A Novel Tensile Testing Method to Characterize the Weld Metal Properties for Laser Welded Blank (LWB) with AHSS
2022-01-0279
03/29/2022
- Event
- Content
- Laser welded blanks (LWB) are produced by laser welding two sheet materials together, typically prior to a forming process. The sheet materials can be identical or dissimilar depending on the application. The LWB process allows the designer to ‘tailor’ the location of the desired material properties in the blank for crashworthiness and light-weighting. The behaviors of an LWB during forming are significantly influenced by blank conditions such as thickness variation and the strength ratio of the two materials, as well as the weld quality. These conditions can cause variation in the local formability of the weld area, making the numerical simulation of forming LWB more complicated than a simulation of monolithic sheets. Unfortunately, the local formability of the LWB weld area is often over-simplified in forming simulations. The base material properties are simulated in the weld area, which completely neglects the heat-affected zone (HAZ) and weld properties. Using this method on conventional steels has been reasonably effective due to the weld and HAZ being stronger than the base metal, causing necking failures to occur in the thinner or softer base metal away from the weld area. However, third-generation advanced high strength steels (GEN3 AHSS) have shown a different trend. Unlike conventional steels, GEN3 steels more frequently exhibit fractures in the weld and HAZ. When the over-simplified simulation method is used on these materials, the physical results do not correlate well with simulation. This can cause costly design changes and production delays. This paper introduces a novel tensile testing method to characterize hardening behavior of the weld material with a digital image correlation (DIC) and apply it as a constitutive hardening model in forming simulations with LWBs of GEN3 steel. Three different formability tests under uniaxial, biaxial, and plane-strain conditions were performed with LWBs of AHSS and GEN3 steel. Experimental results were correlated with FEM predictions that were conducted with and without the weld material model. The results show the weld material model for LWB improves the accuracy of FEM predictions of both necking failures on the base metal as well as cracking on the weld.
- Citation
- Kim, M., Gu, J., and Kim, H., "A Novel Tensile Testing Method to Characterize the Weld Metal Properties for Laser Welded Blank (LWB) with AHSS," SAE Technical Paper 2022-01-0279, 2022, .