scholarly journals Application of J Integral for the Fracture Assessment of Welded Polymeric Components

2020 ◽  
Author(s):  
Zoltan Major ◽  
Daniel Kimpfbeck ◽  
Matei C. Miron
Keyword(s):  
J Integral ◽  
Fracture Assessment

Reliability Assessment of Piping With Cracks Using Advanced First-Order Second-Moment Method

2009 ◽  
Author(s):  
Shinji Yoshida ◽  
Hideo Machida
Keyword(s):  
Safety Factor ◽  
Reliability Assessment ◽  
Limit Load ◽  
Service Level ◽  
Assessment Method ◽  
J Integral ◽  
Reference Stress ◽  
First Order Second Moment ◽  
Fracture Assessment ◽  
Second Moment Method

This paper describes applicability of the 2 parameter assessment method using a reference stress method from the viewpoint of reliability. The applicability of the reference stress method was examined comparing both the GE-EPRI method. As a result, J-integral and limit load at the time of fracture evaluated by the reference stress method is almost equivalent to that by the GE-EPRI method. Furthermore, the partial safety factor (PSF) evaluated by reliability assessment has little difference between two methods, and the required safety factor is enveloped by the safety factor for Service Level-A and B defined in fitness for service (FFS) codes. These results show that of the reference stress method is applicable for J-integral calculation in fracture assessment.

Application of Limit Load Solutions for Engineering Critical Assessment of Embedded Flaws in Evenmatch Pipeline Girth Welds

2020 ◽  
Author(s):  
Aurélien Pépin ◽  
Tomasz Tkaczyk ◽  
Noel O’Dowd ◽  
Kamran Nikbin ◽  
Suresh V. Chettiar
Keyword(s):  
High Strain ◽  
Closed Form Solution ◽  
Limit Load ◽  
Form Solution ◽  
Embedment Depth ◽  
Plastic Collapse ◽  
J Integral ◽  
Crack Driving Force ◽  
Fracture Assessment ◽  
Girth Welds

Abstract Engineering Critical Assessment (ECA) is commonly undertaken to derive the acceptance criteria for girth weld flaws in rigid pipelines deployed subsea by low-strain installation methods, such as S-Lay or J-Lay, or high-strain installation methods, such as Reel-Lay. The ECA generally considers the whole load history seen by the pipeline from fabrication to the end of service, and involves fracture and fatigue assessments. Fracture, which is the main focus of this paper, is deemed to have initiated when either (i) the crack driving force, expressed in terms of the J-integral or the Crack Tip Opening Displacement (CTOD), δ, is greater than the materials resistance, or (ii) the applied load exceeds the bearing capacity of the ligament of a cracked structure, also referred to as the plastic collapse or limit load. The robustness of the ECA procedure relies on the accuracy of the assessment solutions. Most flaws in pipeline girth welds are embedded. Unlike surface breaking flaws, embedded flaws are typically not directly assessed in a high-strain fracture ECA because the available assessment solutions are too conservative. A work-around approach is often followed, where the maximum acceptable surface breaking flaw sizes are also considered acceptable below the surface if the embedment depth is equal to or greater than half of the flaw height. Otherwise, an embedded flaw must be reclassified as a surface breaking flaw with a height equal to the sum of the embedded flaw height and embedment depth. To enable the direct fracture assessment of embedded flaws, the authors undertook in a previous work a parametric finite-element (FE) study on the effect of the embedment depth, the crack height and the crack length on the plastic collapse load of the shorter ligament of embedded flaws. Subsequently, a new limit load solution was proposed for the fracture assessment of embedded flaws in evenmatch pipeline girth welds subjected to tension and/or bending. This closed-form solution was shown to be significantly more accurate for estimating the crack driving force and the ligament plastic collapse load than other solutions available in the literature. For some geometries, however, the predicted limit load still needs to be significantly adjusted (increased) to correctly evaluate the J-integral, in a combined tearing and collapse assessment. This suggests that further enhancement of the solution is possible. This paper describes small-scale fracture tests which were undertaken to determine the load required to collapse a smaller ligament of embedded flaws in a modified middle crack tension (MMCT) specimen. A closed-form solution, which can also be used as a flaw reclassification criterion, is fitted to the test results and then compared to the FE-based solution. Finally, recommendations are made for the direct fracture assessment of embedded flaws in evenmatch pipeline girth welds subjected to load or displacement-controlled conditions.

J and COD Estimation for Throughwall Circumferentially Cracked Elbow Under Closing Moment: Analytical Scheme and Experimental Validation

2005 ◽  
Author(s):  
J. Chattopadhyay ◽  
A. K. S. Tomar ◽  
B. K. Dutta ◽  
H. S. Kushwaha
Keyword(s):  
Crack Opening ◽  
Numerical Test ◽  
Bending Moment ◽  
J Integral ◽  
Opening Displacement ◽  
Pipe Bend ◽  
Elastic Plastic ◽  
Analytical Scheme ◽  
Analytical Estimation ◽  
Fracture Assessment

Leak-before-break (LBB) assessment of primary heat transport piping of nuclear reactors involves detailed fracture assessment of pipes and elbows with postulated throughwall cracks. Fracture assessment requires the calculation of elastic-plastic J-integral and crack opening displacement (COD) for these piping components. Analytical estimation schemes to evaluate elastic-plastic J-integral and COD simplify the calculations. These types of estimation schemes are available for pipes with various crack configurations subjected to different types of loading. However, no such schemes are available for throughwall circumferentially cracked elbow (or pipe bend), an important component for LBB analysis. In this paper, simple J and COD estimation schemes are proposed for throughwall circumferentially cracked elbow subjected to closing bending moment. The ovalisation of elbow cross section has a significant bearing on its fracture behavior. Therefore, unlike conventional deformation theory plasticity analysis, incremental flow theory is adopted considering both material and geometric non-linearities in the development of the proposed estimation schemes. Although it violates Ilyushin’s theorem, it has been shown that the resulting estimation schemes is still reasonably accurate for engineering purposes. Finally, experimental/numerical validation has been provided by comparing the J-integral and COD between numerical/test data and predictions of the proposed estimation schemes.

Rubber Fracture Characterization Using J-Integral

1988 ◽  
Vol 16 (1) ◽  
pp. 44-60 ◽  
Author(s):  
C. L. Chow ◽  
J. Wang ◽  
P. N. Tse
Keyword(s):  
Crack Initiation ◽  
Carbon Black ◽  
Natural Rubber ◽  
Fracture Parameter ◽  
J Integral ◽  
Specimen Length ◽  
Fracture Characterization ◽  
Premature Failure ◽  
Testing Procedures ◽  
Material Evaluation

Abstract The use of the J-integral to investigate fracture characterization in a carbon black reinforced natural rubber is described. Three applications to crack initiation are included: two based on the use of a hypothetical zero specimen length and one on conventional testing procedures for metals. While the validity of the zero-length methods is questionable, the conventional method yielded a consistent Jc value of 1.01 N/mm for a typical tire compound. This value was obtained from 24 combinations of varying specimen geometries and pre-crack lengths. The J-integral is revealed as a valid fracture parameter that is applicable not only for material evaluation but also for designing tire structures to resist premature failure. These conclusions disagree with those from an earlier investigation, so the causes for the discrepancies are examined and discussed.

An Alternative Technique to Evaluate Crack Propagation Path in Hyperelastic Materials

2012 ◽  
Vol 40 (1) ◽  
pp. 42-58 ◽  
Author(s):  
R. R. M. Ozelo ◽  
P. Sollero ◽  
A. L. A. Costa
Keyword(s):  
Constitutive Model ◽  
Crack Propagation ◽  
Experimental Tests ◽  
Growth Direction ◽  
Propagation Path ◽  
J Integral ◽  
Alternative Technique ◽  
Crack Propagation Path ◽  
Hyperelastic Materials ◽  
Material Constitutive Model

Abstract REFERENCE: R. R. M. Ozelo, P. Sollero, and A. L. A. Costa, “An Alternative Technique to Evaluate Crack Propagation Path in Hyperelastic Materials,” Tire Science and Technology, TSTCA, Vol. 40, No. 1, January–March 2012, pp. 42–58. ABSTRACT: The analysis of crack propagation in tires aims to provide safety and reliable life prediction. Tire materials are usually nonlinear and present a hyperelastic behavior. Therefore, the use of nonlinear fracture mechanics theory and a hyperelastic material constitutive model are necessary. The material constitutive model used in this work is the Mooney–Rivlin. There are many techniques available to evaluate the crack propagation path in linear elastic materials and estimate the growth direction. However, most of these techniques are not applicable to hyperelastic materials. This paper presents an alternative technique for modeling crack propagation in hyperelastic materials, based in the J-Integral, to evaluate the crack path. The J-Integral is an energy-based parameter and is applicable to nonlinear materials. The technique was applied using abaqus software and compared to experimental tests.

Prediction of crack growth initiation in paper structures using a J-integral criterion

2000 ◽  
Vol 15 (1) ◽  
pp. 4-11 ◽  
Author(s):  
Pär Wellmar ◽  
Øyvind Weiby Gregersen ◽  
Christer Fellers
Keyword(s):  
Crack Growth ◽  
J Integral ◽  
Integral Criterion ◽  
Growth Initiation
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