Power Flow Response Based Dynamic Topology Optimization of Bi-material Plate Structures

Work on dynamic topology optimization of engineering structures for vibration suppression has mainly addressed the maximization of eigenfrequencies and gaps between consecutive eigenfrequencies of free vibration, minimization of the dynamic compliance subject to forced vibration, and minimization of the structural frequency response. A dynamic topology optimization method of bi-material plate structures is presented based on power flow analysis. Topology optimization problems formulated directly with the design objective of minimizing the power flow response are dealt with. In comparison to the displacement or velocity response, the power flow response takes not only the amplitude of force and velocity into account, but also the phase relationship of the two vector quantities. The complex expression of power flow response is derived based on time-harmonic external mechanical loading and Rayleigh damping. The mathematical formulation of topology optimization is established based on power flow response and bi-material solid isotropic material with penalization(SIMP) model. Computational optimization procedure is developed by using adjoint design sensitivity analysis and the method of moving asymptotes(MMA). Several numerical examples are presented for bi-material plate structures with different loading frequencies, which verify the feasibility and effectiveness of this method. Additionally, optimum results between topological design of minimum power flow response and minimum dynamic compliance are compared, showing that the present method has strong adaptability for structural dynamic topology optimization problems. The proposed research provides a more accurate and effective approach for dynamic topology optimization of vibrating structures.

Nonlinear Dynamics Seismic Response of Container Crane Based on Contact Friction Theory

To evaluate the dynamic behavior of a container crane under seismic loads accurately,the contact state between the wheels and the rails or the ground that significantly affect the seismic response of the structure must be considered elaborately.This paper has proposed a modeling method based on the theory of contact and friction for simulating the nonlinear seismic response of large and flexible structure of a jumbo movable container crane,including the contact problem regarding the wheels attached to the bottom of its legs and the rails on which they ride.These models are used to perform extensive dynamic time-history analysis in order to find out their nonlinear dynamic behavior under various excitation modes.It is found that the presented numerical modeling method simulates the nonlinear seismic response of a container crane quite well.Notably,it can verify and expand our understanding of the seismic behaviors by evaluating response performance for the large seaport cranes.

POWER FLOW ANALYSIS FOR A NEW ISOLATION SYSTEM-FLEXIBLE FLOATING RAFT

A new model for a raft isolation system is proposed, in which the raft supports two ma- chines on a flexible foundation via a series of isolators. The interaction between the flexible floating raft and the non-rigid foundation is studied by the novel approach of power flow. The power flow input and transmitted in the complicated compound system are then formulated in closed forms, in which the coupling between the raft and the foundation is considered . The effect of the raft flexibili- ty on power flow spectra is also revcaled. This study shows that it may lead to an overoptimistic evaluation to the effectiveness of the raft isolation when simplifying the raft to an ideal rigid struc- ture. Thereby, the reliable estimation and effective design for raft isolation system are provided.

汽车悬架同步振动抑制与能量收集综述与展望

悬架是汽车中的核心关键部件,具有承载和减振的双重功能。传统的悬架系统采用黏性液体或干摩擦阻尼器将振动能量转化为热量耗散出去实现减振,造成能量浪费,这尤其对新能源汽车不利。近十年来,既能抑制振动又能收集电能的新型悬架系统受到了高度关注和广泛研究。为了全面掌握汽车悬架同步振动抑制与能量收集技术领域的最新进展,回顾汽车悬架的发展历程,总结汽车悬架从路面激励中可收集的振动能量,重点梳理汽车能量回收悬架技术研究现状,探讨当前面临的技术挑战并对未来发展方向进行了展望。该研究有助于国内同行快速准确地掌握本领域的技术现状,有望为国内新型汽车悬架技术的发展提供重要参考。

Power flow in the coupled dynamic system of machinery and building floor

The transmision mechanism of vibrational power flow in the complex flekible coupled system of machinery mouned on a multi-storey plant building via isolators are studied in this paper from the viewpoint of energy. In view of practical isolation designs in engineering,an asymmetric isolation system with mtiltiple isolators on a fiekible foundation is modeled, in which the interactions between the machine and the floor, and among different mouating points are taken illto account. Moreover, the transmission characteristics of power flow in the system concerned are analyzed with the use of subsystem mobility synthetic techaique. Further more,the power flow spectra of the asymmetric system are calculated and compared with those of symmetric one to reveal the effects of asymmetricity and system parameters on the power flow.Finally, new approaches to the control of structural vibration and acoustics for this kin of problems are proposed.

Power flow transmission influenced by vibration source impedance for a compound system

In this paper we present the effect of vibration source on the power flow transmission in a compound flexible system. Considering the internal impedance of the source, a general model is here proposed, and the generalized transfer equations of the system and the closed form solutions for power flow in the fiexible system are then developed, with which the effects of the source characteristics on power flow transmission are discussed. The investigation shows that when the source and receiver impedances are comparable, substantial error can occur in the power flow estimation if the source is assumed to be an ideal constant force source (CFS)or a constant velocity source (CVS).