• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1542-1547
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• 2007

Laser surface treatment technologies have been used to improve characteristics of wear and to enhance the fatigue resistance for mold parts. The optical lens with the elliptical profile is designed to obtain a wide surface hardening area with a uniform hardness. The objective of this research work is to investigate the influence of the process parameters, such as power of laser and defocused spot position, on the characteristics of laser surface treatment for the case of SKD61 steel and SCM4 steel. From the results of the experiments, it has been shown that the maximum average hardness is approximatly 700${\sim}$780 Hv when the power, focal position and the travel of laser are 1,095 W, 0mm and 0.3 m/min, respectively. In samples treated with lower scanning speeds, some small carbide particles appear in the interdendritic regions. This region contains fine martensite and carbide in proportions which depend on the local thermal cycle.

• 한국결정성장학회지
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• 제33권6호
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• pp.282-287
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• 2023

본 연구에서는 Laser Powder bed fusion(L-PBF) 공정을 사용하여 제작된 Ti-6Al-4V 합금 적층성형품의 응력제거 열처리 온도와 시간의 변화에 따른 미세조직, 잔류응력 그리고 경도의 변화를 연구하였다. 잔류응력 제거를 위한 열처리 시험 결과 823 K에서는 240분, 873K에서는 60분 이상 열처리시 치수변화 및 기계적 특성 저하를 야기하는 결정립 성장 및 상변화 발생 없이 대부분의 잔류응력이 3 0 MPa 이하로 감소되는 것을 확인하였다. 또한, 열처리 온도 및 시간의 증가와 함께 경도가 증가하는 경향을 보였다. 이러한 결과는 XRD 및 SEM-EBDS의 phase map 분석을 통해 확인되지 않지만, 773~873 K 온도범위에서 등온 열처리시 국부적인 침상 Martensitic α' 상의 미세화가 원인으로 추정된다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.118.1-118.1
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• 2016

The laser surface modification has been reported for its functional applications for improving tribological performance, wear resistance, hardness, and corrosion property. In most of these applications, continuous wave lasers and pulsed lasers were used for surface melting, cladding, alloying. Since flexibility in processing, refinement of microstructure and controlling the surface properties, technology utilizing lasers has been used in a number of fields. Especially, femtosecond laser has great benefits compared with other lasers because its pulsed width is much shorter than characteristic time of thermal diffusion, which leads to diminish heat affected zone. Moreover, laser surface engineering has been highlighted as an effective tool for micro/nano structuring of materials in the bio application field. In this study, we applied femtosecond and nanosecond pulsed laser to treat biometals, such as Mg, Mg alloy, and NiTi alloy, by heating to improve corrosion properties and functionalize their surface controlling cell response as implantable biomedical devices.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.121-123
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• 2006

The aim of present study is to investigate the effect of welding parameters and heat treatment conditions on the formability of the laser welded silicon steel sheet. It was found that there is optimum range of the heat input ($0.6{\sim}0.7kJ/cm$) and gap distance ($0.125{\sim}0.150mm$) for the high tensile strength and the avoidance of the fracture in weld metal, Also, it was essential for the improvement of formability to perform pre- and post-welding heat treatment which cause the uniform mixture of base metal and welding consumable.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.373-379
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• 2011

Current therapeutic methods for suppressing muscle spasticity are intensive functional training, surgery, or pharmacological interventions. However, these methods have not been fully supported by confirmed efficacy due to the aggravation of the muscle spasticity in some patients. In this study, a combined system was developed to treat with a low-level laser and to monitor the region of the treatment using an optical spectroscopic probe that measures oxygen saturation and deoxygenation during low-level laser therapy (LLLT). The evaluation of the wavelength dependence for LLLT was performed using a Monte Carlo simulation and the results showed that the greatest amount of heat generation was seen in the deep tissue at ${\lambda}$ = 830 nm. In the oxy- and deoxygenation measurements during and after the treatment, oxygen-Hb concentration was significantly increased in the laser-irradiated group when compared to the control group. These findings suggest that LLLT using ${\lambda}$ = 830 nm may be of benefit in accelerating recovery of muscle spasticity. The combined system that we have developed can monitor the physiological condition of muscle spasticity during the laser treatment in real time and may also be applied to various myotonia conditions such as muscle fatigue, back-pain treatment/monitoring, and ulcer due to paralysis.

• 오토저널
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• 제24권4호
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• pp.22-26
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• 2002

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.265-266
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• 2007

• 소성∙가공
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• 제15권3호
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• pp.213-219
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• 2006

To improve the strength of glass is being studied in order to contribute to weight saving of flat panel displays. Generally, the strength achieved of glass-ceramics is higher as is the fracture toughness by the formation of a heterogeneous phase inside glass. In this study, Ag-doped $45SiO_2-24CaO-24Na_2O-4P_2O_5\;and\;70SiO_2-10CaO-24Na_2O-10TiO_2$ glasses were irradiated to strengthen by crystallization using femto-second laser pulse. XRD, Nano-indenter and SEM etc., irradiation of laser pulse without heat-treated samples was analyzed. Samples irradiated by laser had higher value($4.4{\sim}4.56^*10-3Pa$) of elastic modulus which related with strength of glass than values heat-treated samples and these are $1.2{\sim}1.5$ times higher values than them of mother glass. This process can be applicable to the strengthening of thinner glass plate, and it has an advantage over traditional heat-treatment and ion-exchange method.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.171-174
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• 2005

To improve the strength of glass is being studied in order to contribute to weight saving of flat panel displays. Generally, the strength achieved of glass-ceramics is higher as is the fracture toughness by the formation of a heterogeneous Phase inside glass. In this study, Ag-doped $45SiO_2-24CaO-24Na_2O-4P_2O_5$ glasses were irradiated to strengthen by crystallization using femto-second laser pulse. UV/VIS, Spectroscope, XRD, nano-indenter and SEM etc. irradiation of laser pulse without heat-treated samples was analyzed. Samples irradiated by laser had higher value$(4.4\~4.56{\ast}10-3Pa)$ of elastic modulus which related with strength of glass than values heat-treated samples and these are $1.2\~1.5$ times higher values than them of mother glass. This process can be applicable to the strengthening of thinner glass plate, and it has an advantage over traditional heat-treatment and ion-exchange method.

• 한국정밀공학회지
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• 제30권5호
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• pp.499-506
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• 2013

Heat-treatment is one of the core technologies to enhance various characteristics such as strength, hardness, toughness, abrasion resistance and fatigue resistance for the mold material. This paper focuses on characteristics of the laser heat-treatment according to the cylindrical bar diameter variation in case of the SM45C. From the results of the experiments, it has been observed that the maximum hardness is 744Hv when the power is 1630W and the travel of laser is 0.5m/min. And then, the hardness width, depth and microstructure were observed for characteristics. Finally, when the cylindrical bar diameter size grow, the hardness width decrease whereas hardness depth increase.