Three dimensional temperature rise model and analysis for nanoscale orthogonal cutting a single-crystal silicon

• Main Authors: Yu-Heng Shen, 沈鈺恆
• Other Authors: Zone-Ching Lin
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/13035976020858462980

碩士 === 國立臺灣科技大學 === 機械工程系 === 100 === The quasi-steady molecular statics orthogonal nanocutting model of single-crystal silicon developed by the paper not only can calculate the cutting force, equivalent stress and equivalent strain, but also can calculate the temperature rise of the cut workpiece, and furthermore, can analyze the temperature distribution of the cut workpiece. The paper supposes that the temperature rise of the cut workpiece during orthogonal nanocutting is produced by two heat sources, namely plastic deformation heat and friction heat. The calculation method of equivalent stress and equivalent strain of single-crystal silicon developed by the paper is the use of three-dimensional quasi-steady nanostatics nanocutting model to simulation calculation. The paper applies the concept of force balance, and Hooke-Jeeves search method to solve the force balance equation, solve the newly displaced position of each atom of the cut workpiece, and then calculate the shape of chips and size of cutting force during cutting. After the position where the atoms are deformed and displaced is acquired, and employing the paper’s finite-element shape function concept, the paper develops cutting of single-crystal silicon material. Atoms are regarded as nodes, and lattices are regarded as elements. The paper conducts numbering of each node in the single-crystal silicon, and carries out cutting of lattices. The paper cuts lattices into 36 constant -strain tetrahedron, and conducts numbering of each of the cut lattices. Then the three-dimensional equivalent strain of the cut workpiece can be obtained. Using the flow stress-strain relational equation acquired after regression treatment of stress-strain curve in nanoscale thin-film tensile numerical experiment, the paper uses flow curve to calculate the equivalent stress produced under equivalent strain of elements. The flow deformation heat developed by the paper can be calculated by the equivalent stress and equivalent strain of the single-crystal silicon workpiece being cut. Furthermore, the paper develops the calculation method for temperature rise of the cut workpiece produced by flow deformation heat. Besides, the paper additionally develops the method of friction heat produced by workpiece atoms on the tool flank performing orthogonal nanocutting of single-crystal silicon, and the calculation method of temperature rise of workpiece atoms on tool flank. Regarding these methods, Morse force is decomposed to be friction force on tool flank, and the heat produced from the power of friction force is calculated. Such heat is then distributed to workpiece atoms on tool flank and to atoms of cutting tool. Furthermore, the numerical value of temperature rise of workpiece atoms on tool flank is calculated. The temperature rise produced from those two heat sources are added up, and the total temperature rise of the various atoms of the cut single-silicon workpiece can be obtained for making analysis of temperature field. Besides, the paper also further substitutes the total temperature rise of the various atoms of the cut single-crystal silicon workpiece in the three-dimensional finite-difference heat transfer equation in order to perform heat transmission. It refers that the workpiece temperature, calculated by substituting the numerical value of total temperature produced at each step in the heat transfer equation, is just the initial temperature of workpiece at the next step. This method is used to calculate the temperature field of the single-crystal silicon workpiece having undergone orthogonal nanocutting at each step, and further analysis is made. Finally, comparison is made with the numerical values of temperature rise of the various atoms of the cut single-crystal silicon workpiece being calculated above without consideration of finite-difference heat transfer.