Nonlinear Incompressible Finite Element for Simulating Loading of Cardiac Tissue—Part II: Three Dimensional Formulation for Thick Ventricular Wall Segments

1988 ◽  
Vol 110 (1) ◽  
pp. 62-68 ◽  
Author(s):  
A. Horowitz ◽  
I. Sheinman ◽  
Y. Lanir
Keyword(s):  
Finite Element ◽  
Cardiac Tissue ◽  
Large Deformations ◽  
Three Dimensional ◽  
Shear Stiffness ◽  
Cardiac Mechanics ◽  
Nonlinear Finite Element ◽  
Constitutive Law ◽  
Ventricular Wall ◽  
Collagenous Matrix

A three dimensional incompressible and geometrically as well as materially nonlinear finite element is formulated for future implementation in models of cardiac mechanics. The stress-strain relations in the finite element are derived from a recently proposed constitutive law which is based on the histological composition of the myocardium. The finite element is formulated for large deformations and considers incompressibility by introducing the hydrostatic pressure as an additional variable. The results of passive loading cases simulated by this element allow to analyze the mechanical properties of ventricular wall segments, the main of which are that the circumferential direction is stiffer than the longitudinal one, that its shear stiffness is considerably lower than its tensile and compressive stiffness, and that, due to its mechanically prominent role, the collagenous matrix may affect the myocardial perfusion.

Finite Element Simulation of a Strong-Post W-Beam Guardrail System

SIMULATION ◽  
2002 ◽  
Vol 78 (10) ◽  
pp. 587-599 ◽  
Author(s):  
Ali O. Atahan
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Full Scale ◽  
Nonlinear Finite Element ◽  
Crash Test ◽  
Original Design ◽  
Dynamic Interactions ◽  
Crash Testing ◽  
Element Simulation ◽  
Test Requirements

Computer simulation of vehicle collisions has improved significantly over the past decade. With advances in computer technology, nonlinear finite element codes, and material models, full-scale simulation of such complex dynamic interactions is becoming ever more possible. In this study, an explicit three-dimensional nonlinear finite element code, LS-DYNA, is used to demonstrate the capabilities of computer simulations to supplement full-scale crash testing. After a failed crash test on a strong-post guardrail system, LS-DYNA is used to simulate the system, determine the potential problems with the design, and develop an improved system that has the potential to satisfy current crash test requirements. After accurately simulating the response behavior of the full-scale crash test, a second simulation study is performed on the system with improved details. Simulation results indicate that the system performs much better compared to the original design.

Numerical analysis of the dynamic interaction between a non-pneumatic mechanical elastic wheel and soil containing an obstacle

2016 ◽  
Vol 231 (6) ◽  
pp. 731-742 ◽  
Author(s):  
Xianbin Du ◽  
Youqun Zhao ◽  
Qiang Wang ◽  
Hongxun Fu
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Interaction Model ◽  
Dynamic Interaction ◽  
Constitutive Law ◽  
Elastic Wheel ◽  
Non Linear ◽  
Dimensional Finite Element ◽  
Mechanical Elastic Wheel ◽  
Three Dimensional Finite Element

An innovative non-pneumatic tyre called the mechanical elastic wheel is introduced; significant challenges exist in the prediction of the dynamic interaction between this mechanical elastic wheel and soil containing an obstacle owing to its highly non-linear properties. To explore the mechanical properties of the mechanical elastic wheel and the soil, the finite element method is used, and a non-linear three-dimensional finite element wheel–soil interaction model is also established. Hyperelastic incompressible rubber, which is one of the main materials of the mechanical elastic wheel, is analysed using the Mooney–Rivlin model. The modified Drucker–Prager cap plasticity constitutive law is utilized to describe the behaviour of the soil, and the obstacle is represented as an elastic body. Simulations with different rotational speeds of the mechanical elastic wheel were conducted. The stress distribution and the displacement of the mechanical elastic wheel and the soil were obtained, and the effects of different rotational speeds on the displacement, the velocity and the acceleration of the hub centre are presented and discussed in detail. These results can provide useful information for optimization of the mechanical elastic wheel.

Evaluation of Analytic Estimates of Ventricular Wall Stress Using the Finite Element Method

2008 ◽  
Author(s):  
Christopher M. Ingrassia ◽  
Shantanu Y. Jani ◽  
Kevin D. Costa
Keyword(s):  
Finite Element ◽  
Circumferential Stress ◽  
Wall Stress ◽  
Cardiac Mechanics ◽  
Ventricular Wall ◽  
The Finite Element Method ◽  
Regional Wall ◽  
Circumferential Wall Stress ◽  
Theoretical Assumptions ◽  
Accurate Quantification

The importance of ventricular wall stress to cardiac function has been well-documented [1, 2], although accurate quantification remains a challenge. In this study, three popular analytic formulas for estimating circumferential wall stress were comprehensively evaluated to identify the conditions for which their use may be appropriate. In particular, the equations of Laplace [3], Mirsky [4], and Janz [5] are commonly used in the fields of cardiology and echocardiography; despite the inaccuracy of key theoretical assumptions, they have been attractive for their simplicity. For validation, we employed specialized finite element methods, developed specifically for cardiac mechanics applications [6], to compute regional wall stress in a series of model chambers having systematically varying geometric and material complexity. We limited our analysis to circumferential stress for consistency with the theoretical equations, and because of its relevance to cardiac mechanics.

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