Papers by Author: Jose M. Atienza

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: The stress-strain curve of a material is usually obtained from the load-displacement curve measured in a tensile test, assuming no strain localisation up to maximum load. However, strain localisation and fracture phenomena are far from being completely understood. Failure and strain localisation on plane tensile specimens has been studied in this work. A deeply instrumented experimental benchmark on steel specimens has been developed. Surface strain fields have been recorded throughout the tests, using an optical extensometer. This allowed characterisation of the strain localisation and failure processes. Tests have been numerically modelled for a more detailed analysis. Preliminary results show a substantial influence of geometrical specimen defects on the strain localisation phenomena that may be critical on the stress-strain curves obtained and in the failure mechanisms.