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Stability analysis of a noise control system in a duct by using delay differential equation

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Acta Mechanica Sinica 2009年第1期25卷 131-137页

作者： Masakazu Haraguchi moe key laboratory of structure mechanics and control for aircraft Nanjing University of Aeronautics and Astronautics

The paper deals with the criteria for the closed- loop stability of a noise control system in a duct. To study the stability of the system, the model of delay differential equation is derived from the propagation of acoustic wave governed by a partial differential equation of hyperbolic type. Then, a simple feedback controller is designed, and its closed- loop stability is analyzed on the basis of the derived model of delay differential equation. The obtained criteria reveal the influence of the controller gain and the positions of a sensor and an actuator on the closed-loop stability. Finally, numerical simulations are presented to support the theoretical results.

关键词： Stability analysis Delay differential equation Closed-loop stability Noise control Acoustic system

Parameter identification of hysteretic model of rubber-bearing based on sequential nonlinear least-square estimation

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Earthquake Engineering and Engineering Vibration 2010年第3期9卷 375-383页

作者： Yin Qiang Zhou Li Wang Xinming moe key lab of structure mechanics and control for aircraft Institute of Structures ＆ Strength Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

In order to evaluate the nonlinear performance and the possible damage to rubber-bearings （RBs） during their normal operation or under strong earthquakes, a simplified Bouc-Wen model is used to describe the nonlinear hysteretic behavior of RBs in this paper, which has the advantages of being smooth-varying and physically motivated. Further, based on the results from experimental tests performed by using a particular type of RB （GZN 110） under different excitation scenarios, including white noise and several earthquakes, a new system identification method, referred to as the sequential nonlinear least- square estimation （SNLSE）, is introduced to identify the model parameters. It is shown that the proposed simplified Bouc- Wen model is capable of describing the nonlinear hysteretic behavior of RBs, and that the SNLSE approach is very effective in identifying the model parameters of RBs.

关键词： parameter identification rubber-bearing hysteretic behavior Bouc-Wen model sequential nonlinear least- square estimation

Costate estimation for dynamic systems of the second order

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Science China(Technological Sciences) 2009年第3期52卷 752-760页

作者： WEN Hao JIN DongPing HU HaiYan Institute of Vibration Engineering Research MOE Key Lab of Structure Mechanics and Control for AircraftNanjing University of Aeronautics and AstronauticsNanjing 210016China

The dynamics of a mechanical system in the Lagrange space yields a set of differential equations of the second order and involves much less variables and constraints than that described in the state space. This paper presents a so-called Legendre pseudo-spectral (PS) approach for directly estimating the costates of the Bolza problem of optimal control of a set of dynamic equations of the second order. Under a set of closure conditions, it is proved that the Karush-Kuhn-Tucker (KKT) multipliers satisfy the same conditions as those determined by collocating the costate equations of the second order. Hence, the KKT multipliers can be used to estimate the costates of the Bolza problem via a simple linear map- ping. The proposed approach can be used to check the optimality of the direct solution for a trajectory optimization problem involving the dynamic equations of the second order and to remove any conver- sion of the dynamic system from the second order to the first order. The new approach is demonstrated via two classical benchmark problems.

关键词： costate estimation second order pseudo-spectral method

INTERFACIAL BEHAVIOR OF PIPE JOINTS UNDER TORSION LOADS

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Acta Mechanica Solida Sinica 2015年第5期28卷 521-535页

作者： Jun Han Hong Yuan Jiayu Wu moe key lab of Disaster and control in Engineering Institute of Applied Mechanics Jinan University

The interfacial behavior of pipe joints is studied in this paper. Firstly, through nonlinear fracture mechanics, the analytical expressions of interfacial shear stress and the load- displacement relationship at loaded end of pipe joints under torsion loads are obtained. Thus the shear stress propagation and the debonding process of the whole interface for different bond lengths can be predicted. Secondly, through the analytical solutions, the influences of different bond lengths on the load-displacement curve and the ultimate load are studied. The stress trans- fer mechanism, the interface crack propagation and the ductility behavior of the joints can be explained.

关键词： interface failure mechanism softening debonding torsion pipe joints

Extraction of real modes and physical matrices from modal testing

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Earthquake Engineering and Engineering Vibration 2011年第2期10卷 219-227页

作者： Wang Tong Zhang Lingmi Tee Kong Fah moe key lab of Structural mechanics and control for aircraft Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of Civil Engineering University of Greenwich United Kingdom

A technique to extract real modes from the identified complex modes is presented in this paper, which enables the normalized real mode shapes, modal masses, and full or reduced mass and stiffness matrices to be obtained. The theoretical derivation of the method is provided in detail. An 11-DOF vibration system is used to validate the algorithm, and to analyze the effects of the number of modes utilized and measurement DOFs on the extraction results. Finally, the method is used to extract real modes from both experimental modal analysis and operational modal analysis.

关键词： modal analysis complex mode real mode normalized mode shape modal mass

Peeling behavior and spalling resistance of CFRP sheets bonded to bent concrete surfaces

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Acta Mechanica Sinica 2010年第2期26卷 257-264页

作者： Hong Yuan Faping Li moe key lab of Disaster Forecast and control in Engineering Institute of Applied mechanics Jinan University 510632 Guangzhou China

In this paper, the peeling behavior and the spalling resistance effect of carbon fiber reinforced polymer （CFRP） sheets externally bonded to bent concrete surfaces are firstly investigated experimentally. Twenty one curved specimens and seven plane specimens are studied in the paper, in which curved specimens with bonded CFRP sheets can simulate the concrete spalling in tunnel, culvert, arch bridge etc., whereas plane specimens with bonded CFRP sheets can simulate the concrete spalling in beam bridge, slab bridge and pedestrian bridge. Three kinds of curved specimens with different radii of curvature are chosen by referring to practical tunnel structures, and plane specimens are used for comparison with curved ones. A peeling load is applied on the FRP sheet by loading a circular steel tube placed into the central notch of beam to debond CFRP sheets from the bent concrete surface, meanwhile full-range load-deflection curves are recorded by a MTS 831.10 Elastomer Test System. Based on the experimental results, a theoretical analysis is also conducted for the specimens. Both theoretical and experimental results show that only two material parameters, the interfacial fracture energy of CFRP-concrete interface and the tensile stiffness of CFRP sheets, are needed for describing the interfacial spalling behavior. It is found that the radius of curvature has remarkable influence on peeling load-deflection curves. The test methods and test results given in the paper are helpful and available for reference to the designer of tunnel strengthening.

关键词： FRP sheet · Interfacial fracture energy ·Debonding · Spalling resistance · Bent concrete surface

Advances in dynamics and control of tethered satellite systems

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Acta Mechanica Sinica 2008年第3期24卷 473-473页

作者： Hao Wen Dongping Jin Haiyan Hu moe key lab of structure mechanics and control for aircraft Nanjing University of Aeronautics and Astronautics210016 Nanjing China

The concept of tethered satellite system (TSS) promises to revolutionize many aspects of space exploration and exploitation. It provides not only numerous possible and valuable applications, but also challenging and interesting problems related to their dynamics, control, and physical implementation. Over the past decades, this exciting topic has attracted significant attention from many researchers and gained a vast number of analytical, numerical and experimental achievements with a focus on the two essential aspects of both dynamics and control. This review article presents the historic background and recent hot topics for the space tethers, and introduces the dynamics and control of TSSs in a progressive manner, from basic operating principles to the state-of-the-art achievements.

关键词： Tethered satellite system Space tether Dynamics control

A Unified Approach Toward Simulating Constant and Varying Amplitude Fatigue Failure Effects of Metals with Fast and Efficient Algorithms

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Acta Mechanica Solida Sinica 2021年第1期34卷 53-64页

作者： Si-Yu Wang Lin Zhan Hui-Feng Xi Heng Xiao College of mechanics and Construction Engineering and moe key lab of Disaster Forecast and control in Engineering Jinan UniversityGuangzhou510632China

A new finite strain elastoplastic J2-flow model is established with an explicit formulation of work-hardening and softening effects up to eventual failure,in which both a new flow rule free of yielding and an asymptotically vanishing stress limit are *** novelties of this new model are as follows:(i)Fatigue failure effects under repeated loading conditions with either constant or varying amplitudes are automatically characterized as inherent response features;(ii)neither additional damage-like variables nor failure criteria need to be involved;and(iii)both high-and low-cycle fatigue effects may be simultaneously treated.A fast and efficient algorithm of high accuracy is proposed for directly simulating high-and medium-high-cycle fatigue failure effects under repeated loading *** this goal,a direct and explicit relationship between the fatigue life and the stress amplitude is obtained by means of explicit and direct procedures of integrating the coupled elastoplastic rate equations for any given number of loading-unloading cycles with varying stress *** examples suggest that the new algorithm is much more fast and efficient than usual tedious and very time-consuming integration procedures.

关键词： Metals Finite strain Elastoplasticity Fatigue failure Direct algorithm

THEORETICAL MODEL ON INTERFACE FAILURE MECHANISM OF REINFORCED CONCRETE CONTINUOUS BEAM STRENGTHENED BY FRP

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Acta Mechanica Solida Sinica 2009年第2期22卷 161-170页

作者： Hong Yuan Zifeng Lin moe key lab of Disaster Forecast and control in Engineering Institute of Applied mechanics Jinan University Guangzhou 510632 China

Fiber reinforced polymer （FRP） composites are increasingly being used for the re-pair and strengthening of deteriorated concrete structural components through adhesive bonding of prefabricated strips/plates and the wet lay-up of fabric. Interfacial bond failure modes have attracted the attention of researchers because of the importance. The objective of the present study is to analyse the interface failure mechanism of reinforced concrete continuous beam strength-ened by FRP. An analytical solution has been firstly presented to predict the entire debonding process of the model. The realistic bi-linear bond-slip interfacial law was adopted to study this problem. The crack propagation process of the loaded model was divided into four stages （elastic,elastic-softening,elastic-softening-debonded and softening-debonded stage）. Among them,elastic-softening-debonded stage has four sub-stages. The equations are solved by adding suitable stress and displacement boundary conditions. Finally,critical value of bond length is determined to make the failure mechanism in the paper effective by solving the simultaneously linear algebraic equations. The interaction between the upper and lower FRP plates can be neglected if axial stiffness ratio of the concrete-to-plate prism is large enough.

关键词： FRP interface bond-slip law critical length continuous beam ultimate load