Abstract

This report is the third part of serial expriments which are being made to survay the effect of welding sequence on transverse shrinkage and residual stresses. In this report the analysis about the part of residual stress and dislocation through 1st to 4th serieses of experiment are mentioned. The size of specimen and welding conditions for each specimen were already stated in preceding papers.The measurement of residual stress was performed using electric resistance-wire strain-gauges as shown in Fig. 1. The values of measured strain change and the distribution of residual stress are shown in Fig. 2 and 3, respectively.The results obtained so far are summarized as follows.1) When the specimen is welded by one block, the value of transverse stress σy is tensile along welding bead, but is compressive in the mother material taking its maximum value in the vicinity of weld and decreasing accordingly with the increase of distance from the weld. The value of longitudinal stress σx. is also tensile at the center of weld and gradually decreases in accordance with the increase of distance from the center. The maximum value of σx is larger than that of σy, reaching nearly the value of yield stress of mother material. The value of σy increases as the increase of degree of constraint as shown in Fig. 5.2) When the specimen is welded by two or more blocks, there occurs a fairly different phenomenon. Though the average tendency is nearly the same as that in the case of one block, the distribution of residual stress becomes much complicated on the welding bead as shown in Fig. 3. This phenomenon was observed not only in case of block welding but also in multilayer sequence. Therefore, it seems to be meaningless to attempt to control the residual stresses on the weld zone by the change of welding sequence.3) Dislocation occured by slitting along the weld line was also measured. The form of dislocation is quite similar to that of transverse shrinkage as shown in Fig. 6.There exist close connections among transverse shrinkage, dislocation and transverse stress. These connections were studied from some viewpoints. For instance, some attempts to estimate the value of σy from the transeverse shrinkage were tried (Fig. 7 & 8).

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