• Laser Solutions
• /
• v.6 no.2
• /
• pp.1-7
• /
• 2003

Defocused CO$_2$ laser beam irradiation strengthening of 60kgf/$\textrm{mm}^2$ grade steel sheet was investigated to obtain the tensile strength similar to that of fully penetrated one by the focused beam. The melted line width by the defocused beam was 3∼4 times larger compared to that of the focused beam. However, the increase of tensile strength with 1 line irradiation by the defocused beam was similar to that of 2~3 lines by the focused beam. The increase(37.6%) of bending strength with 1 line by the defocused beam was higher than the increase(12.9%) of tensile strength. Also, the effect of cooling gas to strengthening was observed.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.5
• /
• pp.228-234
• /
• 2002

The CO$_2$ laser beam irradiation strengthening of 35kgf/mm$_2$ grade steel sheet is investigated to reduce the weight of bumper beam. The increase of tensile strength is dominated by the number of fully penetrated melting lines. The optimal laser irradiation pattern is obtained by 3-point bending test of hat-type specimens. Laser should be irradiated not only on the center specimen densely in the width direction, but also on the edge densely in the longitudinal direction. Local laser strengthening may be effective for the weight reduction of automobile bumper beam.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.1053-1057
• /
• 1997

Laser thin film process with a Q-switch pulsed YAG laser was performed for micro machining. In this research, we performed basic Cr thin film on glass substrates removal machining experiments. Form experiments, it happens not only evaporration of thin film but also spatter and cohesion of melting substance in working region, when machining a Cr thin film by Q-switch YAG laser beam irradiation. Critical energy of surface irradiation type by irradiation direction of laser in a face composing thin film on the glass is higher than that of back irradiation type, but the latter is favorable because of spatter appearance. In case of image formation position when laser beam is irradiated, the defocus is permitted to a certain extent within forcus depth. Ifexceeds focus depth, formation of pattern is vanishing step by step.

• Journal of the Korean Society of Safety
• /
• v.16 no.2
• /
• pp.27-35
• /
• 2001

For the purpose of healing the degradation part, $CO_2$ laser beam was irradiated with different irradiation condition (porer, diameter, velocity and beam type) to find out optimum irradiation condition. The test series of hardness, residual stress measurement, and fatigue were carried out after the irradiation. Experimental results show that micro-hardness values on the surface of the irradiated specimens m approximately 2.5 times higher than those of un-irradiated ones. Fatigue tests show that the fatigue life was improved by the compressive residual stress after laser beam irradiation. However, some specimens with different conditions show the shorter fatigue life. It means that laser beam irradiation with optimum irradiation condition and optimum absorb energy, Q can improve the fatigue strength.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.26 no.1
• /
• pp.44-49
• /
• 2017

Titanium has been used in various fields due to its good corrosion and erosion resistance, and superior mechanical properties. The process for selective electro-deposition on a titanium surface using laser beam is proposed in this paper. The process consists of laser irradiation, electro-deposition, and ultrasonic cleaning. Laser irradiation can change the surface morphology of titanium. Through laser irradiation, the surface cleaning effect and a rough surface can be achieved. The surface roughness of titanium was measured according to the laser beam conditions. The characteristics of selective electro-deposition on titanium surface according to surface roughness are investigated by various analytical methods such as SEM, and EDS.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.1
• /
• pp.31-37
• /
• 2011

Recently, the technology of surface treatment is being more important which affects the material cost reduction and substitution to the expensive material. The material used for the mechanical processing should have not only high intensity, but also strength toughness, wear resistance and corrosion resistance. In order to increase the durability and have better quality of the parts using such kind of tooling material, various kinds of research of the surface hardening through many kinds of heat resources is being done and practically applied. In this study, the characteristics of hardening surface zone for high strength of the press die material through laser beam irradiation are researched. In this study, it is experimentally observed by the status of the surface morphology, tensile strength, the hardness distribution of the base metal and wear condition by the surface hardness pattern by the laser beam based on the process parameters of $CO_2$ laser by using SM45C and STD11 used for press tool. Through this research, the characteristics of surface hardened zone for high strength of the thin metal by laser beam irradiation is done.

• Proceedings of the Optical Society of Korea Conference
• /
• 1990.02a
• /
• pp.45-48
• /
• 1990

CO2 laser beam was focused by a ZnSe lens onto the center of the occlusal surface f extracted lower molars. K-type thermocouple was contacted with the pulp chamber and the changes of temperature in the during and after the laser irradiation were measured as function of the power of laser beam, the time of laser irradiation and thickness of the sample. An empirical formula for temperature effect was derived from the measured data.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.06a
• /
• pp.761-762
• /
• 2009

• Restorative Dentistry and Endodontics
• /
• v.10 no.1
• /
• pp.43-53
• /
• 1984

The purpose of this study was to suggest the use of laser energy in the the field of operative dentistry without considerable pulpal damage and significant effects on the dental hard tissue, additionally to find out the methods which could control the temperature rise. The laser beam (CW $CO_2$ laser, output: 6W, beam diameter: 1.5mm) was focused on the center of the occlusal surface of extracted lower molars. A Ge lens (focal length 200mm) was used to focus the primary laser beam. In order to vary the total amount of the same irradiated energy, experimental subjects were devided into three groups: continuously irradiated group, intermittently irradiated group, and water-cooled group after continuous laser irradiation. Temperature changes in the pulp chamber after laser irradiation were measured and recorded by the digital thermometer and recorder. The following results were obtained: 1. Temperatures in the pulp chamber were raised up in the order of the continuously irradiated group, intermittently irradiated group, water-cooled group after continuous laser irradiation. 2. In the continuously irradiated group, the temperature was raised up $1.7^{\circ}C$, $3.8^{\circ}C$, $7.3^{\circ}C$, $17.2^{\circ}C$ after 2, 4, 8, 16 seconds of the irradiation of laser. In the intermittently irradiated group, the changes were $1.2^{\circ}C$, $3.4^{\circ}C$, $6.3^{\circ}C$, $11.1^{\circ}C$, respectively. In the water-cooled group after continuous laser irradiation, the changes were $0.0^{\circ}C$, $0.8^{\circ}C$, $1.6^{\circ}C$, $6.9^{\circ}C$, respectively. 3. The starting time of temperature rise in the pulp chamber had no connection with laser irradiation time.

• Journal of Welding and Joining
• /
• v.21 no.6
• /
• pp.20-25
• /
• 2003

Various welding methods such as Gas Tungsten Arc Welding(GTAW), magnetic force electrical resistance welding and Laser Beam Welding(LBW) are now available for end cap closure of nuclear fuel rods. Even though the resistance and GTA welding processes are widely used in manufacturing commercial fuel rods, they can not be recommended for the remote seal welding of fuel rods in the hot cell Facility due to the complexity of the electrode alignment, the difficulty in replacing parts in a remote manner and the large heat input for the thin sheath. Therefore, the Nd:YAG laser system using optical fiber transmission was selected for the end cap welding of irradiation fuel rods in the hot cell. The remote laser welding apparatus in the hot cell Facility was developed using a pulsed Nd:YAG laser of 500 watt average power with an optical fiber transmission. The weldment quality such as microstructure and mechanical strength was satisfactory. The optimum conditions of laser welding for encapsulating irradiation fuel rods in the hot cell were obtained.