In the computed-based analysis of
forming processes, for example, manufacturing sheet
metal parts for the automobile industry, the material loading is represented by
major and minor strains εI, εII and is visualised with respect to a forming
limit strain curve. In the method according to the invention, one proceeds from a target state (4n) of the material, as has been determined in the computed
simulation of the forming process. A proportional trajectory of a loading and thus of the state variables of the material, in particular of the stresses (σ), is determined, which leads to the same target state. The associated proportional strain trajectory is evaluated for this proportional loading trajectory. The strain state (4p) which results from this strain trajectory, is called the equivalent strain state (4p) and may be used in the forming
limit strain diagram for assessing the target state. Thereby, the equivalent strain state is set in relation to the forming
limit strain curve (1) for the proportional trajectories.