A photoelastic examination of the stresses in rolls during rolling

The paper describes some experiments to determine the stress distribution in rolls during the rolling of pure lead. The rolls were made from a hard transparent resin and the isochromatics and isoclinics were recorded whilst rolling was in progress. From these recordings the stress distributions were obtained. Particular reference was made to conditions of normal and shear stress at the contacting surfaces. The paper gives results for three roll diameters and for each of these four roll loads were applied. The experiments were carried out for both dry and lubricated conditions. The results of this work show a variation of the shear stress at the surface of contact accompanied by a change of sign at the neutral point. The normal roll-pressure curves are in general agreement with those found by workers using other techniques. The results also indicate a significant variation in the ratio (shear stress/normal pressure) over the contact surface, although this was decreased by lubrication. For a given roll load and diameter lubricated rolling, as opposed to dry rolling, increases the reduction but appears to have no effect on lateral spread. For a given roll load a decrease in roll diameter results in an increase in reduction, lateral spread, mean roll pressure, and friction.