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Criterion for Failure of Internally Wall Thinned Pipe Under a Combined Pressure and Bending Moment (내압과 굽힘의 복합하중에서 내부 감육배관의 손상기준)

  • Kim, Jin-Weon;Park, Chi-Yong
    • Journal of the Korean Society of Safety
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    • v.17 no.4
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    • pp.52-60
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    • 2002
  • Failure criterion is a parameter to represent the resistance to failure of locally wall thinned pipe, and it depends on material characteristics, defect geometry, applied loading type, and failure mode. Therefore, accurate prediction of integrity of wall thinned pipe requires a failure criterion adequately reflected the characteristics of defect shape and loading in the piping system. In the present study, the finite element analysis was performed and the results were compared with those of pipe experiment to develop a sound criterion for failure of internally wall thinned pipe subjected to combined pressure and bending loads. By comparing the predictions of failure to actual failure load and displacement, an appropriate criterion was investigated. From this investigation, it is concluded that true ultimate stress criterion is the most accurate to predict failure of wall thinned pipe under combined loads, but it is not conservative under some conditions. Engineering ultimate stress estimates the failure load and displacement reasonably for al conditions, although the predictions are less accurate compared with the results predicted by true ultimate stress criterion.

Evaluations of vital signs and echocardiographic left ventricular function after the constant rate infusion of lidocaine and/or ketamine in Beagle dogs

  • Kim, Ye-Won;Choi, Miru;Kim, Tae-Jun;Hyun, Changbaig
    • Korean Journal of Veterinary Research
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    • v.55 no.4
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    • pp.215-219
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    • 2015
  • Cardiopulmonary depression of long-term constant rate infusion (CRI) administration of multiple analgesic drugs is important, especially in critically ill dogs. Therefore, this study was conducted to evaluate the effects of lidocaine, ketamine or combined lidocaine-ketamine combination CRI treatment on vital signs and left ventricular (LV) function in healthy dogs. Six adult Beagle dogs were administered either ketamine (initial loading dose of 0.5 mg/kg followed by $10{\mu}g/kg/min$ CRI), lidocaine (initial loading dose of 2 mg/kg followed by 0.025 mg/kg/min CRI), or combined lidocaine-ketamine intravenously. Arterial blood pressure (BP), heart rate (HR), respiratory rate (RR), body temperature (BT) and echocardiographic LV dimensions were measured before administration of medications, immediately after administration of drugs, and then every 10 min for 2 h. There were no significant changes in HR, RR, BT and BP after the administration of either lidocaine CRI, ketamine CRI, or combined lidocaine and ketamine CRI. There were also no significant changes in LV dimensions and stroke volume. The results revealed that treatment with either lidocaine, ketamine or combined lidocaine-ketamine may not cause cardiopulmonary suppression in healthy dogs.

Effect of Wall Thinned Shape and Pressure on Failure of Wall Thinned Nuclear Piping Under Combined Pressure and Bending Moment (감육형상 및 내압이 원자력 감육배관의 파단에 미치는 영향 -내압과 굽힘모멘트가 동시에 작용하는 경우-)

  • Shim, Do-Jun;Lim, Hwan;Choi, Jae-Boong;Kim, Young-Jin;Kim, Jin-Won;Park, Chi-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.5
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    • pp.742-749
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    • 2003
  • Failure of a pipeline due to local wall thinning is getting more attention in the nuclear power plant industry. Although guidelines such as ANSI/ASME B31G and ASME Code Case N597 are still useful fer assessing the integrity of a wall thinned pipeline, there are some limitations in these guidelines. For instance, these guidelines consider only pressure loading and thus neglect bending loading. However, most Pipelines in nuclear power plants are subjected to internal pressure and bending moment due to dead-weight loads and seismic loads. Therefore, an assessment procedure for locally wall thinned pipeline subjected to combined loading is needed. In this paper, three-dimensional finite element(FE) analyses were performed to simulate full-scale pipe tests conducted for various shapes of wall thinned area under internal pressure and bending moment. Maximum moments based on true ultimate stress(${\alpha}$$\sub$u,t/) were obtained from FE results to predict the failure of the pipe. These results were compared with test results, which showed good agreement. Additional finite element analyses were performed to investigate the effect of key parameters, such as wall thinned depth, wall thinned angle and wall thinned length, on maximum moment. Also, the effect of internal pressure on maximum moment was investigated. Change of internal pressure did not show significant effect on the maximum moment.

Numerical Investigation on Combined Load Carrying Capacity and Consolidation Behavior of Suction Piles (석션파일의 조합하중 지지력 및 압밀거동에 관한 수치해석 연구)

  • Yoo, Chung-Sik;Hong, Seung-Rok
    • Journal of the Korean Geotechnical Society
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    • v.30 no.1
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    • pp.103-116
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    • 2014
  • This paper presents the results of a numerical investigation on the load carrying capacity and consolidation behavior of suction piles. Three dimensional numerical models which reflect realistic ground conditions and installation procedures including the ground-suction pile interface were adopted to conduct a parametric study on variables such as the length-diameter ratio and the loading configurations, i.e, vertical, horizontal, and combined loads. The results indicated that the load carrying capacity of a suction pile can only be realistically obtained when the interface behavior between the suction pile and the ground is correctly modeled. Also carried out was the stress-pore pressure coupled analysis to investigate the consolidation behavior of the suction pile after the application of a vertical loading. Based on the results, failure envelops and associated equations were developed, which can be used to estimate load carrying capacity of suction piles installed in similar conditions considered in this study. The results of consolidation analysis based on the stress-pore pressure coupled analysis indicate that no significant excess pore pressure and associated consolidation settlement occur for the loading configuration considered in part due to the load transfer mechanism of the suction pile.

Damage Index of Steel Members under Severe Cyclic Loading

  • Park, Yeon-soo;Han, Suk-yeol;Suh, Byoung-chal;Jeon, Dong-ho;Park, Sun-joon
    • Computational Structural Engineering : An International Journal
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    • v.3 no.1
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    • pp.9-17
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    • 2003
  • This paper aims at investigating the damage process of steel members leading to the failure under strong repeated loading, proposing the damage index using various factors related to the damage, and developing the analysis method for evaluating the damage state. Cantilever-type steel members were analyzed under uniaxial load and combined with a constant axial load, considering a horizontal displacement history. In analyzing the models, loading patterns and steel types (SS400, SM570, Posten80) were considered as main parameters. From the analysis results, the effects of parameter on the failures mode, the deformation capacity, the damage process are also discussed. Each failure process was compared as steel types. Consequently, the failure of steel members under strong repeated loading was determined by loading. Especially it was seen that the state of the failure is closely related to the local strain.

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Pollutant Control using the Separation Wall between Stormwater and Sewage in a Combined Sewer System (우오수분리벽을 이용한 합류식 하수관거의 오염물질 제어효과)

  • Lee, Kuang Chun;Choi, Bong Choel;Lim, Bong Su
    • Journal of Korean Society of Water and Wastewater
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    • v.18 no.4
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    • pp.461-469
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    • 2004
  • This research is to determine the stormwater effects on sewer concentrations by measuring and comparing the flow and pollutant concentrations during dry and rainy periods in the existing BOX type combined sewer pipes. The monitoring was carried out in two sites, which are the Daesachen outfall having PE separation wall in BOX type combined sewer pipes and the Yongunchen outfall not having seperatioin wall. The average flow-weighted BOD concentraion in Yongunchen outfall is 2-fold lower than in Daesachen outfall because of the dilution effect from ravine water. However, the pollutant mass loading is 16 fold higher in Yongunchen outfall than in Daesachen outfall because of more flows. According to the research, the separation wall controls 52% pollutant mass during a storm period (11.5 mm/hr rainfall intensity). Therefore, the Yongunchen combined sewer system (CSS) need separation wall to control and to prevent more pollutant input in stream. In Daesachen area, the maximum sewer flow rate during a storm period measured about 10 fold bigger than average sewer flow during dry periods. Also the concentrations between rainy and dry periods increase approximately 33 fold for BOD and 120 fold for SS. In Yongunchen area, it increases about 9 fold for the maximum flow rate, 18 fold for BOD and 22 fold for SS during a storm. Therefore, the research is concluded that the separation wall between stromwater (or ravine water) and sewage can decrease the dilution effect in CSS and control the pollutant loading.

Noise prediction of Centrifugal Compressor Impeller based on rapid loading calculation (Rapid Loading계산을 이용한 압축기 임펠러 소음 예측)

  • 안광운;이승배;백승조;김창준;전완호
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.504-511
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    • 2001
  • In this research, we developed a computer program that designs a centrifugal impeller and diffuser, and predicts the far-field noise from the impeller. To design the impeller optimally, the TEIS model, which was originally developed by Japkise(1985), and the mean-line analysis are combined to predict the performance and design the optimal impeller simultaneously. The geometric configurations are provided by a GUI software (iDesignComp). The noise from impeller can be computed by the rapid loading procedure, which generates a surface between two blades and calculates the pressure distributions on the suction and pressure sides. The steady loading noise is computed by the rotating dipole source distribution via Ffowcs Williams & Hawkings equation.

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Finite Element Analysis of Thermal Fatigue Safety for a Heavy-Duty Diesel Engine (대형디젤엔진의 열적 피로안전도 분석을 위한 유한요소해석)

  • 조남효;이상업;이상규;이상헌
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.1
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    • pp.122-129
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    • 2004
  • Finite element analysis was performed to analyze structural safety of a new heavy-duty direct injection diesel engine. A half section of the in-line 6-cylinder engine was selected as a computational domain. A mapping method was used to project heat transfer coefficients from CFD results of engine coolant flow onto the FE model. The accurate setting of thermal boundary condition on the FE model was expected to result in improved prediction of temperature, cylinder bore distortion, and stresses. Characteristics of high cycle fatigue were investigated by assuming the engine was operated under the following five loading conditions repeatedly; assembly force, assembly force with thermal loading, alternating maximum gas pressure loading at each cylinder combined with assembly force and thermal loading. Distribution of fatigue safety factor was calculated by using it Haigh diagram in which the maximum and the minimum stresses were selected from the five loading cases.

Fracture Behavior of Rail Steel under Mixed Mode Loading (혼합모드하에서의 레일강의 파괴거동)

  • Chang, Dong Il;Kim, Sung Hoon
    • Journal of The Korean Society of Civil Engineers
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    • v.14 no.4
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    • pp.761-769
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    • 1994
  • Actual load acting on rail surface in the track is the combined mode loading due to the contact rolling load of the wheels. To investigate the fracture behavior on rail steel under combined modes I and II, fracture tests were performed by using the test jigs and fracture specimen which were designed by Richard. The analysis results of experimental fracture data were compared with various fracture criteria that have been introduced for determination of the crack propagation direction and the critical stress of fracture of a crack submitted to a mixed mode loading. From the results, it was shown that the actual crack propagation direction of rail steel agree with the crack propagation directions predicted by maximum tangential stress criterion and strain energy density criterion, and that fracture criterion follows principal strain criterion.

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Concrete structures under combined mechanical and environmental actions: Modelling of durability and reliability

  • Vorechovska, Dita;Somodikova, Martina;Podrouzek, Jan;Lehky, David;Teply, Bretislav
    • Computers and Concrete
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    • v.20 no.1
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    • pp.99-110
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    • 2017
  • Service life assessments which do not include the synergy between mechanical and environmental loading are neglecting a factor that can have a significant impact on structural safety and durability assessment. The degradation of concrete structure is a result of the combined effect of environmental and mechanical factors. In order to make service life design realistic it is necessary to consider both of these factors acting simultaneously. This paper deals with the advanced modelling of concrete carbonation and chloride ingress into concrete using stochastic 1D and 2D models. Widely accepted models incorporated into the new fib Model Code 2010 are extended to include factors that reflect the coupled effects of mechanical and environmental loads on the durability and reliability of reinforced concrete structures. An example of cooling tower degradation by carbonation and an example of a bended reinforced concrete beam kept for several years in salt fog are numerically studied to show the capability of the stochastic approach. The modelled degradation measures are compared with experimental results, leading to good agreement.