Abstract
In this research, T-edge method and Lz method, in which inherent strains are dealt as parameters, are applied to measurement of three-dimensional welding residual stress distributions produced by electron beam welding (EBW). Accuracy of the measured residual stresses are discussed. As a result, characteristics of three-dimensional residual stress distributions due to EBW are clarified.
The main conclusions are as follows:
1) Validity and availability of T-edge method, developed in order to save. measuring time and expense, are demonstrated. by showing concretely the accuracy of three-dimensional welding residual stress distributions measured by this method.
2) Discussion on accuracy of residual stresses measured by T-edge method and Lz method suggested that residual stresses produced by EBW should never be uniform along the weld line, however continuous welding is applied for long weld length under the same restraint condition.
3) Residual stress in the welding direction, σx, produced in the weld metal distributed in the plate thickness direction varies from spot to spot in magnitude and distributes complicatedly. Since melting region is very narrow in EBW, dynamical restraint condition of the weld metal becomes so severe that the same large tensile residual stress as in HAZ is produced in the weld metal.
4) Residual stresses produced in the weld metal perpendicular to the weld line, σy, and in the plate thickness direction, σz, show characteristic distributions; i.e., σy is compressive on the top and bottom surfaces and tensile in the middle of the plate thickness, and σz is compressive in the plate thickness direction. The same stress distributions appear when instantaneous plane heat source is placed in the cross section of a plate. In case of EBW, it maybe assumed that instantaneous heat source is placed in the cross section, though no such assumption as moving plane heat source is placed continuously along the weld line can be made.
