Limitations of small-scale yielding for fatigue crack growth

Nuclear power plant safety under seismic conditions is an important consideration. The piping systems may have some defects caused by fatigue, stress corrosion cracking, etc., in aged plants. These cracks may not only affect the seismic response, but may also grow and break through causing loss of coolant. Therefore, an evaluation method needs to be developed to predict crack growth behavior under seismic excitation. This paper describes efforts conducted to analyze and better understand a series of degraded pipe tests under seismic loading that was conducted by Japan Nuclear Energy Safety Organization (JNES). A special “cracked-pipe element” (CPE) concept, where the element represented the global moment-rotation response due to the crack, was developed. This approach was developed to simplify the dynamic finite element analysis. In this paper, model validation was conducted by comparisons with a series of pipe tests with circumferential through-wall and surface cracks under different excitation conditions. These analyses showed that reasonably accurate predictions could be made using the ABAQUS connector element to model the complete transition of a circumferential surface crack to a through-wall crack under cyclic dynamic loading. The JNES combined-component test was analyzed in detail. The combined-component test had three crack locations and multiple applied simulated-seismic block loadings. Comparisons were also made between the ABAQUS FE analyses results to the measured displacements in the experiment. Good agreement was obtained and it was confirmed that the simplified modeling is applicable to a seismic analysis for a cracked pipe on the basis of fracture mechanics. Pipe system leakage did occur in the JNES tests. The analytical predictions using the CPE approach did not predict leakage, suggesting that cyclic ductile tearing with large-scale plasticity was not the crack growth mode for the acceleration excitations considered here. Hence, the leakage was caused by low-cycle fatigue with small-scale yielding. The procedure used to make predictions of low-cycle fatigue crack growth with small-scale yielding was based on the Dowling ΔJ procedure, which is an extension of linear-elastic fatigue crack growth methodology into the nonlinear plasticity regime. The predicted moments from the CPE approach were used using a cycle-by-cycle crack growth procedure. The predictions compare quite well with the experimental measurements.

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Numerical Analysis of JNES Seismic Tests on Degraded Combined Piping System

Journal of Pressure Vessel Technology ◽

10.1115/1.4005055 ◽

2011 ◽

Vol 134 (1) ◽

Cited By ~ 1

Author(s):

Tao Zhang ◽

Frederick W. Brust ◽

Gery Wilkowski ◽

Do-Jun Shim ◽

Jinsuo Nie ◽

...

Keyword(s):

Finite Element ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Fracture Mechanics ◽

Crack Growth ◽

Low Cycle Fatigue ◽

Small Scale ◽

Cycle Fatigue ◽

Small Scale Yielding ◽

Scale Yielding

Nuclear power plant safety under seismic conditions is an important consideration. The piping systems may have some defects caused by fatigue, stress corrosion cracking, etc., in aged plants. These cracks may not only affect the seismic response but also grow and break through causing loss of coolant. Therefore, an evaluation method needs to be developed to predict crack growth behavior under seismic excitation. This paper describes efforts conducted to analyze and better understand a series of degraded pipe tests under seismic loading that was conducted by Japan Nuclear Energy Safety Organization (JNES). A special “cracked-pipe element” (CPE) concept, where the element represented the global moment-rotation response due to the crack, was developed. This approach was developed to significantly simplify the dynamic finite element analysis in fracture mechanics fields. In this paper, model validation was conducted by comparisons with a series of pipe tests with circumferential through-wall and surface cracks under different excitation conditions. These analyses showed that reasonably accurate predictions could be made using the abaqus connector element to model the complete transition of a circumferential surface crack to a through-wall crack under cyclic dynamic loading. The JNES primary loop recirculation piping test was analyzed in detail. This combined-component test had three crack locations and multiple applied simulated seismic block loadings. Comparisons were also made between the ABAQUS finite element (FE) analyses results to the measured displacements in the experiment. Good agreement was obtained, and it was confirmed that the simplified modeling is applicable to a seismic analysis for a cracked pipe on the basis of fracture mechanics. Pipe system leakage did occur in the JNES tests. The analytical predictions using the CPE approach did not predict leakage, suggesting that cyclic ductile tearing with large-scale plasticity was not the crack growth mode for the acceleration excitations considered here. Hence, the leakage was caused by low-cycle fatigue with small-scale yielding. The procedure used to make predictions of low-cycle fatigue crack growth with small-scale yielding was based on the Dowling ΔJ procedure, which is an extension of linear-elastic fatigue crack growth methodology into the nonlinear plasticity region. The predicted moments from the CPE approach were used using a cycle-by-cycle crack growth procedure. The predictions compare quite well with the experimental measurements.

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Investigation on Evaluation Method Based on J Integral for Retardation of Crack Growth Due to Excessive Loading Beyond Small Scale Yielding Condition

ASME 2010 Pressure Vessels and Piping Conference: Volume 6, Parts A and B ◽

10.1115/pvp2010-25563 ◽

2010 ◽

Cited By ~ 4

Author(s):

Yoshihito Yamaguchi ◽

Jinya Katsuyama ◽

Kunio Onizawa ◽

Hideharu Sugino ◽

Yinsheng Li

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Evaluation Method ◽

Plastic Zone Size ◽

Retardation Effect ◽

Small Scale ◽

J Integral ◽

Small Scale Yielding ◽

Scale Yielding

Niigata-ken Chuetsu-Oki earthquake occurred in July 2007, whose magnitude was beyond the assumed one provided in seismic design. Therefore it becomes an important issue to evaluate the effect of excessive loading, in particular, for the components with existing crack. Fatigue crack growth rate is usually expressed by Paris’s law using the range of stress intensity factor (ΔK). However, applicability of the model to loading conditions beyond the small scale yielding remains as an issue since ΔK is inappropriate in such a high loading level. In this study, the fatigue crack growth behaviors after applying the excessive loads were investigated using austenitic stainless steel and carbon steel. Instead of ΔK, J-integral value for crack growth evaluation due to cyclic loading has been applied based on the experimental data to treat the excessive loading beyond small scale yielding. The finite element method (FEM) analyses were conducted to evaluate the stress distribution and plastic zone size for the excessive loading condition. The modified Wheeler model using J-integral range, ΔJ, has been proposed for the prediction of retardation effect on crack growth after excessive loading. It was indicated that retardation effect by excessive loading beyond small-scale yielding could be quantitatively evaluated using the J-Wheeler model.

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Characterization of Fatigue Crack Growth in Intermediate and Large Scale Yielding

Journal of Engineering Materials and Technology ◽

10.1115/1.2903373 ◽

1991 ◽

Vol 113 (1) ◽

pp. 15-22 ◽

Cited By ~ 23

Author(s):

R. C. McClung ◽

H. Sehitoglu

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Crack Closure ◽

Large Scale ◽

Small Scale ◽

Parameter Estimates ◽

Growth Data ◽

Elastic Plastic ◽

Scale Yielding

Parameters previously proposed for the correlation of elastic-plastic fatigue crack growth data are critically reviewed and compared from a pragmatic engineering standpoint. Commonly employed estimates for the four most common parameters are shown to have essentially the same structure and to be numerically similar, despite their widely differing theoretical backgrounds. The significance of fatigue crack closure for crack growth under these conditions is considered. Elastic-plastic finite element analyses of crack closure are presented and compared with experimental data and simple analytical models. Normalized crack opening stresses are shown to change significantly between small scale and large scale yielding conditions, especially for R= − 1 loading. Different schemes for incorporating closure information into the crack growth parameters are examined, and the consequences of closure for the numerical structure of the parameter estimates are demonstrated. Experimental crack growth data from 1026 and 1070 steels are correlated with estimates of ΔK and ΔJ, both considering and neglecting the effects of crack closure. The data comprise wide ranges of maximum stress, plastic strain amplitude, and crack length, including conditions of small, intermediate, and large scale yielding. Correlations which include an explicit correction for crack closure are shown to be superior.

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Advantageous Description of Short Fatigue Crack Growth Rates in Austenitic Stainless Steels with Distinct Properties

Metals ◽

10.3390/met11030475 ◽

2021 ◽

Vol 11 (3) ◽

pp. 475

Author(s):

Lukáš Trávníček ◽

Ivo Kuběna ◽

Veronika Mazánová ◽

Tomáš Vojtek ◽

Jaroslav Polák ◽

...

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Stainless Steels ◽

Growth Rates ◽

Large Scale ◽

J Integral ◽

Scale Yielding ◽

Residual Fatigue ◽

Crack Growth Rates

In this work two approaches to the description of short fatigue crack growth rate under large-scale yielding condition were comprehensively tested: (i) plastic component of the J-integral and (ii) Polák model of crack propagation. The ability to predict residual fatigue life of bodies with short initial cracks was studied for stainless steels Sanicro 25 and 304L. Despite their coarse microstructure and very different cyclic stress–strain response, the employed continuum mechanics models were found to give satisfactory results. Finite element modeling was used to determine the J-integrals and to simulate the evolution of crack front shapes, which corresponded to the real cracks observed on the fracture surfaces of the specimens. Residual fatigue lives estimated by these models were in good agreement with the number of cycles to failure of individual test specimens strained at various total strain amplitudes. Moreover, the crack growth rates of both investigated materials fell onto the same curve that was previously obtained for other steels with different properties. Such a “master curve” was achieved using the plastic part of J-integral and it has the potential of being an advantageous tool to model the fatigue crack propagation under large-scale yielding regime without a need of any additional experimental data.

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Fatigue Crack Growth Properties of a Cryogenic Structural Steel at Liquid Helium Temperature

Journal of Engineering Materials and Technology ◽

10.1115/1.2805922 ◽

1996 ◽

Vol 118 (1) ◽

pp. 109-113 ◽

Cited By ~ 1

Author(s):

Shinji Konosu ◽

Tomohiro Kishiro ◽

Ogi Ivano ◽

Yoshihiko Nunoya ◽

Hideo Nakajima ◽

...

Keyword(s):

Stainless Steel ◽

Fatigue Crack ◽

Austenitic Stainless Steel ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Liquid Helium ◽

Liquid Helium Temperature ◽

Small Scale ◽

Helium Temperature ◽

Growth Properties

The structural materials of the coils of superconducting magnets utilized in thermonuclear fusion reactors are used at liquid helium (4.2 K) temperatures and are subjected to repeated thermal stresses and electromagnetic forces. A high strength, high toughness austenitic stainless steel (12Cr-12Ni-10Mn-5Mo-0.2N) has recently been developed for large, thick-walled components used in such environments. This material is non-magnetic even when subjected to processing and, because it is a forging material, it is advantageous as a structural material for large components. In the current research, a large forging of 12Cr-12Ni-10Mn-5Mo-0.2N austenitic stainless steel, was fabricated to a thickness of 250 mm, which is typical of section thicknesses encountered in actual equipment. The tensile fatigue crack growth properties of the forging were examined at liquid helium temperature as function of specimen location across the thickness of the forging. There was virtually no evidence of variation in tensile strength or fatigue crack growth properties attributable to different sampling locations in the thickness direction and no effect of thickness due to the forging or solution treatment associated with large forgings was observed. It has been clarified that there are cases in which small scale yielding (SSY) conditions are not fulfilled when stress ratios are large. ΔJ was introduced in order to achieve unified expression inclusive of these regions and, by expressing crack growth rate accordingly, the following formula was obtained at the second stage (middle range). da/dN = CJ ΔJmJ, CJ = AJ/(ΔJ0)mJ, where, AJ = 1.47 × 10−5 mm/cycle, ΔJ0 = 2.42 × 103N/m.

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