Abstract
This study investigates and compares the effects of different shot peening treatments including conventional and severe shot peening on microstructure, mechanical properties, fatigue behavior, and residual stress relaxation of AISI 1060 steel. Shot peening treatments were applied with two Almen intensities of 17 and 21 A and a wide ranges of coverage (100%–1500%). Various microstructural observations were carried out to analyze the evolution of microstructure. Microhardness, residual stress and surface roughness measurements and also axial fatigue test were performed. Moreover, the extent of the residual stress relaxation during cyclic loading was investigated by means of XRD measurements. Furthermore, numerical simulation of residual stress relaxation due to fatigue loading was carried out and validated against experimental investigations. The comparison indicated a good agreement for the surface residual stress relaxation up to 100 cycles. The experimental results indicated the efficiency of severe shot peening processes in obtaining nanostructured surface layer and achieving superior mechanical properties and fatigue behavior. Also, residual stress measurements revealed that stress relaxation started with a high rate at the initial stages of loading and gradually increased at higher number of cycles which was lower in the case of severely shot peened samples compared to the conventionally treated ones.Graphic
Highlights
Most failures and fractures in engineering components initiate from the surface, and the mechanical and metallurgical properties of the components’ surface play an important role in their service lifetime [1]
Cross-sectional field emission scanning electron microscopy (FESEM) observations of the as-received and shot peened specimens with different treatments indicate that the depth of the highly deformed layer that corresponds to the grain refined level is increasing by enhancing of kinetic energy of the Shot peening (SP) treatment
Six different shot peening treatments including 17A and 21A Almen intensities with surface coverages of 100, 700, 1500, 2000 and 3000% were performed
Summary
Most failures and fractures in engineering components initiate from the surface, and the mechanical and metallurgical properties of the components’ surface play an important role in their service lifetime [1]. The increased density of microstructural defects, their annihilation and rearrangement, result in formation of finer grain structure These changes can be made by two types of SP treatment including conventional shot peening (CSP) and severe shot peening (SSP) that depend on the main parameters of the SP process (i.e., Almen intensity and coverage). SSP process, on the other hand, using unconventional high Almen intensities and coverage, has been employed to introduce more compressive residual stresses and to refine the grains of the treated material surface layer [18]. The fatigue behavior of the specimens was investigated under axial fatigue loading and the residual stress relaxations of the both CSP and, SSP were studied and compared in the surface and depth. In order to investigate the efficiency of the numerical method as an alternative approach, a novel finite element (FE) simulation was developed to study the residual stress relaxation in shot peened specimens under cyclic loading
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