2012
,
Ullner, Christian
,
Brauser, Stephan
,
Subaric-Leitis, Andreas
,
Weber, Gert
,
Retmeier, Michael
For spot-welded joints, the resistance to mechanical stress depends on the local strength properties and gradients in the weld area. The commonly used methods for investigating the stressstrain behaviour across the weld area are connected with a high level of sample preparation and with considerable limitations in local resolution. A promising method for determining locally resolved stressstrain curves is the instrumented indentation test in connection with the method of representative stress and strain (RS) and the method of artificial neural networks (NNs). The stressstrain properties of the weld nugget and the base metal determined by these two methods are compared and discussed, additionally in relation to the stressstrain curves obtained from the tensile test. The measured Vickers hardness across the weld area is compared with the evaluated local stressstrain properties. Three steels used in automobile manufacturing are investigated: mild steel DC04 and two advanced high-strength steels (TRIP steel HCT690T and martensitic steel HDT 1200M). The results of the two methods (RS and NN) show good correspondence for the base metal area but some significant differences for the weld nugget. Comparing the data across the weld area, no evidence of the presence of residual stress (which would influence the results) was found.