✍ Scribed by H. Wu; Y. Oshida; S. Hamada; H. Noguchi
No coin nor oath required. For personal study only.
In order to safely use precipitation strengthening type A286 stainless steel in high cycles, the fundamental fatigue strength characteristics were investigated using fatigue tests at room temperature. During the fatigue test, the author paid attention to the behaviour of small fatigue cracks in order to clarify the fatigue strength properties in more detail than the usual fatigue test. As a result of the fatigue test, the fatigue strength characteristic of the A286 steel became clarified as shown below. The fatigue strength ratio of the A286 steel is lower than 0.5 which is the ratio value of most steels. The cracks propagate which result in a failure even after 10 7 cycles. It was found that there are two crack mechanisms propagation of the A286 steel; i.e., in a high load-stress, the cracks monotonously propagate and result in failure. Under a low load-stress, the cracks intermittently propagate even after 10 7 cycles. The non-propagating cracks coalesce with a new crack which initiates near the crack tip and it becomes longer, finally resulting in a failure. This is the reason why the fatigue failures occur even after 10 7 cycles.
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