Dependence of the longitudinal velocity of sound in constructional ceramicmaterials on pressure and damage rate

The effect of porosity and concentration of planar microcracks on the veloc ity of elastic waves in polycrystalline SiC, Al2O3, B4C, and ZrO2 ceramics is numerically studied. The mechanical behavior of ceramics is described us ing the model of a damaged medium. Various dependences that describe the re lationship between the effective moduli of elasticity of the medium materia l and the relative volume of damages are analyzed as applied to predicting wave dynamics. For porosities tip to 20%, a satisfactory prediction of the velocity of longitudinal waves in ceramics is ensured by the use of exponen tial and linear dependences. Within this range of porosities, the velocity of elastic waves decreases linearly with increasing relative volume of dama ges. The influence of the pulse amplitude on the velocity of elastic waves is analyzed. It is shown that the velocity of elastic waves in construction al ceramics increases in proportion to pressure tip to 5% within the range of pulse amplitudes that do not exceed the Hugoniot limit of elasticity. Nu merical values of coefficients in the relation between the velocity of the longitudinal elastic wave and the velocity of material particles are determ ined for ceramic materials considered. As the Hugoniot limit of elasticity is exceeded, the values of the coefficients decrease by 10-30% for differen t ceramic materials. The resultant values of the coefficients are in good a greement with experimental data found in the literature.