Yanhua, L. and Lin, J., "Evaluation of Global and Local Deformation Behaviors of Similar Laser Welded Joints using Digital Image Correlation," SAE Technical Paper 2014-01-0832, 2014, doi:10.4271/2014-01-0832.
Similar laser welded blanks with same material and same gauge have been extensive applied in automobile body for improving the material utilization and extending maximum coil size. It is known that, for TWBs with dissimilar material and thicknesses, the difference of material properties and/or thickness of the welded blanks, change of the material properties in the weld seam and heat-affected zones (HAZ) as well as location and orientation of the weld seam are reasons for reduced formability. However, the plastic deformation capacity of TWBs is reduced even when the material and thickness are the same.The aim of this paper is to evaluate the deformation behaviors of similar laser welded joints. Uniaxial tensile of five laser welded joints, with 90°,60°,45°,30°and 0°weld orientations, were tested by using optical measurement-DIC (Digital Image Correlation). Strain /strain ratio distribution and evolution of each joint was analyzed and compared with base material. In addition, mechanical property of weld was determined using rule of mixture and hardness testing. Characterization of similar laser welded joints was interpreted based on the analyses of experimental results.The results show that, for steel TWBs where laser weld is characterized with higher strength and lower ductility than base materials, the deformation in the soft base material is constrained by the strong laser weld. Tensile stress develops in the laser weld and compressive stress develops near the interface in the base material. The stress states were transferred due to the effect of strength mismatch between laser weld and base material, which also accounting for the decreased formability.