Impact of low and high frequency on reflection phenomena in plane wave propagation governed by the Moore–Gibson–Thompson model

This study investigates the propagation and reflection of harmonic plane waves in a homogeneous, isotropic, heat-conducting elastic medium governed by the Moore–Gibson–Thompson (MGT) thermoelasticity model. Using a perturbation technique for frequency-dependent analysis, we examine two coupled longitudinal waves—CP-type (elastic-dominant) and CT-type (thermal-dominant)—which exhibit dispersion and attenuation, while the uncoupled SV-type shear wave remains non-dispersive and undamped. At low frequencies, the CP-wave phase speed decreases by ∼4.6% and its attenuation rises by 15% as the thermoelastic coupling constant increases from 0.01 to 0.1. At high frequencies, the CT-wave attenuation is ∼40% lower than the CP-wave, indicating enhanced long-range energy transport. Reflection of CP-waves at rigid boundaries under insulated and isothermal conditions is analyzed, with copper showing a CT-wave reflection peak of 0.68 at ∼65° incidence, highlighting significant mode conversion. This work, focusing solely on the MGT model without non-local effects, provides quantitative insights into wave behavior, relevant for ultrasonic testing, seismic modeling, and thermal stress management.