| In the face of the rapid development of industrial modernization,gear system is widely used in various mechanical transmission fields.High speed and heavy load become the inevitable trend of gear system development.In the design of gear system,the calculation of gluing strength and the control of temperature rise are essential for the gear transmission system running under high speed and heavy load conditions.Because of the high working temperature of gear system under high speed and heavy load,it is very easy to produce pitting,peeling and gluing faults,so the calculation of gluing strength and temperature rise control of gear system has become one of the main research directions in the design of gear system at present.For the calculation of the bonding strength and the control of the temperature rise of the gear system,one of the difficulties is the study of the transient temperature field of the gear surface.How to accurately calculate the transient temperature field of the gear surface has become the focus of scholars and enterprises.Starting with the heat transfer and Hertz contact theory,this thesis studies the gear system in different tooth shape parameters and different working conditions.At the same time,the transient temperature field of gear system with fault is analyzed.Based on the data of transient temperature field,the dynamic characteristics of gear system considering temperature are studied.The results of this thesis not only provide a new research idea for the method of fault diagnosis using temperature,but also lay a solid theoretical foundation and reliable data support for the research of thermal characteristics and temperature control design of gear system.(1)Taking the contact analysis of gear system as the starting point,the friction heat flux between tooth surfaces and the related calculation methods are analyzed theoretically.The transient temperature field of spur/helical gear system with different load,different speed,different friction coefficient between teeth and different tooth shape parameters is studied in detail.(2)The dynamic characteristics of the gear system under the structure-thermal coupling are studied.By calculating the transient temperature field of the gear system,the parameters of the transient temperature field are substituted into the dynamic simulation analysis of the gear system,so as to change the physical and mechanical properties of the materials in the operation process of the gear system,so as to achieve the purpose of the structural-thermal coupling dynamic analysis of the gear system.In this thesis,the meshing stiffness of the gear system under the consideration of temperature is analyzed,and the dynamic model of the gear system structure-thermal coupling is established.The STFT spectrum of the vibration acceleration and the dynamic load of the gear system under the condition of structure-thermal coupling are studied.The transient contact stress between the structure and the thermal coupling of the gear system is calculated,and the transient contact stress of the gear system with and without temperature is compared.The variation law of the transient contact stress between the structure and the thermal coupling of the gear system under different working conditions is revealed.(3)The matrix formula of the stiffness load ratio of the gear system with two teeth meshing is derived,the transient contact stress of the gear system with different crack depth is analyzed,and the influence of crack fault and crack depth on the transient contact stress of the cracked teeth and the surrounding tooth region is revealed.Based on the transient contact stress,the transient temperature field of the cracked tooth and the surrounding tooth region is calculated,and the influence of different crack depth,load and friction coefficient on the transient contact temperature of the cracked tooth and the surrounding tooth region is analyzed.(4)Through the establishment of three-dimensional model of gear system with two kinds of mechanical errors of shaft misalignment and excessive wheelbase,the influence of two kinds of mechanical errors on the contact process of gear system is analyzed.The transient temperature field of spur gear and helical gear with two kinds of mechanical errors is calculated respectively.By comparing the transient temperature field of no fault and mechanical error fault,the influence rule of two kinds of mechanical errors on the transient temperature field of spur gear and helical gear system is obtained.At the same time,the transient temperature field of spur gear and helical gear system is studied under different error amount.(5)The dynamic model of the multi degree of freedom gear rotor system with root crack and shaft crack is established.By calculating the transient temperature field of the gear rotor system with different crack positions,the STFT spectrum of the vibration acceleration of the gear rotor system considering the temperature is obtained.The STFT spectrum of the vibration acceleration of the rotor system is analyzed when the root of driving wheel and driven gear is cracked at the same time.Based on the FFT spectrum of the vibration acceleration of the system,the dynamic characteristics of the gear rotor system with the crack of the driving shaft and the simultaneous crack of the driving shaft/driving gear root are studied.The STFT spectrum of the vibration acceleration of the system with the crack of the driving shaft and the simultaneous crack of the driving shaft/driving gear root is studied through the acceleration experiment.Finally,the modal analysis of the system is carried out,and the influence of different crack size and location on the natural frequency of the gear rotor system is analyzed.(6)The FZG(closed power flow)gear test-bed is built and improved.The test gear is tested under different working conditions.The temperature of the experimental gear is monitored by three different measuring methods,and the temperature field data of the experimental gear under different working conditions are collected.The temperature field of the test gear is calculated by the finite element method,and the correctness of the research method and the accuracy of the data are verified by comparing the experimental results and the finite element results. |
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