Papers by Author: Jesus Ruiz-Hervias

Abstract: In this work, autogenous laser welding was used to join thin plates of low carbon ferritic and austenitic stainless steel. Due to the differences in the thermo-physical properties of base metals, this kind of welds exhibit a complex microstructure, which frequently leads to an overall loss of joint quality. Four welded samples were prepared by using different sets of processing parameters, with the aim of minimizing the induced residual stress field. Microstructural characterization and residual strain scanning (by neutron diffraction) were used to assess the joints’ features.

Abstract: This work shows the effect of the initial residual stress state on the stress relaxation behavior of cold-drawn steel rods. The evolution of residual strains at several locations along the rod diameter was measured in-situ by neutron diffraction during a stress relaxation experiment. It was found that if residual stresses are significant, stress relaxation is not homogeneous in the cross-section of the rods. This also explains the higher stress losses found in the rods with high residual stresses.

Abstract: Residual strain profiles were measured by synchrotron X-ray radiation in Al2O3/Y-stabilized ZrO2 (YSZ) ceramic laminates. Different stacking sequences were employed, including alternating layers containing 5 and 40 vol.% YSZ. Residual strains were found to be fairly constant within each layer; although they change at the interface between layers with different compositions. Different behaviour is observed for the strains along the in-plane and normal directions.

Abstract: Residual stress profiles were measured by neutron diffraction in Al2O3/Y-TZP ceramic composites containing 5 and 40 vol.% Y-TZP fabricated by conventional slip casting and by a novel tape casting route. Residual stresses in the zirconia are tensile and increase as its volume fraction decreases. For the alumina matrix, residual stress is compressive and increases with the zirconia volume fraction. In the composite with 5 vol.% zirconia, the processing route does not have an influence on residual stresses. However, in the composite with 40 vol.% zirconia, residual stresses are different in the samples obtained by both processing routes.

Abstract: Cold-drawing is employed to fabricate wires and rods, which are mainly used as structural reinforcements in construction as well as in the tyre industry. As a consequence of processing, a residual stress profile is developed. In this paper, residual stress profiles are measured by neutron diffraction in cold-drawn pearlitic steel rods subjected to different deformations (true strain from 0.3 to 1.7). The results show that the residual stress profile produced by cold-drawing is similar in all the samples, irrespective of the degree of deformation.