Surface tilting effects on elastic constants in acoustic microscopy investigations

Using the acoustic ray model for planar surfaces in acoustic microscopy, the influence of the surface inclination, α, of a specimen on the elastic constants is investigated via approximative and exact methods. It is found that the Young´s and shear moduli vary with surface tilting. A shift of up to 20% is predicted for a 30° inclination. A universal analytical formula of the form ΔG_a /G=ΔE_a/E=1-cosα is derived and a reference curve, to determine the exact values of these constants, is established for all materials