Decoupling analysis of ultrasonic scattering characteristics in porous polycrystalline materials using phase field and finite element methods

Abstract

Since porous polycrystalline materials are widely encountered in various industrial applications, understanding the propagation and scattering of ultrasonic waves within these materials is crucial. We investigate the attenuation and group velocity of ultrasonic wave in porous polycrystalline models with porosities below 3 %. This work aims to decouple the contributions from grain and pore structures. The phase field method is used to generate three distinct models: porous polycrystalline models, porous models without grains, and polycrystalline models without pores. The flexibility of the phase field method allows for precise control of microstructural parameters, such as grain size, porosity, and pore size. Finite element models are then employed to assess the effects of microstructural parameters and crystal anisotropy on both attenuation and group velocity. A decoupling method is proposed to approximate the attenuation and velocity of porous polycrystalline model, using a linear combination of those of porous model and polycrystalline model. Our findings reveal that the linear combination model offers a highly accurate approximation of attenuation at lower frequencies. However, at higher frequencies, the decoupling method shows errors in attenuation predictions, particularly when the models exhibit larger microstructural parameters. In contrast, the group velocity could be well-predicted by the linear combination model. In addition, crystal anisotropy influences both attenuation and velocity, with larger Zener anisotropy indices intensifying the coupling effects. This work provides a robust methodology to decouple the effects of grain and pore structures, and it paves the way for building more precise theoretical ultrasonic scattering models in the future.