• 상하수도학회지
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• 제20권2호
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• pp.281-287
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• 2006

Maintaining adequate chlorine residual is crucial in water treatment facilities, Treatment technique, newly promulgated regulation, requires sufficient disinfection in order to control more resistant microorganisms such as Viruses and Giardia lamblia. Each water treatment plant should report various water qualities including chlorine residual and disinfection by-products, thus plenty of data has been generated. Even though statistical analysis using these data are forced to investigate the status and effect of water qualities in water facilities very few researches have been performed in korea. This study performed statistical analysis of chlorine residual during three years in Korean drinking water. The average chlorine residual concentrations were 0.701mg/L, 0.738mg/L, 0.763mg/L in 2002, 2003, 2004, respectively. Monthly variations of chlorine residual was not significant. ANOVA result showed that yearly variance of chlorine residual is different in only less than $5000m^3/day$ of water treatment capacity. The statistical analysis can help government to establish new regulation with scientific basis.

• 대한기계학회논문집A
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• 제34권4호
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• pp.413-421
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• 2010

본 연구에서는 실제 용접 과정을 모사하는 유한요소 해석을 이용하여 강도 불일치를 가지는 매설 천연가스 배관 용접부의 잔류응력 분포를 계산한다. 유한요소 해석 절차의 타당성을 검증하기 위해 온도 및 잔류응력 해석 결과들은 실제 용융부 형상과 API 579 적용 결과와 비교된다. 기계적 강도 차이, 용접 금속의 강도, 덧살 및 입열량 등과 같은 용접 및 재료 변수들이 잔류응력 분포에 미치는 영향을 평가하기 위해 Parametric Study가 수행된다. 최종적으로 Parametric Study 결과에 근거하여 용접 및 재료 변수들의 영향이 고찰된다. 특히, 모재들 사이의 강도 불일치는 잔류응력 분포에 미미한 영향을 미침을 확인하였다.

• 대한의용생체공학회:의공학회지
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• 제16권3호
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• pp.325-330
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• 1995

혈압에 의한 안쪽벽의 변형을 집중현상으로 인한 동백 전단부의 변형율 gradient의 심각성은 잔유 변형율에 의해 감소되거나 없을 수 있다는 가정을 실험적으로 시도했다. 잔유변형율과 압력에 의한 변형율을 측정하여 잔유변형율이 원주변형율에 끼치는 영향을 알아 보았다. 결과로서 변형율 gradient를 줄이거나 없을수도 있으나 negative gardient가 평균적으로 나타났다. 즉 전체변형율(원주변형율+잔유변형율)은 안쪽벽이 낮고 바깥쪽이 높은 것으로 나타났다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권1호
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• pp.72-79
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• 2018

Purpose: Numerical and experimental study was performed to evaluate the effect of peening temperature on the residual compressive stress distribution and magnitude of residual compressive stress at the material surface. Methods: A compressive air-propelled warm peening equipment was designed and manufactured for warm peening test. Results: 3D dynamic finite element (FE) model of the warm peening test was proposed and validity of the proposed FE model was verified by comparing the predicted residual stresses with the measured residual stresses in the open literature. Maximum warm peening temperature and a proper peening time were investigated with the proposed FE model. Conclusion: Compressive residual stress increased remarkably with peening temperature increased. But, peening temperature is greater than $350^{\circ}C$, the effect of peening temperature disappeared. Therefore, maximum peening temperature possibly applicable for warm peening industry might be $350^{\circ}C$ and peening time is 45s.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1086-1091
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• 2003

The problem of residual stresses and fatigue behavior in welded structures is the main concern of welding research fields. The residual stresses and distortions of structures by welding exert negative effect on the safety of mechanical structures. Postweld heat treatment is usually carried out to relieve this residual stresses of welded joints. In this paper the influence of postweld heat treatment on fatigue life of butt-welded joint was investigated. To predict the effect of PWHT, an analytical model is developed by finite element and local strain approach and the result of fatigue life analysis is compared to experimental results. It is demonstrated that fatigue life estimates closely approximate the experimental results and PWHT provides some increase of fatigue lives in long-life fatigue region and no increase in short-life fatigue region because of the residual stress relaxation under tensile loads.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.94-94
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• 2009

The purpose of this study is to identify the principal factor controlling transverse residual stress at the weldment for joining unit hull blocks. In order to do it, the comprehensive FE analyses were carried out to evaluate the effect of distance between fillet and butt weldments, in-plane and out-of-plane restraint degree on the amount and distribution of transverse residual stress in way of the weldments between unit hull blocks. In accordance with FEA results, principal factor controlling the amount of transverse residual stress at the weldments was identified as in-plane restraint degree of butt weldment for unit blocks. The effect of other variables on the transverse residual stress was very small relatively. Based on the results, it can be concluded that the proper distance between fillet weldment for stiffener and butt weldment for joining unit blocks should be determined in consideration of in-plane restraint intensity of butt weldments.

• 상하수도학회지
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• 제27권5호
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• pp.547-554
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• 2013

Chlorine has strong oxidizing power, also it is many advantages over other disinfectants such as the residual characteristic and economic feasibility. However, chlorine also has disadvantages such as creating disinfection by-products of chlorine as THMs. In particular, the most deadly disadvantage of chlorine is that it is extremely poisonous toxins about all alive lives. Disinfection with electrolysis water can be a very useful way Because you do not have to worry about chlorine's dangerous. In this study, we evaluated the potential as a disinfectant, across the evaluating disinfection effect and generating characteristic of by-products. The electrolyzed water could be obtained removal efficiencies of over 99.9 % the coliform by operating condition such as residence time, current density (voltage), the electrode gap. The residual chlorine be generated 10,000 mg/L in current density $1.0A/dm^2$ and residence time of 10 minutes. The residual chlorine concentration was possible to maintain a stable. The by-products generated by high concentration residual chlorine in the reactor such as trihalomethanes, haloaceticacid, chloralhydrate, haloacetonitrile were detected in less than a water quality standards. At the concentration of less than residual chlorine of 1 ppm, the chlorine disinfection by-products be generated most below the detection limit.

• Tribology and Lubricants
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• 제37권2호
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• pp.54-61
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• 2021

The effect of the sand blasting before TiAlN coating in the manufacture of WC hard metal alloy tips have been studied. For four different tips, according to the status of processing of the sand blasting and the coating, residual stress measurement by X-ray diffraction and several tests for mechanical properties have been conducted. The results suggest that there was no difference in static mechanical properties, such as hardness, surface roughness and elastic modulus, between two coatings. Furthermore, compressive residual stress was generated equally on their surfaces. Additionally, the compressive residual stress in substrate WC was found to increase greatly when subjected to sand blasting treatment. However, the compressive residual stress decrease after coating regardless of sand blasting treatment. Nevertheless, it is confirmed that the compressive residual stress generated in the coating after sand blasting is less than that in the non-sandblasting coating. This was attributed to the plastic deformation occurring in the WC substrate during coating after sand blasting. In contrast to the scratch test results, sand blasting was assumed to have a negative effect on the adhesion between the coating and substrate. This is because there is a high possibility of microcracks due to plastic deformation in the WC substrate under the coating after sand blasting.

• 소성∙가공
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• 제19권4호
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• pp.224-229
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• 2010

During the multi-pass wire drawing process, wires suffer a great amount of plastic deformation that is through the cross-section. This generates tensile residual stress at surface of drawn wires. The generated residual stress on surface is one of the problems for quality of wires so that prediction and reduction of residual stresses is important to avoid unexpected fracture. Therefore, in this study, the effect of process variables such as semi-die angle, bearing length and reduction ratio on the residual stress was evaluated through Finite Element Analysis. Based on the results of the Analysis, a prediction model was established for predicting residual stress on the surface of high carbon steel(AISI1072, AISI1082). To identify the effectiveness of the proposed model, X-ray diffraction is used to measure the residual stresses on the surface. As the result of the comparison between calculated residual stresses and measured residual stresses, the model could be used to predict residual stresses in cold drawn wire.

• Journal of Welding and Joining
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• 제7권1호
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• pp.28-35
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• 1989

The fatigue crack growth behavior in GTA butt welded joints of Al-Alloy 5052-H38 was examined using Single Edge Notched(SEN) specimens. It is well known that welding residual stress has marked influence on fatigue crack growth rate in welded structure. In the general area of fatigue crack growth in the presence of residual stress, it is noted that the correction of stress intensity factor (K) to account for residual stress is important for the determination of both stress intensity factor range(.DELTA.K) and stress ratio(R) during a loading cycle. The crack growth rate(da/dN) in welded joints were correlated with the effective stress intensity factor range(.DELTA.Keff) which was estimated by superposition of the respective stress intensity factors for the residual stress field and for the applied stress. However, redistribution of residual stress occurs during crack growth and its effect is not negligible. In this study, fatigue crack growth characteristics of the welded joints were examined by using superposition of redistributed residual stress and discussed in comparison with the results of the initial welding residual stress superposition.