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.

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.

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.

Stresses and Displacements in an Elastic-Plastic Wedge

1957 ◽  
Vol 24 (1) ◽  
pp. 98-104
Author(s):  
P. M. Naghdi
Keyword(s):  
Plane Strain ◽  
Isotropic Material ◽  
Complete Solution ◽  
Normal Pressure ◽  
Stress Strain ◽  
Included Angle ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Plastic Domain ◽  
Elastic Perfectly Plastic

Abstract An elastic, perfectly plastic wedge of an incompressible isotropic material in the state of plane strain is considered, where the stress-strain relations of Prandtl-Reuss are employed in the plastic domain. For a wedge (with an included angle β) subjected to a uniform normal pressure on one boundary, the complete solution is obtained which is valid in the range 0 < β < π/2; this latter limitation is due to the character of the initial yield which depends on the magnitude of β. Numerical results for stresses and displacements are given in one case (β = π/4) for various positions of the elastic-plastic boundary.

scholarly journals Assessment of DBA-L Pressure Vessel Design Method by a Cylindrical Vessel with Hemispherical Ends

2019 ◽  
Vol 256 ◽  
pp. 02001
Author(s):  
Ren Xincheng ◽  
Hongjun Li ◽  
Xun Huang
Keyword(s):  
Stress Analysis ◽  
Pressure Vessel ◽  
Design Method ◽  
Design Methods ◽  
Cylindrical Vessel ◽  
Elastic Analysis ◽  
Explicit Method ◽  
Elastic Plastic ◽  
Cylindrical Pressure Vessel ◽  
Plastic Stress

Stress categorization is an essential procedure in Design by Analysis (DBA) pressure vessel design methods based on elastic analysis in ASME and EN code. It was difficult to implement especially around structural discontinuities. A new elastic analysis, DBA-L, was proposed recently to avoid stress categorization. A model of the cylindrical pressure vessel with spherical end is used to check the validity of this method by comparing with other design methods based on stress categorization procedures and elastic-plastic stress analysis from ASME and EN code. The results indicate that the DBA-L is an economic and explicit method, and can be used an alternative method to stress categorization.

Sophisticated Creep-Fatigue Life Estimation Scheme for Pressure Vessel Components Based on Stress Redistribution Locus Concept

2004 ◽  
Author(s):  
Takashi Shimakawa ◽  
Kyotada Nakamura ◽  
Ken-Ichi Kobayashi
Keyword(s):  
Thermal Stress ◽  
Pressure Vessel ◽  
Inelastic Strain ◽  
Stress Redistribution ◽  
Inelastic Behavior ◽  
Strain Concentration ◽  
Strain Behavior ◽  
Creep Fatigue ◽  
Current Design ◽  
Estimation Scheme

High temperature components are operated under cyclic thermal transient. Creep-Fatigue is the most dominant failure mode to be considered in Elevated Temperature Design of these components. Design limit for computed thermal stress is allowed to exceed yielding, because thermal stress is generally regarded as a displacement controlled one. Since creep deformation is considered as additional inelastic behavior, methodology to estimate inelastic strain concentration should be prepared in a design standard. Though inelastic FEM analyses can be applied to calculate inelastic strain concentration magnitude, it is well known that prediction is affected by applied constitutive model. Current design codes recommend to apply elastic FEM and to estimate inelastic strain behavior by simplified method. This paper presents sophisticated technique to estimate inelastic strain behavior based on Stress Redistribution Locus (SRL) method. Applicability of SRL concept is discussed with a help of FEM results for representative components of pressure vessel components such as nozzle, skirt and tube sheet.

Vibration Characteristics of a Perforated Plate Immersed in Fluid

2012 ◽  
Author(s):  
Tomohiro Ito ◽  
Atsuhiko Shintani ◽  
Chihiro Nakagawa
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Damping Ratio ◽  
Thermal Power ◽  
Perforated Plate ◽  
Vibration Characteristics ◽  
Chemical Plants ◽  
Perforated Plates ◽  
Stiffness Reduction ◽  
Test Models

Perforated plates are used in many mechanical structures in thermal power plants, nuclear power plants, or chemical plants etc. Cylindrical structures made by the perforated plates are also found in many places. However, vibration characteristics of the structures made by perforated plates are not fully clarified, especially for the structures immersed in liquid. The stiffness of the structures becomes smaller than that of ones made by simple plates with no holes, while the mass of the structures also becomes smaller. According to the balance between the stiffness reduction and mass reduction, natural frequencies will be decided. Moreover, added mass and added damping effects are very large in liquid, and are thought to largely change due to holes. In this study, as a fundamental step, a perforated plate is treated. The vibration characteristics such as natural frequency and damping ratio are studied for various hole numbers or various opening ratios by both numerical simulations and simple test models. Vibration tests are conducted in liquid as well as in air.

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