【作者】 布光斌；

【导师】 王珉； 左敦稳；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 铝合金整体叶轮是小型发动机上的关键部件。近年来,随着国防工业和国民经济的发展,市场对该类零件的需求急剧增长;因此,如何实现该类零件的高效生产已成为工业界和学术界共同关注的课题。本文从叶片加工工艺及其参数优化以及五轴数控铣削加工应用的角度,对铝合金整体叶轮加工增效的关键技术开展理论、试验及仿真研究,旨在实现该类零件加工效率的大幅度提升。本文完成的主要工作及取得的成果如下:1.对五轴数控加工过程中的误差产生原因进行了分析,给出了行距和步距的确定标准。通过刀具矢量控制算法,实现了无干涉的加工路径规划。使用UG软件进行数控编程,采取建立驱动面的侧刃驱动方式,内外公差设置为0.001mm,叶缘头处设置刀轴最大更改值为3o,获得了满意的刀轨程序并生成了五轴数控加工程序,并得到试验验证。2.设计了专用测力工装,采用Kistler测力系统,对叶片四轴和五轴加工过程中动态切削力的分布进行了实验研究。结果表明,四轴和五轴加工过程中的切削合力均随切削速度的提高呈现先上升后下降的趋势;但四轴加工过程中,切削力波动较大,易引起切削不稳;而五轴加工过程中,切削力相对平稳,且在叶背和叶盆区域,其切削合力值基本不变,没有四轴切削时的冲击现象。3.对数控铣削过程中叶片模态的变化进行了实验和仿真研究。结果表明,叶片有两阶模态,其模态频率随材料的去除呈现先增大后减小的趋势,但振型变化不大。在Altinas的理论基础上,考察了毛坯材料去除对Lobes图的影响,建立了三维Lobes图,并通过切削试验验证了该Lobes图的正确性,从而为无振动加工参数选择奠定了基础。4.对五轴数控铣削后叶片表面质量进行了试验研究。结果表明,叶片表面粗糙度值随每齿进给量的减小而减小,并随切削速度的提高而降低;叶片表面纹理随每齿进给量的减少,先后呈现蜂窝状、长矩形、正方形、扁矩形,最后到垄沟状;叶片表面三维形貌也反映了相同的变化趋势;叶片表层硬度比基体高,最大硬化程度达到22.5%;叶片表面变质层深度范围为5μm~10μm,无裂纹等缺陷。5.对叶片四轴和五轴数控加工进行了对比。结果表明,四轴加工有50%左右的无效切削路径,而五轴加工基本没有;在相同的加工参数下,五轴加工时间比四轴加工时间短;四轴和五轴加工的进给速度都存在上限,但五轴的上限值比四轴的高。优化了叶片的加工路线,更换了开槽和铣叶形的机床,用编制的五轴数控程序替代原四轴数控程序,从而使叶轮的精加工效率提高了50%。最后,设计并实现了整体叶轮加工参数推荐系统。更多还原

【Abstract】 As the key part of mini-type turbine engines,the demand for Al-alloy integral impeller has been increasing in recent years along with the development of economy and our national defense. However, how to increase the production efficiency of Al-alloy integral impeller has been a major problem of industry and academia. From the perspective of optimization of manufacture parameter and application of 5-axises milling, this paper aims to do research on key technology to increase NC milling efficiency of Al-alloy impeller. Based on the theoretical analysis and experiments, the manufacture efficiency of this type of integral impeller was increased a lot.Main works and achievements of this paper were shown as follows:1. The cause of error of the 5-axises machining process was analyzed. The standard of feed distance and pick distance was given out based on it. A un-interfere tool path was obtained via tool vector control algorithm. 5-axises NC program was produced by UG. A drive surface was built. Swarf Drive method was used while NC program was built. The tool change value was set 3 degree at the edge of blade. A VERICUT simulation and an experiment were done. A qualified blade was obtained.2. A private clamp was designed and produced. Kistler dynamometer was used to measure the cutting force of 4-aixses and 5-aixses blade machining process. Results showed that cutting force fluctuation was bigger while blade was machined with 4-axises. Cutting forces of 5-axises were comparatively smooth. Resultant cutting forces of both taken on a tendency increased first and then decreased with cutting speed increased.3. The change of blade modal was investigated by experiment and FEA simulation while material removal. Two grade modals in the area could be detected by sensor. The frequency of modal went up at first, and then went down with the material removal. Modal shape was not change with the removal. Based on the theory of Altinas, the influence of stock removal to the Lobes was researched and 3-D Lobes were built. Some cutting experiments were done to validate the 3-D Lobes.4. Surface roughness Ra decreased with the decrease of feed and with the increase of cutting speed. Surface texture changed with feed. It looked like a honeycomb at first and then a rectangle later, with the decrease of feed. Longitude mark vanished with the decrease of feed, at last. Surface topography reflected the same tendency. Surface hardness was higher than base. The max value of work hardening capacity was 22.5%. The thickness of affected layer was between 5μm and 10μm that measured under SEM had the same tendency of hardness. There was no defect in the layer.5. Compared with 4-axises, there were natural advantages when 5-axises machining was used. There was almost no invalid path while cutting with 5-axises compared with 50% invalid while milling with 4-axises. 5-axises milling is more efficient than 4-axises under the same cutting parameters. What’s more, the upper limits of 5-axises is higher than 4-axises machining. Manufacture route was optimized to improve the machining efficiency. The machine of fluting and blade surface milling was changed. 5-axises NC program replaced 4-axises at same time. The manufacture efficiency of integral impeller was increased 50% under the synthesis action of these works. The expert system of cutting parameter on machining Al integral impeller was designed and realized.更多还原