Study Of Piezoelectric Truss Structure's Stability Based On Finite Element Method

Truss structure which is simple and easy to disassemble and transport is extensively used in aerospace, bridges, buildings, vehicles and other industries. Especially with the development of computers, space truss structure has been increasingly widely used. For example, in civil engineering, reticulated structure, spatial grid structure and tower structure belong to it. In aerospace engineering, it can be used in the instrument bay of carrier rocket, satellite antenna tower, interface framework of rocket ships and space station and so on. Because this kind of structure has such property: big deflection, low natural frequency, small damping, light weight, meanwhile it work in the special environment, so it must meet specific requirements of the stability and vibration. So it is one of the best interested subjects in application of finite element method.Currently, there is little research about stability or intelligent control of this type of structure. This is mainly due to stability itself is a very complex issue which is influenced by many factor. And there is not unified useful criterion for the structural instability in academia. Meanwhile stability belongs to nonlinear and large deformation area when structures suffer from the dead loads and seismic loads and other random effects. This will make it more difficult to study. Traditional method of prevent structure failure relies on increasing the main section bar area and controlling the slenderness ratio of bar. When the structure has been designed, manufactured and installed, its performance is not easy to change. It can not satisfy the requirements of continued development of large-span and large space structures.In recent years, materials, controlling, microelectronics and computer science and technology is developing rapidly, In particular the study of intelligent materials achieved a breakthrough progress. So the piezoelectric intelligent material is introduced into the ordinary truss structure in this paper. The special physics performance of piezoelectric material, namely the piezoelectric effect and the counter piezoelectric effect, are applied the initiative stable control of structure. Specific content as follows:At first, based on the basic mechanical properties of piezoelectric material, a piezoelectric initiative bar that suitable for truss structure stability control is designed. When an ordinary bar is embedded piezoelectric pile partly, this bar is formed. In other words, the bar is composed of piezoelectric pile partly. The piezoelectric pile is fold gathers with PZT. It is series connected in mechanics and parallel in electricity. Therefore, it can realize the request of big driving force and big driving displacement. Meanwhile, it also can reduce the requirement of high driving voltage. It has good prospect in the active control of Engineering Structures. The piezoelectric active bar which is designed according to above method can realize initiative control to structure's bearing capacity and can realize initiative stability control to structure.Secondly, a finite element model of piezoelectric truss structure is built. And electromechanical coupling stiffness matrix of piezoelectric truss structure under the static force is derived. Initiative bar and ordinary bar are analyzed. Eigenvalue stability equation of the piezoelectric truss structure is established according to potential in principle. By solving the equation, critical load of the structure is gotten. The effect of piezoelectric material on the static stability control of structure is analyzed.At last, Mathieu-Hill equation of piezoelectric truss structure in the cyclical load is derivate. Consider damping or not, the solution method for the dynamic instability region of the piezoelectric truss structure is derived. The influence of piezoelectric material on structure's dynamic stability region is analyzed. Incremental stiffness equation is built in the step load. And the influence of piezoelectric material on structure's dynamic load is analyzed. The results show that the initiative bar which is introduced in this paper can effectively increase of static stability and dynamic stability .It has a very good prospect in structural stability control.