Characterization of Complex Materials with Elastic Discontinuities using Scanning Acoustic Microscopy

Open Access
Author:
Li, Xin
Graduate Program:
Acoustics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 27, 2014
Committee Members:
  • Richard Laurence Tutwiler, Thesis Advisor
  • Judith Todd Copley, Thesis Advisor
  • Bernhard R Tittmann, Thesis Advisor
Keywords:
  • scanning acoustic microscopy
  • non-distructive evaluation
  • V(z) curve
Abstract:
Joining ceramics to metals is difficult because of residual stresses that can develop during the cooling process. Scanning acoustic microscopy (SAM) is a well-recognized tool to characterize the elastic properties of materials and can be applied to materials with elastic discontinuities such as the interface of a ceramic/metal joint. Acoustic information was obtained by applying the V(z) curve method, which measured the output signal of the transducer as a function of the position, z. The velocity of the surface acoustic waves, V_saw, of the material was calculated from the $V(z)$ curve. In this work, a simulation of the V(z) curve was updated. The pupil-function splitting method was combined with the angular-spectrum approach of V(z) theory in order to obtain the V(z) curve for the interface between different materials. The V_saw value at the interface was calculated from the simulated V(z) curve. A series of experiments were performed to measure the V_saw values at the interface of a Si3N4/Cu joint using the SAM. By comparing the measured values with the calculated values, the reliability of this simulation was verified. The simulation can be used to test the boundary conditions of bimaterial samples.