Abstract
Thermal stresses induced by butt welding of two plates are studied, based on the elastoplastic theory in which temperature dependence of yield stress and workhardening of the plate material are considered. For simplicity, uniaxial temperature distribution varying with time is assumed. Numerical calculations are carried out using a step-by-step procedure in time by means of a digital computer.
The transient and residual strains, stresses and zones of plastic range are elucidated, and then, effects of hardening rate and heat input on the thermal stresses are investigated in detail. All the results are illustrated in figures using dimensionless quantities.
Main conclusions obtained are as follows.
(1) It is found that some central regions are subjected in turn to plastic yielding in compression and in tension whereas other major portions of the plate behave in an elastic manner throughout the cycle as shown in Fig. 7. There is a time interval in which plastic loading and unloading occur simultaneously.
(2) Variations of the transient stresses with time for the different combinations of a hardening rate and an amount of heat input are as shown in Figs. 9 and 12.
(3) Growth patterns of the plastic regions are not affected substantially by the hardening rate, but the magnitude of maximum tensile residual stress increases almost proportionally with increasing hardening rate.
(4) As the amount of heat input increases, the plastic regions widen and the absolute value of uniform compressive residual stress increases as well, but the magnitude of maximum tensile residual stress tends to decrease slightly.
(5) The magnitude and distribution of residual stresses developed by an arbitrary welding conditions may be evaluated approximately by use of Eq. (8), Fig. 10 and Figs. 1315. Some trials by use of these results are good in accord with the experimental data.
