Research And Application For The Parameters Identification Of The Fatigue Test System Based On The Soft Measurement Technology

Electromagnetic resonance high-frequency fatigue testing machine is a resonance-theory based testing instrument which is used to measure the fatigue life of metal materials under alternating load.The instrument has been deeply welcomed by industrial research and development production department as well as institutions of higher learning for its merits like high working efficiency,short testing time,low energy consumption,etc.As the requirement of people to the accuracy of the test results becomes higher and higher,how to improve the accuracy of resonant high-frequency fatigue testing machine is undoubtedly an important problem to solve.When doing the working characteristics of resonant fatigue crack propagation experiments,we find the test vibration system are strongly influenced by its particles mass,and the particles of vibration system are composed of multiple different shapes and material components,which largely limit the direct measurement of particles mass.In this paper,a soft-measuring method is proposed to measure the particles mass of this kind of vibration system.The main contents of the paper are as follows:(1)Taking the Hong Shan PLG-100 electromagnetic resonance high-frequency fatigue testing machine as an example.Based on the working principle of the machine and mechanical vibration theory,three degrees freedom vibration system mechanics model and the dynamic equation are established,the system natural frequency equation concerning system natural frequency,spring stiffness and particle mass is derived.(2)The specimen stiffness under different crack length and each spring stiffness are calculated by finite element method and the system natural frequency under different crack length was measured with frequency measuring experiment method.With substituting resonance frequency value under different crack length and the corresponding specimen stiffness,spring stiffness into system frequency equation,the over determined equations are derived by taking the particles mass we want to identify as the unknown variables,the least-squares solution is obtained by solving the over determined equations,the main vibration mass and shock excitation mass of this vibrating system are obtained by further subsequent processing..(3)Parameter identification system based on LabVIEW8.6 is designed,which can realize test data acquisition,processing,computing,storage for this type of vibration system by programming.(4)The related experiment has been performed to verify the accuracy of the proposed method,Weight is added to the test bench to change the main vibration mass of the vibration system,the proposed method is applied to identify the mass of the added weight and the measurement error is obtained by comparing with the mass of the real weight,the results conform to expectations,which suggests that the proposed method has theoretical significance and application value.The paper obtains the system frequency equation by establishing electromagnetic resonance high-frequency fatigue testing machine vibration mechanics model,and the system parameter is identified by using soft measurement technology.The paper is to analyze the stiffness of test specimen and spring by finite element method,a parameter identification system based on Lab VIEW8.6 is exploited,which can improve work efficiency through friendly man-machine interface.