Low‐cycle fatigue of 1Cr–18Ni–9Ti stainless steel and related weld metal under axial, torsional and 90° out‐of‐phase loading

Abstract

A B S T R A C TThe fatigue behaviour of base metal and weld joints of 1Cr-18Ni-9Ti stainless steel has been studied under uniaxial, torsional and 90 • out-of-phase loading. A significant degree of additional hardening is found for both base metal and weld metal under 90 • out-of-phase loading. Both base metal and weld metal have the same cyclic stable stressstrain relationship under torsional cyclic loading and 90 • out-of-phase cyclic loading. Base metal exhibits higher cyclic stress than weld metal under uniaxial loading, and Young's modulus and yield stress of weld metal are smaller than those of base metal. Weld metal exhibited lower fatigue resistance than base metal under uniaxial and torsional loading, but no significant difference was found between the two materials under 90 • out-of-phase loading. A large scatter of fatigue life is observed for weld metal, perhaps because of heterogeneity of the microstructure. The Wang-Brown (WB) damage parameter and the Fatemi-Socie (FS) damage parameter, both based on the shear critical plane approach, were evaluated relative to the fatigue data obtained.Keywords 1Cr-18Ni-9Ti stainless steel; multiaxial fatigue; welded joint. N O M E N C L A T U R Eb, c = fatigue strength exponent and fatigue ductility exponent, respectively b 0 , c 0 = shear fatigue strength exponent and shear fatigue ductility exponent, respectively E, G = elastic modulus and shear modulus, respectively HB = Brinnell hardness k = material constant in the Fatemi-Socie model S = material constant in the Wang-Brown model δ 5 = elongation ε, γ = axial strain and shear strain, respectively ε e , σ e = equivalent strain and equivalent stress, respectively ε * n = normal strain excursion on the critical plane ε f = fatigue ductility coefficient γ f = shear fatigue ductility coefficient ε, γ = axial strain range and shear strain range, respectively γ max = maxmimum shear strain range on the critical plane ν = Poisson's ratio σ , τ = axial stress and shear stress, respectively σ u = ultimate tensile strength σ f = fatigue strength coefficient σ max n = maximum normal stress in a cycle on the critical plane σ y = yield stress τ f = shear fatigue strength coefficient = reduction in areaCorrespondence: X. Chen.

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