Fracture Mechanics Approach into the Crack Growth of Si3N4 under Ball-on-Plate Contact. (Surface Crack Growth Behavior in the Center of the Contact Area).

Abstract

Surface crack growth behavior of a Si3N4 plate from small pre-indentations located in the contact center was investigated under ball-on-plate contact. Near surface stresses under the spherical Hertzian contact were calculated by the Hanson's analytical solution. The crack growth behavior was discussed in terms of the calculated stresses and the stress intensity factors both under rolling contact and under sliding-including rolling contact. The cracks were observed to grow only in a direction perpendicular to the motion of the ball. The maximum value of KI, KImax, was found to remain constant during the crack growth. The stress intensity factor ranges, ΔKII and ΔKIII, on the other hand, increase with the increase in crack length both under rolling contact and under sliding-including-rolling contact. All the stress intensity factors were increased by the friction force. It was found that the crack growth is controlled by KImax combined with ΔKII and ΔKIII. It was also found that the crack growth is promoted by the increased KImax, ΔKII and ΔKIII by the friction force under sliding-including-rolling-contact.