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This paper presents the quantitative assessment of the thermomechanical conditions of two commonly used laboratory weld solidification cracking tests, the Sigmajig test and the transverse Varestraint test. The local temperature and stress/strain conditions in the vicinity of a weld pool are calculated using the finite element formulations of the heat transfer and continuum solid mechanics, respectively, and are quantitatively related to the welding and testing conditions. The calculated local stresses in the solidification temperature range are able to explain the experimentally observed solidification cracking initiation behaviours under different welding and loading conditions in the Sigmajig test. The local strain conditions in the transverse Varestraint test are related to the testing conditions, particularly to the augmented strains that have been used as an index to measure material susceptibility to solidification cracking. From results obtained using the technique of measurement by means of in situ observation (MISO), the accuracy and the capability of the FE models are critically evaluated. The results in this study support a postulate that the microscopic solidification cracking processes are controlled, to a significant degree, by the development of the local macroscopic stress/strain conditions in the cracking susceptible region.

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A general, three-dimensional, closed-form welding heat-flow solution, which is capable of analyzing thermal behavior of the weldment in its transient state and/or under time-dependent power change during welding, is presented. The analytical model utilizes the finite heat source theory with a Gaussian distribution and also considers the effects of finite plate thickness. The numerical values of the solution are calculated using the computational schemes on a minicomputer. In this paper the welding parameters of the pulsed current GTAW were studied using the solution. Two sets of pulsation parameters were analyzed and their sensitivity to the heat input control were evaluated.