Development of Guideline for Structural Integrity Assessment for Fast Reactor Plants Part II : Evaluation of J-Integral for Cracked Body

2000 ◽  
Vol 2000 (0) ◽  
pp. 609-610
Author(s):  
Naoki MIURA ◽  
Yukio TAKAHASHI ◽  
Yasunari NAKAYAMA
Keyword(s):  
Fast Reactor ◽  
Structural Integrity ◽  
J Integral ◽  
Integrity Assessment

Strain-Based Failure Assessment Based on a Reference Strain Method for Welded Pipelines

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Jae-Sung Lee ◽  
Myung-Hyun Kim
Keyword(s):  
Reference Strain ◽  
Structural Integrity ◽  
Equivalent Stress ◽  
Strain Curve ◽  
Evaluation Procedure ◽  
J Integral ◽  
Element Analysis ◽  
Plastic Energy ◽  
Integrity Assessment ◽  
Strain Method

Abstract Engineering critical assessment (ECA) is an evaluation procedure for structures with flaws and has been widely applied for assessing pipeline integrity. The standards for structural integrity assessment, including BS 7910, involve stress-based ECA, and they are known to produce overly conservative results. Therefore, strain-based ECA has been recently developed as an alternative approach. One of the effective methods for improving the accuracy of strain-based ECA is the reference strain method. However, only a limited number of studies have applied this method to welded pipelines. Therefore, a numerical analysis based on strain-based ECA was performed for girth-welded joints with a circumferentially oriented internal surface crack. Particular attention was given to the strength mismatch effects. The equivalent stress–strain curve in BS7910 was used to reflect the strength mismatch effects in the reference strain. The results of the proposed method were validated with the results of a finite element analysis (FEA) in terms of the J-integral. Previous methods and the proposed method exhibit a reasonable correlation of the J-integral in the case of over-matching (OM). In the under-matching (UM) cases, while the previous procedures tended to underestimate or excessively overestimate the elastic-plastic energy release rate in comparison with the FEA, the proposed method evaluated the J-integral of pipelines with sufficient accuracy.

Evaluation method for structural integrity assessment in core disruptive accident of fast reactor

2004 ◽  
Vol 227 (1) ◽  
pp. 97-123 ◽  
Author(s):  
Toshio Nakamura ◽  
Hitoshi Kaguchi ◽  
Iwao Ikarimoto ◽  
Yoshio Kamishima ◽  
Kazuya Koyama ◽  
...  
Keyword(s):  
Fast Reactor ◽  
Evaluation Method ◽  
Structural Integrity ◽  
Integrity Assessment

Structural integrity of fast reactor components

1990 ◽  
Vol 331 (1619) ◽  
pp. 419-434 ◽  
Keyword(s):  
Fast Reactor ◽  
Structural Integrity ◽  
Ambient Pressure ◽  
Failure Process ◽  
Liquid Sodium ◽  
Secondary Circuit ◽  
Deformation And Failure ◽  
Integrity Assessment ◽  
High Boiling Point ◽  
Materials Used

The paper focuses on the generic aspects of the main structural integrity issues in the liquid-sodium-cooled fast reactor. The choice of sodium as a coolant has important consequences for the deformation and failure process in the materials used for the main plant components. For example, its high boiling point means that the prim ary and secondary circuit containment operates at ambient pressure and the system loading is dominated by thermal stress. The resultant low primary stresses make leak-before-break a viable integrity criterion for all sodium boundary components. Sodium coolant operates at comparatively high temperatures and this, together with the good heat-transfer properties, means that thermal fatigue and creep are of concern, particularly in the hotter parts of the plant. A third factor concerns the steam generators, where the integrity of the sodium—water boundary is particularly important. The paper will consider the failure processes that must be addressed in relation to these conditions and the development of the integrity assessment arguments.

Improved Incremental J-Integral Equations for Determining Crack Growth Resistance Curves

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Integral Equations ◽  
Structural Integrity ◽  
Test Procedure ◽  
Fracture Toughness Test ◽  
J Integral ◽  
Integrity Assessment ◽  
Growth Increments ◽  
Unloading Compliance

The J-integral resistance curve is the most important material properties in fracture mechanics that is often used for structural integrity assessment. ASTM E1820 is a commonly accepted fracture toughness test standard for measuring the critical value of J-integral at the onset of ductile fracture and J-R curve during ductile crack tearing. The recommended test procedure is the elastic unloading compliance method. For a stationary crack, the J-integral is simply calculated from the area under the load-displacement record using the η-factor equation. For a growing crack, the J-integral is calculated using the incremental equation proposed by Ernst et al. (1981, “Estimations on J-integral and Tearing Modulus T From a Single Specimen Test Record,” Fracture Mechanics: Thirteenth Conference, ASTM STP 743, pp. 476–502) to consider the crack growth correction. For the purpose of obtaining accurate J-integral values, ASTM E1820 requires small and uniform crack growth increments in a J-R curve test. In order to allow larger crack growth increments in an unloading compliance test, an improved J-integral estimation is needed. Based on the numerical integration techniques of forward rectangular, backward rectangular, and trapezoidal rules, three incremental J-integral equations are developed. It demonstrates that the current ASTM E1820 procedure is similar to the forward rectangular result, and the existing Garwood equation is similar to the backward rectangular result. The trapezoidal result has a higher accuracy than the other two, and thus it is proposed as a new formula to increase the accuracy of a J-R curve when a larger crack growth increment is used in testing. An analytic approach is then developed and used to evaluate the accuracy of the proposed incremental equations using single-edge bending and compact tension specimens for different hardening materials. It is followed by an experimental evaluation using actual fracture test data for HY80 steel. The results show that the proposed incremental J-integral equations can obtain much improved results of J-R curves for larger crack growth increments and are more accurate than the present ASTM E1820 equation.

Advances in Development of J-Integral Experimental Estimation, Testing and Standardization

2011 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Structural Integrity ◽  
Experimental Testing ◽  
Estimation Method ◽  
J Integral ◽  
Fracture Testing ◽  
Integrity Assessment ◽  
Ductile Materials ◽  
Experimental Estimation

The J-integral is an important concept in the elastic-plastic fracture mechanics, and serves as a critical material parameter to quantify the toughness or resistance of ductile materials against fracture. The relation between the J-integral and crack extension has been widely used as the resistance curve of ductile materials in fracture mechanics design and in structural integrity assessment. Experimental testing and evaluation have played a central role in providing reliable fracture toughness properties to fracture mechanics analysis. Since the J-integral concept was proposed, extensive efforts of investigations have been made to develop its experimental estimation method, testing technique and standardization, as evident in the ASTM E1820 — a commonly used fracture toughness testing standard. In recent years, significant progresses of the J-integral fracture testing and experimental estimation have been achieved, and a part of them was accepted and updated in ASTM E1820. To better understand and use this fracture testing standard, the present paper gives a brief review of historical efforts and recent advances in the development of the J-integral experimental estimation and standard testing.

scholarly journals Applying Fracture Mechanics to Cracked Components Subjected to Unloading

2016 ◽  
Author(s):  
Sam Oliver ◽  
Martyn Pavier ◽  
Mahmoud Mostafavi
Keyword(s):  
Finite Element Analysis ◽  
Structural Integrity ◽  
Fracture Parameter ◽  
J Integral ◽  
Single Cycle ◽  
Element Analysis ◽  
Hardening Material ◽  
Integrity Assessment ◽  
Plastic Materials ◽  
Elastic Plastic Materials

The J-integral is widely used as a fracture parameter for elastic-plastic materials. The J-integral describes the intensity of the stress field close to the crack tip in a power-law hardening material under a set of well-known restrictions. This study investigates what happens when one of these restrictions is broken, namely the requirement for no unloading to occur. In this work, a centre-cracked plate is subjected to a single cycle of load in which unloading occurs. A remote tensile stress is applied, then released, then applied again up to and beyond its initial magnitude. The J-integral at each step of the analysis is calculated using finite element analysis. Its validity as a fracture parameter at each step is discussed with the aid of results from a strip yield analysis of the same problem. The relevance of the results in the context of structural integrity assessment is discussed.

Deformation Versus Modified J-Integral Resistance Curves for Ductile Materials

2012 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Poh-Sang Lam
Keyword(s):  
Fracture Mechanics ◽  
Size Dependence ◽  
Structural Integrity ◽  
Experimental Results ◽  
Integral Parameter ◽  
Fracture Toughness Test ◽  
J Integral ◽  
Resistance Curve ◽  
Integrity Assessment ◽  
Resistance Curves

The J-integral resistance curve (or J-R curve) has been widely used as material property in fracture mechanics methods for structural integrity assessment. ASTM E1820 provides the standard fracture toughness test methods to measure JIc and J-R curves. The conventional J-R curve utilizes the J-integral parameter proposed by Rice [1] based on the deformation theory of plasticity. Due to crack-tip constraint effect, J-R curves of a material depend on specimen size, geometry type and crack length. In order to obtain size-independent resistance curves, Ernst [11] introduced a modified J-integral or Jm to minimize the size dependence and to characterize the resistance curve for large crack extensions beyond the limitation of deformation J-R curves. In the late 1980s and in the early 1990s, different experimental results showed the modified Jm-R curves were still size-dependent and may even behave worse than the deformation J-R curves. However, to date, the Jm-R curves are still regarded as “size-independent” in fracture mechanics analysis. To clarify this, the present paper gives a brief historical review of ductile resistance curves in terms of deformation J-integral and the modified Jm-integral, and evaluates the size dependence using experimental results for various steels and specimens, including A285 carbon steel and SENB specimens. A suggestion how to use the resistance curves is made accordingly.

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