Improvement of spring fatigue strength by new warm stress double shot peening process

Abstract

Shot peening technology plays a very important role in improving the fatigue strength of springs. In the present paper a new warm stress double shot peening (WSDSP) process developed by the authors is described. The authors have previously proposed a warm stress shot peening (WSSP) process, which is a combination of warm shot peening (WSP) and stress shot peening (SSP). Double shot peening (DSP) has been the method employed most widely for improved fatigue strength to date. The fatigue strengths resulting from these shot peening processes are compared in the present work. The new WSDSP process leads to signi® cant improvement of spring fatigue strength because it includes an additional shot peening stage with small shot size (0 . 2 mm dia.), elevated temperature (300°C), and stressed condition (735 MPa), all not found in WSSP. After 300 000 cycles, the standard required life span, WSDSP results in a fatigue strength as high as 735+ 590 MPa. In comparison, DSP gives a fatigue strength of 735+ 300 MPa and WSSP of 735+ 500 MPa. The WSDSP treated material gives the highest performance because the use of small shot size for the additional warm stress shot peening increases the compressive residual stress and hardness near the surface, and decreases the surface roughness.MST/4882

Effect of prestress state on surface layer characteristic of S30432 austenitic stainless steel in shot peening process

“…Shot peening as an important mechanical surface treatment is widely used in industry to enhance the fatigue performance and damage tolerance of treated components [1][2][3][4]. The process of shot peening involves the bombardment of the treated surface with a stream of small hard spherical media.…”

Plasticity Effects in the Hole-Drilling Residual Stress Measurement in Peened Surfaces

“…The incremental hole-drilling technique (IHD) is a widely established technique for measuring residual stresses induced by mechanical surface treatments, such as laser peening, shot peening, stress peening, warm peening, or a combination of these processes [1]. Laser peening, for example, due to the development of laser technology, imparting deeper layer with beneficial residual compressive stress and decreasing surface roughness, improving fatigue and corrosion resistance, has received particular attention of the aeronautical and aerospace industries in recent years [2].…”

Positron annihilation study of aluminum, titanium, and iron alloys surface after shot peening

“…It is known that shot peening changes the macroscopic material properties of many materials. The influence of shot peening conditions on Vickers microhardness and residual stresses distributions was described for spring steel [7]. The results of the research on the residual stresses in shot-peened steels and aluminum alloy specimens are presented in [8] (e.g., the maximum compressive residual stress and the depth of the residual stress field).…”