scholarly journals Investigation of Critical Crack Size that Causes Retardation of Fatigue Crack Propagation by Single Overload

2009 ◽  
Vol 58 (12) ◽  
pp. 1023-1029 ◽  
Author(s):  
Tomoe SUDO ◽  
Masanobu KUBOTA ◽  
Yoshiyuki KONDO
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Size ◽  
Critical Crack ◽  
Single Overload ◽  
Critical Crack Size

scholarly journals Effects of Crack Size, Stress Ratio and Hydrogen on the Near Threshold Fatigue Crack Propagation of High Strength Steel

2005 ◽  
Vol 54 (12) ◽  
pp. 1237-1243 ◽  
Author(s):  
Kazutoshi YANAGIHARA ◽  
Satoshi OHYANAGI ◽  
Masanobu KUBOTA ◽  
Chu SAKAE ◽  
Yoshiyuki KONDO
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
High Strength Steel ◽  
Stress Ratio ◽  
High Strength ◽  
Crack Size ◽  
Near Threshold

Modeling of Random Fatigue Crack Propagation

2013 ◽  
Vol 756-759 ◽  
pp. 105-107
Author(s):  
Xiao Li Zou
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Growth Process ◽  
Crack Size ◽  
Propagation Time ◽  
Fokker Plank Equation ◽  
Eigenfunction Method ◽  
Random Fatigue

A statistical model is proposed for the analysis of fatigue crack propagation, based on the theory of fracture mechanics and stochastic process. The fatigue growth process is approximated as a diffusive Markov process. The associated backward Fokker-Plank equation and boundary conditions are written, and the distribution of crack propagation time under a given crack size is obtained by using an Eigenfunction method. The sought distribution is expressed in the form of a convergent infinite series. An examples is presented to illustrate the application of the method. The predicted results seem to agree with the experimental data.

Fatigue Crack Propagation Prediction under Single Overload Variable Loading

2013 ◽  
Vol 275-277 ◽  
pp. 215-219
Author(s):  
Zhi Fang Liu ◽  
Li Xiong Gu ◽  
Zhong Yong Xu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Variable Loading ◽  
Fatigue Crack Propagation Behavior ◽  
Propagation Behavior ◽  
Single Overload ◽  
Crack Growth Curve ◽  
Propagation Prediction

Reasonably predicting the fatigue life of specimens, depends on the research and understanding of the fatigue crack propagation behavior under variable amplitude loading (VAL) rather than under constant amplitude loading (CAL). The present study aims at evaluating residual fatigue life under single overload VAL by adopting a dynamical coefficient mechanics (DCM) model which we have reported. New formulas connecting the crack length with number of cycles and expressions for the fatigue crack propagation (FCP) under single overload VAL have been derived and were used to predict crack propagation. The ratios of predicted-to-experimental lives range from 1.00 to 1.09, which indicates that the results obtained from this DCM model are in good agreement with experimental data from published literatures and cover all stages of fatigue crack growth curve.

Comparison of Leak-Before-Break Assessment of Main Loop Piping Lines Fabricated of Different Materials

2016 ◽  
Author(s):  
Linwei Ma ◽  
Xiaotao Zheng ◽  
Yan Wang ◽  
Jiasheng He ◽  
Anqing Shu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Material Properties ◽  
Plastic Instability ◽  
Crack Size ◽  
Critical Crack ◽  
Main Loop ◽  
Critical Crack Size ◽  
Leak Before Break

Leak-Before-Break (LBB) assessment is used for the design of nuclear reactor coolant system main loop piping to lower the cost of construction and operation in China. In these applications, the materials of main loop piping lines are cast austenitic stainless steel (CASS) or wrought stainless steel (WSS) due to the different type of reactor design. According to US.NRC SRP3.6.3, LBB assessment includes two major calculations, such as critical crack size calculation and leakage flaw size calculation. The elastic-plastic instability analysis or plastic instability analysis is chosen to perform critical size calculation depending on material properties, especially fracture toughness. In this paper, LBB assessment in the guidance of SRP 3.6.3 was performed to evaluate main loop piping lines of CASS and WSS. The JR curve tests and the adjustment due to thermal aging are performed to achieve reasonable material properties. J integral/tearing modulus approach is used to determine critical crack size of CASS pipe and net section collapse (NSC) approach is used to determine critical crack size of WSS pipe. Leakage flaw size under 1gpm leakage detection capability is determined based on Henry’s homogeneous nonequilibrium critical flow model. In order to demonstrate that fatigue crack growth is not a potential source of pipe rupture for the evaluated piping lines, the fatigue crack growth of a postulated circumferential part-through-wall crack under nuclear power plant full life time operating transients and the fatigue crack growth of a circumferential through-wall crack under one time safe shutdown seismic are analyzed. And the LBB assessment procedure and results of CASS pipe and WSS pipe are compared.

scholarly journals Fatigue Reliability Analysis of Tunnelling Boring Machine Cutterhead with Cracks

2020 ◽  
Author(s):  
jie li ◽  
bin zhang ◽  
chuang liu ◽  
jingbo guo
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Amplitude ◽  
Crack Size ◽  
Initial Crack ◽  
Load Spectrum ◽  
Factors Affecting ◽  
Main Factors ◽  
Fatigue Crack Propagation Life

The cutterhead of tunnel boring machine is a large-scale metal welding structure, which is prone to problems such as wear and cracking during the tunnelling process. For the issue, the fatigue crack propagation rate model of cutterhead under different reliability was established, based on the damage tolerance of cutterhead. Its dangerous position of cutterhead failure was determined by using finite element method. According to the fatigue load spectrum, the fatigue propagation life of cutterhead under different reliability was calculated, the main factors affecting the reliability of cutterhead were analyzed and the engineering experiment is carried out. The results show that three dangerous positions of the cutterhead failure are the junction of the split plane, the maximum deformation of the block and the central cutter seat. The load stress amplitude and initial crack size are the main factors affecting the crack propagation life and the reliability of cutterhead. With the increase of load stress amplitude and initial crack size of cutterhead, the fatigue crack propagation life of cutterhead decreases and the reliability is worse. When the initial crack size of cutterhead is greater than 0.5mm, the fatigue crack propagation life of cutterhead decreases obviously. The research results provide a scientific basis for crack detection, life prediction and reliability evaluation of cutterhead structure.

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