No abstract

In our earlier study, the authors revealed that the fatigue limit of ductile cast iron (DCI) specimens whose shapes are similar to the welded joint shapes is about three times larger than that of the welded joint specimens. However, since many defects are usually included in the DCI specimens, the fatigue limit of DCI joints decreases with increasing the maximum defect size. In this paper, therefore, the maximum defect size is estimated by using statistics of extremes. Then, the lowest fatigue limit corresponding to the maximum defect size is estimated from the 4 parameter model and compared with the lowest fatigue limit of the welded joint. As a result, it was confirmed that the lowest fatigue limit of the DCI specimens is about twice as large as the welded joint.KEY WORDS: fatigue strength; ductile cast iron; welded joint; statistics of extremes; 4 parameter model;area parameter model.

In this study fatigue experiments are conducted for ductile cast iron (DCI) to compare with the fatigue strength of cruciform welded joints. Here, several DCI specimens are prepared to have nearly the same fatigue strength in smooth specimens before welding and to have similar cruciform shapes in the welded joints. It is found that the fatigue strength of DCI specimen is about three times larger than that of the welded joint specimens. The fatigue strength improvement can be explained in terms of the small stress concentration factor, notch insensitivity and compressive residual stress generated by shot blasting for DCI joints.

In this study fatigue experiments are conducted for ductile cast iron (DCI) to compare with the fatigue strength of cruciform welded joints. Here, several DCI specimens are prepared to have nearly the same fatigue strength in smooth specimens before welding and to have similar cruciform shapes in the welded joints. It is found that the fatigue strength of DCI specimen is about three times larger than that of the welded joint specimens. The fatigue strength improvement can be explained in terms of the small stress concentration factor, notch insensitivity and compressive residual stress generated by shot blasting for DCI joints.

In our earlier study, the authors revealed that the fatigue limit of ductile cast iron (DCI) specimens whose shapes are similar to the welded joint shapes is about three times larger than that of the welded joint specimens. However, since many defects are usually included in the DCI specimens, the fatigue limit of DCI joints decreases with increasing the maximum defect size. In this paper, therefore, the maximum defect size is estimated by using statistics of extremes. Then, the lowest fatigue limit corresponding to the maximum defect size is estimated from the 4 parameter model and compared with the lowest fatigue limit of the welded joint. As a result, it was confirmed that the lowest fatigue limit of the DCI specimens is about twice as large as the welded joint.