Research On Electromagnetic Strengthening Method Of Nonlinear Vibration Absorber

Compared with the traditional linear vibration absorber,the nonlinear vibration absorber is no longer limited to taking effect near the natural frequency of the main vibrator,but can absorb the vibration energy of the main vibrator in a wider excitation frequency band.Nonlinear Energy Sink(NES)is characterized by the targeted energy transfer,and energy is unidirectionally transmitted from the main oscillator to the vibration absorber and dissipated in the form of heat through damping.This paper focuses on applying the electromagnetic force with nonlinear mechanical characteristics into the design and improvement of NES.Apart from that,it investigates the vibration absorption performance of several new electromagnetic non-linear vibration absorbers in the environment with great changes of the amplitude of simple harmonic excitation,and highlights the suppression effect of several NESs after the high branch response of the main system.The main contents are as follows:A new type of magnetic nonlinear vibration absorber is proposed,and the mechanical characteristic curve of the electromagnet-permanent magnet structure in the vibration absorber is characterized by strong nonlinearity as well as a flat middle part and steep ends.In addition,the dynamic equation of linear oscillators with the vibration absorber is derived and the vibration reduction performance of the vibration absorber attached to oscillators with different stiffness is analyzed by Runge-Kutta method.As shown by the results,the vibration absorber can not only effectively absorb vibrational energy from broadband frequency ranges,but also have a high vibration damping performance for linear main oscillators with different stiffness after being activated.Moreover,it can help improve the performance of the vibration absorber by appropriately reducing the distance between the electromagnet and the permanent magnet.A new type of strongly nonlinear vibration absorber with variable stiffness,which consists of symmetrically placed springs and an electromagnetic suction device,is proposed.The nonlinear stiffness of the vibration absorber can be controlled by changing the current of the electromagnetic device.Beyond that,the dynamic equation of the linear primary oscillator connected to the vibration absorber is deduced,and the vibration reduction performance for harmonic and shock loads is analyzed by Runge-Kutta method.According to the results,the multi-level control of electromagnetic force can effectively eliminate the higher branch of response for large excitation amplitude,avoid the occurrence of sudden failure,and further broaden the effective excitation range of the vibration absorber under harmonic excitation.Similarly,under the impact load,the vibration absorber can always reach the higher vibration absorption efficiency through the control of the electromagnetic force.This paper has proposed a non-smooth nonlinear vibration absorber based on opposed springs and an electromagnetic suction device with trigger conditions.Furthermore,the proximity switch is used to prevent the mass of the vibration absorber from electromagnetic attraction when the displacement is small,and to receive electromagnetic attraction when the displacement of the mass is large,so that the non-smooth nonlinear mechanical characteristics are realized.At the same time,the dynamic equation of the linear main oscillator connected to the vibration absorber is deduced,and its vibration reduction performance under harmonic load and shock load is analyzed by Runge-Kutta method.According to the research results,by setting reasonable vibration absorber parameters,the vibration absorber could effectively eliminate the high branch response of the system when the amplitude of the simple harmonic excitation is large,without affecting the vibration absorption performance of the small harmonic excitation.In addition,under the impact excitation,the vibration absorber always has the high vibration absorption efficiency.