A B S T R A C T Flaking type failure in rolling-contact processes is usually attributed to fatigue-induced subsurface shearing stress caused by the contact loading. Assuming such crack growth is due to mode II loading and that mode I growth is suppressed due to the compressive stress field arising from the contact stress, we developed a new testing apparatus for mode II fatigue crack growth. Although the apparatus is, as a former apparatus was, based on the principle that the static K I mode and the compressive stress parallel to the precrack are superimposed on the mode II loading system, we employ direct loading in the new apparatus. Instead of the simple four-point-shear-loading system used in the former apparatus, a new device for the application of a compressive stress parallel to the pre-crack has been developed. Due to these alterations, mode II cyclic loading tests for hard steels have become possible for arbitrary stress ratios, including fully reversed loading (R = −1); which is the case of rolling-contact fatigue. The test results obtained using the newly developed apparatus on specimens made from bearing steel SUJ2 and also a 0.75% carbon steel, are shown.

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