14th International Conference on Shot Peening

Surface Residual Stress Relaxation Of Shot-Peened Induced Stresses On Steel Din 34crnimo6 Under Different Axial Loading

Nelson Leguinagoicoa , Joseba Albizuri

Department of Mechanical Engineering, Escuela de Ingeniería de Bilbao, University of the Basque Country. Alameda de Urquijo s/n 48013, Bilbao, Spain – joseba.albizuri@ehu.eus / nleguinagoicoa@gmail.com

Introduction

Shot-peening treatment improves the rotating bending fatigue performance of DIN 34CrNiMo6 (Q+T) steel specimens due to the introduction of compressive residual stresses in the near-surface area. However, this residual stress field tends to reduce or relax under cyclic loading [1]. The fatigue performance under axial load is now studied with similar DIN 34CrNiMo6 (Q+T) specimens and SP treatment (ISP 8A & C:200%). Furthermore, relaxation of surface residual stresses is analysed under quasi-static loading (5 load levels with tensile and compressive), 4 levels of cyclic loading (R: -1) and cyclic loading (R ≠ -1) with non-zero mean stress (tensile 9 cases and compressive 4 cases).

Objectives

1) Determinate the fatigue improvement by the SP treatment on the samples compared with only machined and surface polished specimens, by comparison of SN curves. 2) Study the influence of the sign (tensile or compressive) and magnitude of the load in the quasi-static test of surface residual stress relaxation. 3) Study the surface residual stress relaxation under alternating axial cyclic loading. 4) Study the surface residual stress relaxation under axial cyclic loading with non-zero mean stress, tensile or compressive, using the relaxation mechanisms learned on quasi-statics tests and proposing an empirical model for stress relaxation prediction.