Effect of Constraint on Fatigue Crack Propagation in T-Plate Welded Joints

2007 ◽  
Author(s):  
Xin Wang ◽  
Qing Gao
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
Crack Tip ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Propagation Rate ◽  
Rate Model ◽  
Crack Tip Constraint

It has been observed that the loss of crack tip constraint leads to enhanced resistance to both cleavage and ductile tearing. Recent developments on constraint-based fracture mechanics have enabled the practical assessment of defective components including the constraint effect. However, how to quantify the effect of crack tip constraint on the fatigue crack propagation rate is still an open issue. It is common practice to use the Paris crack propagation law, which is based on the stress intensity factor alone. In this paper, the effect of crack tip constraint on the fatigue crack propagation of small cracks at T-plate welded joints is investigated. A fatigue crack propagation rate model is developed incorporating both low and high constraint conditions. It is shown that the effect of constraint on crack propagation rate is significant when the crack is small (within the stress concentration of the weld joints). This effect can be accounted for by using the proposed fatigue crack propagation rate model.

Effect of Constraint on Fatigue Crack Propagation in Notched Plates

2010 ◽  
Author(s):  
Xin Wang
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Tip ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Propagation Rate ◽  
Rate Model ◽  
Propagation Law ◽  
Crack Tip Constraint

It has been observed that the loss of crack tip constraint leads to enhanced resistance to both cleavage and ductile tearing. Recent developments on constraint-based fracture mechanics have enabled the practical assessment of defective components including the constraint effect. In fatigue analyses, it is common practice to use the Paris crack propagation law, which is based on the stress intensity factor alone. Although in recent years several research attempts have been made to investigate the effect of constraint on fatigue, how to quantify the effect of crack tip constraint on the fatigue crack propagation rate is still an open issue. In this paper, the effect of crack tip constraint on the fatigue crack propagation of small cracks at notched plates is investigated. A fatigue crack propagation rate model developed earlier which incorporates both low and high constraint conditions is used. It is shown that the effect of constraint on crack propagation rate is significant when the crack is small (within the stress concentration of the notches). This effect can be accounted for by using the fatigue crack propagation rate model.

The Characteristics of Propagation for Mixed-Mode Fatigue Crack under Stress Re-Distribution at Fatigue Crack Tip

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1922-1927 ◽  
Author(s):  
Sam Hong Song ◽  
Jeong Moo Lee
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Mixed Mode ◽  
Applied Load ◽  
Crack Tip ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Stress Redistribution ◽  
Fatigue Crack Propagation Rate

The practical condition of applied load represents mixed-mode loading condition due to complications of element geometry and applied load. Also, the characteristics of fatigue crack propagation under mixed mode were affected by constrained shape of structures and applied load variation. There are continuous variations of stress condition at crack tip on the fatigue crack during propagation. Therefore, it is necessary to investigate the propagation behavior of mixed-mode fatigue crack under stress redistribution condition. We established the experimental method in order to form the stress redistribution condition. It is assumed that the stress around the crack tip under mixed-mode fatigue loading is redistributed. This test consisted of the 1st and the 2nd round of tests. The stress re distribution was formed by changing the loading direction at propagating mixed-mode fatigue crack tip. In this study, the behavior of mixed-mode fatigue crack affected by stress redistribution was investigated by comparing fatigue crack propagation rate, fatigue crack propagation paths and fatigue crack branch angle. From the experiment, as loading application angle and thickness change, the fatigue crack propagation rate and angle under mixed mode were affected by stress redistribution.

Finite Element Analysis of the Influence of Crack Tip Stress Distributionon Fatigue Crack Propagation Rate of 5XXX Aluminum Alloy

2015 ◽  
Vol 817 ◽  
pp. 698-705 ◽  
Author(s):  
Jia Ju Liu ◽  
Hui Huang ◽  
Ran Liu ◽  
Li Rong ◽  
Wei Wang ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Tip ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Propagation Rate ◽  
Intensity Factors ◽  
Paris Region ◽  
Crack Tip Stress

5XXX aircraft skin aluminum alloy needs relatively high fatigue performance to sustain complex pneumatic loading in service. Stress intensity factors are important parameters to compute fatigue crack propagation rate. XFEM was used to calculate the crack tip stress, as well as stress intensity factors (SIF) and fatigue crack propagation rate on the 5E62 alloy. Simulation results showed that the values of SIF calculated by XFEM were quite close to the theoretical values. Both the values of crack tip stress and SIF increase as crack length increasing in Paris region, resulting the increasing of fatigue crack growth rate. Fatigue crack propagation rate calculated by XFEM are consistent with the theoretical values and experimental values in Paris region.

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