Transient Thermal Stresses of Weld Heat-Affected Zone by Both-Ends-Fixed Bar Analogy

Transient thermal stresses of weld heat-affected zones were evaluated by a rigid frame apparatus as shown in Fig. 1. Round bar specimens set into the rigid frame were put to thermal cycles by induction heating and transient thermal stresses were recorded on the oscillograph connected to the loadcell. Four kinds of steel of different mechanical and metallurgical properties were used. The types of applied thermal cycle were single thermal cycle, multi thermal cycles of constant peak temperature type, increasing- or decreasing- peak temperature type (see Figs. 11 a, b).Test results of the transient thermal stress as a function of temperature are shown in Figs. 6 thru 9, Figs. 12 thru 16, Figs. 18 and 19. Residual stresses as a function of peak temperature applied are shown in Fig. 10 for single thermal cycles and in Fig. 17 for multi thermal cycles. The transient thermal stresses and residual stresses are influenced by the mechanical and metallurgical properties of steels used.Analysis of mechanical strains during thermal cycles was made using a connected bar-spring model as illustrated in Fig.2 b and a long rectangular plate as in Fig. 23 on they-axis of which an instantaneous plane heat source was applied. The analysis revealed the difference in mechanical strains between the model and the rectangular plate. The transient thermal stresses or elastic strains in plastic zones of the rectangular plate were approximately estimated by both-ends-fixed bar analogy.