Welded metal sheets of different ferrous materials, so called tailoredblanks, gain increasingly more importance in automotive industry.Microstructure, micro hardness and residual stress are important materialproperties for workpiece behaviour. The forming quality of tailored blanksis influenced by residual stress induced nearby the welding zone. Residualstress also plays an important role for the behaviour of welded componentsin practice. Stress occurs due to localised elastic expansion or contractionof the material lattice. Especially in welding processes this causes plasticdeformations of the joint sheets. In later forming operations the formingquality is considerable influenced by these residual stress. Also prematurefailure is attributed to inadequate residual stress. Annealing processeshave to be used right after welding to modify the residual stress state.This paper deals with micromagnetic testing used as a non-destructivemonitoring technique for determining residual stress nearby welding zones inferromagnetic sheets. The difficulties which have to be bridged are thechange in microstructure nearby the weldment joint during welding. Thischanges influence the micromagnetic parameters of the specimen like residualstress does. Hence, different parameters have to be taken into account todetermine the residual stress and to eliminate the influence ofmicrostructure changes. In this paper additional quantities of themicromagnetic signal were investigated concerning there dependence ondifferent material properties. Based on this experiences a mathematicalequation was developed for the determination of residual stress nearby aweldment joint by micromagnetic testing which is able to suppress theinfluence of microstructure. The results are in accordance with X-rayinvestigations and residual stress evaluated by micromagnetic testing.
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