Development Of Testing Temperature Cutter With NiCr/NiSi Thin Film Thermocouple For Transient Cutting

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.