New pseudo stress correction method for estimating local strains at notch under multiaxial cyclic loading

• Published in: International journal of fatigue 2017-10, Vol.103, p.280-293
• Main Authors: Tao, Zhi-Qiang, Shang, De-Guang, Sun, Yu-Juan
• Format: Article
• Language: English
• Subjects: Constitutive equations; Constitutive relationships; Correlation analysis; Cyclic loads; Elastic-plastic; Elastoplasticity; Hardening; Iterative methods; Materials fatigue; Mathematical models; Methodology; Methods; Multiaxial cyclic loading; Non-proportional hardening; Notched component; Strain; Stress-strain; Stress-strain curves; Stress-strain relationships; Stresses; Titanium alloys; Titanium base alloys
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2017.06.010

•A new method is proposed to calculate notch elastic-plastic stresses and strains.•The advantage of the proposed method is that it does not require iteration.•Pseudo stress increments can be directly corrected to obtain real stress increments.•Correction doesn’t limit the direction and magnitude of real backstress increment.•Utilizing pseudo notch strains to estimate non-proportionality factor is proposed. A notch correction method is proposed under multiaxial cyclic loading, in which the real stress increments can be directly obtained by correcting the pseudo stress increments at the notch. Moreover, the proposed method does not inherently restrict the direction and magnitude of real backstress increment in the real stress space. Additionally, on the basis of Kanazawa et al.’s model, the proposed method utilizes pseudo notch strains in replacement of measured strains to take account of the additional hardening due to the non-proportionality of external loadings. Based on the proposed correction method integrated with constitutive equations using Garud’s hardening model, a notch stress-strain estimation methodology is developed to calculate the local elastic-plastic stress-strain responses at the notch area. The presented methodology does not require iteration. The applicability of the presented methodology was verified by the experimental data of TC21 titanium alloy notched tubular specimens in this study and SAE 1070 steel notched shaft specimens from the literature. The results showed that the calculated notch strains correlate well with the measured strains under proportional and non-proportional loadings.