A Constitutive Law for Mitral Valve Tissue

1998 ◽  
Vol 120 (1) ◽  
pp. 38-47 ◽  
Author(s):  
K. May-Newman ◽  
F. C. P. Yin
Keyword(s):  
Mitral Valve ◽  
Transversely Isotropic ◽  
Quantitative Information ◽  
Substantial Improvement ◽  
Material Behavior ◽  
Constitutive Law ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Mechanical Models ◽  
Biaxial Mechanical Testing

Biaxial mechanical testing and theoretical continuum mechanics analysis are employed to formulate a constitutive law for cardiac mitral valve anterior and posterior leaflets. A strain energy description is formulated based on the fibrous architecture of the tissue, accurately describing the large deformation, highly nonlinear transversely isotropic material behavior. The results show that a simple three-coefficient exponential constitutive law provides an accurate prediction of stress–stretch behavior over a wide range of deformations. Regional heterogeneity may be accommodated by spatially varying a single coefficient and incorporating collagen fiber angle. The application of this quantitative information to mechanical models and bioprosthetic development could provide substantial improvement in the evaluation and treatment of valvular disease, surgery, and replacement.

scholarly journals Finite Element Software for Rubber Products Design

2018 ◽  
Vol 3 (1) ◽  
pp. 13-20
Author(s):  
Dávid Huri
Keyword(s):  
Finite Element ◽  
Complex Analysis ◽  
Large Deformations ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Material Models ◽  
Finite Element Software ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Different Types

Automotive rubber products are subjected to large deformations during working conditions, they often contact with other parts and they show highly nonlinear material behavior. Using finite element software for complex analysis of rubber parts can be a good way, although it has to contain special modules. Different types of rubber materials require the curve fitting possibility and the wide range choice of the material models. It is also important to be able to describe the viscoelastic property and the hysteresis. The remeshing possibility can be a useful tool for large deformation and the working circumstances require the contact and self contact ability as well. This article compares some types of the finite element software available on the market based on the above mentioned features.

The propagation of elastic waves in a certain class of inhomogeneous anisotropic materials. I. The refraction of a horizontally polarized shear wave source

1992 ◽  
Vol 436 (1898) ◽  
pp. 449-478 ◽  
Keyword(s):  
Shear Wave ◽  
Isotropic Material ◽  
Displacement Vector ◽  
Transversely Isotropic ◽  
Constitutive Law ◽  
Coarse Grained ◽  
Wave Source ◽  
Uniform Asymptotic Expansion ◽  
Wide Range ◽  
Steel Welds

This paper is the first in a series of articles describing the refraction and propagation of infinitesimal disturbances in a 'coarse grained’ inhomogeneous anisotropic material which is fused to an isotropic substrate. Here, the basic constitutive law for the material is motivated by applications to the non-destructive evaluation of austenitic steel welds, although it is clear that the phenomena described and the mathematical analysis used is also of interest in geophysics, the study of composite materials and several other areas of continuum mechanics. This work is concerned with the refraction of a horizontally polarized shear wave source at the fusion interface between a homogeneous isotropic material and transversely isotropic material. The latter is inhomogeneous by virtue of the fact that the zonal axis or axis of symmetry of the crystals varies in direction with the distance from the interface. The mathematical boundary-value problem is solved exactly, and, in the highfrequency limit, a uniform asymptotic expansion for the displacement vector is found. It is shown that in this limit, and for a wide range of material constants, the refracted energy which penetrates certain regions of the ‘weld material’ is totally internally reflected. This conclusion is highly significant in the design of inspection procedures for structurally important welds.

Multiphase Poroelastic Finite Element Models for Soft Tissue Structures

1992 ◽  
Vol 45 (6) ◽  
pp. 191-218 ◽  
Author(s):  
Bruce R. Simon
Keyword(s):  
Finite Element ◽  
Soft Tissue ◽  
Material Behavior ◽  
Constitutive Law ◽  
Finite Strains ◽  
Finite Element Models ◽  
Tissue Fluid ◽  
Biomechanical Models ◽  
Highly Nonlinear ◽  
Tissue Structures

During the last two decades, biological structures with soft tissue components have been modeled using poroelastic or mixture-based constitutive laws, i.e., the material is viewed as a deformable (porous) solid matrix that is saturated by mobile tissue fluid. These structures exhibit a highly nonlinear, history-dependent material behavior; undergo finite strains; and may swell or shrink when tissue ionic concentrations are altered. Given the geometric and material complexity of soft tissue structures and that they are subjected to complicated initial and boundary conditions, finite element models (FEMs) have been very useful for quantitative structural analyses. This paper surveys recent applications of poroelastic and mixture-based theories and the associated FEMs for the study of the biomechanics of soft tissues, and indicates future directions for research in this area. Equivalent finite-strain poroelastic and mixture continuum biomechanical models are presented. Special attention is given to the identification of material properties using a porohyperelastic constitutive law and a total Lagrangian view for the formulation. The associated FEMs are then formulated to include this porohyperelastic material response and finite strains. Extensions of the theory are suggested in order to include inherent viscoelasticity, transport phenomena, and swelling in soft tissue structures. A number of biomechanical research areas are identified, and possible applications of the porohyperelastic and mixture-based FEMs are suggested.

Identification of Material Constitutive Laws for Machining—Part II: Generation of the Constitutive Data and Validation of the Constitutive Law

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Bin Shi ◽  
Helmi Attia ◽  
Nejah Tounsi
Keyword(s):  
Shear Zone ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Orthogonal Cutting ◽  
Material Behavior ◽  
Constitutive Law ◽  
Primary Zone ◽  
Wide Range ◽  
Static Conditions ◽  
Secondary Shear Zone

This paper presents an integral methodology to obtain a wide range of constitutive data required for the identification of the constitutive equation used in simulating cutting processes. This methodology is based on combining the distributed primary zone deformation (DPZD) model developed in Part I (Shi et al., 2010, ASME J. Manuf. Sci. Eng., 132, p. 051008.) of this study with quasi-static indentation (QSI) tests, orthogonal cutting tests at room temperature (RT) and high temperature. The QSI tests are used to capture the material properties in the quasi-static conditions, which solve the unstable solutions for the coefficients of the constitutive law. The RT cutting tests are designed to fulfill the assumptions embedded in the developed DPZD model in order to provide the distributed constitutive data encountered in the primary shear zone. To capture the material behavior in the secondary shear zone, the orthogonal cutting tests with a laser preheating system are designed to raise the temperature in the primary zone to the level encountered in the secondary zone. As an application of the generated constitutive data, the Johnson–Cook model is identified for Inconel 718. This constitutive law is further validated using high speed split Hopkinson pressure bar tests and orthogonal cutting tests combined with finite element simulations. In comparison with the previous approaches reported in the open literature, the developed DPZD model and methodology significantly improve the accuracy of the simulation results.

An Advanced Cap Model for Soil

2003 ◽  
Author(s):  
C. S. Tsai ◽  
Ching-Shyang Chen ◽  
Zhen-Yu Zhang ◽  
Bo-Jen Chen ◽  
J. C. Chen
Keyword(s):  
Failure Surface ◽  
Material Behavior ◽  
Constitutive Law ◽  
Octahedral Plane ◽  
Sensitive Material ◽  
Stress Strain ◽  
Stress Strain Relation ◽  
Highly Nonlinear ◽  
Cap Model ◽  
Strain Relationship

Soil, which is a pressure-sensitive material, is frequently encountered in the engineering profession. To ensure the safety of super-structures, it is prerequisite to fully understand the mechanical behavior of soil. The stress-strain relation of soil is highly nonlinear and complex. Therefore, problems involving soil need an appropriate constitutive model to describe its stress-strain relationship. This paper presents a new cap-type constitutive law for soil. The model is prominent in the sense that it satisfies the compatibility between the failure surface and the yield cap. It has modified the classical cap model to obtain smooth yield surfaces. In addition, the model effectively describes strength variations along various directions on the octahedral plane. The model has shown to realistically simulate soil responses in experiments by 7 parameters. The proposed concept can also be extended to include as many previous models published in the past for describing various observed material behavior as it is required.

A Hyperelastic Constitutive Law for Aortic Valve Tissue

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Karen May-Newman ◽  
Charles Lam ◽  
Frank C. P. Yin
Keyword(s):  
Aortic Valve ◽  
Energy Function ◽  
Strain Energy ◽  
Strain Energy Function ◽  
Material Behavior ◽  
Constitutive Law ◽  
Biaxial Testing ◽  
Strain Behavior ◽  
Wide Range ◽  
Strain Invariants

The objective of the present study was to perform biaxial testing and apply constitutive modeling to develop a strain energy function that accurately predicts the material behavior of the aortic valve leaflets. Ten leaflets from seven normal porcine aortic valves were biaxially stretched in a variety of protocols and the data combined to develop and fit a strain energy function to describe the material behavior. The results showed that the nonlinear anisotropic behavior of the aortic valve is well described by a strain energy function of two strain invariants, which uses only three coefficients to accurately predict the stress-strain behavior over a wide range of deformations. This structurally-motivated constitutive law has many applications, including computational modeling for clinical and engineering valve treatments.

An Advanced Cap Model for Concrete Materials

2003 ◽  
Author(s):  
C. S. Tsai ◽  
Ching-Shyang Chen ◽  
Yong-Zhang Lin ◽  
Bo-Jen Chen ◽  
J. C. Chen
Keyword(s):  
Material Behavior ◽  
Constitutive Law ◽  
Octahedral Plane ◽  
Sensitive Material ◽  
Stress Strain ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Highly Nonlinear ◽  
Cap Model ◽  
Concrete Materials

Concrete is a pressure-sensitive material. To ensure the safety of structures, it is required to understand the mechanical behavior of concrete. The stress-strain relation of concrete is highly nonlinear and pressure dependent. Therefore, design problems involving concrete materials need an appropriate constitutive model to quantify its stress-strain relation. Presented in this paper is a new cap-type constitutive law for concrete. The model is prominent in the sense that it satisfies the compatibility between the failure surface and the yield cap. It has modified the classical cap model to obtain smooth yield surfaces. In addition, the model effectively describes strength variations along various directions in the octahedral plane. The model has shown to realistically predict concrete responses in experiments by 7 parameters. The proposed concept can also be extended to include as many previous models for describing various observed material behavior as it is required.

scholarly journals Quantitative linear dichroism imaging of molecular processes in living cells made simple by open software tools

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Alexey Bondar ◽  
Olga Rybakova ◽  
Josef Melcr ◽  
Jan Dohnálek ◽  
Petro Khoroshyy ◽  
...  
Keyword(s):  
Biological Systems ◽  
Linear Dichroism ◽  
Quantitative Information ◽  
Living Cells ◽  
Software Tools ◽  
Model Systems ◽  
Membrane Properties ◽  
Polarization Microscopy ◽  
Molecular Processes ◽  
Wide Range

AbstractFluorescence-detected linear dichroism microscopy allows observing various molecular processes in living cells, as well as obtaining quantitative information on orientation of fluorescent molecules associated with cellular features. Such information can provide insights into protein structure, aid in development of genetically encoded probes, and allow determinations of lipid membrane properties. However, quantitating and interpreting linear dichroism in biological systems has been laborious and unreliable. Here we present a set of open source ImageJ-based software tools that allow fast and easy linear dichroism visualization and quantitation, as well as extraction of quantitative information on molecular orientations, even in living systems. The tools were tested on model synthetic lipid vesicles and applied to a variety of biological systems, including observations of conformational changes during G-protein signaling in living cells, using fluorescent proteins. Our results show that our tools and model systems are applicable to a wide range of molecules and polarization-resolved microscopy techniques, and represent a significant step towards making polarization microscopy a mainstream tool of biological imaging.

scholarly journals Machine learning for multi-dimensional optimisation and predictive visualisation of laser machining

2021 ◽  
Author(s):  
Michael D. T. McDonnell ◽  
Daniel Arnaldo ◽  
Etienne Pelletier ◽  
James A. Grant-Jacob ◽  
Matthew Praeger ◽  
...  
Keyword(s):  
Short Pulse ◽  
Surface Texturing ◽  
Laser Surface Texturing ◽  
Laser Machining ◽  
Laser Materials ◽  
Parameter Optimisation ◽  
Short Pulse Laser ◽  
Alternative Approach ◽  
Highly Nonlinear ◽  
Wide Range

AbstractInteractions between light and matter during short-pulse laser materials processing are highly nonlinear, and hence acutely sensitive to laser parameters such as the pulse energy, repetition rate, and number of pulses used. Due to this complexity, simulation approaches based on calculation of the underlying physical principles can often only provide a qualitative understanding of the inter-relationships between these parameters. An alternative approach such as parameter optimisation, often requires a systematic and hence time-consuming experimental exploration over the available parameter space. Here, we apply neural networks for parameter optimisation and for predictive visualisation of expected outcomes in laser surface texturing with blind vias for tribology control applications. Critically, this method greatly reduces the amount of experimental laser machining data that is needed and associated development time, without negatively impacting accuracy or performance. The techniques presented here could be applied in a wide range of fields and have the potential to significantly reduce the time, and the costs associated with laser process optimisation.

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