Qing Sun

An adaptive beam model and dynamic characteristics of magnetorheological materials

Magnetorheological (MR) materials show variations in their rheological properties when subjected to varying magnetic fields. They have quick time response, in the order of milliseconds, and thus are potentially applicable to structures and devices when a tunable system response is required. When incorporated into an adaptive structural system, they can yield higher variations in the dynamic response of the structure. This study presents a detailed analysis of dynamic characteristics of adaptive beam based on MR materials. The relationship between the magnetic field and the complex shear modulus of MR materials in the pre-yield regime is researched using oscillatory rheometry techniques. A structural dynamic modelling approach is discussed and vibration characteristics of MR adaptive structures are predicted for different magnetic field levels. In addition to the model predictions, actual MR adaptive beam is fabricated and tested. Both studies illustrate the vibration minimization capabilities of the MR adaptive beam at different magnetic field levels.

Semi-active Control Strategy using Genetic Algorithm for Seismically Excited Structure Combined with MR Damper

Magnetorheological (MR) damper is a prominent semi-active control device for earthquake response mitigation of structures. The most important topic for the intelligent MR structures is choosing the control current of MR damper quickly and accurately. The typical control strategy is on-off control strategy, while inherent time-delay and coarse control precision lie in this strategy. This article proposes a semi-active control strategy for restricting the MR structures efficiently, in which the genetic algorithm (GA) is adopted to search for the optimal feedback control gain in time-delayed dynamic equations forming a GA controller, and next optimize the control current of the MR damper accurately by a series of GA procedure. The GA strategy has the capability to effectively control the MR structure involving time delay and adjusting for controlled current of the MR damper timely and accurately. Accordingly, numerical examples are used to testify that the feedback gain optimized by GA has the capability to reduce a given objective response dramatically. In addition, a comparison between GA controller and LQR controller indicates that the proposed approach performs much better than LQR method, especially in time-delay systems. Finally, simulation results for a seismically excited structure subjected by the MR damper are presented to verify that the semi-active strategy using GA is predominant in mitigating the dynamic structure efficiently. The strategy and the results presented will also throw light on the development and control of other novel structures.

Techno-Economic Analysis of Fiber Reinforced Polymer Substation

This paper studies on the technical and economic analysis of fiber reinforced polymer (FRP) substation framework. Firstly, based on the comparison of the material performance and price, we select the suitable fiber and resin as the main building material for substation framework. Then on the basis of numerical simulation, the bearing capacity of FRP substation truss-column under axial compression and bending is researched, and the initial geometric imperfection is considered in the models. Finally, the behavior of the typical two-span FRP gantry of substation is analyzed, and the economy of FRP substation framework is compared with the steel gantry which owns the same capability.

Study on Structural Vibration Control by GA Controller Involving Time Delay

Active-control algorithms such as optimal control or impulse control methods generally achieve satisfactory control effectiveness, but it often fails to control dynamic systems with time-delay effectively. In view of this reason, a novel active controller using Genetic Algorithm (GA) is proposed in this paper, which is based on discrete motion equation of multi-freedom degree system with time delay. It can solve such subsistent problems as effective control for a seismically excited structure with an explicit time delay. Meanwhile it is also prone to achieve a desired vibration state in accordance with different control objectives. Finally in order to verify its validity, the GA controller are applied to a three-storey and a eight-storey structures excited by different seismic forces, numerical examples of which are given to prove it capable of providing satisfactory control effect with time delay.

Parameter Identification and Simulation of the Noise-Involved Hysteretic Model Using Improved Genetic Algorithm

Hysteresis is a specific character of a wide range of physical systems and devices, such as electromagnetic fields, mechanical stress–strain elements, and electronic relay circuits. The extended Bouc-Wen model is one of the most widely accepted phenomenological models of hysteresis in mechanics. However the multi parameters have plagued its further application because the capability of computer and algorithm available currently can not meet the need completely. Thus to exploit an efficient and accurate parallel algorithm is very essential and significant. This paper is committed to propose an improved genetic algorithm (GA) so as to identify the parameter of the Bouc-Wen model effectively. Finally a large amount of noise-involved data is employed to verify the proposed approach is very effective and accurate.

Experimental Study on the Durability of Glass Fiber Reinforced Polymer Pole and Tower for Power Transmission

This paper studied the durability of Glass Fiber Reinforced Polymer (GFRP) Pole and Tower for power transmission under the UV and adverse temperature environment. The results show that both UV and adverse temperature environment influence the performance of GFRP material, with its strength significantly reduced, and its elastic modulus increased, while the Poissons ratio changed slightly. Xenon lamp aging affects the material properties of the specimens with protective coatings more slightly than those without any protective coatings. High temperature environment affects the material properties of specimens more obviously than low temperature environment does. Therefore, when designing the GFRP Pole and Tower for power transmission exposed in UV and adverse temperature environment long-term, designers should consider the negative impacts of the external environment, and take appropriate protective treatments.

Experimental study on dynamic nonlinear electromechanical behaviour of the macro fiber composite

The primary objectives of this work are about the experimental study on the nonlinear electromechanical behaviour of the macro fiber composite (MFC), and to analyse the affecting factors of the inconstant parameters d33 and d31 which can arouse nonlinearities of MFC. Both longitudinal and transverse output strains are measured by actuating the MFC specimen under different DC voltages and a range of peak-to-peak sinusoidal voltages (VPP) at various frequencies, which can investigate how the voltage amplitude and frequency affect nonlinear hysteretic behavior. The experimental results of both DC voltages and AC voltages indicate that the relationship of the applied voltage and output strain displays nonlinear hysteretic behavior. The responses of the AC voltages also indicate that hysteresis nonlinearity behaviour of the MFC actuator is sensitive to the varying voltage amplitude and frequency. The higher the voltage and frequency are, the more obvious the hysteresis phenomenon are.

Research on Stability of E-Glass Fiber/Epoxy Composite Material Tube

This paper studies on the stability capacity of E-glass fiber reinforced polymer (GFRP) tubes under axial compression in order to get the formula, which can be applied to structure design. Firstly, on the basis of test data, finite element analysis is carried out and initial geometric imperfection is considered in the models. Then, its proved that edge-failure criterion is suitable for stability analysis of GFRP slender components by comparison of results derived from several classic formulas. Finally, a modified Perry-Robertson stability formula is proposed so as to ascertain corresponding stability coefficients for GFRP tubes with different slenderness ratio.

Nonlinear Fatigue Life Modeling of FRP Composite Materials Based on Genetic Algorithm

In this paper, three fatigue models are employed and proposed for modeling the fatigue life of different fiber-reinforced composite material systems. In order to identify the unknown parameters in these models, Genetic Algorithm (GA) is used for estimating its values. This technique is a stochastic process that leads straight to different S-N curves that predicts the trend of the experimental data without the need for any assumptions. The calculation results show that these three models, especially the nonlinear regression model, whose parameters are assigned by using GA are all satisfied with the experimental data, and the average value of RMSE is below 0.1. The method of fatigue damage simulation presented should have a very good application prospect.

Anti-Noise Simulation of the Hysteresis Mathematic Model Using Computationally-Efficient GA

Hysteresis is a particular feature of a wide range of physical systems and devices such as electromagnetic fields, mechanical stress–strain elements and electronic relay circuits. The extended Bouc-Wen model is one of the most widely used hysteresis models in mechanics. It has the capability to emulate the behavior of a wide class of hysteretic systems. However multi parameters have plagued its further application because the capability of computer and algorithm available currently can not meet the need completely. Thus to exploit an effective parallel algorithm is very essential. This paper is committed to propose a novel Genetic Algorithm (GA) so as to identify the parameters of the Bouc-Wen model with noise disturbance efficiently and accurately. Finally a large amount of noise-involved experimental data obtained from a real MR damper is employed to verify the proposed approach has the capability to estimate the satisfactory parameters of the Bouc-Wen model. Also suggested are the implications of the present study on other nonlinear hysteretic models or other complex mathematical models.