Stress gradient study by X-ray diffraction using Fourier analysis

Residual stress determines the mechanical behavior of the alloys. The modern surface treatments techniques introduce residual stress characterized by strong gradient. In this context became important the development of reliable experimental methods for measurement and control of this stress. The X-ray diffraction method is widely used in the measurement of stress; however it presents limitations in the data interpretation when the penetration depth of the radiation is comparable with the variation of the stress caused by the gradient. This difficulty related to the non-linearity of the θφψ, VS sin2ψ dependency in the presence of stress gradient, for that reason the traditional sin2ψ method could not be used on the stress distribution calculation in material surface with strong gradient stress. The Fourier transform is an important and successful tool applied in crystallography diffraction methods. In this work we present a methodology based on the Fourier analysis to obtain the stress distribution function in surfaces with strong gradient. Also is shown the computational simulation of some types of stress distribution functions and its effects in the diffraction profile and numerical results of stress distribution functions obtained starting from enlargement diffraction profiles. (author)