The main objective of the performed Control and Exploitation of Thermal Distortions (DISCO) project was to seek an overall concept for the control of thermal distortions. The scope of the project was limited to structural steels and to the processes most important to the participating industry. The possibility to apply the inherent strain method for modelling thermal deformations was examined by establishing an inherent strain database for the target arc welding and thermal cutting situations. The project was executed in cooperation with Lappeenranta University of Technology and four Finnish enterprises. Osaka University, Japan, was consulted concerning the inherent strain method. The work focused on structural steels representing two strength levels, and GMAW, FCAW, SAW and MAG welding processes. The computational practices were revealed for treating thermal distortions. Further actions included testing and modelling of welded T-joint with various plate thicknesses. The relationship between plastic strains and angular distortion (out-of-plane deformation with the weld as the axis of rotation) of fillet welded plate T-joints were studied using numerical analyses. A three dimensional thermo-elastic-plastic analysis incorporating the effects of a moving heat source and non-linear material properties was performed to obtain the plastic strain distributions and deformations. Procedures to define a simplified strain distribution (inherent strain) and to compute deformations were presented. The comparison of detailed thermo-elastic-plastic computation and measurements yielded a good correspondence. The simplified inherent strain type analysis underestimated somewhat the deformations. The technical basis for the creation of an inherent strain database was presented.
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