Experimental investigation on the subsurface stress distributions in specimens with different strengths after ultrasonic impact treatment

Ultrasonic impact treatment (UIT) was carried out on three specimens with different strengths and, to measure the subsurface stress distribution of the specimens, the layer-by-layer removal x-ray diffraction method was applied. The stress redistribution due to material removal was corrected by finite element analysis. The effect of material strength on the after-UIT subsurface stress was investigated. The results show that the UIT can cause a compressive stress layer with a depth of over 2.5 mm for specimens with different strengths, while the material strength has no significant effect on the depth of UIT-induced stress. The UIT-induced peak compressive stresses in the three specimens exceed the material yield strength, appearing at the depth of 0.2 mm beneath the surface and increasing with the increase of material yield strength. The ratio of UIT-induced peak compressive stress magnitude to material yield strength decreases with the increase of material yield strength.