【作者】 吕尤；

【导师】 韩志武；

【作者基本信息】 吉林大学 ， 仿生科学与工程， 2012， 博士

【摘要】 在汽车行驶过程中，汽车变速箱齿轮就成为了传递动力的主要载体之一，但是，由于齿面长期承受滚动与滑动交变的接触应力作用，使得齿根长期承受弯曲应力作用，轮齿次表层将出现疲劳裂纹的形核与扩展，最终导致断齿。这就将造成不可估量与不可挽回的人民群众生命财产安全方面的损失，由此可见，增强汽车变速箱齿轮的抗疲劳性能对人民群众的生产生活具有十分重要的现实意义。本文以工程仿生学的研究方法为基础，采用激光表面热处理技术在齿轮表面局部区域制备网格型仿生表面形态，进而改善齿轮的抗疲劳性能，并应用有限元软件进行数值分析，从多个方面研究仿生表面形态对齿轮抗疲劳性能的影响。本文主要工作与结论如下：根据工程仿生学的研究方法，设计了9组网格型仿生表面形态参数组合，并以CT—200Ⅱ数控激光刻花机作为实现仿生表面形态的主要设备，在齿轮表面局部区域制备仿生表面形态，也即在齿轮表面制备出了硬度较高的硬化层。仿生表面形态齿轮的接触疲劳试验：首先，根据试验优化设计方法编排试验方案，然后，通过对辊试验来完成仿生表面形态参数的优化选择过程。应用显微镜直接观察法来探究仿生表面形态、试件表面疲劳损伤和点蚀率之间的变化规律。试验结果表明：所有仿生表面形态辊子的抗疲劳性能均不同程度地优于普通辊子试件，其中2号辊子试件的点蚀率最小，其点蚀率为2.46%。最终优选出最佳网格型仿生表面形态为条纹宽度50μm、条纹横向间距150μm、条纹纵向间距250μm。随后进行了最优仿生表面形态齿轮和普通齿轮的台架对比试验，通过最优形态齿轮与普通齿轮的平均点蚀率的比较表明，最优网格型仿生表面形态能够将齿轮的抗疲劳强度提高2.91倍，且仿生表面形态改变了齿轮的接触疲劳失效规律，使得节圆附近区域的点蚀更少，具有仿生表面形态的齿轮在试验前后齿向误差值的变化更小。仿生表面形态齿轮的弯曲疲劳试验：根据试验优化设计方法编排试验方案，采用双齿脉动载荷作为弯曲疲劳试验的加载方式，进行了9种网格形态与普通齿轮的弯曲疲劳试验，以达到弯曲疲劳失效标准时的应力循环次数为弯曲疲劳寿命。试验结果表明：与普通齿轮的抗弯曲疲劳性能相对比，所有具有仿生表面形态的齿轮的抗弯曲疲劳性能都显著增强，仿生表面形态将齿轮的弯曲疲劳寿命提高了1.06～1.42倍，其中1号形态齿轮的弯曲疲劳寿命最长，为121.5×10~3。最终优选出最佳的网格型仿生表面形态为条纹宽度150μm、条纹横向间距150μm、条纹纵向间距250μm。通过对具有仿生表面形态的齿轮和普通齿轮的弯曲疲劳试验和接触疲劳试验的结果数据分析，就能够探究仿生表面形态与齿轮抗疲劳性能之间的变化规律，进而能够揭示出仿生表面形态改善齿轮抗接触疲劳性能的机理：通过激光表面热处理工艺所获得的硬化层能够显著提高齿轮的抗接触疲劳强度，能够阻止疲劳裂纹的形核与扩展；激光表面热处理技术能够在齿轮表面的一定深度的范围之内积累了一定的的残余压应力。在齿轮的运行过程当中，这些残余压应力的逐渐释放，就将有助于改善齿轮的抗接触疲劳性能；另外，仿生表面形态还具有阻止疲劳裂纹的形核和扩展；储存磨屑；改善齿轮副运转过程中的润滑条件等各种优点。应用MSC.Nastran有限元软件进行了齿轮静力学问题的数值模拟。通过齿轮静力学问题的数值模拟所得到的形变位移云图和等效应力云图表明，在承受相同强度的均布载荷作用时，仿生表面形态齿轮和普通齿轮的形变趋势基本相同，形变量峰值均出现在齿顶。但由于仿生表面形态的存在，使得齿轮的形变量明显降低，从而，更有利于提高齿轮的抗疲劳强度，有利于减少由轮齿形变而引起的断齿等疲劳失效情况的发生。且二者的等效应力分布趋势基本相同，等效应力峰值均出现在齿根。但由于仿生表面形态的存在，使得齿轮的应力值明显降低，从而，有助于改善齿轮的抗疲劳性能，延长齿轮的疲劳寿命。应用MSC.Nastran有限元软件进行了齿轮动力学问题的数值模拟。通过齿轮瞬态频率响应和瞬态冲击响应问题的数值模拟所得到的曲线表明，在承受相同强度的频率和冲击激励作用时，仿生表面形态有效地降低了齿轮的形变量，进而能够减少由于轮齿变形而引起的折断等疲劳失效情况的发生。通过齿轮模态问题的数值模拟分析结果表明，仿生表面形态齿轮和普通齿轮的振型类型均为5种，且二者振型类型相同，但振型变化顺序有所区别，主振型均为弯曲振。仿生表面形态齿轮基本上各阶的最大振幅均小于普通齿轮。仿生表面形态齿轮的固有频率范围更集中，且上升趋势更平缓。由于仿生表面形态的存在，将有效地降低齿轮运行过程中的振动与噪声，从而，改善齿轮的动力学性能，延长齿轮的疲劳寿命。应用MSC.Nastran有限元软件进行了齿轮热力学问题的数值模拟。通过齿轮热传导问题的数值模拟所得到的温度分布云图和温度梯度云图表明，当齿面承受相同强度的热载荷时，仿生表面形态齿轮的温度峰值小于普通齿轮。随着润滑油温度的升高，润滑油的粘度会降低，形成油膜的能力将减弱，齿面更易形成点蚀，因此，仿生表面形态齿轮齿面的较低温度能够有利于减缓润滑油的失效，改善齿轮的润滑条件。普通齿轮的齿面出现两个温度峰值区域，而仿生表面形态齿轮的温度峰值区域只有一个，且区域面积较小，这都有利于延长齿轮的疲劳寿命。仿生表面形态齿轮的最大温差值小于普通齿轮，仿生表面形态的存在增大了齿面的受热面积，有利于迅速散热，从而，使得仿生表面形态齿轮齿面的温度梯度变化更为均匀，均匀的温度梯度变化对齿轮裂纹的萌生和扩展具有一定的遏阻作用。更多还原

【Abstract】 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.更多还原