The Study On The Natural Characteristics Of Rod Fastening Rotor Influenced By Temperatures

Starting from the analysis of microscopic characteristics on the material surface,the present research establishes a wheel contact model using the fractal contact theory of rough surface,makes further study of contact stiffness problem of rod fastening rotor in theory.The thesis calculates normal and tangential contact stiffness of the rod fastening rotor by MATLAB,and gets the stiffness curves with different pre-tightening force and roughness.Also the modality of the rod fastening rotor is analyzed through adding a series of stiffness values to the contact model.The thesis uses ANSYS to analyze the finite element model of the rod fastening rotor-bearing system after the dynamic coefficients of the journal bearing are calculated.The natural characteristics of the rod fastening rotor with different pre-tightening force in the rigid support or journal bearing support are studied,and the laws of dynamic coefficients of journal bearing oil film with the changing speed are researched also analyzes the influence of the performance of journal bearing on natural characteristics of the rod fastening rotor.Finally the changes of contact stiffness and natural frequency of the rod fastening rotor-bearing system under the influence of temperatures are analyzed.The analysis shows that contact stiffness mainly relates to the pre-tightening force and surface roughness.With the increase of the pre-tightening force,the contact stiffness value grows slowly after a beginning rapid increase,and gradually reaches a constant value.The smoother the contact interface,the higher the contact stiffness and the natural frequency.As rod fastening rotor speed increases,rigidity and damping coefficients of journal bearing will decline.The natural frequency of the rod fastening rotor is higher in the rigid support than in the journal bearing support.And in the journal bearing support,the natural frequency of the rod fastening rotor rises following the increase of speed with positive vortex frequency,and the reverse vortex frequency descends with the increase of speed.With the increase of temperatures,the material properties of rotor will change,leading to the decrease in contact stiffness of rod fastening rotor,as well as its natural frequency.In order to validate the effectiveness of the model,the natural characteristics are tested through hammering experiment,and the amplitude-frequency curves of the model rotor are obtained.The specific work is as follows.The pre-tightening force of each rod of the model rotor is calibrated separately.Assembling and debugging the experiment rig of rod fastening rotor,the hammer experiment of the rotor with different speed and pre-tightening force is carried out.The consistency of the analysis results with the experimental data can illustrate that the model established and the method used in this thesis is able to accurately reflect mechanics properties of the rod fastening rotor and correctly analyze the dynamics problems of the rod fastening rotor.