【作者】 张凤莲；

【导师】 王秀伦；

【作者基本信息】 大连交通大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 工程陶瓷不易被氧化、具有耐腐蚀、耐高温和耐磨损等优良性能。随着加工技术的发展,它有着替代其它材料的可能性,但工程陶瓷又是硬脆难加工的材料,采用传统的加工方法,使其加工成本高,加工效率低,加工质量不理想,并且有特殊形状要求的产品很难加工完成,限制了它的应用范围。对于工程陶瓷而言,磨料水射流(AWJ)加工是经济有效的非传统加工技术,它没有热、电和化学反应过程,在工件内不产生冶金、化学或物理特性的变化。可以加工出优质高效具有特殊性能的新型工程陶瓷产品。使其广泛应用于机械、电子、航空航天、国防工业、生物工程等领域。目前我国在磨料水射流切割工程陶瓷机理及关键技术方面的研究还很不充分,国内磨料水射流设备主要靠进口。此外由于缺少对磨料水射流切割机理的深入研究,引进设备的性能没有得到充分利用,加工产品的质量、效率及成本都与发达国家有相当大的差距。因此,本文研究成果的实施和进一步推广,会提高工程陶瓷产品的加工能力和扩大工程陶瓷的应用领域,对改善国内磨料水射流加工现状具有重要的现实意义。本文在实验的基础上,结合计算机仿真技术,对磨料水射流切割工程陶瓷机理及关键技术进行了深入研究。1.概述了工程陶瓷特殊加工技术和磨料水射流切割技术及其理论研究领域的最新发展。分析了磨料水射流切割工程陶瓷的关键技术,阐明了本文研究的目的和意义。2.应用两相流理论,分析磨料水射流的混合机理和流动特点,建立冲击力模型,进一步研究磨料水射流切割工程陶瓷,得出其切割机理是,磨料水射流喷射到工程陶瓷上,产生强大的冲击力,破坏陶瓷表面,形成微裂纹。水进入微裂纹形成水楔作用,在裂纹尖端拉应力集中;带有锋利棱角的磨粒对陶瓷进行微切削;液固两相高能束流对陶瓷产生强烈的冲蚀作用。在这几方面的作用下,裂纹进一步扩展,形成切槽。3.采用不同的工艺参数组合,用磨料水射流对几种常用工程陶瓷进行切割实验。研究分析了射流压力、磨料水喷嘴横移速度、靶距、磨料流量等工艺参数对切割效率和切割质量的影响。4.以理论为基础,应用实验数据得出模糊推理规则,建立了模糊控制模型。这个特殊的模糊控制模型可以预测在任何给定一组加工参数时,磨料水射流切割工程陶瓷材料可获得的切割深度。在给定切深的条件下,遗传算法结合模糊模型可以自动确定磨料水射流切割多种材料时的最佳参数组合。5.磨料水射流在磨料水喷嘴内流动时,对磨料水喷嘴会造成磨损,本文对磨损因素进行分类和确定。分别在实验和模拟仿真两种情况下,研究磨料水喷嘴的磨损规律,优化磨料水喷嘴结构。在实验的基础上研究了磨料水喷嘴的材料与加工工艺,提出了磨料水喷嘴国产化的途径。通过对磨料水射流理论的研究,为我国磨料水射流设备的设计和开发提供理论参考,通过实验得到的实验数据为生产磨料水射流系统中的关键部件提供设计参数。通过对工艺参数的研究,有效地利用各切割参数,达到切割效率和切割质量的最佳结合。基于混合策略优化工艺参数,节省了大量的实验工作,得到最佳切割效果。本文应用Fluent软件对磨料水喷嘴内部结构进行仿真,优化磨料水喷嘴结构,选用WC—Co粉末为磨料水喷嘴材料,用冷等静压压制喷嘴毛坯,用真空烧结成型。采用数控电火花高速穿孔机床加工磨料水喷嘴内部结构,加工出磨料水喷嘴内孔后,采用“挤压珩磨”加工,研制出的磨料水喷嘴与进口磨料水喷嘴相比,成本节省了50%。更多还原

【Abstract】 Engineering ceramics have good properties such as resistant to corrosion, high temperature resistance, wear resistance and impact resistance.With the development of processing technology, It has the possibility of substitution of other materials. However, using the traditional processing methods, there are the following issues: the high processing costs, processing efficiency is low, processing quality is not satisfactory, and there are special shapes required processing of the product is difficult to complete. These issues limit the scope of application of engineering ceramics.For engineering ceramics, the abrasive water jet machining is cost-effective non-traditional processing technology. It does not heat, electricity and chemical reaction process, the workpiece does not produce the metallurgical, chemical or physical properties change, AWJ can processe high quality and special properties of new engineering ceramic products. Engineering ceramic products are widely used in machinery, electronics, aerospace, defense industry, bio-engineering and other fields. At present, China in the abrasive water jet cutting mechanism of Engineering Ceramics and key technical aspects of the research is still far from fully. Domestic abrasive water jet equipment mainly imported. In addition, due to the lack of the abrasive water jet cutting mechanism of the in-depth study, The introduction of equipment performance has not been fully utilized. Abrasive Water Jet Machining product quality, efficiency and cost with a considerable gap between the developed countries. Therefore, this research to further promote the implementation and will facilitate the engineering ceramics processing and applications development, improve the domestic status of abrasive water jet machining has important practical significance.In this paper, based on the experiment, combined with computer simulation technology, abrasive water jet cutting of engineering ceramics mechanism and key technologies are studied.1. Engineering Ceramics special processing techniques and abrasive water jet cutting technology and its latest developments in the field of theoretical research are outlined. Analysis of the abrasive water jet cutting engineering ceramics key technologies, and clarify the purpose and significance of this study.2. Application of two-phase flow theory,abrasive water jet mixing mechanism and flow characteristics are analyzed, Impact force model is established, further study of abrasive water jet cutting engineering ceramics, obtain its cutting mechanism, the abrasive water jet spray to engineering ceramics, resulting in a strong Impact force, destruction of ceramic surface to form micro-cracks, water into the cracks to form water wedge in the crack, Tensile stress is concentration at the crack tip; Abrasive with sharp edges and corners, it is micro-cutting ceramics; liquid-solid two-phase high-energy beam on the ceramic produced a strong erosion effect. The role in these areas, the crack expanded, forming notch.3. Using different combinations of the parameters, abrasive water-jet cuts several commonly used engineering ceramics. Influence of the jet pressure, abrasive water nozzle traverse speed, target distance, abrasive flow rate of process parameters on cutting efficiency and cutting quality are researched and analysed.4. Based on theory and application of experimental data obtained fuzzy inference rules, the fuzzy control model is established. This particular fuzzy control model can predict cutting depth for any given set of processing parameters. At a given depth of cut conditions, the genetic algorithm combined with fuzzy models can automatically determine the best parameter combination of abrasive water jet cutting.5. Nozzle is worn when the abrasive water jet in the nozzle flow. Wear factors are classified and defined. Respectively, in the experiment and simulation both cases, the nozzle wear law being studied to optimize nozzle structure. On the basis of the experimental study of the nozzle materials and processing technology, proposed nozzle localization approach.Through the study of the theory of abrasive water jet, for equipment design and development provide a theoretical reference. The experimental data to provide design parameters for the production of key components Through the process parameters of the study, The cutting parameters are the effective use.Cutting efficiency and cutting to achieve the best combination of quality Optimization of process parameters with the hybrid method, save a lot of experimental work, get the best cutting results. In this paper, Fluent software to simulate the internal structure of the nozzle, optimizing the nozzle structure, and selection of WC-Co powder as the nozzle material, cold isostatic pressing to suppress the nozzle blank, using a vacuum sintering. Use of CNC EDM Machine, the internal structure of the nozzle is processed. Nozzle hole is honed with "Extrude Hone." Developed the nozzle compared with imports, the cost savings of 50%.更多还原