| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 104 === The paper applies three-dimensional quasi-steady nanocutting model of molecular statics to conduct simulation of offset cycle cutting in cutting of trapezium groove on single-crystal silicon nanochannel by AFM probe. The paper can calculate not only the cutting force, equivalent stress and equivalent strain, but also the temperature rise of the single-crystal silicon workpiece being cut. Furthermore, the temperature distribution of the single-crystal silicon workpiece being cut can be analyzed. Besides, the abovementioned total temperature rise of all atoms of the single-crystal silicon workpiece being cut can be substituted in finite-difference heat conduction equation. The calculated numerical values of thermal convection coefficients of air and water are also substituted in finite-difference heat conduction equation. The paper calculates the change in temperature field of the single-crystal silicon workpiece being cut during each step of offset cutting and cutting of nanoscale trapezium groove. The study employs two-path offset cutting method to cut multilayered trapezium groove on nanochannel of single-crystal silicon substrate. First of all, a fixed cutting depth is cut for cutting of single-crystal silicon trapezium groove. After completion of the first cutting path on the first cutting layer, rightward offset cutting for the second cutting path at a fixed offset amount is made. The paper intends to analyze two cutting models for two-path offset cutting method. For the first model, a randomly set cutting depth is cut for the first cutting path on the second cutting layer. Then the same cutting depth is cut for offset cutting of the second cutting path, and the change in down force and cutting force is analyzed. As to the second model, a fixed down force is applied for the first cutting path on the first cutting layer. Specific down force energy (SDFE) equation and CAD software are used to simulate the removed volume during cutting, and calculate the required cutting depth. After rightward offset is completed, cutting of the second cutting path is completed. The same model is used to cut the second cutting paths on the second cutting layer and the third cutting layer, and the change in cutting force and down force is analyzed. Finally, the cutting force and down force obtained from calculation of the SDFE theoretical equation is compared with the cutting force and down force obtained from simulation of the abovementioned three-dimensional quasi-steady nanocutting model of molecular statics, proving the rationality of the simulation results. Furthermore, using the displaced amount, cutting force and down force of each atom acquired from simulation, the equivalent strain and equivalent stress of single-crystal silicon being cut are calculated. The paper supposes that for the cutting model, the temperature rise of the single-crystal silicon workpiece being cut is caused by two heat sources: plastic deformation heat and friction heat. In the paper the plastic deformation heat can be calculated by multiplying equivalent stress by equivalent strain of the single-crystal silicon workpiece being cut. The paper also calculates the temperature rise caused by friction heat. The paper adds up the temperature rise caused by the two heat sources, and achieves the total temperature rise of all atoms of the single-crystal silicon workpiece being cut, for analysis of temperature field. Besides, the abovementioned total temperature rise of all atoms of the single-crystal silicon workpiece being cut is further substituted in the finite-difference heat conduction equation. The paper proposes applying the thermal convection equation and calculation procedures of the upper surface heating plate, and calculates the thermal convection coefficients of air and water under 25oC. The obtained thermal convection coefficients are substituted in the finite-difference heat conduction equation. Then the paper can calculate the change of temperature field of each atom on the surface of the single-crystal silicon workpiece being cut and on the surface of the single-crystal silicon workpiece not being cut during each step of offset cutting of nanoscale trapezium groove. Finally, the paper analyzes how the thermal convection of water under room temperature affects the surface of the workpiece being cut, and how the thermal convection of air under room temperature affects the temperature distribution of the single-crystal silicon being cut.
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