It is well knovm that a characteristic plastic flow occurs when two discs are rolled together at loads exceeding the yield point; even in the case of rolling contact without slip, a deformed layer shows marked plastic flow with respect to the direction opposite to the rolling direction. This phenomenon was first found by Crook and Welch. Later, Johnson and his co-workers explained why the forward flow occurs under pure normal stresses.

The aim of the present study is to reproduce the various types of plastic flow under different testing conditions of rolling contact, such as nearly pure rolling contact, rolling contact by friction drive, and rolling-sliding contact. After a test of repeated rolling contact, the mode of plastic flow and the residual stress distribution at the surface of the specimen were observed. Further, the experimental data were compared with the result of analytical calculation by the method of Merwin and Johnson.