On-line inspection of weld quality based on dynamic resistance curvein resistance spot welding and weldbonding

摘要

In order to reduce destructive testing of car sub-assemblies, on-line inspection of weld quality has gained more and moreconcern in terms of both resistance spot welding (RSW) and weldbonding. Dynamic resistance directly determines theamount of heat generated by current flow and consequently reflects nugget formation and growth, which is one of themost effective technologies for quality inspection. Under the measurements of voltage and current at the secondarycircuit of a welding transformer, this paper proposes a method for on-line inspection of weld quality based on twoindicators from dynamic resistance curve: time to nugget initiation and durable time to nugget expansion. Firstly, duringthe welding process of RSW and weldbonding, the proper range of time to nugget initiation and durable time to nuggetexpansion for good welds is set up. Then on-line inspection of weld quality on the basis of the developed proper range ofthese two indicators is carried out. The experimental results show the following conclusions: it is clearly able to separateaccepted welds without expulsion from the welds of unaccepted nugget size in both RSW and weldbonding; the properrange for good welds, independent of electrode wear, is obtained only for a new electrode.