Dynamic Analysis And MRE Damping Research Of Wind Tunnel Tail Support System

Wind tunnel test of aircraft model is an important link in the process of aircraft development and plays an irreplaceable role in the field of aerospace.In the wind tunnel test,the aircraft model and tail support rod are easy to produce low frequency and large amplitude vibration under the action of the airflow pulsation load,which affects the normal work of the force balance,resulting in inaccurate test data.In serious cases,it will also cause damage to the wind tunnel model test system and threaten the safety of the wind tunnel operation.The key to solve this problem is to develop an intelligent vibration damping method with wide controllable stiffness damping range,good adaptive performance and fast response speed.Passive vibration isolation structure parameters are fixed,which is unable to adapt to the time-varying vibration damping requirements.Meanwhile,the output displacement of the piezoelectric actuator is small(the suppression effect of large amplitude is poor in the case of resonance),the stability is poor(it is sensitive to the structural parameters of the model)and the cost is high.The magnetorheological elastomer(MRE)semi-active vibration reduction scheme based on magnetorheological principle has the advantages of fast response speed(millisecond),wide range of variation,low energy consumption,similar vibration reduction effect to active control,and good stability and reversibility.In this paper,aiming at the problem of low-frequency and large amplitude vibration of wind tunnel tail support in the process of wind tunnel test,the dynamic characteristics of the model of tail support bar were analyzed,the MRE vibration reduction method was proposed,and the vibration reduction mechanism of MRE base tail support bar and the design method of vibration isolator were studied mainly from the following aspects:(1)Based on Euler-Bernoulli beam theory,the vibration equation of the beam during the wind tunnel experiment is established.Meanwhile,considering the variable section structure of the strut,the theoretical mode of the strut model is calculated by combining with the finite element method.Then COMSOL is used to analyze the modal simulation of the tail support and verify the theoretical calculation results.The simulation results show that the first-order natural frequency of the wind tunnel tail brace model is about 30.5hz and the second-order natural frequency is about 204 Hz.(2)The wind tunnel tail brace model test system was set up in the laboratory environment,and the wind tunnel tail brace model was tested by means of hammer and sweep respectively.In order to obtain a more accurate vibration mode of the model,the vibration of the aircraft and the strut at different positions was tested in the wind tunnel environment,and the theoretical analysis data were used to determine whether the theoretical analysis is correct.(3)The vibration damping system of tail support bar in MRE based wind tunnel is equivalent to the cantilever beam structure with variable material and variable section.Then the control effect of different working modes of MRE vibration absorber is simulated and analyzed by finite element method.The magnetic field strength,MRE thickness,length and other parameters of the shear-extrusion MRE shock absorber are optimized to determine the specific structure of the MRE base tail brace support system.(4)The experimental system of vibration reduction control for MRE-based wind tunnel tail support system was established,and the vibration reduction effect of the wind tunnel tail support system under different excitation current was analyzed by means of sweep frequency experiment and single frequency sinusoidal signal excitation at31.25 Hz.The experimental results show that the MRE-based wind tunnel tail support system has a good vibration damping effect on the vibration of the tail support system in the first mode.When the excitation current is 3A,the maximum vibration damping effect can reach 17.2%.The above study discussed the feasibility of vibration reduction of wind tunnel tail support bar based on MRE material,and determined the vibration reduction scheme of MRE-based wind tunnel tail support bar,which provided a basis for the subsequent controller design.