Fatigue Strength Assessment For Structural Stresses At Welded Joints

Fatigue failure is the major factor caused structural failure in the field of naval architecture and ocean engineering. Fatigue prediction became one of the most significant contents in the design of naval structure while a mass of cost are needed when service and replacement of the failure members. Fatigue strength and result of prediction influence the manufacturing engineering, costing and availability directly.In the FEM analysis of fatigue life assessment, the stresses and strains can be strongly dependent on the size of mesh. Controling of mesh drains much on human and material resources and increases the design expenses in the trainditional hot spot stress approach. In the year of 2011, Professor Dong Pingsha of University of New Orleans discussed an structural stress approach named Dong approach, which follows elementary structural mechanics theory and makes the stress not impacted by mesh-size and type. Dong approach can be used either with fine mesh which could simulate the accurate geometry of the weld joints, or with coarse mesh which could lower modeling difficulties. In other words, this approach can change mesh densities at random without the structural stress changed.The content and work this paper had are shown below:(1)Make FEM modeling of several welded joints with different mesh sizes and element types. Get the stress results and give proper handling to the boundaries.(2)Get the hot spot stress through postprocessing with Dong approach, and verify the mesh insensitivity of the approach through comparison of results from different mesh-size and type models.(3)Contrast the hot spot results separately from Dong approach and the traditional linear extrapolation approach, and verify the availability of Dong approach.