Dynamics Investigation On Multi-axis Electro-Hydraulic Vibration Test System With Clearance Joints

Vibration test plays an increasing role in design, reliability and durability of products with the development of modern science and technology, presently, Multi-axis Electro-hydraulic Vibration Test System is widely used in the field of vibration. Multi-axis Electro-hydraulic Vibration Test System witnesses significant application value in the reliability test of motorcycle, where quality and lifetime of motorcycle can be determined through replicating the actual driving environment on the road. Motorcycle is fastened on the table of vibrator via a customized clamp, and motion and energy from the Multi-axis vibrator are transferred to motorcycle through the front shaft and back shaft. Since clearance in practice unavoidably exists between journal and bearing, which leads to the distortion of motion in the course of vibration test and impact load, thus, load transferring is affected, dynamic stress is also increased, and vibration system could even be destroyed in some cases. Deep investigation on dynamics of multi-axis electro-hydraulic vibration test system with clearance joints is implemented, which no doubt brings favorable application value in designing clamp and vibration controller in terms of vibrator.Building model targeted to multi-axis electro-hydraulic vibration test system with clearance joints. First of all, clamp weight and stiffness are given priority based on factor that structure resonance can’t be caused in the range of vibration test. Exciting frequency in research is less than80HZ, Finite element analysis indicates that the first order natural frequency of customized clamp is far greater than effective range of frequency in vibration experiment; therefore, dynamics response of system is immune to the structure coupling resonance. Secondly, general dynamics equation of system with revolute joints clearance is deduced based on virtual work principle. Aimed on the multi-body system dynamics equation, a kind of new standard integration method (DIM) is generalized. Later on, solving the dynamics equation is analyzed, two ways in the course of modeling revolute joints clearance is investigated:continuous contract model and non-continuous contract model. Dynamical model for system with clearance is deduced by applying General impulse-momentum law.Dynamics response investigation for system under the excitation of sinusoidal signal with a certain excitation frequency. Mathematical model for revolute joint with clearance is built aimed at clearance influence on multi-axis electro-hydraulic vibration test system. Nonlinear spring damping impact model based on Lankarani and Nikravesh takes energy loss during the impact into consideration, model related to impact force in normal direction for spherical surface contact and cylindrical surface contact with dry friction against penetration depth is built. Meanwhile, friction force in revolute joint is studied, and the whole system is embedded into dynamical analysis software ADAMS for simulating dynamics response. Simulation is carried out in terms of different exciting frequency and phase difference as well as clearance size, which respectively have a dramatic influence on acceleration response under the excitation of sinusoidal signal. Dynamics response under the excitation of sinusoidal signal for multi-axis electro-hydraulic vibration test system can be correctly predicted based on the above research.Dynamics investigation under random vibration excitation. Friction model of revolute joint with clearance based on LuGre model is studied, and impact model of lubricated revolute joint with clearance is also built. When the journal keeps contact with bearing, the deformation (penetration depth) in contact area occurs, the detailed investigation about energy loss under different restitution coefficients and initial impact velocity is carried out. At the end of the chapter, two typical random signals (El-Centro earthquake wave and Taft earthquake wave)from earthquake process are input to the system, clearance influence on wave reproduction accuracy in terms of correlation coefficient under their actions is investigated.Experimental investigation on dynamics prosperities of multi-axis electro-hydraulic vibration test system with clearance joints is implemented. Firstly, the structure of multi-axis electro-hydraulic vibration test system is introduced according to requirements of test is summarized, the critical technology in the process of setting up that system is clarified, then,two sets of hardware and software platform related to vibration test system is built. Based on research on dynamical properties under sinusoidal signal excitation, the desired experiment is carried out on two set of system respectively, the experiment involves mainly in the influence on the acceleration response under different excitation frequencies and phrase difference, the efficiency of impact model of revolute joint is verified. Finally, aimed at the multi-axis motorcycle electro-hydraulic vibration test system with clearance joints, when random El-Centro earthquake wave and Taft earthquake wave are treated as excitation signals, single clearance influence on the wave reproduction and double clearances influence on the wave reproduction are respectively investigated from the perspective of correlation coefficient in time domain between input signal and output signal, and general patterns of clearance influence on dynamical responses is obtained, which brings favorable and significant conditions for designing reasonable revolute joint with clearance in order to eliminate the nonlinear effect caused by clearance.