Identification Of Mechanical Properties For Weld Zone Materials In Spot-Welded Joints

Lightweight design and increasing crashworthiness are two major trends in todays and future automotive engineering field.Nowadays,the most frequently used joining technology for car bodies is resistance spot-welding.Spot-welded joints consist of different zones with different mechanical properties.These properties highly influence the failure mode of the joints and therefore the crashworthiness of the vehicle.In purpose of weight reduction,engineers choose materials with higher stiffness.For these materials the mechanical properties of the welded zones are often not sufficiently analyzed.This research work deals with the analysis of the mechanical properties of resistance spot-welded zones for high strength steel sheets.Different specimens have been designed with finite element simulation for notched tension and shear tests.Using additional specimen designs for uniaxial,miniature and central hole tension,all tests were conducted under quasi-static conditions with the assistance of digital image correlation technology.Force-displacement and stress-strain curves were extracted for uniaxial tension in the three major weld zones base metal,heat affected zone and fusion zone and for shear tension for the base metal and the fusion zone.Notched and central hole tension tests were used to gain the force-displacement behavior for fracture at different stress triaxialites.