８０ｋｇｆ／ｍｍ｀２´級高張力鋼板を用いたペンストックの塑性曲げ加工と溶接による３次元残留応力分布

Abstract

In the process of fabrication of large size penstock, thick plate is used and cold bending and welding are applied. The resulting residual stresses should exhibit complex three dimensional distribution. These residual stresses should influence brittle fracture and fatigue strength. Therefore, it is worthwhile to measure these residual stresses as accurate as possible.The authors presented the new measuring principle based on the theory of inherent strains and developed several measuring methods for three dimensional residual stresses, which were very accurate, judging from the theory of elasticity, although some approximate methods such as Rosenthal-Norton Method have been used so far.In this paper, the authors develop a new measuring method of residual stresses due to cold bending. For actual measurement, a large size model of penstock of 80 kgt/mm2 class high tensile strength steel plate is fabricated. Residual stresses due to cold bending are measured in the shell plate. Welding residual stresses at the longitudinal and circumferential weld joints are measured by the method which the authors presented before. It is observed that the maximum residual stress is about 50 kgf/mm2 to 60 kgf/mm2 which is less than the yield stress of the material.