Hong-Yan Chen

This work aims at investigating the nonlinear transient response of fluid-conveying pipes made of graphene nanoplatelet (GPL)-reinforced composite (GPLRC) under blast loads and in a thermal environment. A modified Halpin–Tsai model is used to approximate the effective Young’s modulus of the GPLRC pipes conveying fluid; the mass density and Poisson’s ratio are determined by using the Voigt model. A slender Euler–Bernoulli beam is considered for modeling the pipes conveying fluid. The vibration control equation of the GPLRC pipes conveying fluid under blast loads is obtained by using Hamilton’s principle. A set of second-order ordinary differential equations are obtained by using the second-order Galerkin discrete method and are solved by using the adaptive Runge–Kutta method. Numerical experiments show that GPL distribution and temperature; GPL weight fraction; pipe length-to-thickness ratio; flow velocity; and blast load parameters have important effects on the nonlinear transient response of the GPLRC pipes conveying fluid. The numerical results also show that due to the fluid–structure interaction, the vibration amplitudes of the GPLRC pipes conveying fluid decay after the impact of blast loads.

In this paper, the nonlinear dynamic characteristics of statically piezoelectric actuated vibrating beam micro-gyroscopes are studied. The comprehensive nonlinear model including curvature, inertia and electrostatic force nonlinearities is considered. In the research of electrostatic micro-gyroscopes, it’s a novel way to tune the primary resonance by piezoelectric actuation and multiple nonlinearities. The multiple scales method and numerical continuation technique are used to characterize the frequency-amplitude and force-amplitude responses of the micro-gyroscopes. The effect of varying the size-dependent, fringing field, statically piezoelectric voltage and nonlinear curvature and inertia on the dynamic response of the micro-gyroscope is investigated in detail. The frequency-response results show that small vibrations produce a symmetrical frequency response curve in sense direction while the system actually has a significant softening characteristic in drive direction. The nonlinear multi-value problem effectively reduces in sense direction under the size-dependent effect, which plays an important role in the design of detection instruments for micro-gyroscopes. Choosing a positive piezoelectric actuation voltage will obtain a higher sensitivity. Increasing the curvature nonlinearity and reducing the inertial nonlinearity of the gyroscopic system will help the micro-gyroscope obtain better sensitivity, and may eliminate multi-valued responses as much as possible.