• Journal of Ocean Engineering and Technology
• /
• v.10 no.4
• /
• pp.75-83
• /
• 1996

Polymeric composites can be subjected to a wide variety of environmemtal conditions in practical use. One of most important conditions to be considered in the stuctural design using such materials is the miisture envirnment. Thus the moisture effect on interlaminar fracture toughness $G_IC$ and $G_IIC$ of CFRP(carbon fiber reinforced plastic) composed of carbon fibers and epoxy resin is studied in this paper. Specimens were first processed in 25, 50, $80^{\circ}C$ flesh water and $25^{\circ}C$ sea water for various periods of time. After that, the water absorption and fracture toughness tests were performed under laboratory atmosphere. As result, the specimen processed in $80^{\circ}C$ flesh water indicates the highest misture absorbing capability, the second in $50^{\circ}C$ flesh water, the third in $25^{\circ}C$ sea water, and the specimen in $25^{\circ}C$ flesh water does the lowest. The interlaminar fracture toughness $G_IC$ increases, approaches to the maximum, and decreases as the immersion time increases. In case of interlaminar $G_IIC$, the value of the specimen processed in $80^{\circ}C$ flesh water turns out to be higher than others. In addition, the scanning electron micrographs(SEM) of fracture surfaces were also examined in order to explain the mechanism of fracture.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1240-1245
• /
• 2003

Reduced activation ferritic steel (JLF-1) is considered as a promising candidate material for blanket or first-wall structure of D-T fusion reactors. The fracture tests of fracture resistance curve (J-R curve) and $J_{IC}$ are desirable to investigate the exact fracture toughness of JLF-1 steel, since it has a high ductility. The fracture toughness of JLF-1 steel is affected by the configuration of test specimen such side groove, specimen thickness or specimen size. In this study, the fracture toughness tests were performed with various size(plane size and thickness) and various side groove of specimens. The test results showed the standard specimen with the side groove of 40 % represented a valid fracture toughness. The fracture resistance curve increased with increasing plane size and decreased with increasing thickness. However, the fracture resistance curve of half size specimen was similar to that of the standard specimen.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.5
• /
• pp.353-357
• /
• 1998

Cracking problem of Epoxy Molding Compound(EMC) is critical for the reliability of the plastic package during temperature cycling and IR-reflow condition. Fracture toughness of EMC, which is defined as the resistance of EMC to the crack propagation, is a useful factor in ht estimation of EMC against package crack. Thus, development of EMC having high fracture toughness at a given loading condition would be important for confirming the integrity of package. In this study, toughness of several EMC was measured by varying the test conditions such as temperature, loading speeds, and weight percent of filler in order to quantify the variation of toughness of EMC under various applicable conditions. It was found from the experiments that toughness of all EMC has following trends, i.e., it rapidly decreases over the glass transition temperature, remains almost same or little decreases below $0^{\circ}C$. It decreases with the growth of cross head speed in EMC and the weight percent of filler as the degree of brittleness of EMC increases with the amount of filler content.

• Journal of Sensor Science and Technology
• /
• v.8 no.1
• /
• pp.38-44
• /
• 1999

In this paper, we have constructed a self-diagnostic circuit which could detect erroneous signals in most cases that a eight-beam piezoresistive accelerometer were destroyed more than its one beam. To confirm the function of the circuit, PSPICE simulation was carried out. An IC chip was fabricated with a layout of KA 324 amplifier using a bipolar standard processing. After a package of the chip was sealed using a plastic package with 24 pins, the self-diagnostic characteristics were investigated. Then, the measured self-diagnostic characteristics of the circuit were compared with the PSPICE simulated result.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2003.05a
• /
• pp.300-305
• /
• 2003

Reduced activation ferritic (JLF-1) steel is leading candidates for blanket/first-wall structures of the D-T fusion reactor. In fusion application, structural materials will suffer effects of repeated changes of temperature. Therefore, the data base of tensile strength and fracture toughness at operated temperature $400^{\circ}C$ are very important. Fracture toughness ($J_{IC}$) and tensile tests were carried out at room temperature and elevated temperature ($400^{\circ}C$). Fracture toughness tests were performed with two type size to investigate the relationship between the constraint effect of a size and the fracture toughness resistance curve. As the results, the tensile strength and the fracture toughness values of the JLF-1 steel are slightly decreased with increasing temperature. The fracture resistance curve increased with increasing plane size and decreased with increasing thickness. The fracture toughness values of JLF-1 steel at room temperature and at $400^{\circ}C$ shows an excellent fracture toughness ($J_{IC}$) of about $530kJ/m^2\;and\;340kJ/m^2$, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.4 s.247
• /
• pp.420-427
• /
• 2006

The structural and leakage integrity of steam generator tubes should be sustained against all postulated loads even if a crack is present. During the past three decades, most of the efforts with respect to integrity evaluation of steam generator tubes have been focused on limit load solutions but, recently, the applicability of elastic-plastic fracture mechanics was examined cautiously due to its effectiveness. The purpose of this paper is to introduce a testing method to estimate fracture resistance characteristics of steam generator tubes with a through-wall crack. Due to limited thickness and diameter, inevitably, the steam generator tubes themselves were tested instead of standard specimen or alternative ones. Also, a series of three dimensional elastic-plastic finite element analyses were carried out to derive closed-form estimation equations with respect to J-integral and crack extension for direct current potential drop method. Since the effectiveness of $J_{IC}$ as well as J-R curves was proven through comparison with those of standard specimens taken from pipes, it is believed that the proposed scheme can be utilized as an efficient tool for integrity evaluation of cracked steam generator tubes.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.23 no.3
• /
• pp.238-243
• /
• 2001

Purpose : The purpose of this study was to determine radiologic variables affecting extraction of impacted mandibular third molar. Materials and Methods : This study was investigated on 44 consecutive extractions of unilateral impacted mandibular third molars (Male;34, Female;10, Mean age;24.98, Age range;19-35). Fourteen radiologic variables, which were actual value except only one, were evaluated to establish their relation to the operation time. The Pearson correlation coefficient and Stepwise procedures for regression analysis were carried out. Results : Eight variables (depth, angulation, ramus width, relationship to the second molar, distal ramus depth, mesial ramus depth, mesial periodontal ligament width and follicle) showed a statistically significant relation to the operation time(Pearson correlation coefficient, p<0.05). Two variables, depth and mesial periodontal ligament width, showed the most powerful and just relation to the operation time($r^2$ = 0.349, p<0.05). Conclusion : This study shows that our results can help general practioner to estimate the operation time of extraction of impacted mandibular third molars by measuring two radiologic variables ; depth and mesial periondontal ligament width.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.5
• /
• pp.1140-1147
• /
• 2001

This paper describes the effect of various molding pressure for Mode I. Mode II interlaminar fracture toughness of carbon fiber reinforced plastic composites by using double cantilever beam(DCB), end notched flexure(ENF) and end loaded split(ELS) Specimen. The value of $G_{IC}$, $G_{IIC}$ as a function of various molding pressure is almost same at 307, 431, 585 kPa, however it shows highest value under 307kPa molding pressure, The SEM photographs show good fiber distribution and interfacial bonding of composites when the molding pressure is the 307kPa.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1680-1682
• /
• 2007

The integrated circuits such as inverters, ring oscillators, NAND and NOR gates, and rectifiers were fabricated on PEN substrate by using pentacene TFTs. The OTFTs used bottom contact structure and produced the average mobility of $0.26\;cm^2/V.sec$ and on/off current ratio of $10^5$. All circuits worked successfully like the simulation results. Especially, the rectifier was able to operate up to 1 MHz input signals, and ring oscillator exhibited oscillation frequency of 1MHz at-40V.

• Journal of the Korean Society of Safety
• /
• v.11 no.1
• /
• pp.11-15
• /
• 1996

For the assessment of fracture behaviors of structural components, various fracture mechanics parameters have been applied to date. New approaches to analyze structural fracture performance under elastic-plastic condition have been proposed by the development of testing methods for characterization of material behavior which is defying to the analysis by conventional fracture parameters. In this study, on the assumption that, initiation of crack propagation of a piping materials occurs when the crack tip strain field reaches "the local fracture strain", following two major issues are discussed ; 1) The relationship between the critical value of J-integral($J_{IC}$) and the local fracture strain (${\varepsilon}_c$) in uniaxial tensile test in the region of maximum reduction area was described. 2) To proved the validity of above relations a series of tests were performed under various temperature and on the different piping materials.materials.