Hygrothermal mechanical behaviors of axially functionally graded microbeams using a refined first order shear deformation theory

The present work discusses mechanical behaviors of an axially functionally graded (AFG) beam in micro scales subjected to a moving mass. The AFG microbeam is exposed to hygrothermal environments with a uniform temperature rise and a moisture concentration rise. The material properties of AFG microbeam are assumed to vary along the axial direction of the beam according to a power-law function and are temperature dependent. A microbeam model is developed based on a refined first order shear deformation theory (FSDT) in conjunction with the closed-form solution technique, in which the modified couple stress theory is implemented to account for size effect. The minimum energy strategy is applied to derive the eigenvalue equations associated to buckling and free vibrations of the microbeams, while the equations of motion related to the dynamic response are obtained by adoption of Lagrange method and solved using the Newmark-beta method. A ceramic-metal AFG microbeam with simply-supported end constraints is taken as a numerical illustration to show the effects of hygrothermal environments, small scale on the mechanical behaviors of AFG microbeams subjected to a moving mass.