User report:
Materials testing after Tailored Tempering

Sheet metal parts

Testing of partially press-hardened sheet metal components

Tailored tempering is becoming increasingly popular in the production of weight-reduced and safety-relevant sheet metal components. In addition to solid martensitic areas, soft and ductile zones can also be adjusted, this is achieved by a locally limited heat treatment. The material testing of these press-hardened sheet metal parts takes on an essential role.

"With the indentation method, the different strengths in the hot-formed components could be demonstrated. Thus, the indentation method has proven its worth in the field of testing strength curves for mechanical properties."
(Fa. schwartz GmbH / 2019)

Crash-relevant components protect vehicle occupants from injury in the event of an impact. This is made possible by controlled containment and dissipation of the impact energy. For example, a B-pillar is embossed with a strength curve, whereby the upper two thirds of the pillar are higher strength, so a lot of energy is absorbed with little deformation. This means that the passengers are in a stable and protected passenger cell. The lower third, on the other hand, is stretchable enough to absorb a lot of impact energy. The design enables safe crash behaviour in the event of an impact.

Figure 1: Strength levels of a B-pillar after tailored annealing

Investigation of strength curves with the aid of the indentation method

The examination of the strength curves is carried out by schwartz GmbH with the Testing machine i3D BVR according to DIN SPEC 4864 from Imprintec. Local strengths, such as the yield stress YS  and the ultimate tensile strength UTS, are determined automatically by means of a small indentation or the material throw-up and a calculation behind it. In this way, schwartz can examine their strength curves quickly and precisely (Fig. 1).

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