Prediction of crack propagation life of heavy duty transmission gears under different stress ratios

Multiply both sides of Paris formula by Da and integrate to obtain the formula:

By substituting the stress ratio r = 0.1 and R = 0.6 into the formula respectively, the relationship between crack length and cycle times is obtained, as shown in the formula:

The corresponding stress intensity factor parameters obtained by simulation are respectively substituted into the formula to obtain the corresponding cycle times N, and the calculated n is plotted. The relationship between the two groups of data is shown in the figure.


It can be seen from the figure that under the same crack length, the number of cycles obtained from the test is always higher than the theoretical value obtained by simulation, but there is little difference between the two. That is to say, when the sample is extended to the same crack length, the number of cycles is always calculated by using the numerical simulation method. When the numerical simulation calculation shows that the sample has been fatigue damaged, but in fact, the sample has not reached the fatigue life.

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