Author(s)

K. Kusukawa & K. Takao

Abstract

Rotating bending fatigue tests have been carried out on a notched commer- cially pure titanium pre-strained by 0% and 10% in tension. The result of fatigue tests shows that a pre-strained titanium has long fatigue life compared to an annealed one in the range of finite life. Conversely, the fatigue limit of pre-strained decreases by 12%. The notch sensitivity of an annealed one is very low, however, it increases due to pre-straining. No non-propagating macro crack is observed, but some microscopic non-propagating cracks are observed on a sharp notch with a radius of 0.25mm. The crack initiation behavior was investigated through successive observations. On the surface of annealed one, multiple micro cracks initiated along slip bands, within a few grains in contact at a notch and join together to grow beyond grain bound- aries. On the ot

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