• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2001.04a
• /
• pp.191-193
• /
• 2001

This paper presents the result of groundwater analysis in Changwon area and the characteristics of the groundwater properties. Changwon city conducted groundwater analysis at 551 sites in 1996 and 1997. The water quality is suitable as groundwater use at 466 sites (84.6 %) and exceeds maximum contaminant levels (MCLs) at 85 sites (15.4 %). Major contaminants are total bacteria, coliform and nitrate-N. DNAPLs, e.g. TCE and PCE are detected in the areas of industrial complex and residence. The detection of TCE and PCE is due to organic solvents from manufacturing companies. They are also derived from laundries, Photographer's studios, septic tanks, etc. In addition, fifty groundwater samples were analyzed. Iron, manganese, zinc, copper, lead, aluminum and fluorine are detected in nearly all the groundwater samples. The groundwaters shown on the Piper diagram mostly belong to Ca-HCO$_3$ type.

• 유체기계공업학회:학술대회논문집
• /
• 2001.11a
• /
• pp.441-447
• /
• 2001

This paper presents numerical method of investigating flow characteristics of reed valves of reciprocating compressors. The numerically determined effective flow areas agreed within $5.4\%$ of those obtained from experimental measurements. Reasonably good agreements between the experimental and numerical results have been found, implying that the effective flow and force areas of reed valves could be obtained by CFD alone with enough accuracy. A computer simulation of reciprocating compressor has been performed using a numerical results of reed valves. The calculated P-V diagram shows a good agreement with experimental result.

• Proceedings of the KWS Conference
• /
• 2004.05a
• /
• pp.249-251
• /
• 2004

According to our fatigue tests carried out at 20 ㎐, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short hie range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

• Journal of Biosystems Engineering
• /
• v.1 no.1
• /
• pp.64-72
• /
• 1976

This experimental work was carried out to investigate the fatigue bending strength on various shapes and sizes of notches of the domestically manufactured steel plate. The notch types tested were a circular hole, U-and V-notches. The S-N diagram for different notch shapes were discussed in relation to plan bending strength and stress concentration factor of notches .The results of the experiments are summarized as follows : (1) The difference between stress concentration factor and notch factor was greater as the radium of notch root became smaller, and these values approached to an identical value as the radium of notch root increased. (2) It was shown that the plane bending fatigue limit of bar without notch for the hotrolled steel having the tensile strength of 33.1kg/$mm^2$was 17.0kg/$mm^2$. (3) U-and V-notch had a greater effect of stress concentration factor on the endurance limit, but O-hole showed the same effect only for $\o\pm2mm$. (4) For the same radius of notch root, U-notch showed a lower value of fatigue limit compared to V-notch and O-hole.

• Proceedings of the Korea Contents Association Conference
• /
• 2016.05a
• /
• pp.341-342
• /
• 2016

제조 산업에서 키워드로 많이 다뤄지는 4M데이터(man, method, machine, martial)는 생산에 효율성을 높이기 위한 중요한 요소이다. 규모가 작은 기업일수록 4M관련 데이터 관리가 잘 안되고 있다. 관리를 잘하는 기업이라도 수집하고 저장만 하고 있는 현실이다. 본 논문에서는 수집하고 저장되어 있는 4M데이터를 활용해 생산한 상품에 대한 생산당시 상황을 추적할 수 있는 시스템을 제안한다. 제안한 시스템을 이용해 생산라인의 상황을 한 눈에 파악이 가능하고 주로 문제가 발생하는 공정과 관련 요인 파악을 통해 불량률을 줄이는 연구를 할 수 있다.

• 한국기계연구소 소보
• /
• s.13
• /
• pp.3-13
• /
• 1984

Fatigue failure of axle housing could cause many injuries and much financial loss. This challenges the engineer to improve design decisions involving fatigue. Endurance evaluation of axle housing is great interest to auto-mobile manufacturers for the sake of safety and reliability. Axle housing is subjected to gross vehicle weight(G.V.W)as mean load and alternating load. Theoretical design diagram involving mean and alternating stresses is used for the evaluation of axle housing fatigue endurance with the equivalent stress of fatigue critical area on the axle housing. Four point bending fatigue tests on axle housing with constant amplitude loading at approximately R=0 were performed with 50 ton servohydraulic strucural fatigue testing machine developed at KIMM. Specimens were made with the same material STKM 13B as the axle housing and tested to obtain S_N data. Five specimens of STKM 13B were tested at 253.61 MPa and weibull distribution was obtained at the same stress level. Material data and structural data were compares and fatigue stress property factor and fatigue life property factor were obtained.

• Design & Manufacturing
• /
• v.14 no.1
• /
• pp.49-55
• /
• 2020

In this study, the fatigue behavior and fatigue life characteristics of PA2200 specimens fabricated by SLS 3D printer were studied. Fatigue tests were performed according to the standard specification (ASTM E468) and fatigue life curves were obtained. In order to perform the fatigue test, mechanical properties were measured according to the test speed of the simple tensile test, and the self-heating temperature of the specimen according to the test speed was measured using an infrared temperature measuring camera in consideration of heat generation due to plastic deformation. There was no significant difference within the set test speed range and the average self-heating temperature was measured at 38.5 ℃. The mechanical strength at the measured temperature showed a relatively small difference from the mechanical strength at room temperature. Fatigue test conditions were established through the preceding experiments, and the loading conditions below the tensile strength at room temperature 23 ℃ were set as the cyclic load. The maximum number of replicates was less than 100,000 cycles, and the fracture behavior of the specimens with the repeated loads showed the characteristics of Racheting. It was confirmed that SLS 3D printing PA2200 material could be applied to the Basquin's S-N diagram for the fatigue life curve of metal materials. SEM images of the fracture surface was obtained to analyze the relationship between the characteristics of the fracture surface and the number of repetitions until failure. Brittle fracture, crazing fracture, grain melting, and porous fracture surface were observed. It was shown that the larger the area of crazing damage, the longer the number of repetitions until fracture.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.7 no.1
• /
• pp.47-55
• /
• 2004

In this paper, The statistical properties of ocean waves in the sea area of Hong-do, Korea are examined based on 1998-2002's wave data from a directional wave buoy. Wave data aquisition rate, mean wave heights, frequency of wave direction are summarized. Wave height and period scatter diagrams and n-year return period wave heights are estimated. Wave periods of maximum wave heights are also estimated. Large amplitude wave characteristics during the typhoon Prapiroon in 2000, Rusa in 2002 are also examined.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.310-311
• /
• 2008

We have studied electro-optical characteristics of fringe-field switching (FFS) mode with high $d{\Delta}n$ according to the electrode position. In this device, the fringe-electric field drives the LCs to rotate so that the dielectric torque is electrode-positional dependent, which results in electrode-position dependency in the LC's rotating angle. We confirmed polarization microscope image and chromaticity diagram at the different electrode position with LC that have high $d{\Delta}n$. Since the FFS mode is influenced by horizontal and vertical electric field, the FFS mode modulates light using both phase retardation and polarization rotation effect, which had already been verified with previous studies. However, from another point of view, tight modulation of FFS mode has been demonstrated by performing experiment and calculated simulation at the high $d{\Delta}n$ LC cell.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.1
• /
• pp.82.1-82.1
• /
• 2012

We present results of searching for the Very Low Luminosity Objects (VeLLOs; internal luminosity Lint<0.1Lo) candidates in the Gould Belt's clouds using infrared observations from 3.6 to 70 micron by the Spitzer Space Telescope. More than 100 VeLLO candidates were selected through the criteria by Dunham et al. and our additional ones. The candidates in Northern sky were recently observed with high density tracers such as N2H+ (1-0) and HCN (1-0) using Korea VLBI Network (KVN) 21m telescope at Yonsei site to check their embeddedness in dense gas envelopes. A total of 25 out of 74 VeLLO candidates were detected in either N2H+ or HCN (1-0) line while 9 candidates were detected in both tracers. These are more likely bona fide VeLLOs which need to be studied further in future. In this study the bolometric luminosities for 40 VeLLOs (25 from this study and 15 from Dunham et al.) were estimated and found to be significantly smaller than those given by various theoretical model tracks with constant accretion rate in a BLT diagram, indicating the constant accretion process suggested by standard star formation models can not explain the faintness of the VeLLOs. In the talk we will discuss on some possible explanation of why the VeLLOs are faint.