Fracture Mechanics Approach into the Crack Growth Behavior in Ceramics under Ball-on-Plate Rolling Contact

Surface crack growth behavior of a Si I D23个D 2 N个D 24个D 2 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.1。Crack Driving Forces under Ball-on-Plate ContactThe cracks were observed to grow only in a direction perpendicular to the motion of the ball.The maximum value of K II D2，K D2 Imax D2，was found to remain constant during the crack growth.The stress intensity factor ranges，KⅡD2ⅡD2 and KⅡD2，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 K I D2 Imax D 2 combined with K I D2 II II D 2 and K I D 2 III文件D 2.It was also found that the crack growth is promoted by the increased K I D2 ImaxⅡD2，KⅡD2 and KⅡD2 by the friction force under sliding-including-rolling contact.2.Crack Growth Behavior under Shear StressIt was found that the crack was grew by the shear stress under spherical Herzian contact，whereas KⅡD2IⅡD2 and KⅡD2 IIIⅡD2 were superimposed with the phase shifted.The crack propagation tests under shear stress were carried out with the use of a bending-torsion testing machine.It was found that the cracks were propagated by the lower K I D2 II I D2 than that caused by the spherical Hertzian contact.Therefore，it was concluded that the crack propagated in mode II under spherical Hertzian contact.

Surface crack growth behavior of a SiィイD23ィエD2NィイD24ィエD2 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.1. Crack Driving Forces under Ball-on-Plate ContactThe cracks were observed to grow only in a direction perpendicular to the motion of the ball. The maximum value of KィイD2IィエD2, KィイD2ImaxィエD2, was found to remain constant during the crack growth. The stress intensity factor ranges, △KィイD2IIィエD2 and △KィイD2IIIィエD2, 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 KィイD2ImaxィエD2 combined with △KィイD2IIィエD2and △KィイD2IIIィエD2. It was also found that the crack growth is promoted by the increased KィイD2ImaxィエD2, △KィイD2IIィエD2and △KィイD2IIIィエD2 by the friction force under sliding-including-rolling contact.2. Crack Growth Behavior under Shear StressIt was found that the crack was grew by the shear stress under spherical Herzian contact, whereas KィイD2IィエD2KィイD2IIィエD2 and KィイD2IIIィエD2 were superimposed with the phase shifted. The crack propagation tests under shear stress were carried out with the use of a bending-torsion testing machine. It was found that the cracks were propagated by the lower △KィイD2IIィエD2 than that caused by the spherical Hertzian contact. Therefore, it was concluded that the crack propagated in mode II under spherical Hertzian contact.