FATIGUE STRENGTH EVALUATION OF RECONDITIONED PRESTRAINED MATERIALS

If a ship sustains serious failure involving structural distortions such as indentations and buckling, the failed portions are reconditioned either by welding or fairing. If the failed portion is cropped and rewelded, the near-original state might be restored. However, problems lie in reconditioning the failed portion by fairing involving the bending process, the reconditioned portion might give the false impression that it had been repaired satisfactorily. This poses the potential danger of a serious failure originating from the very portion reconditioned during service after the repair. This paper discusses the fatigue life of materials following reconditioning by the cold bending process, which is often used as a stop-gap measure. The change in the properties of a material considered from a failure due to distortion; i.e., plastic deformation is work hardening, which is generally believed to contribute to improving fatigue strength. However, work hardening and surface failures cannot be readily classified, and no reports have been presented on a quantitative assessment of how and to what degree.