【作者】 陈根余；

【导师】 李力钧；

【作者基本信息】 湖南大学 ， 机械制造及其自动化， 2006， 博士

【摘要】 青铜金刚石砂轮具有异常优良的磨削性能,在难加工材料的磨削、精密磨削、高效磨削和磨削自动化中有广泛的应用前景。近年来,由于砂轮制造问题得以突破及陶瓷、玻璃等难加工材料应用增多,青铜金刚石砂轮应用急剧增加。由于金刚石硬度极高,传统的单一的“硬碰硬”修整方法不适应青铜金刚石砂轮的修整,严重影响了其优良磨削性能的充分发挥。青铜金刚石砂轮的修整是其进一步推广应用的瓶颈问题和数控精密磨床中迄今未完全解决的关键技术难题。寻找一种从根本上解决青铜金刚石砂轮修整问题的修整方法,成为各国学者研究的目标。本文综述了国内外研究现状后,从青铜金刚石修整的本质出发,指出关键问题是:找到能有效直接微米级去除金刚石的方法;能实现选择性去除,能有效、高效提高修整精度;同时能突破传统概念,既能整形又同时实现修锐。传统的基于力和电的方法不能有效直接去除金刚石,较理想的方法是基于微区热作用的激光烧蚀微细加工激光修整。笔者从理论和试验上全面开展了研究。首先,提出声光调Q脉冲激光以其单脉冲功率密度高、脉宽窄、占空比小、易于控制等特点,是青铜金刚石砂轮修整的合适光源。自行试制了一台声光调Q Nd:YAG激光器,通过测量,该激光器输出的最大平均功率可达100W,最小脉宽约为170 ns,重复频率0.5~50kHz。其次,为了寻找合适的烧蚀去除金刚石磨粒和结合剂的激光参数,使得烧蚀后磨粒无微裂纹,变质层浅,烧蚀后仍具有良好的磨削性能,修整后可得到良好地形地貌,分别进行了单脉冲激光烧蚀青铜结合剂和金刚石磨粒及青铜金刚石砂轮的理论和试验研究。通过理论计算确定了在不同脉宽情况下青铜结合剂与金刚石磨粒单脉冲激光烧蚀功率密度阈值。表明声光调Q脉冲激光可有效去除金刚石和青铜,建立了脉冲激光烧蚀单晶金刚石颗粒的数学模型。通过模拟计算,得到脉冲激光的脉宽和占空比是影响变质层厚度和表面微裂纹的最主要的因素。同时通过试验,找到了合适的激光烧蚀参数。针对砂轮,建立了二维几何和数学模型,采用数值计算的手段模拟烧蚀去除时情况,并通过试验验证了当激光功率密度在1.41×107 W/cm2～2.85×108 W/cm2(f=1kHz)时,只可进行修锐;而当激光平功率密度达到2.85×108 W/cm2(f=1kHz)后,可进行整形,并可实现整形和修锐的合二为一。通过理论和试验分析了激光修整青铜金刚石砂轮的机理是在短脉冲高功率密度激光作用下,大部分能量用于气化去除材料,主要是通过浅层气化机制实现材料烧蚀去除。随后,针对目前尚无有效和高效纠正青铜金刚石砂轮圆跳动误差的方法,本文采用激光径向辐照,基于光学三角测量方法,测量光源与加工光源合二为一,研制了闭环控制电路控制脉冲激光,在线检测待加工表面相对于指定位置的偏移,当测量信号表明被测点高于预定位置时,发出巨脉冲激光对该点进行微量烧蚀,否则不发出巨脉冲激光,从而进行选择性烧蚀,可快速消除砂轮较大的圆跳动误差,达到10μm左右精度。试验证实激光整形同时可实现修锐。进一步研究了激光-机械复合精密修整技术,该技术适合于磨粒尺寸较大的青铜金刚石砂轮精密修整。最后,为了检验激光的修整效果和激光参数对修整效果的影响规律,进行了激光修整青铜金刚石砂轮磨削氧化铝陶瓷磨削力和工件表面粗糙度试验研究。表明合适的激光和工艺参数修整后,可进行有效磨削。并且激光修整法优于碳化硅滚轮修整法修整效果。本文主要创新成果如下:1、首次采用声光调Q YAG脉冲激光径向辐照烧蚀青铜金刚石砂轮,实现金刚石磨粒的无损伤微量去除,为实现青铜金刚石砂轮精密修整奠定基础;2、突破传统概念,打破目前超硬磨料砂轮整形和修锐要分两道工序进行的模式。实现整形与修锐同时进行,两道工序合二为一;3、创造性地将光学三角测量及闭环控制系统与激光修整装置集成,自行研制了闭环测控系统;4、通过理论与试验研究,选择合理的激光、运动参数,闭环控制激光径向辐照,实现了青铜金刚石砂轮的精密修整;验证了激光修整后的砂轮的磨削性能。更多还原

【Abstract】 With excellent grinding performance, the Bronze-bonded diamond wheels have a wide application prospect in the field of precision, ultra-precision, high efficiency grinding, grinding automation and difficult processing material forming. In recent years, Because of the breaking through of the grinding wheels manufacture question and the Increasing application to difficult processing materials such as ceramics, glasses and so on, Bronze-bonded diamond wheel’s application growth sharply. Because of the ultrahigh hardness of diamond, It’s difficultly for traditional truing and dressing method which was based on the interacton of force to promot.which really affects the grinding performance of Bronze-bonded diamond wheels, and also is the key problem which up to now not solved completely in the accurate numerical controlling grinding machines. A new method which to solve Bronze-bonded diamond wheel’s truing and dressing problems fundamentally truing has attracted much attention all over the world .This article summarized the present research situation on domestic and foreign countries. Embark on the essence of Bronze-bonded diamond wheel’s truing and dressing,to pointed out the key question: found methods to remove micron level diamond directly and effectively; and also can removed selectively, enhanced the precision effectively; simultaneously can break through the tradition concept. The traditional methods which based on strength and electricity cannot remove the diamond effective directly. The ideal method is which item was based on the accurate laser machining with little heat effec.The author has carried out the research comprehensively from the theory and the experiment.Fist, with high peak power, low duty ratio, short pulse duration, high repetition frequency and controllable feature, the acoustic-optic Q-switched pulsed laser is considered to be suitable for truing and dressing Bronze-bonded diamond wheels. An acoustic-optic Q-switched Nd:YAG laser has be developed and tested independently. Through measured the maximum average power is 100W; the minimum pulse duration is 170ns; the repetition frequency is 0.5~50kHz.Next, in order to seek the appropriate laser ablation parameters of bonds and abrasives, this causes the abrasives to have not micro crack after ablation, to get shallow deterioration level, to have good grinding performance under ablation, and also to obtain Better surface topography after truing and dressing. Theory and experiment study has separately carried on bonds and abrasives and Bronze-bonded diamond wheels with single pulse laser ablation. The single pulsed laser ablation power density threshold value of bonds and abrasives has determined through theoretical calculation. Indicated that the acoustic-optic Q-switched laser can be possible to remove diamond and bronze in effectively. The mathematical model of the unit crystal diamond pulse laser ablation has been established. Through analog computation, obtained the result those pulse duration and duty ratios are the most primary factor for the deterioration level thickness and the superficial micro crack. And through experimental confirmation, the appropriate laser ablation parameter had been found. The actual process of pulsed laser ablation on a bronze bonded diamond wheel is extremely complex. Just for wheel (but is not alone aims at bonds or abrasives) the two-dimensional geometry model and mathematical model both has been established to simulate the ablation situation. Meanwhile, through experiments can determine that when the laser average power density is lower than 30×107 W/cm2, only dressing can be carried on. But after the laser average power density achieved 30×107 W/cm2, truing and dressing both be realized at the same time.Analyzed the mechanism of laser truing and dressing bronze diamond grinding wheel under the short pulse duration、high power density laser function, the majority energies were used to remove the material in gasify, ablation material which to be removed was mainly realized through the mechanism of shallow layer gasification Afterwards, the method which to corrected the circle beats erroneous of bronze-bonded diamond grinding wheel in highly effective was still not existence at present .this article based on optics triangulation method with laser exposure in wheels radial direction has development the closed-loop electric circuit to control pulse laser and obtained the output signal of great pulse laser controlled by closed-loop circuit. An accurate online machining system to measured the laser’s emission was designed, the pulsed laser was controlled to ablate the wheels, solved the problem which can’t control the precision of direction optical axis of laser ablation and obtain the satisfactory result. Further more, we found that the truing and dressing can carry out at the same time ,which changed the tradition that truing and dressing must be carried out by two steps.The precisely truing and dressing technology of laser-machinery which was suitable to truing and dressing bronze-boned diamond wheels with bigger abrasives in size, has been studied in further, Finally, in order to examine the effect of truing and dressing and the influence rule caused by laser parameters, the survey experiment of grinding force and surface roughness of work piece of aluminum oxide ceramics which grinded by the bronze-bonded diamond wheels was studied. Indicated that the wheels could be carry on grinding effectively after truing and dressing with appropriate laser parameters, and the effect of truing and dressing with laser was surpass to silicon carbide hoop.This article’s main innovation achievements as follows:1.The first time to use the acoustic-optic Q-switched Nd:YAG laser to ablation bronzed-bonded diamond wheel in radial direction, the realization of non-damage abrasive’s micro removes lays the foundation for precisely truing and dressing to realize2. Further more, we found that the truing and dressing can carry out at the same time ,which changed the tradition that truing and dressing must be carried out by two steps.3. Creatively makes top observable and controllable system.4. Through studying in theory and experimental、choosing reasonable laser process parameters, the precisely truing and dressing of bronze-bonded diamond wheels was realized and the grinding performance after truing and dressing by laser was confirmed.更多还原