Mechanical behavior of functionally graded cantilever beams under photothermal excitation considering molecular dynamics

This paper investigates the dynamic response of Functional Graded Material (FGM) beams with surface effect immersed in liquid under high-frequency photothermal excitation. Based on the Euler–Bernoulli beam theory, the dynamic governing equations of FGM beams with surface effects are derived. The forced vibration solution is also derived using the Fourier series variable expansion method, based on the photothermal driving force and fluid dynamic load proposed by Sader. The mechanical properties of FGM with different volume distributions are predicted by molecular dynamics simulation, and the required surface parameters are calculated. The theoretical results show that the surface parameters, volume fraction index, and fluid characteristics have an important influence on the dynamic response. At the nanoscale, the surface elastic modulus and surface residual stress play a major role in the surface effect. For Cu-Ni FGM beams, the surface effect will reduce the stiffness of the beam. As the volume fraction index n increases, the decreasing effect of surface effects on beam stiffness decreases. Compared with the surface effect, the influence of the fluid environment on the frequency response of FGM beams is more stable.