Validation of material models for sheet metals using new test equipment

Abstract

Validation is an important step after a calibration of models in order to assess their quality. In this work, new test equipment is presented that provides a comprehensive database for validation of material models for numerical analyses using FE simulation in sheet metal forming: the MUC-Test (acronym for Material Under Control). The introduced validation strategy is based on a comparison of experimental results with a numerical representation of the MUC-Test in terms of punch force and major and minor strain. The data comparison approach uses a full-field comparison over a wide range of punch stroke and thus considers the hardening behavior of the models. Extensive parameter studies are performed to investigate numerical, process and material model parameters regarding their influence on the test results. The presented validation method is applied to three materials of different material classes: The microalloyed steel HC340LA, the dual-phase steel DP590HD and the aluminum alloy AA5754. Furthermore, different material models based on the same database are compared for the DP590HD, showing the potential to identify suitable material models for specific requirements. Finally, equivalent material models based on different calibration strategies are compared. In conclusion, it is shown that the MUC-Test can be used to evaluate and compare different material models in terms of their ability to represent real material behavior in an effective and efficient way.

Innovative experimental setup for the investigation of material models with regard to strain hardening behavior

“…It is also advantageous for validation not only to be able to compare an initial and final state, but also to be able to carry out continuous validation during the forming process. [2] Various experiments have been established for the validation of material models. One example is the cross-die, in which a wide range of strain states is achieved in the specimen material [7].…”

“…Here, the major and minor strains after a forming process are compared with the simulation. In this test setup, however, friction dominates and validation is only possible at the end of the forming process [2]. Another validation test, which we will also investigate further in this paper, is the so-called MUC-Test [8].…”

“…The material model to be validated is used. By comparing the major and minor strain over the entire punch stroke as well as the punch force of experiment and simulation, a validation of the material model can be carried out [2].…”

“…The area visible to the DIC system through the opening of the die is highlighted in color for a 110 mm specimen. In this area we can determine the strains of the specimen surface [2].…”

“…In the production of deep drawing parts, it is essential to investigate numerically the components at an early stage and during the development process in order to define tool geometries and test processes digitally [1]. The use of a suitable material model is essential for the quality of the simulation results [2]. It has long been proven that the complexity of the material model has an influence on the simulation result [3].…”