Reflection phenomena of plane wave at an initially stressed nonlocal triclinic half-space with stress-free interface

In this study, we have investigated the reflection of plane quasi-P (qP), quasi-SV (qSV) and quasi-SH (qSH) waves at the stress-free boundary of an initially stressed nonlocal triclinic half-space. Closed-form mathematical expressions for the phase velocity, reflection coefficients and energy ratios are derived which provide a comprehensive understanding of wave behavior in this complex medium. The study addresses a significant gap in the literature by analyzing the combined effects of initial stress and nonlocal parameters which have been underexplored in previous research on wave propagation in triclinic media. Our results reveal that the reflection coefficients and energy ratios for the reflected (qP, qSV and qSH) waves are highly sensitive to the incident angle and depend on elastic constants, initial stress, and nonlocal parameters. Numerical computations are performed using Vosges sandstone as the triclinic material and the results are presented graphically. These graphs provide insights into how different material properties and boundary conditions influence wave reflection. For validation, the model is reduced to special cases and compared with pre-established results. The findings of this work contribute advance understanding of wave reflection in anisotropic media and offering potential applications in geophysics, materials science, and seismic analysis.