Xiuchang Huang

Dynamic response of shear deformable laminated plates under thermomechanical loading and resting on elastic foundations

Abstract This paper deals with the dynamic response of shear deformable laminated plates exposed to thermomechanical loading and resting on a two-parameter (Pasternak-type) elastic foundation. The temperature field considered is assumed to be a uniform distribution over the plate surface and through the plate thickness. The material properties are assumed to be independent of temperature. The formulations are based on Reddy’s higher order shear deformable plate theory and include the plate-foundation interaction and thermal effects due to temperature rise. All four edges of the plate are assumed to be simply supported with no in-plane displacements. Analytical solutions of dynamic response for symmetric cross-ply and antisymmetric angle-ply laminated plates subjected to a transverse dynamic load and exposed to a uniform temperature rise are obtained by using the state variable approach. The numerical illustrations concern the free vibration and dynamic response of shear deformable laminated plates resting on Pasternak-type elastic foundations with the Winkler elastic foundations being a limiting case. Effects of foundation stiffness, plate side-to-thickness ratio, and temperature rise on the dynamic response are also studied.

An Analytical Method for the Response of Coated Plates Subjected to One-Dimensional Underwater Weak Shock Wave

An analytical method based on the wave theory is proposed to calculate the pressure at the interfaces of coated plate subjected to underwater weak shock wave. The method is carried out to give analytical results by summing up the pressure increment, which can be calculated analytically, in time sequence. The results are in very good agreement with the finite element (FE) predictions for the coating case and Taylor’s results for the noncoating case, which validate the method that is suitable for underwater weak shock problem. On the other hand, Taylor’s results for the coating case are invalid, which indicates a potential application field for the method. The extension of the analytical method to q-layer systems and dissipation case is also outlined.

Vibration isolation characteristics of finite periodic tetra-chiral lattice coating filled with internal resonators

Owing to their locally resonant mechanism, internal resonators are usually used to provide band gaps in low-frequency region for many types of periodic structures. In this study, internal resonators are used to improve the vibration attenuation ability of finite periodic tetra-chiral coating, enabling high reduction of the radiated sound power by a vibrating stiffened plate. Based on the Bloch theorem and finite element method, the band gap characteristics of tetra-chiral unit cells filled with and without internal resonators are analysed and compared to reveal the relationship between band gaps and vibration modes of such tetra-chiral unit cells. The rotational vibration of internal resonators can effectively strengthen the vibration attenuation ability of tetra-chiral lattice and extend the effective frequency range of vibration attenuation. Two tetra-chiral lattices with and without internal resonators are respectively designed and their vibration transmissibilities are measured using the hammering method. The experimental results confirm the vibration isolation effect of the internal resonators on the finite periodic tetra-chiral lattice. The tetra-chiral lattice as an acoustic coating is applied to a stiffened plate, and analysis results indicate that the internal resonators can obviously enhance the vibration attenuation ability of tetra-chiral lattice coating in the frequency range of the band gap corresponding to the rotating vibration mode of internal resonators. When the soft rubber with the internal resonators in tetra-chiral layers has gradient elastic modulus, the vibration attenuation ability and noise reduction of the tetra-chiral lattice coating are basically enhanced in the frequency range of the corresponding band gaps of tetra-chiral unit cells.

Modeling and Optimization of Octostrut Vibration Isolation Platform by FRF-Based Substructuring Method

AbstractThis paper addresses dynamic modeling and performs optimization of a passive multistrut vibration isolation platform (VIP) in vibration isolation for an assembly of control moment gyroscopes (CMGs). Each strut of the VIP is composed of a metal rod and a three-parameter isolator in series. First, the frequency response function (FRF)–based substructuring method was developed to establish the dynamic model of a whole satellite system. This method can take into account the influence of the flexibility of the satellite bus and the CMG assembly as well as the gyroscopic effects of CMGs. Then, an optimization model was developed, and the FRF-based sensitivity analysis was employed to optimize the characteristic parameters of a strut under two objective functions. Finally, a numerical model was developed to verify the validity and effectiveness of the proposed method. The dynamic characteristics of an octostrut VIP were analyzed. The isolation performance was greatly enhanced after optimization. This stu...

Experimental and numerical research on the underwater sound radiation of floating structures with covering layers

This paper presents experimental and numerical investigation into the underwater sound radiation characteristics of a free-floating stiffened metal box covered with three different kinds of covering layers and subjected to mechanical excitation. One box is bare while the other three are, respectively, covered with solid covering layers, chiral covering layers, and chiral covering layers filled with expanded polystyrene (EPS) foams. The equivalent elastic modulus of chiral covering layer is obtained by the homogenization theory. The finite element method and boundary element method are used to calculate the underwater sound pressure. The measured and numerical results are illustrated and the sound insulation mechanisms of three covering layers are discussed. The measured results agree with the numerical results well. The covering layers can obviously reduce the underwater sound radiation of floating structures. Compared with the solid covering layer, the chiral covering layer is less effective in suppressing the sound radiation in the low-frequency range but more effective in the medium- and high-frequency range. The chiral covering layer filled with EPS foams shows the best performance, which is more effective in suppressing the sound radiation both in the low-frequency range and in the medium-frequency range. The EPS foams have a high contribution to the added damping of the chiral covering layer.

Underwater explosion approximate method research on ship with polymer coating

Battle damage survivability is the prime design criterion of naval ships. Composites and hybrid structures such as polymer coating attract much attention to increase the ship survivability. Aiming to develop the parameter optimization design of the coating and to assess the underwater explosion shock environment and the blast-resistant effect of polymer coating efficiently, an approximate numerical method was performed in this preliminary study. An equivalent continuum model based on the homogenization theory was introduced to simulate the dynamic behavior of the coating. The test data of full-scale underwater explosion tests and the numerical simulation results were investigated. The blast-resistant property of the polymer coating was elaborated. The core strength had an important influence on the ship dynamic response: under low-intensity underwater explosion shock load, “soft” core had greater blast-resistant effect than the other ones, while under high-intensity underwater explosion shock load, “ordinary” core and “hard” core had better blast-resistant effect than the “soft” core.

Investigation into the Impact and Buffering Characteristics of a Non-Newtonian Fluid Damper: Experiment and Simulation

Dampers are widely applied to protect devices or human body from severe impact or harmful vibration circumstances. Considering that dampers with low velocity exponent have advantages in energy absorption, they have been widely used in antiseismic structures and shock buffering. Non-Newtonian fluid with strong shear-thinning effect is commonly adopted to achieve this goal. To obtain the damping mechanism and find convenient methods to design the nonlinear fluid damper, in this study, a hydraulic damper is filled with 500,000 cSt silicone oil to achieve a low velocity exponent. Drop hammer test is carried out to experimentally obtain its impact and buffering characteristics. Then a coupling model is built to analyze its damping mechanism, which consists of a model of impact system and a computational fluid dynamics (CFD) model. Results from the coupling model can be consistent with the experiment results. Simulation method can help design non-Newtonian fluid dampers more effectively.

Design scheme of a passive isotropic multi-strut vibration isolation platform constructed by three-parameter isolators based on the optimum damping frequency concept

A design procedure based on the optimum damping frequency of the three-parameter isolator is proposed to construct a passive isotropic multi-strut vibration isolation platform (VIP) with three-parameter isolators. Two steps are necessary to implement the proposed design scheme. The first step is determination of the optimal damping frequency of the three-parameter isolator; the second step is designing the isofrequency VIP with natural frequencies tuned as the optimal damping frequency in three orthogonal directions. Three methods are summarized to identify the optimal damping frequency theoretically or experimentally. A frequency response function (FRF)-based substructuring method is proposed to predict natural frequencies of the VIP in an isolation system, which accounts for the coupling between different directions and structural flexibilities. Analytical expressions of configurations to implement isofrequency VIP are derived from FRF-based substructuring method for special cases. The three-parameter isolator by employing bellows is manufactured and a hexapod VIP is built. The proposed design scheme is verified by identifying the optimal damping frequency and comparing acceleration transmissibility under vertical and horizontal base displacement excitation for varying loaded mass. The study can shed some light on the design of a passive multi-strut VIP with three-parameter isolators.

Stochastic Response Analysis of a Built-Up Vibro-Acoustic System with Parameter Uncertainties

In this paper, the quantification of uncertainty effects on stochastic responses of interior vibro-acoustic interaction systems with moderate geometry complexities and uncertain design parameters i...

Force Identification Based on Subspace Identification Algorithms and Homotopy Method

This paper addresses an inverse problem to determine dynamic forces acting on a structure from response data. Data-driven subspace algorithms and the linear regression are used to facilitate the estimation of the state sequences and system parameters. The force identification model is then reasonably established on the basis of the estimated system model. A weighted algorithm based on the homotopy analysis method is employed to discretize the well-known ill-posed problems. Moreover, a criterion based on L-curves is adopted for choosing the level of regularization. Finally, laboratory experiments are presented to demonstrate robustness and effectiveness of the proposed solution technique.