Showing papers on "von Mises yield criterion published in 1983"

Indentation of a half‐space with a rigid indentor

Abstract: In this work the problem of indentation of a half-space by a spherical rigid indentor is investigated using the finite element method. A system of constitutive equations applicable to elasto-plastic materials subjected to large deformations is used to determine the deformations and stresses for the contact problems. These equations represent the simplest generalization for the large-deformation conditions of the classical theory of plasticity of metals based on the von Mises yield condition and the associated flow rule. The material formulation of the kinematical and dynamical relations will be used. These equations combine the kinematic and the isotropic strain-hardening models. The results obtained from this work are compared with existing solutions for this problem that are confined to small strains and elastic, ideal-plastic materials.

Analysis of the puncture of a bisphenol-a polycarbonate disc

Abstract: The finite element technique is applied to analytically predict the response of a disc made of BPA-polycarbonate during a displacement-controlled puncture test with a hemispherical indenter. The analysis includes effects of contact load, large displacements and rotations, and large strains and material yielding. Two general topics are addressed with this analysis. First, it is shown that the load-displacement behavior of impacted, BPA-polycarbonate plates can be accurately predicted over a wide range of engineering interest (strains up to 30 percent) using a bilinear representation of the stress-strain curve and flow theory of plasticity. For this purpose, the von Mises criterion is applied to define yielding in a generalized biaxial stress state, and strain rate effects are incorporated through the use of a yield stress consistent with the initial strain rate during the test. Second, in order to broaden the understanding of results associated with this widely used test, a number of mechanical and material effects are discussed, including large displacements, friction at the clamped support and indenter head, and clamping pressure at the support. Lack of agreement between the present analysis and experimental results with regard to ultimate load at puncture suggests that strain hardening and strain rate hardening of the material during the high-strain portion of the test (30 percent-60 percent) must be more accurately modeled for improved predictive capability.

Elastoplastic Boundary Element Analysis

Abstract: In this chapter the boundary element equations presented in the last chapter are employed to solve problems concerned with the inviscid or classical theory of plasticity. An application of the initial strain equations for incompressible plastic strains is first introduced in conjunction with the von Mises yield criterion and Mendelson’s successive elastic solutions method [63]. This simple solution technique, also called “elastic predictor — radial corrector method” by Schreyer et al. [92], has proved to be very efficient and stable with reference to the load increment size. The initial stress equations, on the other hand, are more general and are here implemented to handle four different yield criteria (Tresca, Mises, Mohr-Coulomb and Drucker-Prager), with two different iterative routines. The first is a pure incremental technique comparable to what was used by Zienkiewicz et al. [93] for finite elements. The second deals with accumulated values of the initial stresses in a similar fashion to the initial strain implementation.

Finite Element Results of Pressurized Thick Tubes Based on Two Elastic- Plastic Material Models

Abstract: : The loading and unloading problems in thick tubes subjected to uniform internal pressure have been analyzed with the ADINA finite element code. The elastic-plastic materials are modeled by two strain-hardening rules- isotropic and kinematic. The von Mises yield condition, the associated flow theory, and a numerical results of the stresses and displacements for thick tubes with different wall ratios are obtained as functions of loading history. A comparison of numerical results based on two material models is made.

Von Mises’ Method

Abstract: In this chapter we present the general structure of von Mises’ approach to the analysis of the asymptotic behavior of statistical functional. The basic technique was introduced by von Mises (1947) and has been extended in various directions by several authors: Filippova (1962), Reeds (1976), Huber (1977, 1981), and Serfling (1980). One result of these extensions is that the field has become divergent, with ad hoc techniques applied in different situations. In the chapters that follow we shall try to establish a unified methodology that can be applied to wide classes of statistics.

Anisotropic yield surfaces in cyclic plasticity

Abstract: — An anisotropic form of the Von Mises yield criteria is presented which includes linear terms and therefore enables Bauschinger effects to be considered when constructing yield or loading surfaces. The coefficients representing the state of anisotropy are expressed in terms of the uni-axial and shear yield stress of the material. It is suggested that this form of the yield or loading surface can be used to determine the plastic strains for a range of multi-axial and cyclic plasticity problems and results are presented for the particular case of a tube subjected to cyclic plastic torsion with an axial stress.

A unified thermodynamic theory of elasticity and plasticity

Abstract: A thermodynamics is developed for a unified theory of elasticity and plasticity in infinitesmal strain. The constitutive equations which relate stress and strain deviators are rate type differential equations. When they satisfy a Lipschitz condition, uniqueness for the initial value problem dictates that the stress and strain will be related through elastic relations. Failure of the Lipschitz condition occurs when a von Mises yield condition is achieved: Plastic yield then occurs and the deviator relations turn into the Prandtl-Reuss equations. The plastic yield solution is stable during loading and unstable during unloading. The requirement that the solution followed during unloading be stable dictates entry into an elastic regime. Appropriate thermodynamic functions are constructed. It then appears that stress deviator (not strain deviator) is a viable state variable, and the thermodynamic relations are constructed in terms of a Gibbs function. The energy balance leads to satisfaction of the Clausius-Duhem inequality (and thus the second law of thermodynamics) in an elastic regime because it is shown that in an elastic regime entropy production is caused only by heat flux. During yield, the proper method of differentiating yields entropy production terms in addition to those arising from heat flux. These terms are positive during loading, whence it is concluded that the requirement that a stable solution be followed leads to satisfaction of the Clausius-Duhem inequality during plastic as well as elastic behavior.

An Optimal Design of Simple Symmetric Laminates Under Von Mises Failure Criterion

Abstract: N THE PROBLEMS OF OPTIMAL LAMINATE DESIGN, IT IS WELL UNDERSTOOD th4t the most important design variables are ply orientation angles, ply thicknesses and volume fractions of fibers. Park [1] has considered an optimal laminate design problem, in which an optimal ply orientation angle was computed for various multiple loadings (N,, N2, N6) under the first ply failure criterion. This paper considers a similar problem extending the failure criterion to the Von Mises failure criterion. Various simple symmetric laminates of the composite material T300/5208, such as

Elasto-Plastic Analysis of Fibrous Composite Shells Using ‘Semiloof’ Finite Elements

Abstract: A finite element formulation is presented for conducting nonlinear analysis of fibrous composite shells structures. The Semiloof elements, which have proved to be one of the most efficient families of finite elements available for linear elastic thin shell analysis, have been extended for elasto-plastic fibrous composite shell analysis. Inelastic material behaviour is modelled with flow theory of plasticity adopting the von Mises yield criterion.

Method for analyzing elastoplastic stress

Abstract: PURPOSE:To determine a stress state quantitatively with respect to general structures, by writing down the rule of hardening by movement, the rule of flow, etc. with respect to a plane stress state by the use of a bilinearly approximated stress-strain relation. CONSTITUTION:The stress-strain curve a of material is bilinearly approximated by an alternate long and short dash line c. The rule of hardening by movement using the initial yield conditions of Von Mises, the rule of flow of Prandtl Lewis and the relations between the quantity of hardening by movement and strain are written down with respect to a plane stress state as the equations for describing the plastic stress state. young's modules E and coefft. C of work hardening are determined from monoaxial tension tests of material, and the strain increments in the two directions of the noticed points are measured continuously with strain gages and are substd. in the equations. The stress increments, the equivalent plastic strain increments and the extents of movements of the origin of the yield curve are determined. The stress analysis which takes work hardening and Bauschinger effect into consideration is accomplished and the behavior of plastic stress and residual stress are determined quantitatively.

The earthquake stability of earth structures

Abstract: The main aim of this study is to develop a practicable computer method for analysis of the dynamic response of a two dimensional soil structure, which takes into account the generation of excess pore pressures and can predict final deformations. A secondary aim is to investigate the dynamic behaviour of a silt and the effect of variations in the stress-controlled dynamic triaxial test method on the measured sample response. The soil model employed in the developed method of dynamic analysis uses a set of nested yield surfaces to represent shear stress-strain behaviour. These yield surfaces are defined by von Mises failure criterion, have an associated flow rule and undergo both kinematic and isotropic hardening. An empirical model is used to calculate the rise in pore pressure due to cyclic shear stresses. The changes in yield surface radii and hardening constants are defined by experimentally determined relationships between maximum shear modulus, shear strength and mean effective confining stress. A combination of critical state soil mechanics and volumetric considerations is used to relate increments in mean strain to increments in mean stress. The soil structure is divided into elements and a finite difference scheme used to solve the equations of motion. An energy transmitting boundary is incorporated in the analysis. The program has the capacity to analyse the dynamic response of a soil structure to both shear and compression waves approaching the base of the structure from any angle. The dam constructed for the Patea hydroelectric scheme was used as a practical application of the computer program. An input earthquake record considered appropriate to the site was chosen. The dynamic analysis of the dam with an empty reservoir indicated that in this state the dam can satisfactorily withstand the design earthquake. The dynamic analysis of the dam with a full reservoir subject to the same uniform base excitation suggests that a slide in the downstream shoulder would develop. The input earthquake waves travelling along the base of the dam from the upstream toe to the downstream toe, accentuate these displacements. These displacements are caused by the generation of high pore pressures which redistribute after the earthquake to temporarily reduce the stability of the dam further. The assumptions and approximations inherent in the method of analysis tend to make the results pessimistic. It was found that the vertical component of earthquake excitation was the major cause of the generated pore pressure. The results of an extensive programme of laboratory tests carried out on the main construction material in the dam, are presented. The test programme consisted of undrained triaxial, isotropic consolidation, free vibration torsion and stress controlled dynamic triaxial tests. Factors influencing the pore pressure generation characteristics obtained from the stress-controlled dynamic triaxial tests, were found to include the compacted dry density, the cyclic shear stress, the initial effective confining stress, the…

소형풍차용 Clark - Y형 blade 의 유한요소법에 의한 응력해석

Abstract: The Stress analysis of the windmill blade used in this study was performed by FEM, and the theory of aircraft airfoil and propeller was applied. Also, Von Mises equation was applied to abtain the equivalent stress distribution at each section and the equivalent stress distribution along the longitudinal direction. And the conclusion is as following ; 1) The maximum equivalent stress of longitudinal direction appears in vicinity of 0.2l (l = Whole length of the blade) distance from the fixed edge. 2) The maximum equivalent stress at the each section appears on the center of lower surface at the fixed edge and, as it far from the fixed edge, the maximum equivalent stress appears on the trailing edge.

Sliding Forces and Normal Loads on Projectile Rotating Bands.

Abstract: : A theory is presented to determine the projectile sliding forces in interior ballistics. Emphasis is placed on the barrel entrance region where the projectile rotating bands are impelled on to the rifling. It is proposed that the contact stress is constant and is given by a modified von Mises failure criterion. Normal loads and friction forces are dependent on the growth of the contact area which is derived from the geometrical details of the projectile and barrel. Radial displacements at the contact are included. The theory is in agreement with quasi-static and dynamic laboratory tests. (Author)