Peening

About: Peening is a research topic. Over the lifetime, 5538 publications have been published within this topic receiving 73073 citations.

Effects of fatigue and fretting on residual stresses introduced by laser shock peening

Abstract: The effects of fatigue and fretting fatigue on the distribution of residual stresses in shot and laser shock peened Ti–6Al–4V samples have been investigated. Residual elastic strains have been determined using high-energy synchrotron X-ray diffraction. Laser shock peening introduces a considerable compressive residual stress, the compressive zone extending 1.5 mm below the surface. The effects of fatigue loading have been investigated using a notched three-point bend geometry. The residual stress field was found to be largely insensitive to fatigue cycling, at least for the applied stress range studied. For fretting fatigue, while the residual stresses at depth were little affected, within 0.5 mm of the surface significant stress relaxation was observed; the extent of relaxation being greatest in the direction parallel to the fretting direction. The states of residual stress have been quantified using the concept of eigenstrain, which quantifies the retained plastic misfit resulting from peening. Finite element modeling has been used to determine the eigenstrain profiles causing the measured elastic strain profiles, and the changes to these eigenstrain profiles due to fretting. Our results suggest laser shock peening confers much greater fretting fatigue resistance than traditional shot peening alone due to the much deeper compressive zone.

Ultrafine-grained textured surface layer on Zr–1%Nb alloy produced by ultrasonic impact peening for enhanced corrosion resistance

Abstract: An ultrafine-grained (UFG) surface layer was produced on Zr–1%Nb alloy using severe plastic deformation process induced by ultrasonic impact peening (UIP). XRD analysis and TEM observations allow establishing the links between the microstructure formed at different extents of the effective strain ē and superficial microhardness and corrosion resistance. In the topmost surface layer about 10 μm thick, average grain size diminishes down to approx. 100 nm after the UIP process for 4 min ( ē ≈ 0.86). The mechanism of the grain subdivision is discussed on the basis of TEM observations of microstructure in surface layer at different strain extents with taking into account the dynamic recrystallization process facilitated by deformation induced heating. XRD analysis reveals high compressive residual stresses and strong basal texture. Two features of the surface layer formed after the UIP process, viz. UFG structure and strong basal texture, are considered to play the major roles in essential increase in microhardness (from 1 to 2.35 GPa) and corrosion resistance of the Zr-1%Nb alloy in saline solution. Decreased surface roughness and large compressive residual stresses also promote higher corrosion resistance.