Papers by Keyword: Inhomogeneous Plastic Deformation

Abstract: In order to improve the microstructure evolution modeling of dynamic recrystallization (DRX) in agreement with physical experiment, a modified Monte-Carlo (MC) Potts model for simulating DRX process was proposed in this paper under the consideration of the inhomogeneous stored energy distribution related to grain sizes, the nucleation criteria related to critical dislocation density, the site energy change related to grain preferred-growth, the combination of macroscopic thermo-mechanical parameters and microscopic material parameters, and the relationship between MC calculation steps and real DRX time. The results show that the modified model can better simulate the basic characteristics of dynamic recrystallization of metallic materials during forging, which the recrystallized grains nucleate mainly in the deformed regions with high stored energy and preferentially grow up by merging adjacent deformed grains with high stored energy.

Abstract: Instrumented indentation testing has been carried out on steel samples subjected to uniaxial loading. It is distinguished between purely elastic as well as elasto-plastic loading up to plastic strains of 3%. The experimental approach allows the combination of local in-situ residual stress analyses by means of X-ray diffraction and the subsequent realisation of instrumented indentation testing for the same material volumes beforehand irradiated by the X-rays. The aim of the investigations was to explore a potential correlation between the imposed macroscopic stresses and the characteristic values of instrumented indentation testing evaluated from the measured force-indentation depth curves according to the standard ISO EN 14577. The studies illustrate that results of depth sensing indentation testing have to be handled with care for prestressed material states. The effect of mechanical stresses on the results of instrumented indentation testing is not stringently limited on the hardness measures alone. Other indentation parameters like e.g. the indentation modulus EIT or the elastic part of the indentation work η IT are likewise affected by the prestresses, whereas the impact is in the order of magnitude that it has to be taken into account during interpretation of indentation readings.