| Rolling bearing are key components in rotating machinery,which play the role of supporting shaft and transferring power.Due to the compact structure,high mechanical efficiency and high precision,bearing is widely used in aerospace,wind power,automotive industry and other major fields.According to statistics,30% of the faults in rotating machinery are caused by bearings,and 50% of the faults in wind turbine gearbox transmission systems are related to bearings.However,the success rate of early fault diagnosis of rolling bearings is low,which is still a research hotspot in academic cycle and a difficulty in engineering.One of the fundamental reasons is that the internal incentive of the bearing early failure is weak,vibration characteristics are easily influenced by the waviness,bearing clearances and lubrication oil film and other internal incentive effects,as well as the external incentive effect produced by the dynamic load ends and components.As a result,the mapping relationship between vibration characteristics and internal and external incentive of bearings is unclear,and the action mechanism is unclear,which affects the identification of early fault vibration characteristics.Therefore,it is of great theoretical value and engineering application value to carry out the modelling methods of internal and external incentives and vibration characteristics analysis for bearing,to reveal the mapping relationship between internal and external incentive and vibration characteristics of rolling bearings,and to study the influence law of waviness and clearance and other factors on early fault vibration characteristics.Around the simulation method of bearing displacement and stiffness incentive induced by waviness,local defects and clearance,coupled modeling method of internal and external incentive,firstly,the waviness characterization method and internal incentives modeling research is developed,secondly,the multi-scale simulation method based on bearing waviness and local defect,and bearing internal incentive model under multi-factor influence are carried out,finally,a modeling method of bearing-gear coupled dynamic model under the influences of gear meshing incentives and feature extraction method for faulty vibration signal are proposed.The main research contents of the thesis include:(1)In view of the problem that bearing waviness characterization method based on traditional sine signal cannot described enough the detail components of displacement and stiffness incentive induced by real wavy morphology,a waviness simulation method based on Gauss filter is proposed,which can accurately characterize the true morphology of waviness.The computation expressions of displacement and stiffness incentive of waviness are derived.A bearing nonlinear dynamic model considering waviness characteristics is established,the influence of characteristic parameters of waviness on vibration response is studied,and the variation of bearing vibration characteristics with waviness amplitude and order is analyzed.A bearing waviness vibration test rig is designed and built,compared with the experimental results,the validity and correctness of the proposed dynamic model is verified,which provides a theoretical support for accurate recognition of waviness vibration characteristics.(2)In view of the surface of local defects is convex and concave,and its early morphology scale is similar to the scale of waviness,which is difficult to identify the vibration characteristics induced by defect incentive,a multi-scale characterization model of waviness and local defects is established,a computing method for time-varying displacement incentive coupled with waviness and local defects and time-varying stiffness incentive is proposed.The influence law of the size of the local defects on the vibration characteristics is studied,the incidence relationship between the waviness and the size of local defect and the vibration characteristics is analyzed,which provides a new idea for internal incentive simulation of early local defects of bearings.(3)For the internal incentive computing problem affected by factors such as bearing waviness,clearances and oil film,a simulation method considering clearances,oil film thickness and stiffness is proposed.A bearing skidding dynamic model with comprehensive influence of waviness,clearance and oil film is established.The skidding characteristics are analyzed,the influence relationship between bearing clearances and slip characteristics is studied.A test rig is designed and built to verify the effectiveness of the method by comparing with the experimental results,which provides a new method for incentive simulation under combined effect of bearing waviness,clearance and oil film.(4)There is a strong correlation between the incentive of bearing dynamic load ends and components and the vibration characteristics of bearing.In order to clarify the influence law of gear meshing incentives on bearing and gearbox vibration characteristics,a bearing-gear coupled dynamic model is established.The bearing vibration characteristics and transformation law under influence of gear meshing incentives are analyzed.The distribution characteristics of spectrum and frequency sidebands are obtained.Further,a multi-scale demodulation and extraction method of bearing fault characteristics is proposed.The test rig of the gear transmission system is built,which verifies the correctness of the dynamic model and the effectiveness of the feature extraction method.(5)The method of bearing waviness characterization,the method of waviness and local defect scale characterization,and the method of internal incentive simulation for the comprehensive influence of waviness,clearance and oil film,and the bearing-gear coupling modeling method are integrated.A software of bearing internal incentive and response characteristics analysis is programmed,the hardware and software systems are built.The functions of bearing internal and external incentive simulation,vibration characteristic analysis and early fault feature extraction are realized,which are applied in actual projects with good results such as bearing delivery quality inspection and bearing screening. |
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