Relations between the damage in and microstructure of ceramics

Abstract

Crack growth in brittle materials is accompanied by a non-linear process zone which increases in volume as a consequence of microcracking. Microcracking is initiated by internal stresses. More appropriate than the microcrack porosity are local parameters such as the length, orientation and elastic interaction of the microcracks. Apart from the local parameters the integral parameters of the damage zone such as the elastic and fracture parameters determine the failure of a component. The microcrack porosity correlates with the microstructure. The equilibrium between the external and internal forces inside the damage zone correlates with microstructural features such as the grain size distribution. Thus the crack and/or fatigue resistance of a brittle material can be optimized by proper selection of the residual strains, i.e. of the phase content and the grain and pore size distribution as well as the loading conditions. These factors determine the local and integral mechanical parameters of the frontal damage zone.