Ratcheting Behavior of T225NG Titanium Alloy under Uniaxial Cyclic Stressing: Experiments and Modeling

In order to investigate the r atcheting behavior of T225NG alloy, a series of ratcheting tests under uniax ial long cyclic stressing were performed. The results show that the ratchet ing strain of this alloy can get into shakedown after tens ( or hundreds) of thousand cycles. After the ratcheting strain is saturated under the condition that str ess amplitude is half of peak str ess, it will bring about subsequent fatigue failure, and relationship between fat igue life and one of peak stress and saturated r atcheting ( SR) strain meets pow er law . As the alloy is under stress jiggling with str ess amplitude that is 1% 2 5% of peak stress, the r atchet ing str ain still become remarkable and goes into shakedown after sever al hundreds of thousand cycles but there ex ists little accessional strain caused by creep effect. It is notable that, w hen t he peak str ess is 85% 100% of yield stress, t he long cyclic str essing will lead SR str ain to be from 1 4% to 2 5% even if the initial ratio of ratcheting strain is zero. Based on ratcheting thr eshold proper ty of peak stress and monotonicity of relationship between the peak stress and SR str ain, a saturated r atcheting model ( SRM) is developed to predict SR str ain and to estimate saturated creep strain also . In addition, t he classes of r atchet ing evolutions of metals ar e discussed.