Papers by Author: Roman Wawszczak

Abstract: The relation between residual stresses occurring in plastically deformed material and after subsequent annealing is of practical and theoretical importance. In the present work the X-ray multi-reflection method was applied to determine residual stresses and their orientation distribution in rolled and annealed ferrite and austenite steel samples. An important decrease of the first- and the second-order residual stresses was observed during recovery and recrystallization processes. Diffraction peak width was also studied and correlated with stress variation during annealing. Different kinetics of stress relaxation in ferrite and austenite were explained by different levels of stacking fault energy and different types of intergranular interactions occurring in these materials.

Abstract: X-ray diffraction method was applied to measure residual stresses in deformed and annealed polycrystalline austenitic steel. An elastoplastic deformation model was used in analysis of experimental data. As the result, the orientation distribution function of grain stresses, created during elastoplastic deformation was determined and presented in the Euler space. An important decrease of the first and the second order residual stresses was observed during recovery process. It was found that the magnitude of the stresses decreases, while their distribution between different grain orientations remains almost unchanged.

Abstract: Diffraction method was applied to determine the residual stresses in deformed and annealed polycrystalline samples of ferritic steel. The specific stored elastic energy corresponding to the grain stresses was calculated and presented in Euler space. An important decrease of the first and second order residual stresses and consequently stored elastic energy was observed during recovery and recrystallization. The evolution of stresses was correlated with the variation of diffraction peak width (related to dislocations density) and crystallographical texture.

Abstract: ray diffraction method is used to determine the stress field in polycrystalline materials. The measurement of peak shifts enables the determination of the macrostresses and the plastic incompatibility stresses (intergranular stresses). In the interpretation of the experimental results self-consistent model of elatoplastic deformation is used. In the present work, the plastic incompatibility stresses and the elastic energy stored in cold rolled brass and ferritic steel were determinate. The results are discussed and presented in Euler space.

Abstract: The evolution of residual stress and crystallographic texture during thermal treatment was studied using X-ray diffraction. Polycrystalline α-brass samples were examined after cold rolling and afterwards after annealing at different temperatures in the range of 50 0C - 450 0C. Additionally, the width of the diffraction peak was measured in order to estimate the variation of the dislocation density. The interpretation of experimental data was based on a fitting procedure for which the anisotropic diffraction elastic constants calculated by a self-consistent approach were used. As the result of analysis, the values of the first order and second order stresses were determined in each sample.