Third party funded individual grant
Acronym: EFB 07/120
Start date : 01.04.2022
End date : 31.03.2024
In material characterization for analyzing the failure of a material, it is well known that the maximum achievable strains of the material in the region around the plane strain take a minimum compared with the failure under shear or under biaxial tensile loading. Current characterization tests, such as the Nakajima test, to determine the forming limit curve (FLC) have been continuously developed and improved in recent years. Characterization under plane strain has reached its limits, since a direct load path under pure plane strain can only be mapped to a limited extent. The research project pursues the task of improving conventional characterization tests by further characterization measures in order to enable a more precise description of the failure under plane strain. The aim is to determine the exact characteristic values under pure plane strain. This should allow the limits of the material to be better exploited. SMEs in the manufacturing sector benefit from the results through improved utilization of the real material limits, which is reflected in the reduction of manufacturing steps or in reduced material consumption. SMEs in the field of materials testing benefit from the development of new testing methods as they can expand their portfolio. SMEs in the field of software development benefit from improved material maps and thus more precise FE analysis.
The challenge of this research project is the exact design of products made of sheet metal materials. In common practice, components manufactured in this way are nowadays designed by means of numerical simulations. This type of design is significantly influenced by the quality of the input parameters, such as the characteristic values from the material characterization. The assumption of wrong input parameters can predict a component failure too late or a component failure too early. For this very reason, large safety factors are often included in practical applications, leading to a conservative design with only moderate utilization of the material's limits. However, an improvement in the utilization of the material's potential is significantly influenced by an exact material characterization. In particular, the area of plane strain, which is often the cause of failure in deep-drawing or stretch-forming components, must be investigated and improved. Conventional characterization tests under plane strain can show nonlinearities in the strain path or are friction-induced or strongly affected by assumptions due to their test setup. Thus, the objective of this research project is to improve the characterization under plane strain for an improved failure prediction in order to shift the process limits to higher forming ratios and higher achievable drawing depths. The conventional characterization of forming limit change is to be improved to better predict failure under plane strain in order to increase the quality of input parameters for component design.