| At present,welding parts are widely used in engineering practice,and their fatigue failure has been closely concerned by many scholars.The most common form of failure of a weldment is the crack initiation of the weld toe location after cyclic loading,and the crack propagates along the thickness of the plate until it breaks.The stress concentration caused by welding defects has a certain degree of influence on the fatigue life of welded parts,and it is also a major safety hazard for rail trains.There are many methods for evaluating fatigue failure of welded joints at home and abroad,and the master S-N curve method is the latest evaluation method.Based on the traditional fatigue evaluation method,this method considers the factor of stress concentration,combines it with fracture mechanics,and obtains a universal master S-N curve based on a large number of fatigue experimental data.The fatigue analysis calculation by the master S-N curve method can more accurately predict the fatigue life of the weldment and reduce the economic cost caused by a large number of fatigue experiments.This article will use the master S-N curve method to carry out the following research work:First,the theory of the master S-N curve method is summarized and deduced,and combined with ABAQUS and FE-safe software,the evaluation of the fatigue life of the weld by the master S-N curve method is realized.The fatigue calculation results using this method are compared with the existing fatigue experiment results,and the feasibility of the master S-N curve method is verified.Then,through analysis and calculation,the finite element model under the merge connection can more accurately simulate the real weld and prove that the location of the defect has little effect on the fatigue life of the weld.By comparing the fatigue life of T-welds with undercut,asymmetry or excessive convexity defects and butt welding with undercut,ultra-high or stay defects under the three levels of B,C and D specified in ISO5817.The calculated fatigue life at the weld toe is analyzed by data to obtain the change trend of the fatigue life of the weld at different levels for the same welding defect.Different welding defects at the same level have different degrees of influence on the life at the weld toe.The actual working conditions can refer to the corresponding comparison results.Finally,taking a connection of a rail train as an example,the fatigue life of the weld with three D-level defects including undercut,asymmetry,and excessive convexity was evaluated.The calculation results are consistent with the comparison results under corresponding working conditions,which proves that the comparison results of fatigue life of welds with different defects have guiding significance for engineering practice. |
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