Material testing of press hardened sheet metal parts
Determination of local strength values

Tailored Tempering

Tailored Tempering is becoming increasingly popular in the production of weight-reduced and safety-relevant sheet metal components. In addition to solid martensitic zones, soft and ductile zones can also be set, this is achieved by a locally limited heat treatment. Materials testing of these press hardened sheet metal parts plays an important role.

“The indentation method was used to demonstrate the different strengths in the hot-formed components. Thus, the indentation method has proven its worth in the field of testing strength curves for mechanical properties.
(schwartz GmbH/ 2019)
Crash-relevant components protect the occupants of vehicles from injury in the event of a collision. This is made possible by controlled retention and dissipation of the impact energy. For example, a B-pillar is stamped with a strength curve
(see Fig. 1), whereby the upper two thirds of the pillar have a higher strength, thus absorbing much energy with little deformation. This means that the persons are in a stable and protected passenger cell. The lower third, on the other hand, is stretchable enough to absorb a large proportion of the impact energy. The design enables safe crash behaviour on impact.
Figure 1: Tailored Tempering on a B-pillar

Investigation of strength curves using the indentation method

The investigation of the strength courses is carried out at the company schwartz with the test machine i3D BVR according to DIN SPEC 4864 carried out by Imprintec. Local strengths, such as the yield strength Rp0.2 and the tensile strength Rm, are determined automatically by means of a small indentation or the material throw-up and a calculation behind it. This enables the company schwartz to investigate their strength curves precisely and quickly.

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