【作者】 刘志军；

【导师】 全燕鸣；

【作者基本信息】 华南理工大学 ， 机械制造及其自动化， 2013， 博士

【摘要】 现代高生产率工艺往往通过提高切削速度和进给量来增加材料的去除率，其切削过热现象尤为突出，加速切削热的消散一直是急需解决的重要课题。浇注冷却是金属切削加工的主要冷却方式，其切削液的补偿、调度、后处理及环境成本很高。近年，对先进冷却技术的研究取得了许多成果，诸如绿色切削液、准干切削和硬切削。准干切削技术仍需要施加外来的流动介质实现对切削区域的冷却，并且存在自身缺陷。不使用任何介质，基于高性能的机床和刀具来实现的硬切削技术应该是理想的切削方法，但是在机床技术和刀具技术还没有取得质的突破前，切削过热的问题仍然存在。通过刀具/刀柄散热是一种全新的冷却概念，近年国外对在刀具中嵌入高效导热元件——热管来加速散热的冷却方法进行了初步研究，结果显示这种冷却方法可以降低刀柄和刀头的温度，减少刀具的热膨胀量和磨损率。受铣刀难以直接测温和热管铣刀结构复杂等因素的制约，以往热管刀具的研究主要集中于车刀，对旋转类刀具（铣刀和磨削）的研究仅限于通过仿真技术和模拟方法来探索该类热管刀具的有效性，基于这样的现状本文设计、制作出热管立铣刀，对热管铣刀的散热问题进行了较深入的理论研究和技术探讨：（1）提出用热电势信号无线输出方式替代传统的有线式传输，实现对旋转刀具或工件的温度测量，传输过程不会产生附加电势。设计并制作出应用于高速旋转刀具测温的热电偶测温无线传输系统，基于热电势信号采集与发射模块集合结构优化模型和对Protel软件的二次开发，对系统结构进行了全面优化，使之能实现对高速旋转刀具多点温度的同步、准确和实时采集。基于使采集和发射模块尽量简化以利于旋转动平衡的思路，把一般由下位机硬件实现的滤波、放大功能由上位机软件处理，把信号并联处理的方式改为串联处理大大简化了下位机硬件电路。基于数据库和热电阻的参比端温度比较实现了对热电偶参比端温度的动态准确补偿；基于增量变化的人工智能滑动加权平均滤波法对具有温度剧变特征的高速旋转刀具温度信号实现了有效滤波。（2）建立了铣刀体三维非稳态温度场有限差分仿真模型，基于测温点i的温度函数T_F,i（t）与流入切削刃的热流载荷相关性，把铣削测温实验获得的温度函数T_i（t）与不同载荷的温度函数T_F,i（t）进行拟合，确定铣削测温实验切削过程流入铣刀体的热流密度，以该载荷进行三维非稳态温度场有限差分仿真，得到铣削实验工艺条件下的三维温度场。（3）考虑铣床主轴、刀柄结构的限制，设计出热管立铣刀的基本散热结构，基于铣刀三维温度场进行热管铣刀散热基本结构的优化。建立热管铣刀热阻的一维简化函数，得到热管铣刀的总热阻。通过系列基本结构的优化降低热管铣刀总热阻：采用内嵌铜底结构提高热管的吸热能力；铣刀内孔设计成台阶结构以防止热流从热管回流到铣刀；采用翅片散热器有效提高散热面积；采用涡轮风扇以提高散热器与空气的对流换热系数；在刀轴上开口并结合涡轮风扇把封闭在刀轴内的热量快速传导到大气。（4）对热管铣刀散热功能结构参数进行了分析，得出优化的主要结构参数包括：热管的参数（铣刀内孔壁与热管蒸发端外表面的接触长度l、热管蒸发端外表面与翅片内孔的接触长度l₁、热管表面光洁度Ra_g、热管蒸发端与铣刀内孔的配合间隙H₁、热管冷凝端与散热器内孔的配合间隙H₂）；翅片的参数（翅片的直径r、翅片的厚度h₂、翅片的宽度h₁、翅片表面光洁度Ra_c）；涡轮的参数（涡轮内外径差Δ r、涡轮内径与翅片之间间隙Δ r₁、涡轮扇片的偏角α、涡轮扇片的数量x、涡轮扇片的表面光洁度Rα w）。通过正交实验和理论分析，得到结构参数对热管铣刀散热能力影响的判断：热管的五个关键因素对散热能力影响，按显著程度由大到小为：l₁、H₁、l、H₂、 Ra；翅片四个关键参数对散热能力影响，按显著程度由大到小为： r、h₁和h₂、Ra_c；涡轮五个关键参数对散热能力影响，按显著程度由大到小为：α、 Δ r、x、Δ r₁、Rα_w。最后，通过铣削测温实验和温度场仿真，并结合切削区温度反求，发现相比普通铣刀，散热结构优化的热管铣刀能有效降低切削区的温度达50（℃）以上。更多还原

【Abstract】 Increasing the material removal rate is usually by improving the cutting and feedingspeed in the modern high productivity process, but the cutting overheating phenomenon isparticularly prominent when using this cutting process, therefore, how to improve thedissipation speed of cutting heat becomes an important issue. Pouring cooling liquid is still amain cooling way when cutting metal, but processing cutting fluid is very expensive, andcutting fluid damages the environment seriously. In recent years, the researches on theadvanced cooling technology made a lot of achievements: green cutting fluid, dry cutting（which needs auxiliary equipment）, and hard cutting （without using of any medium）. Amongthese results, dry cutting technology has many defects that cannot be overcome. Hard cuttingtechnology should be the ideal cutting method, but unless machine and cutting-toolstechnology make a breakthrough, the cutting overheating problems still exist.Cooling cutting process through tool/tool-holder is a new concept. In recent years,researchers investigated this technology by inserting a heat pipe into cutter to improve coolingspeed. Results show that the method can decrease the temperature of handle and head ofcutter, reduce the amount of tool’s thermal expansion and wear rate. However, because thetemperature of the milling cutter is difficult to measure directly and the structure of heat pipemilling cutter is very complex, researches mostly focus on the heat pipe cutter and mainly usesimulation when study of rotating heat pipe cutter. Therefore, this thesis has studied therelevant theory on how to improve the cooling speed of heat pipe milling cutter. The mainconclusions are as follows:（1）The thermocouple wireless temperature measuring system is established to measurethe temperature of high speed rotating milling. In this system, thermal potential signals areconveyed to the static equipment via wireless module, the thermocouple temperature ofreference end can be accurately compensated, and the geometric structure of thermoelectricpotential signal acquisition and transmission module is optimized. The filtering techniqueused in the situation of large temperature gradient is established.The system is proved to beaccurate through experiments.（2） The three-dimensional simulation model of unsteady temperature field of millingcutter entity is established by using the finite difference method. The study finds that thetime-temperature function of temperature measuring point is related to the heat flow densityflowing into the cutter. In order to simulate the milling temperature field, heat flux is loadedinto the cutter entity through the welding DC power. By measuring the cutting zone temperature, a series of time-temperature function of milling cutter are obtained, withdifferent loaded heat flow density. Time-temperature curve obtained through cuttingtemperature measurement experiment are fitted with time-temperature curve obtained throughsimulation method. There is a curve that is the most closed with the time-temperature curvegetting from temperature measurement experiment, in the entire time-temperature curveobtained through simulation method. The simulation curve corresponds with the curve ofmilling temperature experiment. The cutting zone temperature can be got according of thethree-dimensional unsteady temperature field;（3）Based on the3D temperature field of milling cutter, the basic structure, which isused to transfer heat, of milling cutter had been optimized. The one-dimensional model ofmilling cutter Thermal resistance has been established. The thermal resistance has beenreduced through optimization the basic structure of milling cutter, and then the radiatingeffect will be increased. These optimization results are proved to be reasonable through aseries of experiments. The experimental results are as follows: The cooling effect can beobviously improved if the cutter head is embedded a copper bottom structure; Embeddingcopper bottom in milling cutter, the temperature of measuring point will be reduced6（℃）,Compared with the through-hole structure; The heat dissipation capability of heat pipecutter can be improved, reaming a hole in the end of milling cutter; The temperature will bereduced more than3（℃）, compared with no reaming milling cutter structure; The numbers ofthe ridge sheet structure are limited with the diameter of heat pipe, compared with the finstructure; The fin structure has better heat radiating effect than the sun flower ridge structure;The convective heat transfer coefficient will be increased because a strong wind will beformed on the surface of the radiator if a turbo fan is installed around the finned radiator oronly using a ridge structure radiator; Heat pipe cutter by the comprehensive optimization hasa better heat radiating performance than ordinary milling cutter; The temperature intemperature measurement point of heat pipe cutter reduce16（℃）, the cutting zonetemperature reduce46（℃）.（4）These parameters need to be optimized are determined after analyzing the heatdissipation structure of heat pipe cutter: the parameters of heat pipe is l、l₁、Ra_g、H₁、H₂;the parameters of fin is r、h₂、h₁、Ra_c;the parameters of turbine is Δ r、Δ r₁、α、 x、Rα w.The experimental results are consistent with the results of theoretical calculations: Fivekey factors of heat pipe influencing the cooling capacity, ranking from high to low according to the significant degree, isl₁、H₁、l、H₂、Ra.Their optimal values are50（mm）,70（mm）,0.4（um）,0.02（mm）,0.04（mm）; Four key parameters of fin radiator is r, h₁, h₂andRac.Their optimal values are50（mm）、0.7（mm）、0.8（mm）、6.3（um）;Four key parameters ofturbine is α、 Δr、 x、Δ r₁、Rα_w，Their optimal values are40°、50（mm）、12（pieces）and0（mm）;Experimental results showed that surface roughness of turbine fan blad does notaffect t heat dissipation capability.Finally, comparing with common cutter, we founded that the temperature of heat pipecutter on cutting zone can reduce50（℃）, after milling temperature measurement experimentand temperature field simulation experiment.更多还原