Effect of different shot peening conditions on the fatigue life of 300 M steel submitted to high stress amplitudes. (January 2020)

• Record Type: Journal Article
• Authors: Bag, Amrita; Delbergue, Dorian; Ajaja, Jihane; Bocher, Philippe; Lévesque, Martin; Brochu, Myriam
• Is Part Of: International journal of fatigue. Volume 130(2020)
• Publication Date: 2020-01
• Subjects: Shot peening -- Fatigue -- 300 M -- Statistical analysis -- Inclusion; CRS compressive residual stress -- HRc Rockwell hardness (C-scale) -- HV Vickers microhardness -- σy, 0.2 0.2% offset yield strength -- wt.% weight % -- σUTS ultimate tensile strength -- E Young's modulus -- υ Poisson's ratio -- %El elongation at failure -- Ra arithmetic mean roughness -- Rt distance between highest peak and deepest valley in the total evaluation length -- RSm mean spacing between successive peaks within the sampling length -- Kt, rough stress concentration factor due to surface roughness -- D average shot diameter -- V average shot velocity -- CI confidence interval -- R stress ratio -- SEM scanning electron microscope -- EDS energy dispersive spectroscopy -- XRD X-ray diffraction -- K stress intensity factor -- COD crack opening displacement -- a crack size -- da/dN crack growth rate -- (h, p) Anderson-Darling goodness of fit test coefficients -- GEV generalized extreme value -- pdf probability density function -- fLn(x) pdf of a log-normal distribution -- fGEV(x) pdf of GEV distribution -- k shape parameter -- μ location parameter -- σ scale parameter -- σs surface residual stress -- σmc maximum CRS -- xmc depth of maximum CRS -- x0 depth at which the residual stresses become tensile -- areai effective inclusion area, i.e., square root of inclusion projected area perpendicular to the loading direction -- Nf total number of cycles to failure -- ΔK stress intensity factor range -- C Paris law coefficient -- m Paris law exponent -- ΔKth threshold stress intensity factor range -- U deviation from fully open crack compliance during loading part of fatigue cycle -- ΔPeff effective load range free of crack closure -- ΔP is the closure affected load range -- Pmax, Pmin maximum and minimum load -- PO opening load -- areaR equivalent discontinuity size of a surface roughness feature -- KImax maximum stress intensity factor in opening mode I -- σmax maximum applied stress -- f location constant for inclusions -- KImax, Rt maximum stress intensity factor for surface roughness -- KImax, i maximum stress intensity factor for surface or interior inclusions -- KIc fracture toughness; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2019.105274
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: High compressive residual stresses- low roughness causes subsurface crack initiation. Low compressive residual stresses-high roughness delays short crack propagation. Stress-intensity factor-based model can predict the fatigue crack initiation site. Knowledge of material cleanliness is essential to determine benefit from peening. Sole use of statistical analysis to choose optimum peening condition can be misleading. Abstract: The axial fatigue life of 300 M steel subjected to a high stress amplitude was investigated for 3 peening conditions. Peening-induced roughness, residual stresses and their relaxation during cyclic loading were quantified. B-basis analysis was employed to compare the peened and unpeened specimens' fatigue lives. It was observed that a competition between the detrimental effect of roughness and the beneficial effect of compressive residual stresses determines the fatigue crack initiation site. A stress-intensity factor-based approach was proposed to predict a lower bound for fatigue lives. These analytical fatigue life predictions agreed with the statistical B-basis values for conditions exhibiting low scatter.