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A study is presented on the influence of the clamping support distance on welding distortion of 6 mm thick gas metal arc welded structural steel T joints. Experiments were performed for two clamping conditions and are compared to simulations based on a previously presented model. It was found that clamping closer to the weld seam reduces angular as well as bending distortion. In order to assess the accuracy of the results, sensitivity analyses were performed on the influence of predeformation and material parameters. It is shown that an initial predeformation has an influence on the final welding distortion. Additionally, it has been found that selection of material properties within the range of variations permitted by the material norms has a strong influence on the predicted distortion. Results were improved using material specific data rather than generic data for the relevant material class. Also the assumed phase volume change plays an important role.

Due to increasing demands to reduce C02-emission and to augment occupant’s safety new modern materials are developed ongoing. Because of relatively low production costs, high strength and simultaneously good formability the advanced high strength steels (AHSS) are applied among others for the lightweight design of body-in-white components in the automotive industry. Their already mentioned properties follow from the presence of mixed mild and hard ferrous phases. Due to this multiphase microstructure of the most AHSS steels, a complex material and damage behavior is observed during forming. The damage grows in a ductile manner during plastic flow and the cracks appear without necking. They are often characterized as the so called shear cracks. The damage predictions with standard methods like the forming limit curve (FLC) lack accuracy and reliability. These methods are based on the measurement of linear strain paths. On the other hand ductile damage models are generally used in the bulk forming and crash analysis. The goal is to prove if these models can be applied for the damage prediction in sheet metal forming and which troubles have to be overcome. This paper demonstrates the capability of the Gurson-Tvergaard-Needleman (GTN) model within commercial codes to treat industrial applications. The GTN damage model describes the existence of voids and they evolution (nucleation, growth and coalescence). After a short introduction of the model the finite element aspects of the simulative damage prediction have been investigated. Finally, the determination of the damage model parameters is discussed for a test part.

The automotive industry promotes lightweight design to reduce the CO2-emission and enhances the passenger's safety using high strength steel grades. One limiting factor to the accuracy of modern stamping simulation are the empirical constitutive models. In particular for high strength multiphase steels the modelling techniques like multi-scale methods are becoming more interesting. However they should meet the industrial needs. Not only the accuracy but also features like time, costs and complexity are rapidly increasing. The challenge is the development of finite element technologies and multi-scale methods in an appropriate framework for industrial projects. The crystal plasticity finite element method bridges the gap between the micro level and macroscopic mechanical properties that opens the way for more profound consideration of metal anisotropy in stamping process simulation. Nevertheless new empirical constitutive models are favourable for spring back prediction in forming simulations, even if the number of material parameters and the amount of tests for their identification increases. In this paper the application of crystal plasticity FEM within the concept of virtual material testing with a representative volume element (RVE) is demonstrated.

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