• Journal of the Korean Society of Safety
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• 제21권1호
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• pp.21-27
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• 2006

In this paper, object of experiment is to study on the effect parameters to obtain optimal surface roughness in face turning. Surface roughness is significantly important to be high quality of parts produced by turning process. For this purpose, the optimization of cutting parameters for face turning operation is investigated applying the Taguchi method. An orthogonal array, signal-to-noise, and the analysis of variance are employed to evaluate effect of cutting parameters for face turning. Also confirmation tests were performed to make a comparison between the results predicted from the mentioned correlations and the theoretical results. Cutting experiment is performed without cutting fluid using coated tungsten carbide insert about workpiece of SM45C. And regression analysis technique has been used to study the effects of the cutting parameters.

• Journal of the Korean Chemical Society
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• 제53권3호
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• pp.266-271
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• 2009

In the recently synthesized rare earth transition metal carbide $La_7O_{s4}C_9$ one finds one-dimensional organometallic $[O_{s4}C_9]^{21-}$ polymers embedded in a $La^{3+}$ ionic matrix. The electronic structure of the polymeric $[O_{s4}C_9]^{21-}$ chain was investigated by density of states (DOS) and crystal orbital overlap population (COOP), using the extended Huckel algorithm. A fragment molecular orbital analysis is used to study the bonding characteristics of the $C_2$ units in $La_7O_{s4}C_9$ containing $C_2$ units and single C atoms as well. The title compound contains partially filled Os and carbon bands leading to metallic conductivity. As the observed distances already indicated, the calculations show extensive Os-C interactions. The C-C bond distance in the diatomic $C_2$ units ($d_{C-C}$=131 pm) in the solid is significantly increased relative to $${C_2}^{2-}$$ or acetylene, because antibonding $1{\pi}_g$ orbitals are partially filled by the Os-$C_2(1\;{\pi}_g)$ bonding contribution found at and below the Fermi level.

• Journal of the Korean Society of Manufacturing Process Engineers
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• 제20권10호
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• pp.19-26
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• 2021

In fine-particle injection processing, hard fine particles, such as silicon carbide or aluminum oxide, are injected - using high-pressure air, and a small amount of material is removed by applying an impact to the workpiece by spraying at high speeds. In this study, a two-axis stage device capable of sequence control was developed to spray various shapes, such as circles and squares, on the surface during the micro-particle jetting process to understand the surface-shape micro-particle-processing characteristics. In the experimental device, two stepper motors were used for the linear movement of the two degree-of-freedom mechanism. The signal output from the microcontroller is - converted into a signal with a current sufficient to drive the stepper motor. The stepper motor rotates precisely in synchronization with the pulse-signal input from the outside, eliminating the need for a separate rotation-angle sensor. The major factors of the processing conditions are fine particles (silicon carbide, aluminum oxide), injection pressure, nozzle diameter, feed rate, and number of injection cycles. They were identified using the ANOVA technique on the design of the experimental method. Based on this, the surface roughness of the spraying surface, surface depth of the spraying surface, and radius of the corner of the spraying surface were measured, and depending on the characteristics, the required spraying conditions were studied.

• Korean Journal of Materials Research
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• 제34권2호
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• pp.111-115
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• 2024

Silicon carbide (SiC) has emerged as a promising material for next-generation power semiconductor materials, due to its high thermal conductivity and high critical electric field (~3 MV/cm) with a wide bandgap of 3.3 eV. This permits SiC devices to operate at lower on-resistance and higher breakdown voltage. However, to improve device performance, advanced research is still needed to reduce point defects in the SiC epitaxial layer. This work investigated the electrical characteristics and defect properties using DLTS analysis. Four deep level defects generated by the implantation process and during epitaxial layer growth were detected. Trap parameters such as energy level, capture-cross section, trap density were obtained from an Arrhenius plot. To investigate the impact of defects on the device, a 2D TCAD simulation was conducted using the same device structure, and the extracted defect parameters were added to confirm electrical characteristics. The degradation of device performance such as an increase in on-resistance by adding trap parameters was confirmed.

• Transactions of the Korean Society of Machine Tool Engineers
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• 제10권3호
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• pp.97-103
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• 2001

This paper has focused on the Optimization of the cutting parameters for urning operation based on the Taguchi method. Four cutting parameters. nemely, cutting speed, feed depth of cut and nose radius are optimized with consideration of the surface roughness. The design and analysis of experiments are conducted to study the performance characteristic. The effects of these parameters on the surface roughness have been investigated using signal-to-noise(S/N) ratio and analy-sis of variance(ANOVA). The experiments have been performed using coated tungsten carbide inserts without any cutting fluid. Experimental results illustrate the effectiveness of this approach.

• Journal of the Korean Magnetic Resonance Society
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• 제3권2호
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• pp.90-99
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• 1999

Doping of boron atoms in graphite has been well known method to increase the discharge capacity as the negative electrode material for lithium secondary battery. Herein, the boron-doped graphites are prepared by mixing 1, 2.5, 5, and 7 wt. % of boron carbide in carbon during the graphitizing process. The structural states of boron in boron-doped graphites are investigated by solid-state 11B NMR spectroscopy. The resonance lines for substitutional boron atoms are identified as the second order quadrupolar powder pattern with the quardrupole coupling constant, QCC = 3.36(2) MHz. The quantitative analysis of 11B NMR spectra with boron-doped graphite has also been performed via simulation.

• Transactions of the Korean Society of Machine Tool Engineers
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• 제12권6호
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• pp.36-43
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• 2003

In machining of ceramic materials, they are very difficult-to cut materials because of there high strength and hardness. Machining of ceramics are characterized by cracking and brittle fracture. Generally, ceramics are machined using conventional method such as finding and polishing. However these processes are generally costly and have low MRR(material removal rate). This paper focuses on determining the optimal levels of process parameters for products with CNC machining center. For this purpose, the optimization of cutting parameters is performed based on experimental design method. A design and analysis of experiments is conducted to study the effects of these parameters on the surface roughness by using the S/N ratio, analysis of ANOVA and F-test. Cutting parameters, namely, cutting speed, feed and depth of cut are optimized with consideration of the surface roughness.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• 제21권5호
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• pp.755-760
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• 2012

In this study, three dimensional cutting force components and surface roughness appeared in high speed cutting by using tungsten carbide endmill tools implanted ion or not found mutual relations through several analysis of statistical dispersion. It is showed that cutting force(Fx) is affect with spindle speed and feed rate, cutting force(Fy) is affect with spindle speed and ion implantation time and cutting force(Fz) is affect with feed rate in interaction through the statistical method of ANOVA of cutting force and surface roughness, it is analyzed that it is affected of spindle speed and feed rate in surface roughness.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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• pp.242-248
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• 2000

This paper has focused on the optimization of the cutting parameters for turning operation based on the Taguchi method. Four cutting parameters, namely, cutting speed, feed, depth of cut and nose radius are optimized with consideration of the surface roughness. The design and analysis of experiments are conducted to study the performance characteristic. The effects of these parameters on the surface roughness have been investigated using the signal-to-noise (S/N) ratio, analysis of variance (ANOVA). The experiments have been peformed using coated tungsten carbide inserts without any cutting fluid. Experimental results illustrate the effectiveness of this approach.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.344-349
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• 2005

This paper presents a geometrical error analysis of wheel curve generation method for micro aspheric surface machining using parallel grinding method. In aspheric grinding, wheel wear in process is crucial parameter for profile error of the ground surface. To decrease wheel weal parallel grinding method is adopted. Wheel and work piece (Tungsten carbide) contact point changes during machining process. In truing process of the wheel radius is determined by the angle and distance between wheel and truer. Wheel radius error is predominantly affected by vertical deviation between the wheel rotation center and the truer center Simulation for vertical error and wheel radius error shows same tendency that expected by geometrical analysis. Experimental results show that the analysis of curve generation method matches with simulations and wheel radius errors.