Control Optimization Method Of Piezoelectric Structures And Optimum Design On Structural Buckling

By means of the design optimization method, not only the weight of structures can be reduced, but also the strength, stiffness, vibration behavior, buckling stability, and other performances of structures can be improved efficiently. Now the application of structural design optimization has been promoted in the industries. The piezoelectric material, as an important type of intelligent structure materials, has the mechanical-electric coupling property to be able served as the actuators and the sensors. Therefor, based on the proper mechanical model of structures composed of piezoelectric elements, the control on structural deformation and vibration can be performed conveniently.In this dissertation, firstly, the design optimization method of structural buckling and its engineering application are proposed. Then, the finite element formulation and vibration control model with piezoelectric material is developed. Finally, by applying the optimization method to the deformation and vibration control, the computing methods and design optimization of the structure control have been presented.In Chapter 1, the property of the piezoelectric material and its application to the structure control are discussed. The structure mechanics analysis with piezoelectric material, the design theory of the controller and the optimum layout method of the actuator/sensor are reviewed. Based on the relative research, the main work and research contents in this paper are given.In Chapter 2, a general-purpose model and solution algorithm for the design optimization of buckling behavior is developed for built-up structures and implemented within the JIFEX, a general purpose software for finite element analysis and design optimization. The sensitivity analysis methods accounting for the variations of pre-buckling stresses and external loads have been proposed. The computing formula of the shape optimization is different from that of the size optimizations, and the buckling optimization can also be combined with static, frequency and dynamic response optimizations in order to solve the complicated structure design optimization problem. The sub-layer design optimization of the composite laminated plate is also discussed. Sub-layer means the laminated plate can be divided into several sub-layers and each sub-layer is made of layer plate with the same thickness and fiber-stacking angle. The sensitivity analysis formulation of structural displacement and free-vibration frequency are derived. Particularly the case that the variations of the thickness of sub-layer will change the centerline of the laminated plate has been considered.In Chapter 3, the engineering application examples of the buckling design optimization have been presented in order to demonstrate the effectiveness of the buckling optimization method presented in Chapter 2 and the ability to solve complex structure optimization problem. Additionally some conclusions about typical structure design are the reference of the engineering application.In Chapter 4, the finite element analysis model for the piezoelectric structures has been developed. Based on the DKQ element, the finite element equations of the buckling analysis are derived for the piezoelectric thin plate structures and numerical examples show the mechanical-electric coupling effect can affect the buckling stability of thin plates and regulating external voltages can control buckling stability of piezoelectric thin plate. In the second part of chapter 4, the finite element model for piezoelectric bar composed of a number of piezoelectric thin pieces has been developed and the influence of mechanical-electric property on the buckling stability of piezoelectric trusses has also been discussed.In Chapter 5, on the basis of former finite element method and in counting of the mechanical-electric coupling effect under electric load and mechanical load, the optimum design and sensitivity analysis methods of piezoelectric intelligent trusses on the structural stiffness, buckling stability and free-vibration freq...