| Electromagnetic exciter can transform electromagnetic force into excited force,which can make the component and mechanism realize stable periodic motion or provide a certain amount of stress to component by the device of electromagnet.Electromagnetic high frequency fatigue testing machine can use electromagnetic force to make the component motion.As electromagnetic high frequency fatigue testing machine owes fast response,high frequency,high efficiency and saving energy,it has been widely used in engineering practice.At present,the electromagnetic high frequency fatigue testing machine has small travel and hard to do fatigue testing on some large deformation materials.The other kind of fatigue testing machine has some problems,such as low efficiency and high energy dissipation.In this paper,a kind of electromagnetic exciter is designed to realize large travel.The electromagnetic exciter,designed in this paper,should require the demands of large displacement and high frequency vibration.The main structure of the electromagnetic fatigue testing machine includes three parts,which are the mechanism of electromagnet,excitation mass and excitation spring.The single-degree-freedom system of spring is built and analyzed.Then,the relationship between natural frequency and exciting frequency is investigated,which can provide theoretical basis for design exciter.The modeling analysis for electromagnetic fatigue testing machine is done.And the results show that with the increase of stiffness for exciting spring,the natural frequency of the fatigue testing machine is increased.The influence of the ratio ? between exciting frequency and working frequency on system amplification factor is analyzed,which can confirm the resonant zone and the value of ?.Then the structure of exciter can be designed.The materials and structure of exciting spring and excitation mass can be confirmed based on the analysis.The mathematical model of main component of electromagnetic exciter,the electromagnet,is built and analyzed.Based on the theory of electromagnetic and principle of virtual displacement,the suction equation of electromagnetic is obtained.Finally,obtain the results that the variation of electric current and air-gap are the main factor to influence the electromagnetic force.Electromagnet mechanism is the core components for the electromagnetic vibrator to realize the setting motion.The design way of the empirical method is not reasonable in structure design.However,using the method of finite element simulation analysis to optimize the electromagnet mechanism can greatly improve the performance parameter.The Maxwell is a powerful finite element analysis of the magnetic field software.The armature end shape and the radial distance between armature and coil,coil skeleton thickness and other factors were analyzed to optimize the initial structure design.The simulation results show that the optimized structure of the suction characteristic is better than the initial design structure.After optimization,the static characteristics and transient characteristics for the magnet structure are analyzed.The impact of the number of turns of the coil and voltage to the current variation is analyzed.So it can realize the current increases and decreases in the shortest period of time,which improve the response speed of the excitation.According to the design of the vibration exciter,the prototype is manufactured and the experimental verification is carried out.Firstly,the static suction characteristic test is carried out to verify the correctness of the simulation analysis.And then the dynamic characteristic test is carried out,in the experiment,the voltage,excitation frequency,the number of turns of the coil are treated as the variable and the displacement of the armature response is treated as the observation results.Referencing the magnetic potential,in a certain number of turns,when the voltage is high and the frequency is small,the displacement of armature is large,while the magnetic potential value is great.However,when the excitation frequency is constant,the smaller the number of turns,the higher the voltage,the larger the displacement of the armature,and the magnetic potential can be greater.Finally,it can be concluded that the trend of experimental data agrees with the simulation analysis.The operation time is measured,and the operation characteristics of electromagnet are obtained. |
PDF Full Text Request