Project Y2018/NMT-4668 (Micro-Stress- MAP-CM)

Residual stresses, both macroscopic and microscopic, originate during conventional metallurgical processes.Knowing their magnitude and distribution is of great importance in the structural design in applications where fatigue, stress-corrosion or thermal cycles may occur (e.g., in the nuclear industry). The importance of these stresses is reflected in the large number of articles published in recent years: articles focused primarily on knowing macroscopic stresses. However, to date there are no experimental works that quantify the magnitude of microscopic stresses. This lack is due, on the one hand, to the limitations of diffraction techniques (neutrons and synchrotron radiation). Since the gauge volume is much higher than the variation of these microscopic stresses, its calculation becomes greatly complex since the methods used for the case of macroscopic stresses are not valid for the microscopic ones. In addition, there is no reliable procedure to obtain the unstresses value of the lattice parameter, a key factor in the calculation of residual stresses.

The aim of this project is to develop a methodology that allows to obtain maps of microscopic stresses, particularly in aluminum alloys. The procedure will use experimental diffraction data obtained in European large facilities, primarily by neutron diffraction, and will be analyzed using computational techniques that handle a large number of variables (evolutionary algorithms). The procedure will be based on the analysis of the displacements of the diffraction peaks and, more specifically, of their broadening. In addition, the problem of having a unstresses lattice spacing value requiered for this analysis will be addressed.

It is worth highlighting the need of two complementary research Groups to deal with this problem. One of the Groups (CENIM) will be focuses on the experimental aspects (study of the microstructure of materials, up to the nanometric scale, and diffraction experiments) that will provide the necessary information to address the problem by computational methods. The second Group (UCM) will focus its efforts on the development of the computational techniques /(Evolutionary Algorithms) to provide a solution to the problem proposed. It is necessary a close collaboration between both groups, with very different trajectories and experteese, for the success of the project. (spanish)