In this paper, the dynamic response of a spatial four-bar mechanism with a spherical clearance joint with flexible socket is investigated. Previous research treats the socket as a whole rigid part and neglects the flexibility of the socket. In order to better describe the influence of the spherical clearance joint, a rigid-flexible coupling model of a four-bar mechanism is established, in which the socket of the spherical clearance joint is treated as flexible body. The dynamic responses of this spatial mechanism are discussed for the mechanism with a flexible socket and the case with traditional rigid socket. Furthermore, the effects of clearance size and driving speed are also separately discussed. The results demonstrated that the dynamic response of mechanism is affected by the clearance joint. The socket flexibility can relieve the undesired effects of the clearance on the responses of the mechanism with clearance. The flexible socket acts as a suspension for the mechanism with clearance joint.

Vertical displacement acceleration and the pitch angle record produce the phenomenon of beat vibration when testing a 200 m electro-dynamic suspension (EDS) magnetic levitation (maglev) test vehicle with high-temperature superconducting (HTS) at the CRRC Changchun Railway Vehicles Co., Ltd., where the vehicle is clamped and in planar motion. First, to examine this phenomenon, this paper establishes dynamic equations of the vehicle with three degrees of freedom (DOF), and the levitation force on each superconducting magnet (SCM) is calculated by dynamic circuit theory. Second, the theory vertical equilibrium point is obtained from the average of the levitation force for a different velocity and the magneto-motive force (MMF) of the SCM. Third, this paper decouples SCM levitation forces from each other using MATLAB/SIMULINK, and a multi-body dynamic model with six DOF is developed in SIMPACK. All vertical displacements and acceleration responses, as well as the pitch angle and acceleration response from the simulation, appear to show the phenomenon of beat vibration since there are two closing natural frequencies of approximately 2 Hz and 2.4 Hz. Finally, based on the traversing method considering the influence of the velocity, initial vertical displacement, and the MMF of the SCM, the multi-body dynamic model is frequently utilized to study the response of the mean and amplitude of vertical displacement and that of the pitch angle. The results show that increasing the MMF or velocity could decrease the vertical displacement and pitch angle; the mean vertical displacement is a little larger than the theory equilibrium point; and the amplitude of vertical displacement is small when the initial vertical displacement is near the theory equilibrium point. Both the numerical and experimental results verify the validity of the dynamic circuit model and mechanical model in this paper.

A fatal weakness in flexible electrodes is mechanical fracture of conductive layer that occurs during repetitive stretching and bending deformation. Thereby, suppression of cracks development is crucially important for maintaining the properties of flexible electronics. Herein, topology optimization and structure design methods are utilized to greatly enhance mechanical properties of the existing island-bridge (I-B) structure. The flexible electrodes, with inner-concave honeycomb negative Poisson’s ratio (I-CHNPR) structure and I-B structure, are designed and fabricated via screen-printed process, and conductivity is thoroughly investigated. The research demonstrates that the maximum stretching and bending stress of flexible electrodes with I-CHNPR structure-C are decreased by 30% and 28%, respectively, relative to the I-B structure. Fatigue life is enhanced by 18-fold. In addition, flexible electrode has advantages of better self-recovery and excellent conductivity. The flexible electrode proposed in this article is further applicated to realize the collection of ECG signals which has the advantages of wide application, reusable and high accuracy. The as-obtained flexible electrode with the above advantages is expected to greatly contribute to the emerging research field of flexible electronics.

Controllability plays a key role in the vibration control of a structure, which can keep structural stability. In order to get practical conditions of structural controllability, two necessary conditions of controllability of a repeated eigenvalues system (regular and defective system) and their proofs are given. At the same time two sufficient conditions and their proofs are also presented. Finally we give a method of selecting control force distribution matrix B and some numerical examples.

Numerical and analytical investigations were performed to study the panel flutter generated by the coupling of elastic and aerodynamic loads with thermal loads. Based on large deflection theory and piston aerodynamic theory, the nonlinear dynamic differential equations of heated panels with pre-stretch displacement are derived. The Galerkin method is applied to transform the continuous partial differential equations into a nonlinear system of ordinary differential equations. The analytical expressions of the flutter critical dynamic pressure and flutter frequency, the static divergence stability boundary and the Hopf bifurcation fluttering stability boundary for the initial equilibrium of the panel can be obtained through the algebraic criterion of the Hopf bifurcation. The results show that, compared to the non-pre-stretch condition, when the pre-strain of the panel was merely 0.0328%, the flutter critical dynamic pressure and flutter frequency increased by 380.78% and 223.43%, respectively. Moreover, the pre-stretching method can significantly enhance the capacity of the supersonic panel to sustain temperature loads.