The development of welding stress-strain around welding pool was analyzed based on simulation on surfacing refusion of low-carbon steel sheet. The hypothesis that any cross-section retains flat when the sheet is being welded and cooled is not supported by development of relative deformation of 4 pair cross-section. The another definition of tensile strain and compression strain were put forward when the metal is heated or cooled. The data from simulation indicate that, to any point, the sum of the max compression strain and the max tensile strain, which amplitudes are larger than thermal strain, is equal with residual total strain. It couldnt prove that plastic strain is the token of metal status, compressed or stretched when it is affected by heat. The final distribution of compression strain couldnt be determined on the cross-section with max width welding pool. The result shows that the longitudinal residual stress is higher than yield strength of base metal at room temperature where the max plastic strain exceeds 0.2% and that the residual plastic strain is about 0.2% at the same zone.

The difference between the theory heat input and the heat input calculated by Gauss numerical integral method, which was input by Gauss heat source was discussed, when the different integral zone and mesh element size were taken into account. The numerical result is close to theory value when length side of integral zone is equal to 3 times the effective radius of heat source. The lager zone couldn't improve numerical integral precision. The numerical integral result is lower than theory value when the value of Gauss Point is gained by shape function but higher when it was gained by Gauss distribution function. The numerical precision is very high when the mesh element size is 1/6 times the size of integral zone or 1/2 times the effective radius of heat source. The smaller element size couldn't improve numerical precision.