Approximate Elastic-Plastic J Estimate of Cylinders With Off-Centered Circumferential Through-Wall Cracks

2003 ◽  
Author(s):  
Do-Jun Shim ◽  
Nam-Su Huh ◽  
Yun-Jae Kim ◽  
Young-Jin Kim
Keyword(s):  
Fracture Mechanics ◽  
Strain Hardening ◽  
Combined Loading ◽  
Influence Functions ◽  
Elastic Plastic ◽  
Crack Geometry ◽  
Reference Stress ◽  
Plastic Influence Functions ◽  
Reference Stress Approach

This paper provides approximate J estimates for off-centred, circumferential through-wall cracks in cylinders under bending and under combined tension and bending. The proposed method is based on the reference stress approach, where the dependence of elastic and plastic influence functions of J on the cylinder/crack geometry, the off-centred angle and strain hardening is minimised through the use of a proper normalising load. Based on published limited FE results for off-centred, circumferential through-wall cracks under bending, such normalising load is found, based on which the reference stress based J estimates are proposed for more general cases, such as for a different cylinder geometry and for combined loading. Comparison of the estimated J with extensive FE J results shows overall good agreements for different crack/cylinder geometries and for combined tension and bending, which provides sufficient confidence in the use of the proposed method to fracture mechanics analyses of off-centred circumferential cracks. Furthermore, the proposed method is simple to use, giving significant merits in practice.

Elastic-Plastic Fracture Mechanics Method for Poor Penetration Crack in Welded Piping Branch Junction

2008 ◽  
Author(s):  
Yong-Qiang Bai ◽  
Tong Wang ◽  
Lianghai Lv ◽  
Liang Sun ◽  
Jian Shuai
Keyword(s):  
Fracture Mechanics ◽  
Crack Front ◽  
Crack Depth ◽  
Influence Functions ◽  
Stress Strain ◽  
Elastic Plastic ◽  
Inner Radius ◽  
Plastic Influence Functions ◽  
Remote Stress ◽  
J Estimation

This paper provides two types of engineering J estimation equations for welded piping branch junctions with poor penetration crack under internal pressure. The first type is the so-called GE/EPRI type J estimation equation based on Ramberg-Osgood (R-O) materials. Based on detailed 3-D FE results using deformation plasticity, plastic influence functions for fully plastic J components are tabulated for practical ranges of the inner radius of brace to the inner radius of chord ratio, the thickness of brace to the thickness of chord, the thickness of chord to the inner radius of chord ratio, the crack depth to the thickness of chord ratio, the strain hardening index for the R-O material, and the location along the poor penetration crack front. Based on tabulated plastic influence functions, the GE/EPRI-type J estimation equation along the crack front is proposed. For more general application, the effective remote stress method based on GE/EPRI-type solutions is provided. This method provides a simpler equation for J, which could be used for any stress-strain relationship material, including Ramborg-Osgood (R-O) material and non-R-O materials under monotonic increasing loading. The proposed effective remote stress based J estimation equation is compared with elastic-plastic 3-D FE results using actual stress–strain data for a Type 304 strainless steel. Good agreement between the FE results and the proposed reference stress based J estimation provides confidence in the use of the proposed method for elastic-plastic fracture mechanics of pressurized welded piping branch junction.

An Approximate Model for an Elastic-Plastic Pipe Element Under Combined Loading

1975 ◽  
Vol 97 (1) ◽  
pp. 22-28 ◽  
Author(s):  
L. D. Larson ◽  
W. F. Stokey ◽  
W. E. Franzen
Keyword(s):  
Strain Hardening ◽  
Axial Load ◽  
Analytical Approach ◽  
Limit Load ◽  
Approximate Model ◽  
Experimental Results ◽  
Combined Loading ◽  
Elastic Plastic ◽  
Plastic Pipe ◽  
Plastic Analysis

An approximate model for the elastic-plastic analysis of a pipe element under combined loading is developed. The model is obtained by generalizing a limit load solution for combined pressure, bending, torsion and axial load to include strain hardening. For various combinations of loading of tubes, curvatures and twist angles are predicted and compared with experimental results and those predicted by a more rigorous analytical approach. The comparison shows that good results are obtained from the approximate model.

Estimates of Plastic Limit Loads of Thick-Walled Cylinders With Non-Idealzied Through-Wall Cracks

2013 ◽  
Author(s):  
Tae-Song Han ◽  
Nam-Su Huh ◽  
Do-Jun Shim
Keyword(s):  
Fracture Mechanics ◽  
Structural Integrity ◽  
Limit Load ◽  
Ductile Material ◽  
J Integral ◽  
Plastic Limit ◽  
Limit Loads ◽  
Elastic Plastic ◽  
Reference Stress ◽  
Plastic Limit Load

In order to assess a structural integrity of cracked components made of highly ductile material based on fully plastic fracture mechanics concept, an accurate plastic limit load of components of interest is crucial element. Such a plastic limit load can also be applied to estimate elastic-plastic J-integral based on the reference stress concept. In this context, during last several decades, many efforts have been made to suggest plastic limit load solutions of cracked cylinder. Recent works for evaluating rupture probabilities of nuclear piping indicate that the only use of idealized circumferential through-wall crack leads to very conservative results which in turn gives higher rupture probabilities of nuclear piping, thus the considerations of more realistic crack shape during crack growth due to primary water stress corrosion cracking (PWSCC) and fatigue and axial through-wall crack were recommended to come up with more realistic rupture probabilities of nuclear piping. Then, the needs of fracture mechanics parameters of non-idealized through-wall cracks both in axial and circumferential directions have been raised. In the present work, the plastic limit loads of thick-walled cylinder with non-idealized axial and circumferential through-wall cracks are proposed based on detailed 3-dimensional finite element analyses. The present results can be applied either to assess structural integrity of thick-walled nuclear piping with non-idealized through-wall cracks or to calculate elastic-plastic J-integral using the reference stress concept.

Elastic-Plastic J and COD Estimates for Circumferential Through-Wall Cracks Between Elbows and Straight Pipes Under Bending

2007 ◽  
Author(s):  
Tae-Kwang Song ◽  
Yun-Jae Kim
Keyword(s):  
Crack Opening ◽  
Small Strain ◽  
Opening Displacement ◽  
Limit Loads ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Reference Stress ◽  
Plastic Materials ◽  
Elastic Perfectly Plastic ◽  
Reference Stress Approach

A method for elastic-plastic fracture mechanics analyses is presented for the circumferential through-wall crack in weldment joining elbows and attached straight pipes, subject to in-plane bending, based on the reference stress approach. Based on small strain finite element limit analyses using elastic-perfectly plastic materials, closed-form limit loads for circumferential through-wall cracks in between elbows and straight pipes under bending are given. Then applicability of the reference stress based method to approximately estimate J and crack opening displacement (COD) is proposed.

Effect of the Type of Stress-Strain Law on the Validity of the Reference Stress Approach in Fracture Mechanics

2014 ◽  
Author(s):  
Philippe Gilles ◽  
Gongchen Zhang ◽  
Komlanvi Madou
Keyword(s):  
Fracture Mechanics ◽  
Power Law ◽  
Plasticity Theory ◽  
Material Behavior ◽  
Stress Strain ◽  
Hardening Law ◽  
Reference Stress ◽  
Deformation Plasticity ◽  
Reference Stress Approach ◽  
J Estimation

In fracture mechanics, several J-estimation schemes are based on the reference stress approach. This approach has been developed initially in the frame of the R5 rule for creep and R6 rule for elasto-plastic fracture assessments. Later other methods, based on the reference stress concept, where derived like the Js method introduced in the French RSE-M code en 1997 and the Enhanced Reference Stress (ERS) method in Korea around 2001. However these developments are based on the J2 deformation plasticity theory and well established for a pure power hardening law. Even in this latter case, the reference stress depends on the hardening exponent. Js and ERS attempt to minimize this dependence and propose some corrections for recorded behavior laws which cannot be fitted by a power law. However their validation has been established mainly on cases where the material behavior is governed by a Ramberg-Osgood (R0) law. The question may be raised, as for the bilinear hardening law case, of the existence of a reference stress for non RO laws.

Approximate J Estimates for Circumferential Cracks in between Elbows and Attached Pipes

2007 ◽  
Vol 345-346 ◽  
pp. 521-524
Author(s):  
Tae Kwang Song ◽  
Chang Kyun Oh ◽  
Yun Jae Kim ◽  
Jong Sung Kim ◽  
Tae Eun Jin
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Closed Form ◽  
Limit Load ◽  
Small Strain ◽  
Straight Pipe ◽  
Popular Approach ◽  
Elastic Plastic ◽  
Reference Stress ◽  
Mechanics Analysis

The present work proposes a method for elastic-plastic fracture mechanics analysis of the circumferential through-wall crack in between elbows and attached straight pipes, subject to in-plane bending. Based on small strain finite element limit analyses, closed-form limit load solutions are given first. Then applicability of the reference stress based method to approximately estimate J is proposed. One interesting finding is that a popular approach to assume that the crack locates in the straight pipe could lead to significantly different assessment results.

scholarly journals In-situ elastic-plastic fracture mechanics on the microscale by means of continuous dynamical testing

2018 ◽  
Vol 148 ◽  
pp. 177-187 ◽  
Author(s):  
Markus Alfreider ◽  
Darjan Kozic ◽  
Otmar Kolednik ◽  
Daniel Kiener
Keyword(s):  
Fracture Mechanics ◽  
Elastic Plastic
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