Characterization of Mechanical Properties in Surface-Treated Materials

Abstract

An experimental methodology was developed for identification of mechanical behavior laws, in which the evolution of the stresses and strains in the surface of the samples is determined by X-ray diffraction and electric resistance strain gages, respectively, as a function of the loading in four-point bending tests. The determined stress-strain curve is then characteristic of the near-surface layers of the samples. The method was validated for different steels by comparing the results of samples with homogeneous properties on the cross section with the results of tension tests. The developed methodology was applied to the study of steel samples submitted to surface treatments, presenting gradients of chemical composition, microstructure, and mechanical properties from the surface to the bulk material.

Characterisation of Elastoplastic Behaviour Using Spherical Indentation

“…[2] used the in-depth normalized variation of hardness over the cross sections of shot-peened specimens. Batista and Dias [3] proposed another method for evaluating the mechanical properties of surface-treated steels (shot-peening, nitriding and carbonitriding treatments). In this method, surface-treated specimens are subjected to a specific loading case, using propose-built devices (4-point bending, tensile, etc.…”

On a New Method Based on X-Ray Diffraction to Identify Stress-Strain Laws on Surface-Treated Materials

“…Nevertheless, these methods are of limited application or still require some improvements. On a previous work [9] a characterisation technique has been developed and validated. This technique allows the identification of elastoplastic stress-strain laws on surface treated materials, presenting gradients of mechanical characteristics, microstructure and chemical composition across the treated layer.…”

“…In this work a AISI 4130 steel was selected and subjected to surface treatments of carbonitriding and shot-peening. The proposed X-ray diffraction method [9], using 4-point bending tests, has been applied to the hardened surface and intermediate layers, in order to determine the in-depth evolution of the stress-strain curve. In addition, the in-depth evolution of residual stresses, diffraction peak broadening and retained austenite over the treated depth were analysed.…”