【作者】 崔云先；

【导师】 孙宝元； 张军；

【作者基本信息】 大连理工大学 ， 机械电子工程， 2011， 博士

【摘要】 切削热和切削温度是切削过程中产生的重要物理现象。瞬态切削温度的准确测量是开展现代切削理论与切削工艺技术研究的主要内容之一。国内外目前广泛采用的切削温度测量方法主要有自然热电偶法、人工热电偶法、半人工热电偶法、金相组织观察法和光热辐射测温法等。随着切削速度和加工精度的不断提高,常用的切削温度测量方法由于受到传感器响应速度和切削条件等的限制,难以实现切削区瞬态温度的实时和准确测量。本文针对这一瞬态切削温度测量的技术难题,将薄膜热电偶集成于切削刀具中,成功研制了一种NiCr/NiSi薄膜热电偶测温刀具,可实现切削区瞬态温度准确、方便和实时测量。论文的主要内容包括：从塞贝克效应入手,依据固体材料电导和热导理论,研究了薄膜电导、热导与块体材料电导、热导的关系；利用连续薄膜的电学性质与薄膜的电子输运理论,研究了薄膜电导率与电阻率的主要影响因素；通过引入的玻尔兹曼经典统计和费密狄拉克函数,研究了薄膜电极的绝对热电势率以及薄膜热电偶的塞贝克系数。指出了薄膜热电偶的薄膜性质及其选择的原则。采用双放电腔微波ECR等离子体增强非平衡磁控溅射技术,完成切削测温刀具所需Si02绝缘薄膜的制备,提出一种以相同工艺参数多次重复,可有效避免Si02薄膜制备中表面针孔和大颗粒等缺陷的新方法。所制备的Si02绝缘薄膜厚度小、绝缘性能好,绝缘薄膜与金属基底结合力满足制作测温刀具的要求。采用瞬态热反射方法,对所制备Si02薄膜的热导率进行测试,结果表明：本文所制备的Si02薄膜热导率比文献报道的热氧化法制备的Si02薄膜热导率大,在高速钢基底上制备的Si02薄膜热导率值不稳定,不同厚度的薄膜热导率变化较大,高速钢基底与Si02薄膜接口的热阻要比硅基底与Si02薄膜的大一个数量级。进一步分析得知,本文所制备的Si02薄膜热导率在所测试的厚度下没有明显的尺寸效应依赖关系,且影响热导率的主要因素是薄膜厚度、薄膜-基底界面结构、薄膜-基底温度以及薄膜的制备方式等。采用与制备Si02绝缘薄膜相同的双放电腔微波ECR等离子体增强非平衡磁控溅射技术,通过选择合适的靶材、设计并制作专用的掩膜,制备了测温刀具中NiCr/NiSi热电偶薄膜,所制备薄膜的合金各组元接近靶材,具有致密均匀,平整光滑,连续性好等特点,所制备的NiCr/NiSi薄膜热电偶形状规则、厚度均匀、边界整齐,达到预期制作目标。NiCr、NiSi掩膜采用不锈钢材料经超精密线切割机床加工制成,NiCr、NiSi掩膜厚度均控制在0.5mm以内。所研究的磁控溅射制备合金材料薄膜的工艺和技术,可为今后其他类合金薄膜的制备奠定技术基础。依据切削温度的产生和传出机理,研制了分刀片式、整体式和嵌入式切削测温刀具。由于NiCr/NiSi薄膜热电偶被直接嵌入刀具的刀尖位置,将切削和测温功能集于一体,且薄膜热接点厚度为微米数量级,具有热容量小,响应迅速的特点,因此,所研制的测温刀具可实现切削区瞬态温度的实时测量。采用本文研制的基于LabVIEW的薄膜热电偶温度自动标定系统,记录了NiCr/NiSi薄膜热电偶的升温和降温过程,完成了薄膜热电偶的标定；采用短脉冲激光法测试了NiCr/NiSi薄膜热电偶的时间常数。结果显示,所研制薄膜热电偶的塞贝克系数为67.0μV/℃,非线性拟合误差不大于0.3%,测得动态响应时间为0.083ms。采用热接点宽度不同的系列薄膜热电偶,研究了测温刀具的模拟磨损特性,测试了不同热接点宽度下NiCr/NiSi薄膜热电偶的灵敏度和时间常数。结果显示,当薄膜厚度很小时,NiCr/NiSi薄膜热电偶随刀具部分磨损后不影响其测试性能。通过建立的一维非稳态热传导模型,计算不同热接点厚度薄膜热电偶的动态响应时间,结果表明,影响薄膜热电偶时间常数的主要因素是薄膜材料的热扩散系数、薄膜的导热系数及薄膜厚度。完成了NiCr/NiSi薄膜热电偶测温刀具的组装并将所研制的切削测温刀具用于切削试验,结果显示,切削测温刀具满足瞬态切削温度测试需要,测试系统运行良好。更多还原

【Abstract】 Cutting heat and cutting temperature are crucial physical phenomenon which are produced in the cutting process. The accurate measurement of the transient cutting temperature is one of the main research concentents in developing modern cutting theory and cutting technical skill. At present, the common used methods to measure the cutting temperature are the natural thermocouple method, semi-artificial thermocouple method, artificial thermocouple method, light radiation thermometry and metallurgical structure observational method, etc. With the improvement of the cutting speed and machining precision in the cutting process, the above commonly used methods in measureing cutting temperature are restricted by sensor response time and cutting conditions and are ineffective in accurate measureing the transient temperature of the cutting zone. In this paper, the NiCr/NiSi thin-film thermocouple was embedded directly at the tip of the cutting tool, an NiCr/NiSi thin film thermocouple testing temperature cutter was successfully developed, the accurate, convenient and timely cutting temperature measurement in the cutting zone was realized. The main contents were as follows:The relationship of the conductance and thermal conductivity of thin-film with the conductance and thermal conductivity of the piece body was studied according to the Seebeck effect of the conductance and thermal conductivity theory of solid material. The main factors that influence the conductivity and resistivity of the thin film were studied based on the property of electricity and electron transport theory of continuous thin-film. The absolute thermoelectricity power of thin-film electrode and the Seebeck coefficient of thin-film thermocouple were studied according to Boltzmann classical statistics and Fermi Dirac functions. The property of the thin-film and principle of choosing the thin film thermocouple are prposed.SiO2 insulating film for the testing temperature cutter was prepared using the advanced twinned microwave ECR plasma source enhanced radio frequency (RF) reaction non-balance magnetron sputtering technique. A new method that was multiple coverage with the same technological parameter to overcome large particles, needles holes and other defects on the SiO2 thin-film surface during the thin-film preparation was put forward. The thickness of the prepared SiO2 insulating films was smaller, and the insulating performance of which was better.. The binding force between insulating film and metal basement met the demands of making the testing temperature cutter. The transient heat reflection method was used to measure the thermal conductivity of the prepared SiO2 films. on the metal basement. The results showed that the thermal conductivity of SiO2 films prepared by sputtering in this study was bigger than that by thermal oxidation reported in the literature. The thermal conductivity of the thin-film made on high-speed steel substrates was unstable, changed greatly among different thickness films. The thermal resistance between high-speed steel substrates and SiO2 thin-film was one order of magnitude large than that on SiO2 substrates. There was no significantly size effect of the thermal conductivity of the SiO2 thin-film prepared in this paper under the testing thickness. The factors that influence the thermal conductivity of the thin-film were the thickness of the film, the interface configuration of film-substrate, the temperature of film-substrate and sputtering manner.Advanced twinned microwave ECR plasma source enhanced radio freqency (RF) reaction non-balance magnetron sputtering technique was adopted, which was the same as preparing SiO2 insulating thin-film. By selecting proper ITO, design and manufacturing special Masking Film, NiCr/NiSi thermocouple thin-film of the testing temperature cutter was prepared. The alloy components of the prepared NiCr/NiSi thin-film were close to target, and it was dense and uniform, smooth and continuity, the prepared NiCr/NiSi thin-film had regular shape, uniform thickness and orderly fringe, achieved the expectant goal. The thickness of NiCr/NiSi Masking Film was controlled in the range of 0.5 mm, and they are made by the stainless steel through ultra-precision linear cutting machine. The preparation technology and technology for making alloy thin film material by magnetron sputtering techniques studied in this paper established the foundation for the future study of the other types of alloy thin films.According to the production and transportation mechanism of cutting temperature, the detach-blade testing temperature cutter, integral testing temperature cutter and embedded testing temperature cutter were made. Since the NiCr/NiSi thin-film thermocouple was embedded directly at the tip of the cutting tool, which integrated both cutting and temperature measuring functions, and the thickness of thermo-junction was micron, it has the characteristic of the small thermal capacity and quick response, and it can real-time measure transient temperature of the cutting zone.The temperature automatic calibration system of the thin-film thermocouple obtained in this study was used to record the process of the heating and cooling of the sensor, the automatic calibration of thin-film thermocouple was finished. The short pulse laser method was adopted to test the time constant of NiCr/NiSi thin-film thermocouple. The result showed that the Seebeck coefficient of thin-film thermocouple was 67.0μV/℃, the nonlinear fitting error was less than 0.3% and the shortest dynamic response time was 0.083ms.In order to study the simulation abrasion characteristic of the testing temperature cutter, the sensitivity and time constant of the NiCr/NiSi thin-film thermocouples with different thermo-junction width were tested. The results showed that the thermo-junction had little influence on static and dynamic characteristics when thickness of the film was thin, it means the partial abrasion of thin-film thermocouple didn’t affect its test performance. One-dimensional unsteady heat conduction model was constructed and the dynamic response time was calculated at different thermo-junction width. The result showed the main factors that influence the time constant of the film were thermal diffusivity, thermal conductivity and the thickness of thin film materials.The assembly of thin-film thermocouple testing temperature cutter was completed. The developed thin-film thermocouple testing temperature cutter was used for cutting test. The result showed that the testing temperature cutter meet the needs of measuring the transient cutting temperature and the test system run well.更多还原