Research On The Semi-active Vibration Control Of Body Beam Structure Based On Shape Memory Alloy

In recent years, auto consumers take the more and more high request to the vehicle security, and the calling for environment protection grow louder, therefore the automobile manufacturers have to find more frivolous raw material for making cars. Reducing the weight of a vehicle has become a research focus in the automotive industry. Lightweight body may make body’s stiffness lower, easily to be outside excited to produce strong vibration noise, influencing the drivability, safety and comfort. Shape memory alloys can great improve the rigidity while meeting lightweight body, due to its high power density and producing a lot of restoring force when heated. It can provide new idea and means for structure vibration control by changing the body’s stiffness.The semi-active vibration control of the body beam structure using shape memory alloys is studies. Using the varying stiffness theory for reference in this thesis, the vibration control of smart beams is studied on the aspects of the theories, simulations and experiments. The main contents of the thesis mainly are as follows:(1) The test on the mechanical properties of SMA was carried out, a differential scanning calorimeter(DSC) was employed to study the phase transition temperature; The tensile mechanical properties of Shape memory alloy wires as well as the relationship of stress and strain, strain amplitude and the recovery stress in different pre-strain cases were investigated by means of tensile experiments. This basic performance experiments are prepared for the next numerical simulation, simulated analysis and experiment.(2) Several phenomenological models of the shape memory alloy were summarized. Then the constitutive model applied in this thesis was elaborated. A program that make use of MATLAB to compute the model is compiled to simulate the restoring force of SMA when being heated, and the result was compared with that of experiment.(3) Through the theoretic analysis, we obtain that the relationship between the restoring force generated by SMA and the structural frequency, some numerical simulations are carried out by using MATLAB, and the effect of the distance between SMA and the neutral axis of beam on the system frequencies is inspected.(4) This thesis adopt the method called as ―negative thermal strain‖, along with the commercial finite element software ANSYS to stimulate the vibration characteristic of Beam-SMA smart structures. The influences of temperature, pre-strain, volume ratio of SMA and layout on the beam to structural natural frequencies were investigated numerically.(5) Build the vibration control testing table of smart beam structure and establish the on-off control method in LABVIEW, and verify the effectiveness of on-off control method in controlling the vibration of system, and studied the influence of different controlling current to the effect of suppressing chatter amplitude.The research showed that semi-active control system, active variable stiffness by SMA can suppress the Beam-SMA smart structures vibration.