Most metals are highly formable and even become mechanically stronger during industrial forming processes. Typically the final shape of a product requires application of several forming steps (strain paths). For example, flat sheets of metal are produced by rolling and subsequently stamped into the shape of a car door.
During such a strain path change the mechanical properties of the material are dramatically altered. The result is sudden stress jumps or stress transients, and frequently early material failure occurs. The mechanical transients have their origin in the microstructure of the metal, in terms of crystallographic orientations at the scale of micrometres and dislocation structures at the nanometre scale.
By means of electron microscopy and synchrotron radiation the microstructural changes at several length scales will be investigated in metals subjected to strain path changes in a systematic manner. In parallel the mechanical properties at the micrometre scale will be probed by nanoindentation and the final response of the metal at the macroscopic scale of real samples will also be measured. The aim is to obtain a fundamental understanding of the microstructural mechanisms leading to the transient mechanical behaviour and to formulate a material model capable of predicting these.
The project is supported by The Danish Council for Independent Research | Technology and Production Sciences and involves partners from DTU Mechanical Engineering, DTU Physics, University of Illinois, USA, and Brdr. Jørgensen Components A/S.
The project runs from February 2014 to July 2017.