محمدرضا گل بهار حقیقی

The intention of this study is to estimate fatigue damage and life of different steel alloys under uniaxial variable amplitude loading conditions based on critical plane strain-based models. Fatemi-Socie (FS) damage model evaluates fatigue lives of the samples based on the shear strain and normal stress acting on critical plane where maximum shear strain takes place. The assessment of fatigue damage by means of the Macha, Lohr and Ellisson (LE), Kandil-Brown-Miller (KBM) and Wang-Brown (WB) models are based on linear summation of shear and normal strain whereas Carpinteri-Spagnoli (CS) model involves both axial and shear strain in the nonlinear form on critical plane. A damage model that proposed by Li and sun, using the virtual normal stress range. Uniaxial variable loading spectra is counted and partitioned into the number of reversals by means of the rainflow and range-pair cycle counting methods. The largest stress and strain Mohr’s circles over the counted reversals are constructed to determine the maximum shear strain magnitude and corresponding stress to evaluate damage of each reversal. The total damage over entire loading history is then calculated based on the linear damage rule of Miner. Finally, a modification of LE model proposed by applying the mean stress effect. The predicted lives based on all damage models are compared with those of reported experimental data. Fatigue life data evaluated by modification model criterion with different descriptions show a closer agreement to the experimentally obtained fatigue lives of steel samples against the LE model.