Study on Equivalent Stress to Control Average Inelastic Behavior of Perforated Plates

2014 ◽  
Author(s):  
Yeldos Kultayev ◽  
Naoto Kasahara
Keyword(s):  
Stress Ratio ◽  
Elevated Temperatures ◽  
Equivalent Stress ◽  
Perforated Plate ◽  
Estimation Method ◽  
Inelastic Behavior ◽  
Perforated Plates ◽  
Inelastic Analysis ◽  
Solid Plate ◽  
Simple Models

Next generation reactors which are subjected to elevated temperatures must be designed to account for inelastic deformation along with elastic one. In order to simplify design analysis of perforated portions, conventionally axisymmetric models with equivalent elastic materials are employed. To extend to inelastic analysis, a method of Effective Stress Ratio (ESR) has been studied in recent years. Previous studies have shown that perforated plates have their own ESR and it is a function of geometry and is independent from their materials. In this study the only geometry dependence and physical meaning of ESR were clarified. ESR results were compared with Reference Stress Method (RSM) results for unit-ligaments with various ligament efficiencies. It was revealed that RSM results coincide with ESR. First meaning of ESR is stress ratio between solid plate and perforated plate at the same reference stresses. Second meaning of this ratio is how plasticity properties of equivalent solid plate have to be changed to give the same steady state deformation rate at the same mean boundary stress. Moreover, to clarify stress redistribution control mechanism at different ligament efficiencies, simple models were developed and an estimation method based on simple models was proposed for engineering use.

The Influence of Multiaxial Stress Relaxation on Component Creep Damage Accumulation in Biaxial, Mixed Primary, and Secondary Loading on a Pipe

2020 ◽  
Author(s):  
Nayden Matev ◽  
Robert A. Ainsworth ◽  
Meini Su ◽  
Mark Stevens ◽  
Alan Jappy
Keyword(s):  
Damage Accumulation ◽  
Stress Ratio ◽  
Equivalent Stress ◽  
Creep Damage ◽  
Biaxial Stress ◽  
Multiaxial Stress ◽  
Secondary Stress ◽  
Initial Value ◽  
Inelastic Analysis

Abstract Unless detailed inelastic analysis is followed, high temperature codes base creep relaxation during a dwell period within a cycle on the start-of-dwell equivalent stress. The relaxation of the equivalent stress is then taken to be governed by a uniaxial creep law for the material being considered. Elastic follow-up is also included in such calculations. With this approach, only equivalent values of stress and creep strain rate are obtained and the stress multiaxiality is therefore assumed to remain at its initial value as the stress relaxes. The stress drop is limited to a small fraction (typically 20%) of the initial equivalent stress to ensure that this assumption does not lead to significant inaccuracy. This paper reports creep relaxation results for a pipe subjected to a combination of both primary and secondary stresses. The primary stress is generated by an internal pressure and an axial load, which enable different primary biaxial loading conditions to be generated. The secondary stress is through-wall bending in nature, produced by a through-wall temperature gradient, which influences the initial biaxial stress ratio. Several parameters are varied in order to produce relaxation behaviour in the pipe with an associated elastic follow-up. The starting biaxial stress ratio, the creep law power exponent and the amount of secondary stress result in varying degrees of elastic follow-up being present. The biaxial stress ratio is generally found to change as relaxation occurs and a multiaxial ductility approach is used to evaluate the associated effect on creep damage accumulation. This is compared with the creep damage estimated by assuming relaxation is simply controlled by the equivalent stress with no change in multiaxial stress state during relaxation. It is found that significant equivalent stress drops (up to about 40% of the initial value) can be allowed without the simplified equivalent stress approach being inaccurate. The results have been compared with a number of creep damage models to ensure that the conclusions are not sensitive to the detail of the damage model.

Resonant frequencies of perforated plates with rectangular slots

2016 ◽  
Vol 232 (7) ◽  
pp. 1247-1254 ◽  
Author(s):  
Oumar R Barry ◽  
Emadeddin Y Tanbour
Keyword(s):  
Elastic Properties ◽  
Material Properties ◽  
Natural Frequencies ◽  
Perforated Plate ◽  
Free Vibrations ◽  
Equivalent Material ◽  
Resonant Frequencies ◽  
Perforated Plates ◽  
Rectangular Slot ◽  
Solid Plate

Most previous work on perforated plates employed elasticity theory to determine equivalent material properties that make the deflection of the solid plate identical to that of the perforated plate. However, it will be inaccurate to utilize the proposed elastic properties to predict the natural frequencies of a perforated plate. In this paper, the free vibrations of perforated plates with rectangular slots and rectangular slot-patterns are examined using theoretical and finite-element methods. The natural frequencies are obtained for various cases of perforations. An explicit expression is obtained for the equivalent elastic properties using the regression analysis method. These effective material properties are used in a solid-plate model to predict the natural frequencies of the corresponding perforated plate. To validate the theoretical analysis, the effective resonant frequencies are compared with the exact natural frequencies of the perforated plates. Parametric studies are conducted to examine the effect of both parallel and perpendicular ligament efficiencies on the resonant frequencies.

scholarly journals Features of subsonic air flow around perforated plates

2020 ◽  
Author(s):  
A.G. Golubev ◽  
E.G. Stolyarova ◽  
M.D. Kalugina
Keyword(s):  
Normal Force ◽  
Air Flow ◽  
Angle Of Attack ◽  
Vertical Plane ◽  
Perforated Plate ◽  
Aerodynamic Characteristics ◽  
Perforated Plates ◽  
Subsonic Speed ◽  
Solid Plate ◽  
Zero Degree

The paper considers the process of flow around a flat plate with rounded front and side edges at various degrees of surface perforation. The flow patterns were studied both near the plate with zero degree of perforation, and at the surface of plates with a perforation degree of more than 20%. The features of air flow directly inside the holes at various values of the angle of attack are considered. Isobars of pressure distribution in the vertical plane of the flow over a solid plate are given. A simulation of the flow around a perforated plate at subsonic speed of the incoming air flow is performed, aerodynamic characteristics are obtained and graphical dependencies of the aerodynamic coefficients of longitudinal and normal force on the angle of attack are presented. Special attention is paid to the comparative analysis of aerodynamic characteristics for solid (with zero degree of perforation) and perforated plates.

Elasto-Plastic Analysis of Perforated Plates Containing Triangular Penetration Patterns of 10 Percent Ligament Efficiency

1979 ◽  
Vol 101 (3) ◽  
pp. 210-215 ◽  
Author(s):  
D. P. Jones ◽  
J. L. Gordon
Keyword(s):  
Work Hardening ◽  
Pure Shear ◽  
Perforated Plate ◽  
Stress Distributions ◽  
The Finite Element Method ◽  
Hardening Material ◽  
Perforated Plates ◽  
Solid Plate ◽  
Deformation Plasticity ◽  
Concentration Factors

The finite element method is utilized to obtain the elasto-plastic stress and strain fields in a perforated plate made of a work-hardening material. The perforated plate contains penetrations arranged in a triangular pattern with a ligament efficiency of 10 percent and is considered to be in a state of plane stress. Stress distributions as well as strain concentration factors are presented for the two orthogonal uniaxial and the pure shear load cases. Effective elasto-plastic equivalent solid plate properties are presented in terms of Hill’s anisotropic deformation plasticity theory. The localized stress and plastic strain distributions are discussed in terms of the work-hardening characteristics of the material. Conclusions are drawn relevant to the plastic design and analysis of perforated plates.

High Speed Flow through Perforated Plates

1960 ◽  
Vol 64 (590) ◽  
pp. 103-105
Author(s):  
P. G. Morgan
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Perforated Plate ◽  
Wire Mesh ◽  
Flow Conditions ◽  
High Speed Flow ◽  
Perforated Plates ◽  
Speed Flow ◽  
Flow Through ◽  
Points Of View

The flow through porous screens has been widely studied from both the theoretical and experimental points of view. The most widely used types of screen are the wire mesh and the perforated plate, and the majority of the literature has been concerned with the former. Several attempts have been made to correlate the parameters governing the flow through such screens, i.e. the pressure drop, the flow conditions and the geometry of the mesh.

scholarly journals THE STUDY OF ACOUSTIC CHARACTERISTICS OF THE PERFORATED AND HOMOGENOUS PLATES WITH SIMILAR GEOMETRICAL DIMENSIONS

Akustika ◽  
2019 ◽  
Vol 32 ◽  
pp. 79-82
Author(s):  
Valery Kirpichnikov ◽  
Lyudmila Drozdova ◽  
Alexei Koscheev ◽  
Ernst Myshinsky
Keyword(s):  
Resonant Frequency ◽  
Acoustic Radiation ◽  
Perforated Plate ◽  
Acoustic Characteristics ◽  
Resonant Frequencies ◽  
Perforated Plates ◽  
Resonance Frequencies ◽  
Flexural Vibrations ◽  
Geometrical Dimensions

The resonance frequencies of the flexural vibrations, input vibration excitability and acoustic radiation of the homogeneous and perforated plates were investigated. It is established that the average reduction range of the lower resonant frequency of flexural vibrations of the tested plates with the holes virtually coincides with the predictive estimate. The levels of the input vibration excitability of the perforated plate at the lower resonant frequencies exceeded the levels at the corresponding frequencies of the homogeneous plates greater than the calculated value. The levels of resonance acoustic radiation of the perforated plate were significantly less than of the homogeneous one.

Validation of Inelastic Analysis by Full-Scale Component Testing

1987 ◽  
Vol 109 (1) ◽  
pp. 42-49 ◽  
Author(s):  
D. S. Griffin ◽  
A. K. Dhalla ◽  
W. S. Woodward
Keyword(s):  
Life Prediction ◽  
Elevated Temperatures ◽  
Full Scale ◽  
Prediction Methods ◽  
Material Models ◽  
Component Testing ◽  
Inelastic Analysis ◽  
Creep Buckling ◽  
Design Requirements ◽  
Thermal Striping

This paper compares theoretical and experimental results for full-scale, prototypical components tested at elevated-temperatures to provide validation for inelastic analysis methods, material models, and design limits. Results are discussed for piping elbow plastic and creep buckling, creep ratcheting, and creep relaxation; nozzle creep ratcheting and weld cracking; and thermal striping fatigue. Comparisons between theory and test confirm the adequacy of components to meet design requirements, but identify specific areas where life prediction methods could be made more precise.

The Aerodynamic Drag of Perforated Plates at Zero Incidence

1958 ◽  
Vol 62 (568) ◽  
pp. 301-303 ◽  
Author(s):  
P. Minton ◽  
J. R. D. Francis
Keyword(s):  
Pipe Flow ◽  
Aerodynamic Drag ◽  
Perforated Plate ◽  
Perforated Plates ◽  
Drag Forces ◽  
Flow Experiments

Perforated Plates have been used at large angles of incidence to produce drag forces and evidence on their properties has been published by de Bray. Less appears to be known about the drag forces on such surfaces at zero incidence, although they are usually considered to be aerodynamically rough. This has been confirmed by Ambrose, who carried out pipe flow experiments using perforated liners which fitted tightly in the bore of a pipe. Perforated plates used in this way do not allow flow completely through them and give “pitted” surfaces. If a perforated plate is mounted so that it is possible for cross flows to occur between the main flows on both sides of the plate the drag forces on it may be affected, and in this case the perforations will be referred to as “holes.”

Finite Element Analysis of Local Inelastic Strain Based on Stress Redistribution Locus

2008 ◽  
Author(s):  
Shunji Kataoka ◽  
Takuya Sato
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Loading ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Pressure Vessels ◽  
Stress Redistribution ◽  
Strain Diagram ◽  
Element Analysis ◽  
Inelastic Analysis

Creep-fatigue damage is one of the dominant failure modes for pressure vessels and piping used at elevated temperatures. In the design of these components the inelastic behavior should be estimated accurately. An inelastic finite element analysis is sometimes employed to predict the creep behavior. However, this analysis needs complicated procedures and many data that depend on the material. Therefore the design is often based on a simplified inelastic analysis based on the elastic analysis result, as described in current design codes. A new, simplified method, named, Stress Redistribution Locus (SRL) method, was proposed in order to simplify the analysis procedure and obtain reasonable results. This method utilizes a unique estimation curve in a normalized stress-strain diagram which can be drawn regardless of the magnitude of thermal loading and constitutive equations of the materials. However, the mechanism of SRL has not been fully investigated. This paper presents results of the parametric inelastic finite element analyses performed in order to investigate the mechanism of SRL around a structural discontinuity, like a shell-skirt intersection, subjected to combined secondary bending stress and peak stress. This investigation showed that SRL comprises a redistribution of the peak and secondary stress components and that although these two components exhibit independent redistribution behavior, they are related to each other.

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.

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