Study on Mechanism of Stress-Strain Redistribution by Elastic-Plastic-Creep Deformation

2011 ◽  
Author(s):  
Masakazu Sato ◽  
Hiroki Kikuchi ◽  
Naoto Kasahara
Keyword(s):  
Creep Deformation ◽  
Structural Design ◽  
Rational Analysis ◽  
Stress Strain ◽  
Elastic Plastic ◽  
Pipe Model ◽  
Elastic Core ◽  
Creep Fatigue ◽  
Plastic Creep ◽  
Main Factor

Design of structures subjected to elevated temperature is substantial, especially at structural discontinuities where strain concentration induced by stress-strain redistribution causes a reduction of creep fatigue strength. In the design of those structures, it is needed to consider elastic-plastic-creep deformation. Methods to estimate elastic-plastic-creep deformation are categorized into inelastic FEM analyses and simple methods based on elastic FEM analyses. The latter methods provide the advantages of shorter calculation time and uniqueness of results. Stress Redistribution Locus (SRL) was proposed as one of the simplified methods. Previous analyses indicate that SRL depends on neither constitutive equations nor magnitude of loads. By clarifying the mechanism of stress-strain redistribution, and determining a condition where the SRL coincide, this method can be utilized as a rational analysis for inelastic structural design. The objective of this study is to clarify the mechanism which determines SRL in elastic-plastic-creep deformation. Firstly, elastic-plastic analyses were achieved in a pipe model. Considering an analogy based on the theoretical solution of a two bars model, the pipe model with fixed elastic core ratio was analyzed. In consequence, it was clarified that stress-strain redistribution by elastic-plastic deformation depends on the area of the elastic cores. Secondly, elastic-creep analyses and elastic-plastic-creep analyses were performed in the same model, and it was revealed that the elastic core is the main factor on stress-strain redistribution induced by elastic-plastic-creep deformation.

Study on the Stress-Strain Redistribution Caused by Inelastic Deformation in Perforated Plate

2012 ◽  
Author(s):  
Sho Ikeda ◽  
Masakazu Sato ◽  
Naoto Kasahara
Keyword(s):  
Design Method ◽  
Perforated Plate ◽  
Chemical Plants ◽  
Inelastic Behavior ◽  
Stress Strain ◽  
Elastic Plastic ◽  
Pipe Model ◽  
Elastic Core ◽  
Creep Fatigue ◽  
Breeder Reactors

Fast Breeder Reactors and chemical plants that is operated at elevated temperature must be designed considering creep deformation in addition to elastic-plastic deformation. Especially at structural discontinuities, strain concentration induced by stress-strain redistribution reduces creep-fatigue strength. For this reason, a design method is needed for appropriately evaluating inelastic behavior at a structural discontinuity. As one of simplified methods with elastic analysis, a rational method with Stress Redistribution Locus (SRL) has been studied during recent years. Previous studies have shown that SRL does not depend on constitutive equations or on the magnitude of loading. And through the elastic-plastic-creep analysis of a one-dimensional pipe model, it was revealed that there was a relation between stress-strain redistribution and the size of elastic core. The purpose of this study is to clarify the mechanism of stress-strain redistribution in complex structures like actual components. Multi-dimensional stress-strain distribution and multiaxial stress occur in those structures. For considering those effects, inelastic analyses on perforated plate were performed and the relation between the region of elastic cores and SRL was examined. Then, it was revealed that SRL could be divided into two parts. One half is affected by the region of elastic core and the other half depends on the loading type. Furthermore, this paper proposes the new SRL method based on the mechanism and validates the method.

Full Life Elastic-Plastic-Creep Analysis and Comparison to Tests of Axially Cycled Pressurized Tubular Specimens

1982 ◽  
Vol 104 (2) ◽  
pp. 96-101
Author(s):  
I. Berman ◽  
M. S. M. Rao ◽  
G. D. Gupta
Keyword(s):  
Material Properties ◽  
Fatigue Behavior ◽  
Test Results ◽  
Elastic Plastic ◽  
Creep Analysis ◽  
Creep Fatigue ◽  
Incoloy 800 ◽  
Full Life ◽  
Tubular Specimens ◽  
Plastic Creep

Full life elastic-plastic-creep analyses of axially cycled pressurized tubular 316H stainless steel and Incoloy 800 specimens were run in order to evaluate creep ratcheting and creep fatigue behavior. Analytical results were obtained for the loading conditions and the 593°C (1100°F) material properties of the tests reported by Majumdar [1]. Both “book” value and other material property assumptions were used in the analyses and compared with the test results. Some conclusions from these tests are that book property analyses can, in some cases, underestimate the results. Modification of the material properties to more closely mirror actual conditions can, in some cases, greatly improve the predictions.

On Thick-Walled Cylinder Under Internal Pressure

2003 ◽  
Vol 125 (3) ◽  
pp. 267-273 ◽  
Author(s):  
W. Zhao ◽  
R. Seshadri ◽  
R. N. Dubey
Keyword(s):  
Internal Pressure ◽  
Strain Curve ◽  
Stress Strain ◽  
Piecewise Linearization ◽  
Elastic Plastic ◽  
Plastic Cylinder ◽  
Parametric Functions ◽  
The Difference ◽  
New Formulation ◽  
Walled Cylinder

A technique for elastic-plastic analysis of a thick-walled elastic-plastic cylinder under internal pressure is proposed. It involves two parametric functions and piecewise linearization of the stress-strain curve. A deformation type of relationship is combined with Hooke’s law in such a way that stress-strain law has the same form in all linear segments, but each segment involves different material parameters. Elastic values are used to describe elastic part of deformation during loading and also during unloading. The technique involves the use of deformed geometry to satisfy the boundary and other relevant conditions. The value of strain energy required for deformation is found to depend on whether initial or final geometry is used to satisfy the boundary conditions. In the case of low work-hardening solid, the difference is significant and cannot be ignored. As well, it is shown that the new formulation is appropriate for elastic-plastic fracture calculations.

scholarly journals A Distributed Plasticity Approach for Steel Frames Analysis Including Strain Hardening Effects

2019 ◽  
Author(s):  
Andrius Grigusevičius ◽  
Gediminas Blaževičius
Keyword(s):  
Finite Elements ◽  
Plastic Hinge ◽  
Steel Frames ◽  
Physical Models ◽  
3D Fem ◽  
Stress Strain ◽  
Numerical Application ◽  
Element Analysis ◽  
Plastic Deformations ◽  
Elastic Plastic

This paper focuses on the creation and numerical application of physically nonlinear plane steel frames analysis problems. The frames are analysed using finite elements with axial and bending deformations taken into account. Two nonlinear physical models are used and compared – linear hardening and ideal elastic-plastic. In the first model, distributions of plastic deformations along the elements and across the sections are taken into account. The proposed method allows for an exact determination of the stress-strain state of a rectangular section subjected to an arbitrary combination of bending moment and axial force. Development of plastic deformations in time and distribution along the length of elements are determined by dividing the structure (and loading) into the parts (increments) and determining the reduced modulus of elasticity for every part. The plastic hinge concept is used for the analysis based on the ideal elastic-plastic model. The created calculation algorithms have been fully implemented in a computer program. The numerical results of the two problems are presented in detail. Besides the stress-strain analysis, the described examples demonstrate how the accuracy of the results depends on the number of finite elements, on the number of load increments and on the physical material model. COMSOL finite element analysis software was used to compare the presented 1D FEM methodology to the 3D FEM mesh model analysis.

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