An integral elasto-plastic constitutive theory

This paper proposes an integral elasto-plastic constitutive equation, in which it is considered that stress is a functional of plastic strain in a plastic strain space. It is indicated that, to completely describe a strain path, the arc-length and curvature of the trajectory, the turning angles at the corner points and other characteristic points on the path must be considered. In general, the plastic strain space is a non-Euclidean geometric, space hence its measure tensor is a function of not only properties of the material but also the plastic strain history. This recommended integral elasto-plastic constitutive equation is the generalization of Ilyushin, Pipkin, Rivlin and Valanis theories and is suited to research the responses of material under the complex loading path. The predictions of the proposed theory have a good agreement with the experimental results. (C) 2002 Elsevier Science Ltd. All rights reserved

Continuous Modeling for transient and steady cyclic hardening /softening behavior of metallic materials under amplitude change loading

This paper is concerned with the performance of the plastic strain amplitude measure, originally motivated and then abandoned by Haupt et al. [1]. Reasons for success and failure in modeling for the amplitude dependence are discussed. It is shown that if the memory parameter in the variable to indicate the center of the plastic strain region is determined suitably, the measure gives satisfactory performance in reflecting the amplitude behavior. By incorporating a hardening function dependent on the measure into the intrinsic time scale used in Valanis' endochronic plasticity, various transient and steady cyclic phenomena of hardening materials can be reproduced

Electroelastic analysis of a piezoelectric half-plane with finite surface electrodes

In this paper the problem of the electroelastic fields of piezoelectric ceramic in a half-plane with thin collinear surface electrodes is formulated and analyzed. Using the standard analytic continuation method, a mixed boundary value problem in plane is obtained and then reduced to a standard Hilbert problem. The closed form expressions of electroelastic fields are obtained. Some special cases are discussed. The electroelastic filed has singularity with 1/rootr at the vicinity of the electrode ends. The numerical examples for two surface electrodes are studied to show the practical distributions of the electroelastic fields graphically. (C) 2004 Elsevier Ltd. All rights reserved

The BMAL1/HIF2A heterodimer modulates circadian variations of myocardial injury

Acute myocardial infarction stands as a prominent cause of morbidity and mortality worldwid

Theory of electroelasticity

Theory of Electroelasticity analyzes the stress, strain, electric field and electric displacement in electroelastic structures such as sensors, actuators and other smart materials and structures. This book also describes new theories such as the physical variational principle and the inertial entropy theory. It differs from the traditional method by using the physical variational principle to derive the governing equations of the piezoelectric material, whereas the Maxwell stress is obtained automatically. By using the inertial entropy theory, the temperature wave equation is obtained very easily. The book is intended for scientists, researchers and engineers in the areas of mechanics, physics, smart material and control engineering as well as mechanical, aeronautical and civil engineering, etc. Zhen-Bang Kuang is a professor at Shanghai Jiao Tong University

Finite element analysis of steady flow in stenotic arterial models

This paper carries out a numerical study on flow patterns in arterial models with various stenoses at different Reynolds numbers. Navier-Stokes equations were solved by finite element method for a viscous, incompressible fluid. Steady flow patterns have been computed for three stenoses of 20%, 50%and 80%, at three Reynolds number: Re=100,400 and 800, and for four different stenosis shapes. Velocity profiles, axial pressure drop distributions, wall shear stress distributions,and the separation points were investigated. Results showed that among the three variables: velocity, pressure and wall shear stress, the last one is the most sensitive indicator to the degree of stenosis. This can be very helpful in clinical applications. The maximum velocity ratio(UmaxS/UmaxP)and the peak wall shear stressratio (τmaxS/τmaxP). where the superscript "S" denotes stenotic and "P" denotes Poiseuillean, increase with stenosis percent, but are insensitive to Reynolds number. The pressure drop ratio （△PS/△PP）, on the other hand, is affected greatly by the Reynolds number if the degree of stenosis is high, indicating that the pressure drop is mainly due to area expansion for severe stenosis. and due to fluid viscosity for mild stenoses. The flow separation was observed for all models except for the one with 20% stenosis, at Re=100-800. The reverse flow length at downstream of stenosis increases with the stenosis degree, and in an approximate linear form with Reynolds number under the laminar flow. Otherwise the computed reverse flow length will be shorter than the experimental value due to the disturbances of the flow

Finite element analysis of steady flow in stenotic arterial models

This paper carries out a numerical study on flow patterns in arterial models with various stenoses at different Reynolds numbers. Navier-Stokes equations were solved by finite element method for a viscous, incompressible fluid. Steady flow patterns have been computed for three stenoses of 20%, 50%and 80%, at three Reynolds number: Re=100,400 and 800, and for four different stenosis shapes. Velocity profiles, axial pressure drop distributions, wall shear stress distributions,and the separation points were investigated. Results showed that among the three variables: velocity, pressure and wall shear stress, the last one is the most sensitive indicator to the degree of stenosis. This can be very helpful in clinical applications. The maximum velocity ratio(UmaxS/UmaxP)and the peak wall shear stressratio (τmaxS/τmaxP). where the superscript "S" denotes stenotic and "P" denotes Poiseuillean, increase with stenosis percent, but are insensitive to Reynolds number. The pressure drop ratio （△PS/△PP）, on the other hand, is affected greatly by the Reynolds number if the degree of stenosis is high, indicating that the pressure drop is mainly due to area expansion for severe stenosis. and due to fluid viscosity for mild stenoses. The flow separation was observed for all models except for the one with 20% stenosis, at Re=100-800. The reverse flow length at downstream of stenosis increases with the stenosis degree, and in an approximate linear form with Reynolds number under the laminar flow. Otherwise the computed reverse flow length will be shorter than the experimental value due to the disturbances of the flow

Reflection and transmission of plane waves at the interface of pyroelectric bi-materials

A simple reflection and transmission theory of plane waves at the interface of pyroelectric media is studied in this paper. In an infinite homogeneous pyroelectric medium, there are four bulk wave modes: quasi-longitudinal (QL), two quasi-transversal (QT) and one temperature (T) waves, whose velocities depend on the frequency and incident angle. Simultaneously, a quasi-surface (QS) wave on each side of the interface of pyroelectric bimaterials will appear in the general reflection and transmission problem. The quasi-surface wave has the same wave vector component with the incident waves along the interface plane. So, the reflection and transmission problem is different with the propagation wave in the infinite homogeneous space, but it is still solvable. In the reflection and transmission problem, there are ten complex continuous conditions on the interface, which are satisfied by the bulk and quasi-surface waves together. Numerical calculations are performed for bimaterial PZT-6B/BaTiO3. Incidences of the quasi-longitudinal and quasi-transversal waves from the side of PZT-6B or BaTiO3 medium are discussed. The reflection and transmission amplitude coefficients and energy flow ratios varying with the incident angle are examined. (C) 2012 Elsevier Ltd. All rights reserved.National Natural Science Foundation of China [10802070, 10972188, 11172252]; Natural Science Foundation of Fujian Province of China [2011J01329]; Fundamental Research Funds for the Central Universities [2011121002]; Scientific and Technological Innovation Platform of Fujian Province [2006L2003