Probabilistic fatigue integrity assessment in multiple crack growth analysis associated with equivalent initial flaw and material variability

2016 ◽  
Vol 156 ◽  
pp. 182-196 ◽  
Author(s):  
Jung-Hoon Kim ◽  
Thanh Chau-Dinh ◽  
Goangseup Zi ◽  
Won Woo Lee ◽  
Jung Sik Kong
2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Masayuki Kamaya

High-cycle thermal fatigue is a critical problem in nuclear power plants. To prevent crack initiation, Japan Society of Mechanical Engineers has issued a guideline for design, although growth analysis was not included. In this study, the feasibility of incorporating crack growth analysis into the design and integrity evaluation was investigated. Two characteristics of thermal fatigue loading were considered. The first was the effect of stress gradient in the depth direction. It was shown that the steep stress gradient near the surface significantly reduced the stress intensity factor (SIF) of deep cracks. Assuming that crack growth was arrested by small SIF values, it was judged possible to leave certain detected cracks unrepaired. Otherwise, the cracks should be removed regardless of their size. The other characteristic was the displacement controlled boundary condition. Through finite element analyses, it was revealed that the displacement controlled boundary condition reduced the SIF, and the magnitude of its reduction depended on the crack depth and boundary length. It was concluded that, under thermal fatigue loading, the cracks that were detected in the in-service inspection had already been arrested if they did not penetrate the wall thickness. It is effective to consider the crack arrest scenario for design and integrity assessment of cracked components under high-cycle thermal fatigue loading.


1995 ◽  
Vol 23 (3) ◽  
pp. 219-233 ◽  
Author(s):  
A. Martín-Meizoso ◽  
J.M. Martínez-Esnaola ◽  
M. Fuentes-Pérez

Author(s):  
Z. Y. Li ◽  
C. L. Zhou ◽  
Y. Z. Zhao ◽  
Z. L. Hua ◽  
L. Zhang ◽  
...  

Crack growth analysis (CGA) was applied to estimate the cycle life of the high-pressure hydrogen equipment constructed by the practical materials of 4340 (two heats), 4137, 4130X, A286, type 316 (solution-annealed (SA) and cold-worked (CW)), and type 304 (SA and CW) in 45, 85 and 105 MPa hydrogen and air. The wall thickness was calculated following five regulations of the High Pressure Gas Safety Institute of Japan (KHK) designated equipment rule, KHKS 0220, TSG R0002, JB4732, and ASME Sec. VIII, Div. 3. We also applied CGA for four typical model materials to discuss the effect of ultimate tensile strength (UTS), pressure and hydrogen sensitivity on the cycle life of the high-pressure hydrogen equipment. Leak before burst (LBB) was confirmed in all practical materials in hydrogen and air. The minimum KIC required for LBB of the model material with UTS of even 1500 MPa was 170 MPa·m0.5 in 105 MPa. Cycle life qualified 103 cycles for all practical materials in air. In 105 MPa hydrogen, the cycle life by KIH was much shorter than that in air for two heats of 4340 and 4137 sensitive to hydrogen gas embrittlement (HGE). The cycle life of type 304 (SA) sensitive to HGE was almost above 104 cycles in hydrogen, while the cycle life of type 316 (SA and CW) was not affected by hydrogen and that of A286 in hydrogen was near to that in air. It was discussed that the cycle life increased with decreasing pressure or UTS in hydrogen. This behavior was due to that KIH increased or fatigue crack growth (FCG) decreased with decreasing pressure or UTS. The cycle life data of the model materials under the conditions of the pressure, UTS, KIH, FCG and regulations in both hydrogen and air were proposed quantitatively for materials selection for high-pressure hydrogen storage.


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