Bionic Investigation And Numerical Simulation On Anti-fatigue Resistance To Automobile Gear With Grid Surface Morphology

The gears are often shifting in the automobile gearbox. The gear surface is suffering therolling and sliding alternative contact stress. The gear root is suffering the bending stress.The crack initiation is very easy for the gear. Even the bending fatigue fracture is oftenhappened to the gear. It could be the inducement of the aggravation of crack propagation.The fatigue failure of the gear will lead to the deterioration of automobile performance, thereplacement and maintenance of the parts, the increment of the fuel consumption, etc. Thehuge economic loss will be caused by it. According to the relevant principle of theengineering bionics, the gear surface and gear root had been processed by the laser. The gridbionic surface micro-morphology was processed on the gear by the laser engraving machineto improve the anti-fatigue resistance of the gear. The numerical analysis had been carriedout based on the finite element software. It is to research the influence of the bionic surfacemicro-morphology for the anti-fatigue performance of the gear from various aspects of FEM.According to the relevant principle of the engineering bionics, nine kinds of grid bionicsurface micro-morphology had been designed. It had been processed by the NC laserengraving machine under the appropriate parameters. It had been engraved on the gearsurface and gear root. The hardness test showed that the hardness of gear surface had beenprocessed by laser was much higher than the gear body.The contact fatigue experiment of the gear with bionic surface micro-morphology:According to the principle of the experimental optimum design, the experimental schemehad been arranged by the orthogonal design. The optimization test of rollers with the bionicsurface micro-morphology had been carried out. The situation of the gear fatigue failure hadbeen observed and analyzed by the stereomicroscope. The pitting ratio of the rollers hadbeen gotten. The experimental results showed that the anti-fatigue performance of all therollers with bionic surface micro-morphology was much better than that of the ordinaryroller with different extent. The pitting ratio of No.2bionic surface micro-morphology wasthe lowest among them. It was2.46%. The optimizing parameters of the bionic surfacemorphology was Stripe width50μm, Stripe transverse space150μm, Stripe longitudinal space250μm. Then the contrast test between the gear with the optimizing bionic surfacemicro-morphology and the ordinary gear had been carried out. Through the comparison ofthe average value of the pitting ratio between the two kinds of gears, the anti-fatigueresistance of the gear could be improve to291%by the optimizing bionic surfacemicro-morphology. The law of contact fatigue failure of gear had been changed by theoptimizing bionic surface micro-morphology. The pitting of the gear surface near the pitchcircle had been alleviated. The changes of the longitudinal form error of the gear with theoptimizing bionic surface micro-morphology were much smaller than that of the ordinarygear after the experiment.The bending fatigue experiment of the gear with bionic surface micro-morphology:According to the principle of the experimental optimum design, the experimental schemehad been arranged by the orthogonal design. The pulsating load had been applied to thedouble teeth. The bending fatigue experiment for the gears with nine kinds of gird bionicsurface micro-morphology and the ordinary gear had been carried out. The stress circle timeswere the bending fatigue life of the gears until the gears had come to the standard of thebending fatigue failure. The experimental result showed that the anti-fatigue performance ofall the gears with bionic surface micro-morphology was much better than that of the ordinarygear with different extent. The fatigue life of the gears could be prolonged to106%-142%bythe bionic surface micro-morphology. The fatigue life of No.1bionic surfacemicro-morphology was the longest among them. It was121.5×10~3. The optimizingparameters of the bionic surface morphology was Stripe width150μm, Stripe transversespace150μm, Stripe longitudinal space250μm.Through the analysis of the experimental results between the gear with gird bionicsurface micro-morphology and the ordinary gear, the mechanism of the anti-fatigueresistance had been improved by the bionic surface micro-morphology had been obtained.The hardness of the gear surface had been improved by the laser engraving technology. Andit was beneficial to improve the anti-fatigue resistance of the gear. The residual compressivestress had been accumulated by the laser engraving technology. And the bending tensilestress could be offset by the residual compressive stress release. The fatigue life of gearwould be prolonged by such kind of mechanism. The crack initiation and propagation wouldbe prevented by the grid unit. The existence of the grid bionic surface micro-morphologywas in favor of the storage of the abrasive dust. The abrasive wear could be prevented bysuch kind of mechanism. The existence of the grid bionic surface micro-morphology was infavor of the storage of lubricant. The lubrication conditions could be ameliorated by such kind of mechanism. The existence of the grid bionic surface micro-morphology was in favorof the increment of contact surface. The heat dissipation could be increased. Thethermoplastic deformation of gear could be decreased.The dynamic numerical simulation had been carried out by applying the MSC.Nastransoftware. The analysis curve of transient frequency response and transient shock responsehad been obtained. The results of the numerical simulation showed that the deformation ofthe gear with bionic surface micro-morphology was much smaller than that of the ordinarygear under the same frequency and shock excitation. The deformation of gear tooth and eventhe tooth fracture could be prevented because of the bionic surface micro-morphology. Theresults of the modal analysis showed that they both had five kinds of modal shape. Thevariation order of the modal shape of the gear with bionic surface micro-morphology wasdifferent from that of the ordinary gear. The most of maximum amplitude of the gear withbionic surface micro-morphology was smaller than that of the ordinary gear. The naturalfrequency range of the gear with bionic surface micro-morphology was much narrower thanthat of the ordinary gear. The increased trend of the natural frequency of the gear with bionicsurface micro-morphology was much slower than that of the ordinary gear. Because of theexistence of the bionic surface morphology, the vibration and noise of the gear box could beprevented. The dynamic performance of the gear box could be improved effectively. It isimportant for prolongation of fatigue life of gear.The thermodynamic numerical simulation had been carried out by applying theMSC.Nastran software. The cloud picture of temperature distribution and gradient of hadbeen obtained. The results of the numerical simulation showed that the temperature peak ofthe gear with bionic surface micro-morphology was much lower than that of the ordinarygear under the same thermal load. With the temperature increment of the lubricant, the oilviscosity was decreasing. The oil film was much harder to form. The pitting was much easierto form. The lower temperature on the gear surface with micro-morphology was beneficial toreduce the lubrication failure and to improve the lubrication condition. There were twotemperature peak zones on the ordinary gear surface. And there was only one temperaturepeak zone on the gear surface with micro-morphology. The area of the temperature peakzone was smaller than that of the ordinary gear. It is in favor of prolongation of fatigue life.The largest temperature difference of the gear with bionic surface micro-morphology wasmuch smaller than that of the ordinary gear. Because of the existence of bionic surfacemicro-morphology, the heating area on the gear surface was larger than that of the ordinarygear. It is important for the heat dissipation. The temperature gradient variation of the gear with bionic surface micro-morphology was much more uniform than that of the ordinarygear. The crack initiation and propagation could be prevented by such kind of mechanism.The static numerical simulation had been carried out by applying the MSC.Nastransoftware. The cloud picture of deformation displacement and von mises of had been obtained.The results of the numerical simulation showed that the deformation trend of the gear withbionic surface micro-morphology and the ordinary gear were almost the same under thesame uniform load. The deformation peak value of the two kinds of gears was at addendumcircle area. Because of the existence of the bionic surface micro-morphology, thedeformation of the gear surface with micro-morphology was much lower than that of theordinary gear. The deformation of gear tooth and even the tooth fracture could be preventedbecause of the bionic surface micro-morphology. The von mises distribution trend of twokinds of gears was almost the same. The von mises peak value of the two kinds of gears wasat root circle area. Because of the existence of the bionic surface micro-morphology, the vonmises of the gear surface with micro-morphology was much lower than that of the ordinarygear. The anti-fatigue resistance of the gear had been improved by the bionic surfacemicro-morphology.