Residual Stress Measurements in Ti-6Al-4V and α-Brass with Sub-Surface Flaws Using X-Ray Diffraction Techniques

Abstract

This paper describes a method of characterizing sub-surface flaws by the measurement of residual stresses associated with these flaws. The residual stresses were estimated using the two angle x-ray diffraction method. The flaws were artificially formed within the material using mechanical and metallurgical (diffusion bonding) methods. Specimens with sub-surface flaws were loaded in tension and subsequently unloaded. A clear indication of spatial dependence of residual stress in the vicinity of the flaw was observed. Ti-6Al-4V and α-Brass are the two alloys used in this investigation. The origin of the residual stress is macroscopic in case of a-Brass, which is a single phase alloy as compared to the microscopic origin in case of Ti-6Al-4V, which is a two-phase alloy. Ti-6Al-4V specimens have residual stresses opposite in nature to the applied stress. Residual stress pattern around the drilled hole specimens is opposite in sign to other specimens of the same material and the residual stress distribution is insensitive to the flaw in case of the diffusion bonded specimens.