In-situ Measurement,Modeling And Application For Turning Temperature

As is known to all that cutting temperature and its distribution in the cutting zone directly affect workpiece quality and tool life in cutting process.However,the existing measuring methods for cutting temperature are difficult access to the cutting area for achieving in-situ measurement owing to the harsh environment(high stress/strain,high-temperature gradient)and the narrow cutting area.Hence,it still remains an unresolved issue to develop cutting temperature measurement methods aiming at fast response rate,high spatial resolution,accurate temperature measurement and sensor’s accessibility.In the view of the common problem for cutting temperature,this paper developed in-situ temperature measurement methods in the cutting area,and systematically investigated the tool wear monitoring and temperature field modeling based on the cutting temperature.In view of the current situation that it is difficult to access the cutting area for thin-film thermocouple to achieve in-situ temperature monitoring,an intelligent tool was developed by encapsulating thin film thermocouple with hot-press diffusion bonding.Firstly,the thin film sensor array was fabricated on the cutting insert by MEMS technology.Then the sensor array was encapsulated into the tool interior by the developed hot press diffusion bonding process.Finally,the developed insert was polished to realize in-situ temperature measurement.Experimental setups were built to evaluate the static performance,dynamic performance and cutting performance for the developed insert.The experimental results show that the developed insert has the advantages of fast response,accurate measurement and in-situ temperature field measurement,but it also has the diavantage of premature failure.In view of the problem that the thin-film sensor array encapsulated by diffusion bonding failed prematurely in cutting process,another tool was developed by etching the micro-groove on the flank face as the protection method for the embedded sensor.Firstly,the picosecond laser was used to etch micro-groove on the tool.Then a sensor embedding technology was developed to integrate the thin-film sensor into the micro-groove,following with annealing and packaging for the embedded sensor.Finally,experimental setups were built to evaluate the performance for the fabricated tool.The experimental results show that the developed tool not only has the advantages of fast response,accurate temperature measurement and in-situ temperature measurement,but also can work reliably for a long time under harsh cutting environment.In view of disadvantages like complicated fabrication process,customized tool,large noise with too large cutting parameters or too high temperature for the tool embedded with thin-film thermocouple,a fiber-optic two-color pyrometer,which has fast response,exact measurement,wide application and stable work,was developed based on the principle of colormetric temperature.The experimental platform was built to evaluate the performance of two-color pyrometer.The experimental results show that the platform can effectively make up for the disadvantages of the tool embedded with thin-film sensor.But it also has shortcomings such as insensitive to low temperature(<200℃),punching on the cutting tool.Therefore,measurement method is selected according to the actual application.By comparing the developed temperature methods,the insert with micro-groove protection method was applied to monitor tool wear condition.Six different groups of cutting parameters were chosen in the arithmetic method.Each wear experiment were carried out.The temperature signal and the corresponding tool wear in the whole life cycle were recorded.The experimental results show that there is a great correlation between cutting temperature and tool wear,and the optimal cutting parameters can be sought through the change characteristics of cutting temperature with tool wear.In addition,taking the orthogonal cutting of TC4 titanium alloy with a triangular insert as the research object,the temperature field modeling was carried out in this paper by proposing a novel temperature field prediction model based on the element method.The tool-chip contact region was differentialized based on the orthogonal cutting model.Then the temperature field model proposed by Komanduri-Hou was applied to each discrete element and then the temperature field distribution and discrete heat distribution coefficient in the tool-chip contact region were determined.In order to verify the established model,three groups of cutting parameters were selected and the fiber-optic two-color pyrometer was utilized to measure the cutting temperature.The results show that the prediction results of analytical model matches well with experimental data.In a word,in view of the common problem existing in cutting temperature,this paper investigated the measurement method,tool wear monitoring and temperature field modeling.The research can be widely used in the cutting field.