Simulation And Experimental Study On Operating Temperature Of Plastic Gears

With the rapid development of high-performance engineering plastics,the comprehensive mechanical properties of plastic gears are constantly improved.They are more and more widely used in the power transmission field.However,the decrease of service life,reliability and transmission efficiency caused by the operating temperature significantly restrict the development of plastic gears to the field of higher power transmission.Such as plastic gears’ viscoelastic contact behavior,operating temperature rise,multi heat source effect and so on mechanism have not been clarified.The operating temperature has a significant effect on the modulus of the gear,and the interaction and coupling mechanism of stress-deformation-temperature field further increases the complexity of the operating temperature field analysis of plastic gears.There are many factors affecting the operating temperature of plastic gears,such as lubrication,load and speed,etc.The relationship between the factors is close and complex.It is of great significance to clarify the factors that affect the operating temperature of plastic gears for reducing the temperature field,improving the loading capacity and supporting forward design system construction of plastic gears.Therefore,based on the geometries,operating conditions and material parameters of POM-POM gear pair,a numerical model of plastic gears operating temperature field considering friction heat flux-hysteresis heat flux multi heat source is established.The effects of load,speed and lubrication on steady and transient temperature are clarified,and experimental research is carried out,which has important theoretical value and practical significance.In this thesis,aiming at the problem that the operating temperature of plastic gears is difficult to predict under lubrication and the mechanism of friction – hysteresis heat generation is unclear in power transmission,based on the thermal viscoelastic constitutive equation,temperature-modulus effect,friction heat flux-hysteresis heat flux multi heat source effect and heat conduction theory,a numerical analysis model of plastic gears operating temperature field is established.The distribution of bulk steady temperature field and meshing point transient temperature field of plastic gears are studied.And the influence of multiple sensitive factors on the operating temperature of plastic gears are analyzed.Analysis and test method of operating temperature field of plastic gears are achieved,which provides support for forward design system construction of plastic gears.Main contents are described as follows:(1)A numerical model of temperature field of plastic gears based on multi heat source is established.In order to break through the limitation of Hertz contact theory,a thermos-viscoelastic contact model of plastic gears is established based on macro geometry of gear and thermo-viscoelastic constitutive equation of plastic.The formulas of friction heat flux and hysteresis heat flux based on discrete element method are derived.Considering the effect of temperature-modulus,hysteresis heat flux and friction heat flux under dynamic viscoelasticity,the numerical model of plastic gears operating temperature field is established,and the coupling iterative calculation method of material modulus-mechanical response-heat flux-gear temperature field is realized.(2)The influence factors of plastic gear operating temperature are analyzed.The distribution of steady and transient temperature fields are analyzed,and the difference between the hysteresis and friction temperature rise is analyzed.Considering the changes of operating conditions caused by load,speed and lubrication,the operating temperature rise mechanism,maximum steady and transient temperature are analyzed.The results show that the operating temperature of POM gear is mainly concentrated on the surface of the tooth profile and the contribution of hysteresis temperature rise is no more than 2%.Lubrication conditions have a significant effect on the operating temperature of plastic gears.Under the same load and speed,the operating temperature under grease and oil lubrication condition is significantly lower than that of dry operating condition.(3)Experimental study on operating temperature of plastic gears.Based on the multi-purpose transmission-friction test rig,the operation temperature test of POM gear pair was carried out.The test conditions include different torque,speed and lubrication conditions,namely dry operating,grease lubrication and oil lubrication.The operating temperature of POM gear pair is continuously measured by infrared thermal imager.The results show that the operating temperature of plastic gears increases with the increase of speed and torque under lubrication conditions.The prediction results of numerical model are in good agreement with the test results,and the model accuracy reaches 95%.