EFFECT OF REVERSE BENDING METHOD ON PRE-CRACK STRAIGHTNESS IN CTOD TEST OF WELDED THICK STEEL PLATES

摘要

This study deals with the reverse bending method as a residual stress modification technique for CTOD test of the thick weld. In the reverse bending method, the residual stress around the notch tip of the specimen is redistributed by compressive plastic deformation by reverse bending load. The reverse bending method requires a smaller level of applying load comparing to the local compression method. However, the excessive reverse load may introduce the excessive plastic deformation in way of notch tip which can affect the CTOD value of the weld. So, this study investigates how to establish the proper bending load for ultra-thick weld. In order to do it, stress intensity factor was determined by the plastic zone size around the notch tip by 3-dimensional finite element analysis. The validation of the reverse bending method was verified by examining the configuration of pre-crack at CTOD weld test specimen with various thickness and strength.