• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.12
• /
• pp.1013-1019
• /
• 2016

CFRP is the composite material manufactured by the hybrid resin on the basis of carbon fiber. As this material has the high specific strength and the light weight, it has been widely used at various fields. Particularly, the unidirectional carbon fiber can be applied with the layer angle. CFRP made with layer angle has the strength higher than with no layer angle. In this paper, the property of crack growth due to each layer angle was investigated on the crack propagation and fracture behavior of the CFRP compact tension specimen due to the change of layer angle. The value of maximum stress is shown to be decreased and the crack propagation is slowed down as the layer angle is increased. But the limit according to the layer angle is shown as the stress is increased again from the base point of the layer angle of $60^{\circ}$. This study result is thought to be utilized with the data which verify the probability of fatigue fracture when the defect inside the structure at using CFRP of mechanical structure happens.

• Journal of the Korean Institute of Gas
• /
• v.12 no.2
• /
• pp.105-109
• /
• 2008

A safety valve has a valve mechanism for the automatic release of gas from piping system when the pressure exceeds preset limit cause of a defect of a pressure regulator, condensation of water in a pipe. Therefore, for the safety of pressure regulating station, it is essential to study the flow regime and characteristics of safety valve. This article presents the numerical analysis on the flow analysis, the ejection capacity and required effective discharge area of the safety valve that is established in pressure regulating station. Then, the results are compared and analyzed with domestic and foreign regulations such as API(America Petroleum Institute), EN(European Standard), and NF(Norme Francise). Moreover, the installation number of safety valve is considered by using domestic and foreign regulations and maximum reguired effective discharge area of safety valve.

• Journal of Intelligence and Information Systems
• /
• v.11 no.2
• /
• pp.47-57
• /
• 2005

In this research, the main theme is the system integration of driving simulator and unmanned vehicle. The total system is composed of the mater system and the slave system. The master system has a cockpit system and the driving simulator. The slave system means an unmanned vehicle, which is composed of the actuator system the sensory system and the vision system. The communication system is composed of RS-232C serial communication system which combines the master system with the slave system. To integrate both systems, the signal classification and system characteristics considered DSP(Digital Signal Processing) filter is designed with signal sampling and measurement theory. In addition, to simulate the motion of tele-operated unmanned vehicle on the driving simulator, the classical washout algorithm is applied to this filter, because the unmanned vehicle does not have a limited working space, while the driving simulator has a narrow working space and it is difficult to cover all the motion of the unmanned vehicle. Because the classical washout algorithm has a defect of fixed high pass later, fuzzy logic is applied to reimburse it through an adaptive filter and scale factor for realistic motion generation on the driving simulator.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.4
• /
• pp.315-324
• /
• 2004

In eddy current testing(ECT), differential probes have been frequently used since they .an reduce the number of parameters that influence ECT signals. However, differential signal is actually the difference of the two coils' impedance so that signal prediction and interpretation are not easy, On the other hand, absolute coil signal is rather straightforward to predict and analyze. Therefore, combined use of the two types of signals would increase the test reliability. In this paper, absolute coil signals from Inconel plate and tubes are predicted by the finite element analysis and efforts of lift-off, fill-factor, conductivity, operating frequency, test specimen thickness, inner diameter defects, and outer diameter defects are investigated. As a result, various impedance plane diagrams are drawn and analyzed. Significant practical knowldege about absolute signals is accumulated and similar characteristics of the two types of signal could be understood. Finally, slope angle versus defect depth calibration corves are prepared for three different frequencies.

• Journal of the Korean Magnetics Society
• /
• v.26 no.1
• /
• pp.24-30
• /
• 2016

MFL (Magnetic flux leakage) type nondestructive testing has been used for inspection of underground gas pipelines to find metal defects by detecting magnetic leakage signal. Because the underground gas pipeline is exposed by environment such as high pressure with great humidity, external defects are easily formed on the surface of pipelines and they are being grouped respectively. These adjacent defects cause the signal distortion of leakage flux so that it is hard to estimate the shape information of defects. In this paper, we performed to study of the signal distortion and compensating method for multiple defects in MFL type nondestructive testing system by using 3D FEM simulation. This paper proposes the basic algorithm of defect signal analysis on multiple defects on the surface of 30 inch diameter pipeline.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.2
• /
• pp.1-6
• /
• 2019

With the increase in number of the athletic population and elderly demographic, the demand for orthopedic splints, which are used to support a damaged body, has rapidly increased. Current splints mainly consist of inner and outer parts, which are multiple fabrics covered with polyurethane and nonwoven fabrics, respectively. However, the laminated materials with directly applied pre-polymer coating lead to a high defect rate because of the uneven thickness on the surface. Thus, this study proposes an indirect coating method using a precise clearance controller, which enables the even application of the coating material on multiple inner parts while maintaining a constant thickness. In addition, a roll-to-roll (R2R) technique is applied instead of the sewing mechanism to bond the inner and outer materials together and enhance the productivity in the final stage. In the advanced methods, there is a storage tank that contains polyurethane, a clearance controller, and pairs of rollers in the upper and lower rows. To improve the quality of the products and optimize the equipment, three controllable factors are determined: the viscosity of polyurethane, angle of the gap controller and number of pairs of rollers in the R2R system.

• Korean Journal of Materials Research
• /
• v.31 no.6
• /
• pp.320-324
• /
• 2021

Effects of growth variables and post-growth annealing on the optical, structural and electrical properties of magnetron-sputtered Ga_0.04Mg_0.10Zn_0.86O films are characterized in detail. It is observed that films grown from pure oxygen plasma showed high resistivity, ~10² Ω·cm, whereas films grown in Ar plasma showed much lower resistivity, 2.0 × 10^-2 ~ 1.0 × 10^-1 Ω·cm. Post-growth annealing significantly improved the electrical resistivity, to 4.3 ~ 9.0 × 10^-3 Ω·cm for the vacuum annealed samples and to 1.3 ~ 3.0 × 10^-3 Ω·cm for the films annealed in Zn vapor. It is proposed that these phenomena may be attributed to the improved crystalline quality and to changes in the defect chemistry. It is suggested that growth within oxygen environments leads to suppression of oxygen vacancy (Vo) donors and formation of Zn vacancy (V_Zn) acceptors, resulting in highly resistive films. After annealing treatment, the activation of Ga donors is enhanced, Vo donors are annihilated, and crystalline quality is improved, increasing the electron mobility and the concentration. After annealing in Zn vapor, Zn interstitial donors are introduced, further increasing the electron concentration.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.26 no.4
• /
• pp.526-532
• /
• 2022

With the development of IoT technology, image processing is being utilized in various fields such as image analysis, image recognition, medical industry, and factory automation. Noise is generated in image data from causes such as defect in transmission line. Image noise must be removed because it damages the performance of the image processing application program. Salt and Pepper noise is a representative type of image noise, and various studies have been conducted to remove Salt and Pepper noise. Widely known methods include A-TMF, AFMF, and SDWF. However, as the noise density increases, the performance deteriorates. Thus, this paper proposes an algorithm that performs filtering using a fuzzy logic weight mask only in case of noise after noise determination. In order to prove the noise removal performance of the proposed algorithm, an experiment was performed on images with 10% to 90% noise added and the PSNR was compared.

• Journal of the Microelectronics and Packaging Society
• /
• v.29 no.3
• /
• pp.31-35
• /
• 2022

Recently, with the 4th industrial revolution, the demand for high-density semiconductors for large-capacity data processing is increasing. Researchers are interested in researching the reliability of surface mount technology (SMT). In this study, the effect of PCB pad design on assembly and adhesion reliability of passive component was analyzed using design of experiment (DOE). The DOE method was established using the pad length, width, and distance between pads of the PCB as variables. The assembly defect rate of the passive element after the reflow process was derived according to the misplacement direction of the chip resistor. The shear force between the passive element and the PCB was measured using shear tests. In addition, the shape of the solder according to the pad design was analyzed through cross-sectional analysis.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.26 no.5
• /
• pp.641-648
• /
• 2022

This paper is a study to find out the factors affecting the defects that occur during the use of Electron Beam Melting (EBM), one of the 3D printer output methods, through data analysis. By referring to factors identified as major causes of defects in previous studies, log files occurring between processes were analyzed and related variables were extracted. In addition, focusing on the fact that the data is time series data, the concept of a window was introduced to compose variables including data from all three layers. The dependent variable is a binary classification problem with the presence or absence of defects, and due to the problem that the proportion of defect layers is low (about 4%), balanced training data were created through the SMOTE technique. For the analysis, I use XGBoost using Gridsearch CV, and evaluate the classification performance based on the confusion matrix. I conclude results of the stuy by analyzing the importance of variables through SHAP values.