Abstract：Q235 steel U-shape notched plate specimens are taken as subject investigated. The low-cycle fatigue experiments under tension-compression loading are conducted by controlling the elongations of specimen’s gauge section, which are calculated by finite element method (FEM) prior experiments. Then the local stress-strain method is adopted to analyze the fatigue lives by test. According to the results, it is found that: whether FEM or modified Neuber method is taken to calculate stress and strain of notch root region, for fatigue life assessment the local stress-strain method is applicable only to the specimens with larger notch radius; the estimated lives obviously lower than test data for those specimens with smaller notch radius, and more serious in life estimation for the strain in notch root evaluated by FEM than by modified Neuber equation. On this basis, the effect of strain gradient for notched specimen is investigated. The famous Taylor’s model is applied to estimate the raise of yield stress and flow stress due to the high strain gradient in notch root region, by which the strain distribution of specimen is recalculated. The fatigue life estimation taken the influence of strain gradient into account is found improved for all notched specimens.
2015, Vol. 36 
