Acoustic nonlinearity parameters for transversely isotropic polycrystalline materials.

Area of Science:

• Solid Mechanics
• Materials Science
• Acoustics

Background:

• Polycrystalline materials exhibit macroscopic elastic anisotropy.
• Elastic anisotropy influences the quadratic nonlinearity parameter.
• Second harmonic generation (SHG) is a key phenomenon in nonlinear acoustics.

Purpose of the Study:

• To investigate the effect of elastic anisotropy on the quadratic nonlinearity parameter in polycrystalline materials.
• To analyze the directional dependence of nonlinearity parameters due to transversely isotropic symmetry.
• To explore the generation of SHG from shear waves in anisotropic polycrystals.

Main Methods:

• Developing theoretical estimates for longitudinal and shear wave nonlinearity parameters.
• Relating nonlinearity parameters to single-crystal elastic constants, anisotropy constants, and propagation direction.
• Presenting an inverse model to link measured nonlinearity parameters with macroscopic anisotropy constants.

Main Results:

• Elastic anisotropy leads to a directional dependence of the quadratic nonlinearity parameter.
• Anisotropy enables second harmonic generation from shear waves.
• Nonlinearity parameter estimates are provided as a function of material properties and direction.

Conclusions:

• The developed model accurately estimates nonlinearity parameters in anisotropic polycrystals.
• The findings facilitate the determination of baseline nonlinearity parameters for structural components.
• This research supports the advancement of absolute material damage assessment techniques.