Fatigue Strength And Residual Stress Distribution Of The Work-softened Steel By Shot Peening

Author:  Iida, K. and Tosha, K.
Source:  Conf Proc: ICSP-4, (p.233-242)
Doc ID:  1990031
Year of Publication:  1990
Work-softening and work-nonhardening phenomena generally happen under combined cold deformation, and these phenomena also appear under shot peening. This paper described on the results of the relation between the residual stress distribution and fatigue strength of work-hardened, work-softened and work-nonhardened steels produced by shot peening. Shot peening was performed for carbon steel (0.45%C) with steel shot and a centrifugal blasting machine. Test specimen was rolled as prestrain before shot peening for work-softening and work-nonhardening on the hardness distributions, and ratio of rolling reduction estimated 10 % and 20 %. Obtained factors are hardness distribution, half width, residual stress distribution and S-N curves. Residual stress distribution was measured by window method with X-ray diffraction. The depth of work-softened layer is similar to the depth of work-hardened one. Half width decreased in the work-softened layer and then this suggests the recover of the prestrain by shot peening. The fatigue strength of work-softened specimens increased 53 % and 44 % compared with to prestrained and annealed respectively, and of the specimens which disclosed at surface the maximum work-softened zone by etching were also increased 20 % and 13 % respectively. Generally, the more the surface residual stress, the more the fatigue strength under the same shot peening condition. Descriptors: Shot peening; Work-hardening; Work-nonhardening; Work-softening; Half width; Residual stress; Stress distribution; Hardness distribution; Fatigue strength

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