Creep Analysis for Pressurized Components Under Creep Conditions Based on Isochronous Stress-Strain Curve and Elastic-Perfectly Plastic Material Model

2018 ◽  
Author(s):  
Qi-Wei Xia ◽  
Jian-Guo Gong ◽  
Fu-Zhen Xuan
Keyword(s):  
Elevated Temperatures ◽  
Plastic Material ◽  
Strain Curve ◽  
Inelastic Strain ◽  
Material Model ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Perfectly Plastic ◽  
Creep Analysis ◽  
Elastic Perfectly Plastic

This work is to address the creep analysis for components at elevated temperatures based on isochronous stress-strain curve and the elastic-perfectly plastic material model through numerical analyses. Numerical results presented that the creep deformation is very sensitive to the target inelastic strain chosen for analysis. A small inelastic strain, corresponding to a small yield stress, can cause very conservative result for the case studied. Moreover, the target inelastic strain, corresponding to the minimum inelastic strain along with the given path, is different from each other for various internal pressures.

A General Autofrettage Model of a Thick-Walled Cylinder Based on Tensile-Compressive Stress-Strain Curve of a Material

2005 ◽  
Vol 40 (6) ◽  
pp. 599-607 ◽  
Author(s):  
X. P Huang
Keyword(s):  
Strain Hardening ◽  
Compressive Stress ◽  
Bauschinger Effect ◽  
Strain Curve ◽  
Accurate Prediction ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Perfectly Plastic ◽  
Hardening Models ◽  
Elastic Perfectly Plastic

The basic autofrettage theory assumes elastic-perfectly plastic behaviour. Because of the Bauschinger effect and strain-hardening, most materials do not display elastic-perfectly plastic properties and consequently various autofrettage models are based on different simplified material strain-hardening models, which assume linear strain-hardening or power strain-hardening or a combination of these strain-hardening models. This approach gives a more accurate prediction than the elastic-perfectly plastic model and is suitable for different strain-hardening materials. In this paper, a general autofrettage model that incorporates the material strain-hardening relationship and the Bauschinger effect, based upon the actual tensile-compressive stress-strain curve of a material is proposed. The model incorporates the von Mises yield criterion, an incompressible material, and the plane strain condition. Analytic expressions for the residual stress distribution have been derived. Experimental results show that the present model has a stronger curve-fitting ability and gives a more accurate prediction. Several other models are shown to be special cases of the general model presented in this paper. The parameters needed in the model are determined by fitting the actual tensile-compressive curve of the material, and the maximum strain of this curve should closely represent the maximum equivalent strain at the inner surface of the cylinder under maximum autofrettage pressure.

Inelastic Analysis of Process Vessel Component Under Creep and Primary Load

2020 ◽  
Author(s):  
Quan Hoang Tran ◽  
Daniel Truong ◽  
K. T. Truong
Keyword(s):  
Failure Modes ◽  
Strain Curve ◽  
Inelastic Strain ◽  
Local Failure ◽  
Load Factor ◽  
Stress Strain Curve ◽  
Time Duration ◽  
Stress Strain ◽  
Perfectly Plastic ◽  
Inelastic Analysis

Abstract In vessel component design by analysis, two failure modes are routinely investigated: Protection against plastic collapse and Protection against local failure. In elevated temperature service, creep rupture stress is the basis for elastic numerical analysis for establishing compliance with protection against the first failure mode. When compliance is not met, Elastic Perfectly Plastic (EPP) being a more accurate tool is proposed to verify the design using a factored rupture-based stress as yield (Sy = 1.25S). It seems that related work about adjusted yield stress has not been presented and validations are still needed using ASME VIII-2, part 5 combined load factor. Regarding local failure, an isochronous stress-strain curve has been used to determine the final stage strain for a total time duration, and compare to limits set by ASME III-NH. Code case 861 is also used to evaluate the minimum total inelastic strain and its conservativeness compared to the isochronous stress-strain curve approach.

Simplified Analysis Methods for Primary Load Designs at Elevated Temperatures

2011 ◽  
Author(s):  
Peter Carter ◽  
T.-L. Sam Sham ◽  
R. I. Jetter
Keyword(s):  
Elevated Temperatures ◽  
Design Procedure ◽  
Inelastic Strain ◽  
Temperature Dependent ◽  
Perfectly Plastic ◽  
Reference Stress ◽  
Analysis Methods ◽  
Elastic Perfectly Plastic ◽  
Further Development ◽  
Primary Load

The use of “simplified” (reference stress) analysis methods is discussed and illustrated for primary load high temperature design. Elastic methods are the basis of the ASME Section III, Subsection NH primary load design procedure. There are practical drawbacks with this current NH approach, particularly for complex geometries and temperature gradients. The paper describes an approach which addresses these difficulties through the use of temperature-dependent elastic, perfectly-plastic analysis. Traditionally difficulties associated with discontinuity stresses, inelastic strain concentrations and multiaxiality are addressed. A procedure is identified to provide insight into how this approach could be implemented. Though preliminary in nature, it is intended to provide a basis for further development and eventual Code adaptation.

Shakedown Limits of a 90-Degree Pipe Bend Using Small and Large Displacement Formulations

2006 ◽  
Author(s):  
Hany F. Abdalla ◽  
Mohammad M. Megahed ◽  
Maher Y. A. Younan
Keyword(s):  
Plastic Material ◽  
Limit Load ◽  
Material Model ◽  
Large Displacement ◽  
Small Displacement ◽  
Pipe Bend ◽  
Perfectly Plastic ◽  
Loading Patterns ◽  
Elastic Perfectly Plastic ◽  
Shakedown Limit

In this paper the shakedown limit load is determined for a long radius 90-degree pipe bend using two different techniques. The first technique is a simplified technique which utilizes small displacement formulation and elastic-perfectly-plastic material model. The second technique is an iterative based technique which uses the same elastic-perfectly-plastic material model, but incorporates large displacement effects accounting for geometric non-linearity. Both techniques use the finite element method for analysis. The pipe bend is subjected to constant internal pressure magnitudes and cyclic bending moments. The cyclic bending loading includes three different loading patterns namely; in-plane closing, in-plane opening, and out-of-plane bending. The simplified technique determines the shakedown limit load (moment) without the need to perform full cyclic loading simulations or conventional iterative elastic techniques. Instead, the shakedown limit moment is determined by performing two analyses namely; an elastic analysis and an elastic-plastic analysis. By extracting the results of the two analyses, the shakedown limit moment is determined through the calculation of the residual stresses developed in the pipe bend. The iterative large displacement technique determines the shakedown limit moment in an iterative manner by performing a series of full elastic-plastic cyclic loading simulations. The shakedown limit moment output by the simplified technique (small displacement) is used by the iterative large displacement technique as an initial iterative value. The iterations proceed until an applied moment guarantees a structure developed residual stress, at load removal, equals or slightly less than the material yield strength. The shakedown limit moments output by both techniques are used to generate shakedown diagrams of the pipe bend for a spectrum of constant internal pressure magnitudes for the three loading patterns stated earlier. The maximum moment carrying capacity (limit moment) the pipe bend can withstand and the elastic limit are also determined and imposed on the shakedown diagram of the pipe bend. Comparison between the shakedown diagrams generated by the two techniques, for the three loading patterns, is presented.

Case Study of Shakedown Evaluation of a Shell With Nozzle Based on Elastic-Plastic Analysis

2017 ◽  
Author(s):  
Jun Shen ◽  
Heng Peng ◽  
Liping Wan ◽  
Yanfang Tang ◽  
Yinghua Liu
Keyword(s):  
Temperature Change ◽  
Plastic Material ◽  
Material Model ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Plastic Analysis ◽  
Elastic Perfectly Plastic ◽  
Temperature Loads ◽  
The Impact

In the past, shakedown evaluation was usually based on the elastic method that the sum of the primary and secondary stress should be limited to 3Sm or the simplified elastic-plastic analysis method. The elastic method is just an approximate analysis, and the rigorous evaluation of shakedown normally requires an elastic-plastic analysis. In this paper, using an elastic perfectly plastic material model, the shakedown analysis was performed by a series of elastic-plastic analyses. Taking a shell with a nozzle subjected to parameterized temperature loads as an example, the impact of temperature change on the shakedown load was discussed and the shakedown loads of this structure at different temperature change rates were also obtained. This study can provide helpful references for engineering design.

Continuous Strength Method for Aluminium Alloy Structures

2013 ◽  
Vol 742 ◽  
pp. 70-75 ◽  
Author(s):  
Mei Ni Su ◽  
Ben Young ◽  
Leroy Gardner
Keyword(s):  
Aluminium Alloy ◽  
Strain Hardening ◽  
Plastic Material ◽  
Design Method ◽  
Material Model ◽  
Hardening Material ◽  
Perfectly Plastic ◽  
Base Curve ◽  
Current Design ◽  
Elastic Perfectly Plastic

Aluminium alloys are nonlinear metallic materials with continuous stress-strain curves that are not well represented by the simplified elastic, perfectly plastic material model used in many current design specifications. Departing from current practice, the continuous strength method (CSM) is a recently proposed design approach for non-slender aluminium alloy structures with consideration of strain hardening. The CSM is deformation based and employs a base curve to define a continuous relationship between cross-section slenderness and deformation capacity. This paper explains the background and the two key components - (1) the base curve and (2) the strain hardening material model of the continuous strength method. More than 500 test results are used to verify the continuous strength methodas an accurate and consistent design method for aluminium alloy structures.

Analysis and design of steel plate walls: experimental evaluation

2011 ◽  
Vol 38 (1) ◽  
pp. 60-70 ◽  
Author(s):  
Mehdi H.K. Kharrazi ◽  
Carlos E. Ventura ◽  
Helmut G.L. Prion
Keyword(s):  
Experimental Evaluation ◽  
Steel Plate ◽  
Plastic Material ◽  
Material Model ◽  
Steel Plates ◽  
Ultimate Capacity ◽  
Initial Stiffness ◽  
Analysis And Design ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

In this paper, the effectiveness of the Modified Plate–Frame Interaction (M-PFI) model is evaluated by comparing its outcomes against those from experimental results obtained from a number of steel plate walls (SPWs) tested at different universities. As a result of the comparison, the M-PFI model was found to provide satisfactory predictions for SPW specimens constructed with steel plates welded to column and beam members. The M-PFI model was able to predict the initial stiffness, as well as to evaluate whether the boundary members of the SPW have sufficient capacity to allow for the infill plate to yield entirely. However, the model was found to underestimate the ultimate capacity of the SPW system mainly because, among other reasons, the material model used for its underlying theory is the elastic – perfectly plastic material model.

scholarly journals A Simplified Approach for the Hydro-Forming Process of Bi-Metallic Composite Pipe

2017 ◽  
Vol 62 (2) ◽  
pp. 879-883 ◽  
Author(s):  
M. Zheng ◽  
H. Gao ◽  
H. Teng ◽  
J. Hu ◽  
Z. Tian ◽  
...  
Keyword(s):  
Residual Stress ◽  
Plastic Material ◽  
Material Model ◽  
Forming Process ◽  
Simplified Approach ◽  
Metallic Composite ◽  
Perfectly Plastic ◽  
Proposed Model ◽  
Composite Pipe ◽  
Elastic Perfectly Plastic

AbstractIn this article, it aims to propose effective approaches for hydro-forming process of bi-metallic composite pipe by assuming plane strain and elastic-perfectly plastic material model. It derives expressions for predicting hydro-forming pressure and residual stress of the forming process of bi-metallic composite pipe. Test data from available experiments is employed to check the model and formulas. It shows the reliability of the proposed model and formulas impersonally.

Deformational characteristics of thermally treated sandstone from an underground coalmine fire region, India

2021 ◽  
Author(s):  
Adarsh Tripathi ◽  
Noopur Gupta ◽  
Ashok Kumar Singh ◽  
Nachiketa Rai ◽  
Anindya Pain
Keyword(s):  
Large Scale ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Small Scale ◽  
Carbonaceous Shale ◽  
Deformation Pattern ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Thermomechanical Behaviour ◽  
Thermally Treated

<p>The Jharia region of lower Gondwana in India is one of the largest Underground Coalmine Fires (UCF) affected coalfield in the world. The UCF induced small scale as well as large-scale surface fracturing often creates the life-threatening conditions to coal miners and local surroundings. So, there is a need to understand the thermomechanical behaviour of coal measures rocks to predict the land disturbances in thermo-environmental conditions. It will provide an insight into the UCF induced subsidence mechanism and its preventive measures. The Jharia coal field predominantly consists of sandstone (75-80% by volume) and rest is composed of coal, shale and carbonaceous shale. The present study focuses on thermo-mechanical behaviour of Barakar sandstone (BS) under elevated temperatures. The cores of BS sample were prepared according to the ISRM standards. Further, samples were grouped and thermally treated in temperature range of 25°C, 100°C, 150°C, 300°C, 400°C, 500°C, 600 °C, 700°C and 800°C at a heating rate of 5°C/min for 24 hours in furnace.  Then, these thermally treated BS samples were subjected to laboratory test for stress-strain characteristics. In the process of deformational characteristics evaluation, effect of mineralogical changes and mode of fracture pattern were also studied at the mentioned elevated temperature. Based on the obtained results, the deformational behaviour of thermally treated BS specimens can be grouped into three zones, viz., zone 1 (25-300°C), zone 2 (300-500°C) and zone 3 (500-800°C). In zone 1, the characteristics of the stress-strain curve is similar to those under air dried sandstone specimen. However, small increment in stiffness were observed upto 300°C. The stress-strain curves in this zone shows dominantly brittle fracturing. The increment in stiffness may be related to evaporation of pore water that increases the cohesion between the mineral grains resulting higher stiffness value. In zone 2, the deformation pattern again shows brittle fracturing with continuous decrement in stiffness. The reduction in stiffness may be related to thermally induced porosity and increased microcrack density. In zone 3, the stress strain curve is observed to be concave upward. It indicates the pseudo-ductile behaviour of the thermally treated BS specimens. The observed results suggest a typical behaviour of deformation pattern under UCF induced rock fracturing which may be useful in predicting the land subsidence in UCF affected areas. Present research outcome may be used to design the support measures to reduce the associated hazards.</p>

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