Hongxing Hua

Bending–torsional coupled dynamic response of axially loaded composite Timosenko thin-walled beam with closed cross-section

Abstract An analytical method is presented to determine the bending–torsion materially coupled dynamic responses of axially loaded composite thin-walled beam with solid or thin-walled closed cross-section subjected to various kinds of concentrated and distributed time-dependent loads. The effects of axial force, shear deformation and rotary inertia are included in the present study. The bending–torsion material coupling of practical interest is also considered in the formulations. First, the general governing differential equations of motion of axially loaded composite Timoshenko beam are developed and the free vibration analysis is performed. Once the natural frequencies and mode shapes of the composite beam are obtained, normal mode method is used to compute the bending–torsion coupled dynamic response of axially loaded composite Timoshenko beam. Finally, the proposed method is illustrated by its application to a particular example to investigate the effects of bending–torsion coupling, axial force, shear deformation and rotary inertia on the dynamic behavior of composite beam.

Modal parameter identification through Gabor expansion of response signals

Abstract A new method of identifying modal parameters by decomposing response signals with Gabor transform is presented in this paper to estimate natural frequencies, damping ratios and mode shapes of linear time invariant systems. According to Gabor expansion theory, responses of a multi-degree-of-freedom system can be decomposed into uncoupled signal components, each vibrating at a single natural frequency. From these uncoupled signals, modal parameters are subsequently extracted with common methods. The proposed method can process stationary and non-stationary responses and requires no input signal except for the response signals generated by unknown excitation acting on a system. In the sense of less restriction on the in–out signals, the approach based on time–frequency decomposition is very general. A simulation study on a simply supported beam under non-stationary excitation has demonstrated that the proposed method is effective in parameter estimation.

Acoustic Radiation From an Infinite Laminated Composite Cylindrical Shell With Doubly Periodic Rings

Acoustic radiation from a point-driven, infinite fluid-loaded, laminated composite shell, which is reinforced by doubly periodic rings, is investigated theoretically. The theory is based on the classical laminated composite shell theory, the Helmholtz equation, and the boundary conditions at the shell-fluid interface as well as at the junctions between the shell and the rings. The rings interact with the shell only through normal forces. The solution for the radial displacement in wave number domain is developed by using Mace’s method (1980, “Sound Radiation Form a Plate Reinforced by Two Sets of Parallel Stiffeners,” J. Sound Vib., 71(3), pp. 435‐441) for an infinite flat plate. The stationary phase approximate is then employed to find the expression for the far-field pressure. Numerical results are presented for discussion of the effects of lamination schemes, Poisson’s ratios, ply angles, and damping on the far-field acoustic radiation, which may lend themselves to better understanding the characteristics of acoustic radiation from the laminated composite shells. In addition, the helical wave spectra of the stiffened cylinders are presented, in which the effects of wave number conversion due to the periodic rings are obviously identified as additional bright patterns. DOI: 10.1115/1.2980376

Stochastic vibration of axially loaded monosymmetric Timoshenko thin-walled beam

Abstract An analytical method is presented to perform the flexure–torsion coupled stochastic response analysis of monosymmetric axially loaded Timoshenko thin-walled beam subjected to various kinds of concentrated and distributed stochastic excitations with stationary and ergodic properties. The effects of warping stiffness, axial force, shear deformation and rotary inertia are included in the present formulations. First, the damped general governing differential equations of motion of axially loaded Timoshenko thin-walled beam are developed and the free vibration analysis is performed. Once the natural frequencies and mode shapes are obtained, mode superposition method in conjunction with receptance method is used to compute the mean square displacement response of the axially loaded thin-walled beam. Finally, the method is illustrated by its application to two test examples to investigate the effects of warping stiffness, axial force, shear deformation and rotary inertia on the stochastic response of the thin-walled beams.

Dynamic Stiffness Analysis of a Beam Based on Trigonometric Shear Deformation Theory

The dynamic stiffness matrix of a uniform isotropic beam element based on trigonometric shear deformation theory is developed in this paper. The theoretical expressions for the dynamic stiffness matrix elements are found directly, in an exact sense, by solving the governing differential equations of motion that describe the deformations of the beam element according to the trigonometric shear deformation theory, which include the sinusoidal variation of the axial displacement over the cross section of the beam. The application of the dynamic stiffness matrix to calculate the natural frequencies and normal mode shapes of two rectangular beams is discussed. The numerical results obtained are compared to the available solutions wherever possible and validate the accuracy and efficiency of the present approach.