【作者】 谢兴源；

【导师】 朱旻昊；

【作者基本信息】 西南交通大学 ， 材料科学与工程， 2011， 硕士

【摘要】 根据接触副间相对运动方式的不同,球/平面接触条件下的微动可以分为切向、径向、扭动和转动4种基本模式,目前的研究主要集中在切向微动模式。扭转复合微动是扭动微动和转动微动的复合,常发生于回转体部件中,但相关研究较少。开展扭转复合微动的研究,不仅丰富了微动摩擦学的理论,而且对抗工业微动损伤有着重要的意义。本文基于新型低速高精度转动台和六维传感器成功研制的扭转复合微动试验装置,研究球/平面接触条件下的扭转复合微动运行行为和损伤机理。论文在不同角位移幅值、倾斜角和循环周次下,对7075铝合金与GCrl5钢球配副进行了系统的试验。并在动力学分析的基础上,结合光学显微镜(OM)、扫面电子显微镜(SEM)、电子能谱(EDX)和表面轮廓仪等进行微观分析。从动力学曲线、摩擦系数、耗散能、运行工况图等方面详细讨论了7075铝合金和LZ50钢扭动复合微动运行行为的差异；并以7075铝合金为研究对象,综合比较了扭动微动、转动微动和扭转复合微动这几种不同基本运行模式的异同。获得的主要结论如下：1.摩擦力-角位移幅值(Ft-θ)曲线可以用来表征扭转复合微动的动力学特性。通过大量的试验研究,得到了三种基本的Ft-θ线类型：直线型、椭圆型和平行四边形型。2.建立了7075铝合金扭转复合微动的运行工况微动图(RCFM),发现随倾斜角的增大,7075铝合金的混合区和滑移区向小角位移幅值方向移动。3.7075铝合金扭转复合微动的摩擦系数和摩擦耗散能强烈依赖于倾斜角、角位移幅值和循环次数。4.7075铝合金和LZ50钢扭转复合微动磨损的运行行为存在明显差异,即扭转复合微动强烈依赖于材料性质。5.角位移幅值一定时,7075铝合金扭转复合微动的磨损量随倾斜角的增大而增大,扭动微动时磨损量最小,转动微动的磨损量最大。6.研究表明倾斜角、角位移幅值和循环周次强烈地影响7075铝合金扭转复合微动的磨损行为,主要的损伤特征如下：a)部分滑移区：磨痕呈环状,接触区中心粘着且无损伤,损伤仅发生在接触区边缘的圆环上,磨痕呈非对称性；磨损机制主要为轻微的氧化磨损和磨粒磨损；此时微动白层已形成,但未见裂纹向基体内扩展。b)混合区：磨痕黏着区缩小,损伤区的磨损加重,磨痕非对称性增加；随循环次数的增加,相对运动状态由部分滑移转变为完全滑移；磨损发生在微滑区内,磨损机制主要为氧化磨损、磨粒磨损和剥层；剖面分析发现有明显的倾斜裂纹向基体内部扩展。c)滑移区：整个接触区均发生磨损,损伤严重；有大量的磨屑生成,倾斜角对磨屑的分布有重要的影响；主要磨损机制为氧化磨损、磨粒磨损和剥层；剖面未发现向材料内部扩展的倾斜裂纹,在磨损与疲劳的竞争过程中,滑移区的磨损占据了优势。更多还原

【Abstract】 According to the direction of relative motions, fretting can be defined as four basic modes under a contact configuration of ball-on-flat:i.e. tangential, radial, rotational and torsional fretting. At present, the researches focus on the tangential fretting mode. Dual rotary fretting is combined with torsional and rotational fretting. It usually occurred in many rotary components, but little research focuses on it up to now. Study on dual rotary fretting not only enriches the fundamental theory of fretting, but also has important guidance to palliate fretting damages in industry.Based on a rotary device with low speed and high precision and a six dimensional sensor, a dual rotary fretting tester has been developed to simulate the case of dual rotary fretting in this study under a contact of ball-on-flat. The dual rotary fretting tests for 7075 aluminum alloy against GCr15 steel ball have been carried out under different tilt angles, angular displacement amplitudes and number of cycles. Dynamic analyses in combination with the microscope examinations through optical microscope (OM), scanning electrical microscope (SEM), energy dispersive spectroscope (EDX) and profilometer, have been performed to study the running and damage mechanisms of dual rotary fretting in detail. The difference between 7075 aluminum alloy and LZ50 steel was discussed in dynamic curves, friction coefficients, friction dissipated energy and running condition fretting maps and so on. The similarities and differences of torsional fretting, rotational fretting and dual rotary fretting were also discussed. The conclusions have obtained as follows:1. The friction force vs. angular displacement amplitude curves (Ft-θcurves) could be used to characterize the kinetic characteristics of dual rotary fretting. According to a great deal test results, three types of Ft-θcurves could be obtained, i.e. linear, elliptic and parallelogram.2. Running condition fretting map (RCFM) of 7075 aluminum alloy was established, where the mixed fretting regime and the slip regime of 7075 aluminum alloy shift to the direction of lower angular displacement with the increase of tilt angle.3. The friction coefficients and friction dissipated energy of 7075 aluminum alloy were strongly dependent upon the tilt angle, angular displacement amplitude and number of cycles. 4. The running behaviors of 7075 aluminum alloy and LZ50 steel were quite different, i.e. the dual rotary fretting wear was strongly dependent upon the material properties.5. The wear volume of 7075 aluminum alloy was increased with increase of tilt angle at same angular displacement amplitude. The wear volume of torsional fretting was lowest but was highest of rotational fretting.6. It was found that the dual rotary fretting wear was highly dependent upon the tilt angle, angular displacement amplitudes and number of cycles. The damage features are outlined as follows:a) In the partial slip regime, the wear scar was asymmetric appeared in shape of annularity, and its center was sticking with free damage; and the micro-slip occurred at the outer ring of contact boundary zone, which corresponding with slight wear. The wear mechanisms mainly were slight oxidative wear and abrasive wear. In this regime, fretting white layer has been formed without cracks.b) In the mixed fretting regime, the sticking zone gradually shrank with the increase of the number of cycles, while the contact state transformed from the partial slip to the gross slip. The asymmetry of wear scar was enhanced accordingly. The wear occurred in the micro-slip region, and the wear mechanisms mainly were abrasive wear, oxidative wear and delamination. on the cross-section, some titled cracks propagated to the base alloy were observed.c) In the slip regime, the wear occurred at the whole contact zone, and the damage was severer with a great deal of wear debris. The distribution of wear debris was dependent upon the tilt angle. The wear mechanisms mainly were abrasive wear, oxidative wear and delamination in the slip regime. No tilted crack can be observed on the cross-section, which indicated that the wear held the superiority.更多还原