Discussion on miner's rule in type 304 stainless steel in air at 288degC

The effect of fluctuating stress on the fatigue strength of type 304 stainless steel in air at 288degC was examined. In any of the 2 step increasing stress, 2 step decreasing stress, repeated 2 step stress (high to low), repeated 2 step stress (low to high) and gradual increasing stress, the cumulative usage factor calculated based on the linear damage law exceeds 1. In the 2 step increasing or decreasing stress, the usage factor for the decreasing stress type is larger than the increasing stress type. On the other hand, the cumulative usage factor for the repeated 2 step stress (low to high) is larger than the repeated 2 step stress (high to law), and the usage factor increases with increasing number of cycles at the first stress. The smaller the difference between the first stress and the second stress, the larger the usage factor. In the gradual increasing stress, the usage factor increases with increasing number of cycles at each stress. (author)