In this paper, the fracture toughness of materials, , effects on fatigue crack propagation that can be quantified using the dynamical coefficient mechanics (DCM) model. And we can not only change the material with high value, but also should take other methods into consideration to decrease the fatigue crack growth (FCG) rate when replacing material can’t obviously decrease the FCG rate, which were examined objectively by the test results from literature.

In this paper we first review the inertial effect coefficient model for fatigue crak growth (FCG) under constant amplitude (CA) loading based on static fracture mechanics with thinking about the inertial effect coefficient and its impact to crack tip, and then discuss the relation between threshold stress intensity factor (Kth) and fatigue crak growth rate, which is in good agreement with the result by analysing the relation between dynamical coefficient and fatigue crak growth rate. Comparison of the present analysis with experimental data taken from the literature demonstrates that threshold stress intensity factor (Kth) has a greater impact to the fatigue crack propagation.

The effect of the load ratio, R, or the mean-stress on fatigue life has been recognized for more than a hundred years. In this paper we first describe a novel mechanics model for fatigue crak growth (FCG) under constant amplitude (CA) loading based on static fracture mechanics with thinking about the inertial effect coefficient and its impact to crack tip, and then discuss the relation between R-ratio and fatigue crak growth rate. Comparison of the present analysis with experimental data taken from the literature demonstrates that R-ratio has a greater impact to the fatigue crack propagation.

Since the pioneering work of Paris and Erdogan (1963), the fatigue crack growth (FCG) model has been being modified by worldwide researchers. Research efforts have been devoted by a number of investigators for assessing the fatigue condition of structural components by means of residual stress at the crack tip, threshold stress intensity factor, load ratio, and so on. The parameter C is always as a constant about material and structure, and almost no further research on it. In this paper, we proposed a novel analytical approach to predict the effect of the parameter C on fatigue performance. The inertial effect coefficient model for FCG under constant amplitude (CA) loading is briefly described and then used to verify the parameter C is a variable and analyze the relation between the parameter C and FCG rate. The prediction of the parameter C in this model is in good agreement with experimental data taken from the literature.

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