Measuring Theory of Three-Dimensional Residual Stress Using a Thinly Sliced Plate Perpendicular to Welded Line

A measuring theory of three-dimensional residual stresses, in which inherent strains, the source of residual stresses, are used as parameters was developed and L sub z method and nL sub y method were demonstrated. In these methods, inherent strains are estimated using relaxed strains measured at many points. Necessarily, cutting is required many times. In the cutting process, additional inherent strains may be produced by the effect of cutting heat. Therefore, it is desirable to decrease the number of cuttings as much as possible, which is also very important to improve the accuracy of measurement and to shorten the time required for experiments. To accurately estimate three-dimensional residual stresses produced in a region where residual stresses are uniform along the welded line, a measuring theory and its method using a thin plate cut out perpendicular to the welded line are presented. The main results are as follows: (1) Using relaxed strains measured before and after the cutting of specimen T, effective inherent strain, the source of residual stresses, can be estimated being divided into cross-sectional inherent strain components, { epsilon exp * sub c } = { epsilon exp * sub y , epsilon exp * sub z , gamma exp * sub yz }, and one along the welded line, { epsilon exp * sub x }. (2) Giving the estimated effective inherent strains to the original three-dimensional object, residual stresses are calculated. By this method, three-dimensional welding residual stress at an arbitrary position including the inside of the object can be estimated. (3) The reliability of this method was confirmed by a numerical experiment. (4) By this method, the number of cuttings has been greatly decreased. Accordingly, the time required for experiments can be greatly shortened and experimental expenses reduced. (5) This method is applicable to measurement of three-dimensional residual stresses produced by any cause including welding, if the residual stresses are considered to be uniform in one direction. 6 ref.--AA