical properties of bovine liver tissue using integrating sphere technique

2018 ◽  
Vol 1 (1) ◽  
pp. 248-252
Author(s):  
Halil Arslan ◽  
Yasar Baris Dolukan
Keyword(s):  
Optical Properties ◽  
Liver Tissue ◽  
Tissue Sample ◽  
Bovine Liver ◽  
Integrating Sphere ◽  
Scattering Coefficients ◽  
Single Sphere ◽  
Microscope Slides ◽  
Good Agreement

The optical properties (absorption and reduced scattering coefficients, µa and µs’) of bovine liver tissue for 635 nm has been determined by using integrating sphere and inverse adding-doubling (IAD) techniques. For this purpose, total reflectance and total transmittance values of bovine liver tissue sample, which is placed between two microscope slides, have been measured by using single-sphere system. The measured values have been used as input parameters for IAD program to extract the µa and µs’ of the sample. In this study, µa and µs’ of bovine liver tissue for 635 nm have been determined to be 0.22 mm-1 and 0.51mm-1, respectively. These values, which yield 1.44 mm penetration depth, are in good agreement with the ones in the literature.

scholarly journals A Modified Fractional Maxwell Numerical Model for Constitutive Equation of Mn-Cu Damping Alloy

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2020
Author(s):  
Baoquan Mao ◽  
Rui Zhu ◽  
Zhiqian Wang ◽  
Yuying Yang ◽  
Xiaoping Han ◽  
...  
Keyword(s):  
Constitutive Equation ◽  
Strain Rate ◽  
Constitutive Relation ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Maxwell Model ◽  
Nonlinear Viscoelastic ◽  
Fractional Maxwell Model ◽  
Hysteretic Characteristics ◽  
Nonlinear Elastic

To better describe its constitutive relation, we need a new constitutive equation for an important nonlinear elastic material, Mn-Cu damping alloy. In this work, we studied the nonlinear and hysteretic characteristics of the stress-strain curve of the M2052 alloy with the uniaxial cyclic tensile test with constant strain rate. The strain rate and amplitude correlations of M2052 resembled those of nonlinear viscoelastic material. Therefore, we created a new constitutive equation for the M2052 damping alloy by modifying the fractional Maxwell model, and we used the genetic algorithm to carry out numerical fitting with MATLAB. By comparing with the experimental data, we confirmed that the new constitutive equation could accurately depict the nonlinear constitutive relation and hysteretic property of the damping alloy. Taken together, this new constitutive equation for Mn-Cu damping alloy based on the fractional Maxwell model can serve as an effective tool for further studies of the constitutive relation of the Mn-Cu damping alloys.

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