EFFECT OF FRICTION ON SUBSURFACE STRAIN DISTRIBUTION OF STEEL

The effect of friction on the subsurface strain distribution of a 1018 steel is investigated using a two-ball collision apparatus. After the two balls collided with each other, the friction level was recorded a nd cross sections were made of the balls to examine the surface and su bsurface damage from the collision. Various lubricants were used to co ntrol the level of friction. At frictional levels higher than 0.4, the strain angles as measured by the grain alignment method are almost pa rallel to the surface and the depth of the deformed layer is very shal low. At lower frictional levels, the strain angles are small and the d epth of the deformed layer is deep. A computer program was developed t o map the subsurface gain shape change after each collision. The grain shape reflects the shear strain angle. Results suggest there was a de finite relationship between the friction and the subsurface shear stra in angles.