【作者】 宋桂珍；

【导师】 李元宗；

【作者基本信息】 太原理工大学 ， 机械电子工程， 2010， 博士

【摘要】 磨料流加工是应用粘弹性磨料加工工件的一种特种光整加工方法,能够很好地抛光零件的复杂表面和不可见区域,如窄缝、微孔、交叉孔、异形孔腔等,能够将倒圆角、去毛刺和抛光同时完成,可加工的材料范围宽,不仅能加工金属材料,还能加工陶瓷、硬塑料等。本文从流体磨料、加工机理、工艺参数关系、表面完整性、加工异常等方面对磨料流加工技术进行了理论探讨和实验研究。首先,从改善流体磨料的性能入手,研制了适应不同加工工艺要求的新配方。提出基于模糊数学理论的流体磨料粘度的分级方法,建立了粘度的隶属函数,为加工应用提供了选择依据。提出了基于机电一体化技术的粘度的精确测量方法,为仿真研究奠定了基础。其次,着重研究流体磨料的流变行为及其加工特性。推导了边界条件不为零的流速分布公式。在研究工艺参数对倒圆尺寸影响的过程中,发现了“准倒圆”特性,进而探讨其形成机理,认为是流体磨料的弹性湍流所致。分析了去毛刺机理,讨论了单向加工和双向往复加工的去毛刺效果。从微观的角度研究了微小的单个磨粒的受力情况及其对微观不平表面的抛光机理,揭示了加工过程中磨削与滚压共存的加工机理。通过实验探明加工循环次数对表面粗糙度的影响以及对轮廓支承长度率的影响,结果表明:前几次加工循环对于改善表面质量十分关键,磨料流加工能够提高零件表面的耐磨性,延长使用寿命。分析研究了波纹状表面和漏流强磨等异常现象的产生机制,认为表面产生波纹是由于加工工况使粘弹性流体磨料超过弹性变形极限所致,并预测了可能出现的更加异常的情况,而漏流处工件和夹具均造成强烈磨损是因为此处具有薄壁小孔的结构特点,流速很大。这些研究结论为保证加工质量,预防残次品的出现提供了理论支持。开发了温度的实时检测和控制系统。探明了磨料流加工过程中的温度变化规律,对照加工机理分析了呈现这种规律的必然性。研究了温度对加工表面粗糙度的影响,指出控制温度对稳定加工质量、提高加工效率以及预测加工结果的重要性。课题研究的最终目的是为了合理控制加工参数获得高质量的加工表面,为此特别研究了表面形貌和能谱,检测了表面的显微硬度。结果表明:表面完整、无撕裂,表面显微硬度略有增大。在长期的实验研究中发现磨料流加工表面还具有防锈性,通过分析工艺特点和流体磨料的本质揭示了磨料流加工工艺本身具有这种固有的防锈特性。考虑到现有检测仪器受结构所限,无法检测窄缝、微孔、异形孔腔等适合磨料流加工的特殊部位,提出基于计算机视觉的检测方法,并在部分实例加工中加以应用。最后,通过对模具、热流道板、齿轮、光纤连接器陶瓷套管、摆线转子马达的定子、喷嘴、长管、曲管等零件的加工验证了理论研究结果的合理性和正确性。更多还原

【Abstract】 Abrasive Flow Machining (AFM) is a non-traditional finishing process, which processes component by using a flowable viscoelastic abrasive mixture. AFM possesses excellent capabilities for finishing of complicated surface and inaccessible regions of a component, such as narrow slits of component, micro- voids, cross holes, shaped holes and cavity, and so on. The process can achieve radiusing, deburring, and polishing simultaneously. The AFM can be used for a wide range of materials including metals, ceramic and hard plastics. This paper presents theoretical analysis and experimental results of an investigation into some aspects of the mixture performance, AFM process mechanism, parametric relationships, surface integrity, and abnormal process.First, new formulas, applied in different areas, were developed by improving the properties of flowable mixture. The method of classification for viscosity of flowable mixture on the basis of the fuzzy mathematics theory was indicated. The membership functions of viscosity were founded to provide a way of selecting flowable mixture. The accurate method of measuring viscosity of flowable mixture based upon the integrative technology of mechanics and electrics was also presented to establish the foundation for emulational research.Secondly, the rheological behavior and processing properties of flowable mixture were studied in detail. The velocity formula of flow with a boundary condition of nonzero was derived. In during of investigateing the effect of primary process parameters on the size of radiusing, the characteristic of quasi-radiusing was found and inferred to result from elastic turbulent flow of flowable mixture by investigating the formation mechanism. Then the deburring mechanism of AFM was analyzed. The effects of deburring of single direction process and to-and-fro process were discussed. The load of small and single abrasive was estimated using the microcosmic method, and the polishing mechanism of microscopic and uneven surface was analyzed. The process mechanism that grinding and rolling coexist in during AFM was revealed. The effects of processing cycle times on the surface roughness and the sustaining length ratio of profiles were evaluated. It was found that the first few processing cycles were crucial to improve the quality of surface. It was shown that AFM made the surface of component more wearable and the useful life of component longer.The mechanisms of some abnormal processes, such as corrugated surface and serious wearing surface due to leakage flow, were analyzed. It is thought that the corrugated surface results from the elastic deformation of flowable mixture exceeding allowance because of AFM process parameters. According to the mechanism, much more abnormal phenomenona which appeared possibly were forecasted. The serious wearing occurs at the place of leakage flow between component and fixture because the flowable mixture flows at a high speed through the place which presents the configuration of small hole with short length. These provided theoretically support for insuring process quality and preventing wasters from producing.The equipment of real-time detecting and controlling temperature was developed. Using the equipment, the variation of temperature was revealed during the process of AFM, and the inevitability of the variation was testified corresponding to the process mechanism. The influence of temperature on the surface roughness processed was investigated. The results showed that the temperature was important to stabilize the processing quality, enhance the processing efficiency and predict the processing outcomes.With the ultimate aim of obtaining excellent processing surface through process controll in the thesis, the surface appearance and energy dispersive spectrum (EDS) were investigated. The micro-hardness of surface was measured. The results indicated that the surface was integrated, not tearing. Moreover, the micro-hardness of surface slightly increased. It was found that the surface of AFM was antirust and this was the intrinsic characteristic of the technology for AFM by analyzing the trait of technology and the hypostasis of flowable mixture. In view of the structural limitation in the existing apparatus, the special position adapting to AFM such as narrow cracks, micro-voids, shaped cavity etc can’t be detected. Accordingly, a novel detecting method based on computer vision was developed and applied in some experiments.Finally, the rationality and correctness of the theoretical results were proved by processing some components,such as mould, hot runner, gear, ceramic tube of optical fiber linker, stator of cycloid motor, nozzle, long stainless pipe, bent pipe, and so on.更多还原