| Abstrakt: |
Elber and Walker's effective stress intensity factor range model and Kujawski's two-parameter driving model were used for the normalization of the Crack growth curves under different stress ratios(R). These two models were applied under the condition that the stress ratio only affected the position of crack growth rate curves, but not their shapes. When crack growth curves under different stress ratio were normalized, these two models were only applicable to the intermediate-regions of crack growth threshold. A new improved two-parameter driving model was proposed, which is appropriate for intermediate-region and accelerated region of crack growth curves. In this model, the exponents are a function of these parameters: stress ratio, fracture toughness, stress intensity and the parameter calculated from the two-parameter driving model, when fatigue crack growth rate tends to infinity. The crack growth curves under different R can be normalized into one curve by using this new improved two-parameter driving model, which has different shape in the intermediate-region and accelerated region. The modified two-parameter model was verified by the fatigue crack growth data of PMMA (YB-MD-11 and YB-MD-3) and titanium alloy (Ti-1023). [ABSTRACT FROM AUTHOR] |
