| Abstract | Velocity and mass sensitivity formulae in explicit form for shear-horizontal (SH) plate wave sensors are presented. The sensor geometry consists of an isotropic plate of thickness b and an isotropic thin layer of thickness h. The mass loading layer is assumed to be acoustically thin (h ≪ λ), where λ is the acoustic wavelength. The mass loading sensitivity, Sᵛₘ, of the sensors used in velocity measurements decreases by a factor of (1 − C₂) for all the SH modes due to the effects of the elasticity of the mass loading layer, where C₂ = V²ₛ₂/V²ₛ₁, Vₛ₁ and Vₛ₂ are the shear wave velocities of the two materials, respectively. Because of the inertial effect of the mass loading layer, Sᵛₘ decreases by a factor of (1 + ρ₂h/ρ₁b)⁻¹ for the lowest order mode and by a factor of (1 + 2ρ₂h/ρ₁b)⁻¹ for the other modes, where ρ₁ and ρ₂ are the density of the plate and the loaded mass layer, respectively. We also show that the relation Sᵛₘ = (V/Vg)Sᶠₘ is valid for the composite case, where Sᶠₘ is the sensitivity formula for sensors configured in resonant frequency measurements, and V and Vg are the phase and group velocity of the SH plate modes, respectively. |
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