Использование температурных следов для неразрушающей диагностики остаточных напряжений в сварном соединении

Diagnostics of residual welding stresses based on the layout of temperature traces that (i) characterize isothermals of maximal temperatures within a thermal cycle of welding and (ii) are retained on the metal surface of a welded joint represents a prospective trend of non-destructive methods of control of residual stresses. The traces to be examined include both natural (temper colours and fusion boundaries) and artificial traces formed on the metal surface in the course of fusion of pre-applied temperature indication lines (lines of temperature indication markers, etc.). The layout of temperature traces assures the uniqueness of the solution to an inverse problem of a thermal cycle of welding reconstructed by the researcher. The kinetic pattern of alterations of the stress-deformation state (SDS) of a welded joint in the course of welding, as well as the pattern of residual stresses (the latter solely require the information concerning the cooling stage of a thermal cycle) can be identified on the basis of the reconstructed thermal cycle model. In the paper, the procedure of reconstruction of a thermal cycle on the basis of temperature traces is exemplified by resistance flash-butt welds of metal rods. Despite the one-dimensionality of the model, it presents a widespread type of welding of rails and accessories of building structures; this type of welding is used to connect edges of steel pipes, including those that have a big diameter and are used as underwater gas pipelines. Residual welding stresses of joint welds and the adjacent area can be identified with the help of a thermal marker.