Weld seam inspection
Determination of measurement data from the weld seam as a basis for FEM simulations
The indentation method according to DIN SPEC 4864 could be successfully used in the context of research work on the topic of “resistance spot welding”. In the classical way, the hardness was determined beforehand with the hardness test and conclusions were drawn about the strength. However, the limits of the meaningfulness of the hardness value were quickly reached. It was hardly possible to make reliable statements about the yield point or the hardening behaviour. Even the conversion of hardness into tensile strength was, for example, only possible with a high error tolerance for austenitic materials or aluminium alloys.
With the indentation method, the desired properties for the strength (yield strength Rp0.2 and tensile strength Rm) of the welded joint can be determined. The local flow curves determined by the indentation process are then incorporated into an elastic-plastic deformation simulation. This results in a detailed model representation of the welded joint. The results thus permit the development of a calculation basis for a failure model, on the basis of which an optimised design of the welded joint can be carried out by the designer.
„The Imprintec indentation method has led us to the desired solution. Previously, the weld spots were characterized with the hardness and hardly any statements could be made about the Rp0.2 yield strength. It was not possible to produce tensile specimens as an alternative to investigate the strength curve due to the small sample volume. The indentation method combines the local investigation possibility of the hardness test with the informative value of the tensile test for tensile strength and yield point.“ (2019)