• Transactions of the Korean Society of Mechanical Engineers A
• /
• 제40권3호
• /
• pp.281-288
• /
• 2016

The ballistic performance data of composite materials is distributed due to material inhomogeneity. In this paper, the uncertainty in residual velocity is obtained experimentally, and a method of predicting it is established numerically for the high-speed impact of a bullet into laminated composites. First, the failure strain distribution was obtained by conducting a tensile test using 10 specimens. Next, a ballistic impact test was carried out for the impact of a fragment-simulating projectile (FSP) bullet with 4ply ([0/90]s) and 8ply ([0/90/0/90]s) glass fiber reinforced plastic (GFRP) plates. Eighteen shots were made at the same impact velocity and the residual velocities were obtained. Finally, simulations were conducted to predict the residual velocities by using the failure strain distributions that were obtained from the tensile test. For this simulation, two impact velocities were chosen at 411.7m/s (4ply) and 592.5m/s (8ply). The simulation results show that the predicted residual velocities are in close agreement with test results. Additionally, the modeling of a composite plate with layered solid elements requires less calculation time than modeling with solid elements.

• Restorative Dentistry and Endodontics
• /
• 제15권1호
• /
• pp.217-227
• /
• 1990

The purpose of this study was to evaluate the marginal leakage of esthetic restorative materials according to the filling method in class V cavities. 60 cavities were prepared on buccal surface for dye penetration test and divided into 5 experimental groups according to the filling methods of esthetic materials: group 1 was filled with glass ionomer cement, group 2, 3 and 4 were filled with the chamfer, knife edge and butt joint shaped glass ionomer cement respectively and silux plus/scotchbond 2$^{(R)}$ by sandwich technique, group 5 was lined with Dycal$^{(R)}$ and filled with silux plus/scotchbond 2$^{(R)}$ by bulk filling technique. All the specimens were then thermocycled in a range of $4^{\circ}C-60^{\circ}C$ by and immersed in 2% methylene blue dye solution for 24 hours, and sectioned mesiodistally with carborundum disk into two parts under water spray. All the specimens were observed at the occlusal and gingival margins and statistical analysis was performed. The obtained results were as follows : 1. At the occlusal margins, group 2, 3, 4 and 5 showed less marginal leakage than group 1 (p<0.05) and there were not significant differences among group 2, 3, 4, and 5. 2. At the gingival margins, group 5 showed the least marginal leakage and group 4 and 5 showed less marginal leakage than group 1, 2 and 3 (p<0.05). 3. In the laminated groups, group 4 showed less marginal leakage than group 2 and 3 at the gingival margins. 4. In comparison to the occlusal and gingival margins, all groups showed less marginal leakage at the occlusal margins than at the gingival margins (p<0.05).

• Structural Engineering and Mechanics
• /
• 제80권5호
• /
• pp.503-522
• /
• 2021

This paper investigates experimentally and numerically the influence of drilling process on the mechanical and thermomechanical behaviors of woven glass fiber reinforced polymer (GFRP) composite plate. Through the experimental analysis, a CNC machine with cemented carbide drill (point angles 𝜙=118° and 6 mm diameter) was used to drill a woven GFRP laminated squared plate with a length of 36.6 mm and different thicknesses. A produced temperature during drilling "heat affected zone (HAZ)" was measured by two different procedures using thermal IR camera and thermocouples. A thrust force and cutting torque were measured by a Kistler 9272 dynamometer. The delamination factors were evaluated by the image processing technique. Finite element model (FEM) has been developed by using LS-Dyna to simulate the drilling processing and validate the thrust force and torque with those obtained by experimental technique. It is found that, the present finite element model has the capability to predict the force and torque efficiently at various drilling conditions. Numerical parametric analysis is presented to illustrate the influences of the speeding up, coefficient of friction, element type, and mass scaling effects on the calculated thrust force, torque and calculation's cost. It is found that, the cutting time can be adjusted by drilling parameters (feed, speed, and specimen thickness) to control the induced temperature and thus, the force, torque and delamination factor in drilling GFRP composites. The delamination of woven GFRP is accompanied with edge chipping, spalling, and uncut fibers.

• Journal of Ocean Engineering and Technology
• /
• 제33권6호
• /
• pp.495-503
• /
• 2019

Approximately 90,000 ships are registered in South Korea, and about 80,000 of these ships are used in domestic shipping. Among these, 84% are small ships, such as a fishing vessels that weigh less than 20 tons and are made mostly of an FRP (Fiber Reinforced Plastics). When this fact is taken into account, the greenhouse gas emissions that are released per ton of a composite vessel are sizeable. In this study, the laminated structures of an FRP fishing vessel, many of which currently are being built in Korea, were analyzed by ISO (International Organization for Standardization) and international design rules, and the structures of the hulls are lightweight with optimum glass fiber mass content as determined by the laminate weight minimization algorithm. As a result, it was confirmed that the laminations of the vessels in accordance with the Korean rule could have 6.4% to approximately 11% more design margin compared to the requirements of ISO and other international rules. And the case study of the application of the laminate weight minimization algorithm showed the possibility of reducing the weight of the hull bottom plating by as much as about 19.32% and by as much as about 18.06% in the overall structure.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
• /
• pp.773-775
• /
• 2004

For high end, large area displays, all current LC modes require some degree of optical compensation to improve the front of screen viewing experience. Currently most optical films are laminated to the outside of the LCD cell, between the glass and polariser. In this paper we wish to show how it is possible to integrate the compensating optical film within a VA mode LCD cell. The paper will describe the process of making the biaxial film through the process of in-situ photopolymerisation of an aligned film of reactive mesogens in the cholesteric phase using polarised UV light. The film can be made on the colour filter array side of the LCD panel. In addition the process of fabricating a VA mode LCD containing this film will be described and the performance of this module will be presented

• Journal of the Korean Society for Precision Engineering
• /
• 제21권2호
• /
• pp.195-202
• /
• 2004

This paper presents the fabrication and evaluation of mechanical behavior for a peristaltic micropump by flow simulation. The valve-less micropump using the diffuser/nozzle is consists of the lower plate, the middle plate, the upper plate and the tube that connects inlet and outlet of the pump. The lower plate includes the channel and the chamber, and the plain middle plate are made of glass and actuated by the piezoelectric translator. Channels and a chamber on the lower plate are fabricated on high processability silicon wafer by the DRIE(Deep Reactive Ion Etching) process. The upper plate does the roll of a pump cover and has inlet/outlet/electric holes. Three plates are laminated by the aligner and bonded by the anodic bonding process. Flow simulation is performed using error-reduced finite volume method (FVM). As results of the flow simulation and experiments, the single chamber pump has severe flow problems, such as a backflow and large fluctuation of a flow rate. It is proved that the double-chamber micropump proposed in this paper can reduce the drawback of the single-chamber one.

• Journal of the Korean Wood Science and Technology
• /
• 제45권6호
• /
• pp.828-835
• /
• 2017

Airtightness of buildings is one of critical aspects of its energy performance. To build up references of airtightness of wooden houses built in Korea, blower door tests have been carried out in 42 houses since 2006. Causes of air leakage were investigated recently. The average value of air change rate was $3.7h^{-1}$ for light frame house and $5.5h^{-1}$ for post-beam construction at ACH50 (air change per hour at 50 Pa air pressure difference). Foam type insulation was more advantageous in ensuring building airtightness than glass fiber batt. Airtightness of wooden houses which were constructed after 2010 was improved to have less than $1.5h^{-1}$ of ACH50, threshold for application of artificial air change. The average air change rate of CLT (cross laminated timber) houses showed the lowest value, $1.1h^{-1}$, among the tested structures.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.1186-1190
• /
• 2003

In this paper, a valveless bubble-actuated fluid micropump was has been developed and its performance was tested. The valveless micropump consists of the lower plate, the middle plate, the upper plate and a resistive heater. The lower plate includes the nozzle-diffuser elements and the double-chamber. Nozzle-diffuser elements and a double-chamber are fabricated on the silicon wafer by the DRIE(Deep Reactive Ion Etching) process. The lower plate also has inlet/outlet channels for fluid flow. The middle plate is made of glass and plays the role of the diaphragm. The chamber in the upper plate is filled with deionized water, and which contacts with the resistive heater. The resistive heater is patterned on a silicon substrate by Ti/Pt sputtering. Three plates and the resister heater are laminated by the aligner and bonded in the anodic bonder. Since the bubble is evaporated and condensed periodically in the chamber, the fluid flows from inlet to outlet with respect to the diffusion effect. In order to avoid backflow, the double chamber system is introduced. Analytical and experimental results show the validity of the developed double-chamber micropump.

• Transactions on Electrical and Electronic Materials
• /
• 제18권6호
• /
• pp.338-340
• /
• 2017

Breakdown of solid insulating materials in power equipment could result in undesired outages and replacements, and may be due to an increase in electric stress on the material. Therefore, it is necessary to conduct a proper diagnosis of materials before their practical use. In this work, a few inherent properties of different non-cellulosic insulating materials, such as Nomex, Teflon, laminated Nomex, glass bonded mica, epoxy resin bonded mica paper, and epoxy resin bonded fiberglass, have been evaluated by performing non-destructive dielectric diagnostic measurements, and an attempt has been made to correlate these basic parameters to evaluate the breakdown strength (BDS). An equation has been proposed using a basic theory which defines the correlation between the BDS, dielectric constant, dissipation factor, sample thickness, and volume resistivity. The results obtained from the equation are also compared with the experimental values. The suggested equation will be helpful to predict the BDS of any non-cellulosic material without experimentation in the laboratory.

• Proceedings of the KSME Conference
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.1939-1943
• /
• 2008

Deformation of a mold is measured and analyzed in alignment and curing processes of UV-Imprint Lithography. We are focused on mold deformation caused by a UV resin, which is laminated between a mold and a target glass-panel. The UV resin is viscous in case of liquid state, and the resin will be solidified when being exposed by the ultra-violet light. The viscosity of the resin causes shear force on the mold during the alignment process. Moreover, the shrinkage during phase change from liquid to solid may cause residual stress on the mold. The experiments for measuring temperature and strain are made during alignment and curing process. Strain-gages and thermocouples are used for measuring the strain and variation of temperature on several points of the mold, respectively. The deformation of mold is also simulated and analyzed. The simulation results are compared with the experiments. Finally, sources of alignment errors in large area UV-nanoimprint lithography are discussed.