Nondestructive Evaluation of Surface Properties of Sintered Si3N4 Ceramics with Surface Wave Dispersion

Elastic properties of high-performance ceramics is usually measured with ultrasonic bulk waves [1]. However, the bulk waves gives us only properties averaged over sample thickness. Sintered ceramics often have properties at the surface different from in the middle. Thus we need a method which distinguishes near surface property from the averaged one. Surface wave technique has been applied for nondestructive characterization of ceramics [2–4]. The depth-dependent properties of ceramics, however, has never been reported. Surface wave propagates in subsurface layer of about one wavelength. Therefore we’ll be able to estimate the depth-dependent properties of the ceramics, if we’ll use surface waves of different frequency or wavelength

Mandibular reconstruction and osseointegrated implants after tumour reconstruction

Acoustoelastic stress measurement has been established for bulk shear wave, in particular with birefringence of the wave. This method, however, evaluates only average stress over thickness of a sample. Some preliminary studies have been reported for local surface stress measurement with Rayleigh or leaky Rayleigh wave. An approach using an acoustic microscope operated with burst waves over 100MHz [1, 2] is markedly sensitive to surface roughness and anisotropy of grains due to very short wave length of the wave. The other approach using contact transducers needs long propagation distance [3, 4]