Frequency manipulation of a light-activated shape-memory polymer-laminated cylindrical shell

A light-activated shape-memory polymer is a novel smart material that exhibits a dynamic Young's modulus when exposed to light. The non-contact actuation feature facilitates the lamination of a light-activated shape-memory polymer on host structures for realising frequency control. In this study, we investigated the natural frequency of a simply supported cylindrical shell coupled with light-activated shape-memory polymer patches located arbitrarily on the shell. Initially, we compared the natural frequency of a completely laminated cylindrical shell using two different approaches. Further, we analysed the effect of changes in the length and location of the light-activated shape-memory polymer patch pair on the natural frequency of the cylindrical shell. Based on the experimental results, we propose an optimal scheme, wherein several light-activated shape-memory polymer patch pairs are distributed on the surface of the shell, and the frequency control capability of the proposed scheme is evaluated comprehensively. The results verify that the optimal scheme has an adequate control effect on the natural frequency of the cylindrical shell.

A New Conjugate Gradient Method and Application to Dynamic Load Identification Problems

In this paper, a modified conjugate gradient (MCG) algorithm is proposed for solving the force reconstruction problems in practical engineering. This new method is derived from a stable regularization operator and is also strictly proved using the mathematical theory. Moreover, we also prove the sufficient descent and global convergence characteristic of the newly developed algorithm. Finally, the proposed algorithm is applied to force reconstruction for the airfoil structure and composite laminated cylindrical shell. Numerical simulations show that the proposed method is highly efficient and has robust convergence performances. Additionally, the accuracy of the proposed algorithm in identifying the expected loads is satisfactory and acceptable in practical engineering.

Research on nonlinear vibration control of laminated cylindrical shells with discontinuous piezoelectric layer

In this paper, the nonlinear vibration control of the piezoelectric laminated cylindrical shell with point supported elastic boundary condition is analyzed, in which the geometric nonlinearity is considered by the first-order shear nonlinear shell theory. In the model, different boundary conditions are simulated by introducing a series of artificial springs. The elastic-electrically coupled differential equations of piezoelectric laminated cylindrical shells are obtained based on the Chebyshev polynomials and Lagrange equation, and decoupled by using the negative velocity feedback adjustment. Later, the Incremental Harmonic Balance Method (IHBM) is deduced, and the frequency-amplitude response of the piezoelectric laminated cylindrical shell is obtained by IHBM. Finally, the influence of the constant gain, size and position of the piezoelectric layer on frequency-amplitude response are investigated. The results show that the position, size and constant gain of the piezoelectric layer have a significant influence on its nonlinear vibration control.

Free Vibration Analysis of Closed Moderately Thick Cross-Ply Composite Laminated Cylindrical Shell with Arbitrary Boundary Conditions

A semi-analytic method is adopted to analyze the free vibration characteristics of the moderately thick composite laminated cylindrical shell with arbitrary classical and elastic boundary conditions. By Hamilton’s principle and first-order shear deformation theory, the governing equation of the composite shell can be established. The displacement variables are transformed into the wave function forms to ensure the correctness of the governing equation. Based on the kinetic relationship between the displacement variables and force resultants, the final equation associated with arbitrary boundary conditions is established. The dichotomy method is conducted to calculate the natural frequencies of the composite shell. For verifying the correctness of the present method, the results by the present method are compared with those in the pieces of literatures with various boundary conditions. Furthermore, some numerical examples are calculated to investigate the effect of several parameters on the composite shell, such as length to radius ratios, thickness to radius ratios and elastic restrained constants.