Research On Dynamic Characteristics And Dynamic Load Compensation Method Of Electromagnetic Resonant Fatigue Test System

Fatigue failure is main failure mode for mechanical parts. Fatigue crack initiation and propagation occurs in material or structure while they are subjected to alternating loading, resulting in the action of fatigue. Nowadays, fatigue failure cannot be completely studied by the effective theoretical method, so, the specific materials fatigue test is a subject of considerable importance for studying fatigue life and fracture mechanism, It has a great important significance to improve the reliability and the service life of mechanical products.The electromagnetic resonant fatigue test system is a device to test the metal material fatigue lige and fracture properties under the resonant condition, which is required to trace the system natural frequency precisely and control the test load strictly during the process of fatigue test. To support this, the system dynamic characteristics and dynamic load measurement error are investigated theoretically and experimentally.The paper’s main research works are as follows:1. The electromagnetic resonant fatigue test vibration system model of three degree freedom with damping has been established, the stiffness of compact tension(CT) specimen is calculated using finite element method. In order to use the soft-sensing tecghnology to identify parameter of resonant fatigue test vibration system, the soft-sensing model of system parameters has been established, The least square method was used to solve the over determined linear equations and the Newton iterative method was used to solve the nonlinear equations, and then system mass and stiffness are obtained by further subsequent processing. Finally, the results were verified by experiments.2. The dynamic characteristics of electromagnetic resonant fatigue test vibration system are studied, the variation laws of system natural frequency, the testing load amplitude-frequency curve and resonance amplitude with the damping coefficient, loaded mass, specimen stiffness, specimen crack length and fixture mass during the process of fatigue test are explored. Finally, the results were verified by experiments.3. The dynamic load measurement error formula is inferred based on the electromagnetic resonant fatigue test vibration system model of three degree freedom with damping, the measurement error source of dynamic load are analyzed, the effect of factors to dynamic load measurement error is discussed in detail, and a dynamic load measurement error compensation method is proposed. Finally, the results were verified by experiments.