DENSITY MAPPING OF CERAMIC TILES BY COMPRESSION-WAVE ULTRASOUND

Abstract A range of disc shaped ceramic powder compact samples with controlled densities were produced using manufacturing conditions that mimic those used for industrial tile manufacture. Ultrasonic compression-wave velocity measurements were made, and a straight-line relationship was seen to exist between the ceramic sample bulk density and velocity. This relationship can be used to measure density ultrasonically. This type of relationship for powder compacts has been explained before by incorporating the density or pore fraction dependence of Young's modulus into the expression which relates compressionwave propagation velocity to Young's modulus, density and Poisson's ratio. The dependence of Young's modulus on density in the wall tile material was found to deviate from the form assumed in the theory. However, when the range of densities considered is restricted to the range typically achieved industrially, the existing theory is found to be generally applicable. Using results from production line samples it is inferred that the most significant cause of density variations is the variability in the filling and pressing operation.