Quality Category Approach of Fatigue Assessment for Welded Structures with Surface Cracks

doi:10.3901/JME.2018.14.082

Abstract

Abstract: For fatigue assessment of welded structures contained cracks, fatigue life is calculated by multiple iterations according to Paris law based on traditional fracture mechanics, which will take much time due to the large computation and affect the strategy fast-making. Quality category approach for structures contained cracks is established to achieve rapid fatigue assessment by the equivalent relationship between fatigue strength and S-N curves. The quality category approach for structures contained extended cracks is deduced, which is corresponding to S-N curves. The allowable depth of extended crack at different quality categories is calculated. As for the fatigue propagation analysis for certain size cracks, the depths of equivalent extended cracks corresponding to certain size cracks are calculated based on the equivalent method of the equivalent fatigue strength and equivalent fatigue life. Taken semielliptical surface cracks under the axial stress as a study object, the allowable depths of extended cracks at different quality categories and thicknesses of steel plates are calculated based on the equivalent methods. The equivalent crack size diagram and the quality category diagram of extended cracks are drawn by the calculated depths of extended cracks for different crack shape ratios. Compared with the traditional method based on fracture mechanics, the equivalent method is used to evaluate fatigue of structures contained cracks for the excellent feasibility. The study will contribute to the popularization and application of the quality category approach for fatigue assessment of structures contained cracks, which is of significance to achieve the quick assessment for equipment contained cracks.

Key words: fatigue assessment, quality category, surface cracks, welded structures*

CLC Number:

TH49
TG405

YANG Jianguo, HAO Jiansong, LI Yuebing, ZHENG Wenjian, GAO Zengliang, ZHANG Pengcheng. Quality Category Approach of Fatigue Assessment for Welded Structures with Surface Cracks[J]. Journal of Mechanical Engineering, 2018, 54(14): 82-89.

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