The increasing demand for car body structures with optimised energy absorption capacity and the ability to maintain their structural integrity even under the highest dynamic load has stimulated the development of new thermo-mechanical process routes for the production of pressed and roll-formed sheet metal parts in order to combine both extreme formability and a highest level of strength for the final product. These process routes offer a high potential for further improvements in the field of strength-strain correlation and load adapted property distribution of the components, as well as an enhanced process productivity. A new type of thermo-mechanical tailored processing of sheets and profiles is presented, based on the adequate application of differential heating and cooling strategies. By the control of local microstructural effects, the components develop a property distribution adapted to complex load situations. New tooling concepts complement these developments in order to ensure high process efficiency and reliability.
Study of anelasticity in AZ31 magnesium-based alloy in initial (hot-rolled at 370 оС)
condition and after one and four passes of equal channel angular pressing is carried out. An internal
friction peak was found at 170 °C at a frequency f of about 1 Hz. Two possible mechanisms of this
peak are discussed: it is suggested that the peak origin is the grain boundary relaxation.
The simultaneous influence of both thermal and mechanical treatment was applied to
produce a geometrically complex shaft from 51CrV4 steel. This special treatment led to the
formation of adjacent microstructures which were significantly different from each other. It was
found that these microstructural changes were accompanied by a change of mechanical properties in
terms of hardness, electrical resistivity and especially internal friction. Specimens for structural
studies and study of mechanical and physical properties were taken out from different places of the
produced shaft and tested in order to verify and understand the obtained gradation. The significant
variations in properties could be explained in terms of structure and dislocation behaviour under
applied cyclic stress using mechanical spectroscopy technique. The cold-work (Snoek-Köster) peak
was recognised and analysed in the structure of this steel.
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