Simulation of Curved Fatigue Crack Growth with Calculation of the Plastic Limit Load

2009 ◽  
Vol 417-418 ◽  
pp. 45-48
Author(s):  
Holger Theilig ◽  
Dirk Holländer ◽  
Michael Wünsche
Keyword(s):  
Crack Growth ◽  
Crack Path ◽  
Limit Load ◽  
Simulation Algorithm ◽  
Plastic Limit ◽  
Limit Loads ◽  
Plastic Limit Load ◽  
Fully Automatic ◽  
Piecewise Parabolic ◽  
Automatic Simulation

In this paper a higher order crack path simulation algorithm for multiple interacting cracks is presented using piecewise parabolic curved increments including the consideration of the plastic limit loads. For this reason, the program PCCS-2D has been extended to analyse the crack growth and the plastic limit load for each crack propagation step in a fully automatic simulation. The proposed solution algorithm provides a powerful tool for flaw assessment with the FAD proce¬dure in combination with a numerical crack path simulation. Several numerical examples are pre¬sented to show the accuracy and the efficiency of the crack path simulation including the analysis of the plastic limit loads

Numerical Simulation of Multiple Fatigue Crack Growth with Additional Crack Initiation

2011 ◽  
Vol 488-489 ◽  
pp. 444-447
Author(s):  
Dirk Holländer ◽  
Michael Wünsche ◽  
S. Henkel ◽  
Holger Theilig
Keyword(s):  
Numerical Simulation ◽  
Fatigue Crack ◽  
Crack Growth ◽  
Growth Process ◽  
Limit Load ◽  
Simulation Algorithm ◽  
Plastic Limit ◽  
Curved Crack ◽  
Bound Theorem ◽  
Plastic Limit Load

In this paper, advanced numerical simulations of curved crack growth in the case of mul­tiple crack systems in combination with the analysis of the plastic limit load by the lower bound theorem of plasticity are presented. In order to take additionally initiated cracks during the crack growth process into account, the numerical simulation algorithm has been extended by using the Smith-Watson-Topper (SWT) parameter in combination with a linear fatigue damage accumula­tion.

Plastic Limit Loads for Slanted Through-Wall Cracks in Cylinder and Plate Based on Finite Element Limit Analyses

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Doo-Ho Cho ◽  
Young-Hwan Choi ◽  
Nam-Su Huh ◽  
Do-Jun Shim ◽  
Jae-Boong Choi
Keyword(s):  
Finite Element ◽  
Crack Opening ◽  
Limit Load ◽  
Correction Factors ◽  
Plastic Limit ◽  
Opening Displacement ◽  
Limit Loads ◽  
Axial Tension ◽  
Reference Stress ◽  
Plastic Limit Load

The plastic limit load solutions for cylinder and plate with slanted through-wall cracks (TWCs) are developed based on the systematic three-dimensional (3D) finite element (FE) limit analyses. As for loading conditions, axial tension, global bending, and internal pressure are considered for a cylinder with slanted circumferential TWC, whereas, axial tension and internal pressure are considered for a plate and a cylinder with slanted axial TWC. Then, the verification of FE model and analysis procedure employed in the present numerical work was confirmed by employing the existing solutions for both cylinder and plate with idealized TWC. Also, the geometric variables of slanted TWC which can affect plastic limit loads were considered. Based on the systematic FE limit analysis results, the slant correction factors which represent the effect of slanted TWC on plastic limit load were provided as tabulated solutions. By adopting these slant correction factors, the plastic limit loads of slanted TWC can be directly estimated from existing solutions for idealized TWC. Furthermore, the modified engineering estimations of plastic limit loads for slanted TWC are proposed based on equilibrium equation and von Mises yield criterion. The present results can be applied either to diverse structural integrity assessments or for accurate estimation of fracture mechanics parameters such as J-integral, plastic crack opening displacement (COD) and C*-integral for slanted TWC based on the reference stress concept (Kim, et al., 2002, “Plastic Limit Pressure for Cracked Pipes Using Finite Element Limit Analyse,” Int. J. Pressure Vessels Piping, 79, pp. 321–330; Kim, et al., 2001, “Enhanced Reference Stress-Based J and Crack Opening Displacement Estimation Method for Leak-Before-Break Analysis and Comparison With GE/EPRI Method,” Fatigue Fract. Eng. Mater. Struct., 24, pp. 243–254; Kim, et al., 2002, “Non-Linear Fracture Mechanics Analyses of Part Circumferential Surface Cracked Pipes,” Int. J. Fract., 116, pp. 347–375.)

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.

Analytical Limit Loads for Tube Sections With Circumferential Degradation

2004 ◽  
Author(s):  
W. Reinhardt ◽  
X. Wang
Keyword(s):  
Analytical Solutions ◽  
Load Capacity ◽  
Bending Moment ◽  
Limit Load ◽  
Thin Wall ◽  
Plastic Limit ◽  
Tubes And Pipes ◽  
Limit Loads ◽  
Plastic Limit Load ◽  
Analytical Limit

The fracture mechanics evaluation of tubes and pipes with circumferential degradation typically requires that the plastic limit load capacity be evaluated under a combination of axial force and bending moment loading. Most available analytical solutions are thin-wall approximations and may not work well for heavy-wall applications. The present paper derives an analytical limit load for a cylindrical pipe or tube with a partial circumferential, partial through-wall flaw and its bounding cases (through wall partial circumferential and uniform circumferential part-throughwall flaw). The solution is not in closed form, but can be easily solved with available mathematical software like MathCAD. The obtained limit loads for a steam generator tube are compared to those from simplified analytical solutions. The effect of tube supports on the limit load of a tube with non-axisymmetric flaw is discussed with a simplified model.

Plastic Limit Loads for Slanted Circumferential Through-Wall Cracked Pipes Based on Finite Element Limit Analysis

2011 ◽  
Author(s):  
Hyun-Min Jang ◽  
Doo-Ho Cho ◽  
Jae-Boong Choi ◽  
Young-Jin Kim ◽  
Nam-Su Huh ◽  
...  
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Crack Opening Displacement ◽  
Crack Opening ◽  
Limit Load ◽  
Correction Factors ◽  
Plastic Limit ◽  
Opening Displacement ◽  
Limit Loads ◽  
Plastic Limit Load

Based on detailed three-dimensional (3-D) finite element (FE) limit analyses, the plastic limit load solutions for pipes with slanted circumferential through-wall cracks (TWCs) subjected to axial tension, global bending and internal pressure are reported. The FE model and analysis procedure employed in the present numerical study were validated by comparing the present FE results with existing solutions for plastic limit loads of pipes with idealized TWCs. To quantify the effect of slanted crack on plastic limit load, the slant correction factors for calculating plastic limit loads of pipes with slanted TWCs from pipes with idealized TWCs were newly proposed via extensive 3-D FE calculations. These slant correction factors are presented in a tabulated form for practical ranges of geometry and each loading conditions. Moreover, the present FE plastic limit loads were also compared with the existing solutions of pipes with slanted TWCs. These FE plastic limit load solutions can be applied to estimate elastic-plastic fracture mechanics parameters and creep fracture mechanics parameters, such as elastic-plastic J–integral and crack opening displacement, creep C*-integral and creep crack opening displacement, based on the reference stress concept considering more realistic crack shape.

Shakedown and Limit Analysis of 45-Degree Piping Elbows Under Internal Pressure and Cyclic In-Plane Bending

2019 ◽  
Author(s):  
Heng Peng ◽  
Yinghua Liu
Keyword(s):  
Internal Pressure ◽  
Limit Analysis ◽  
Limit Load ◽  
Plastic Limit ◽  
Limit Loads ◽  
Integrity Assessment ◽  
Elastic Plastic ◽  
Plastic Limit Load ◽  
Interaction Curves ◽  
Shakedown Limit

Abstract This paper carries out the shakedown and limit analysis of 45-degree piping elbows subjected to steady internal pressure and cyclic in-plane closing, opening and reverse bending moments by means of the recently proposed stress compensation method (SCM). Different geometries of the piping elbows and various combinations of these applied loads are investigated to create various shakedown limit and plastic limit load interaction curves. The plastic limit loads for single internal pressure and single bending moment calculated with the SCM are compared to those calculated with the twice-elastic-slope method. Full step-by-step elastic-plastic incremental finite element analyses are utilized to verify the structural cyclic responses on both sides of the curves obtained and further to confirm the correct shakedown limit loads and boundaries. It is shown that the SCM calculates the shakedown limit load accurately and possess more than 40 times the computational efficiency of the step-by-step elastic-plastic incremental method. The effects of the ratios of bending radius to mean radius and mean radius to wall thickness of the piping elbow as well as loading conditions on shakedown limit and plastic limit load interaction curves are presented. The results presented in this work provide a comprehensive understanding of long term response behaviors of the piping elbow under the combined cyclic loading and offer some essential points to be concerned for the design and integrity assessment of piping systems.

Plastic Limit Loads of Pad Reinforced Cylindrical Vessels Under Out-of-Plane Moment of Nozzle

2005 ◽  
Vol 128 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Z. F. Sang ◽  
H. F. Wang ◽  
L. P. Xue ◽  
G. E. O. Widera
Keyword(s):  
Finite Element ◽  
Limit Load ◽  
Plastic Limit ◽  
Element Analysis ◽  
Limit Loads ◽  
Test Models ◽  
Out Of Plane ◽  
Scale Test ◽  
Plastic Limit Load ◽  
Strain Responses

The purpose of this work is to study the plastic limit load of pad reinforced cylindrical vessels with different d/D ratios under out-of-plane moment loading on a nozzle. Three full-scale test models were designed and fabricated. A 3-D nonlinear finite element numerical analysis was also performed. Data on plastic limit moment is obtained from load-displacement and load-strain responses. The results indicate that plastic limit loads determined by test (including displacement and strain measurements) and finite element analysis are in agreement.

Shakedown and Limit Analysis of Kinematic Hardening Piping Elbows Under Internal Pressure and Bending Moments

2021 ◽  
Author(s):  
Heng Peng ◽  
Yinghua Liu
Keyword(s):  
Yield Strength ◽  
Internal Pressure ◽  
Limit Analysis ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Bending Moments ◽  
Plastic Limit ◽  
Plastic Limit Load ◽  
Interaction Curves ◽  
Shakedown Limit

Abstract In this paper, the Stress Compensation Method (SCM) adopting an elastic-perfectly-plastic (EPP) material is further extended to account for limited kinematic hardening (KH) material model based on the extended Melan's static shakedown theorem using a two-surface model defined by two hardening parameters, namely the initial yield strength and the ultimate yield strength. Numerical analysis of a cylindrical pipe is performed to validate the outcomes of the extended SCM. The results agree well with ones from literature. Then the extended SCM is applied to the shakedown and limit analysis of KH piping elbows subjected to internal pressure and cyclic bending moments. Various loading combinations are investigated to generate the shakedown limit and the plastic limit load interaction curves. The effects of material hardening, elbow angle and loading conditions on the shakedown limit and the plastic limit load interaction curves are presented and analysed. The present method is incorporated in the commercial finite element simulation software and can be considered as a general computational tool for shakedown analysis of KH engineering structures. The obtained results provide a useful information for the structural design and integrity assessment of practical piping elbows.

The Effects of Classification of Misalignment-Induced Stresses in Engineering Critical Assessments of Welded Joints With Some Misalignment

2010 ◽  
Author(s):  
Liwu Wei
Keyword(s):  
Welded Joints ◽  
Driving Force ◽  
Limit Load ◽  
Surface Cracks ◽  
Plastic Limit ◽  
Secondary Stress ◽  
Butt Weld ◽  
Crack Driving Force ◽  
Plastic Limit Load

In the ECA of a structure or component such as a pipeline girth weld, the bending stress component arising from misalignment across the weld is often classified as primary, partly because standards such as BS 7910 and API 579-1/ASME FFS-1 do not give definitive guidance on this subject. This approach may be over-conservative as the σmis is localised. In order to obtain a more realistic assessment of the structural integrity of structures containing misalignment, it is necessary to understand the conservatism or non-conservatism in an ECA associated with the classification of σmis. To address the above concerns, systematic investigations were carried out of surface cracks in a plate butt-weld including some misalignment, external circumferential surface cracks and external fully circumferential cracks in a misaligned pipe connection. FEA of these cracked welded joints with some misalignment (typically from 1mm to 2mm) was performed to calculate crack driving force and plastic limit load. The results from FEA were compared with the existing solutions of KI and σref in BS 7910 generated by assuming three options of treating the σmis. The three options were: (1) classification of σmis wholly as primary stress; (2) 15% of σmis as primary and 85% of σmis as secondary stress; and (3) classification of σmis wholly as secondary stress. Variations in parameters (eg misalignment, crack size, loading, weld overmatch and base material properties) were taken into account in order to determine the effects of these parameters on plastic limit load and crack driving force. The implication of different classifications of σmis in terms of ECAs of misaligned welded joints was revealed by conducting BS 7910 Level 2B assessments with the use of a FAD. It was found in this work that for the cases examined, use of the σmis as entirely primary bending in an ECA was over-conservative, and even treatment of σmis as entirely secondary bending was generally shown to be still conservative, when compared with the assessments based on FEA solutions. Furthermore, caution should be exercised in using the solutions of KI and σref given in the existing BS 7910 for crack-containing structures subjected to a bi-axial or tri-axial stress state. A non-conservative estimate may result from the use of these solutions which have been derived based on a uniaxial stress condition.

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