• Title, Summary, Keyword: Safe End

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Effects of Similar Metal Weld on Residual Stress in Dissimilar Metal Weld According to Safe End Length (동종금속용접이 이종금속용접부 잔류응력에 미치는 영향 평가 시 안전단 길이에 따른 효과)

  • Song, Tae-Kwang;Chun, Yun-Bae;Oh, Chang-Young;Bae, Hong-Yeol;Kim, Yun-Jae;Lee, Sang-Hoon;Lee, Kyoung-Soo;Park, Chi-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.7
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    • pp.664-672
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    • 2009
  • Nozzle in nuclear power plant is connected to pipe using safe end. Dissimilar metal weld between nozzle and safe end is followed by similar metal weld between safe end and pipe. And thus residual stress in dissimilar metal weld can be affected by similar metal weld. Similar metal weld impose bending stress on dissimilar metal weld, which is according to the length of safe end. In this study, simple nozzle model which covers various radius to thickness ratios was proposed to quantify residual stress in dissimilar metal weld based on finite element analyses. As a result, short length of safe end was proved to be more effective to mitigate residual stress in dissimilar metal weld and critical effective length of safe end is provided according to the radius to thickness ratio.

Estimation of Residual Stress Distribution for Pressurizer Nozzle of Kori Nuclear Power Plant Considering Safe End (고리 원전 가압기 노즐 용접부 잔류응력 예측 시 안전단 고려가 이종 금속 용접부 잔류응력 분포에 미치는 영향)

  • Song, Tae-Kwang;Bae, Hong-Yeol;Chun, Yun-Bae;Oh, Chang-Young;Kim, Yun-Jae;Lee, Kyoung-Soo;Park, Chi-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.8
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    • pp.668-677
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    • 2008
  • In nuclear power plants, ferritic low alloy steel nozzle was connected with austenitic stainless steel piping system through alloy 82/182 butt weld. Accurate estimation of residual stress for weldment is important in the sense that alloy 82/182 is susceptible to stress corrosion cracking. There are many results which predict residual stress distribution for alloy 82/182 weld between nozzle and pipe. However, nozzle and piping system usually connected through safe end which has short length. In this paper, residual stress distribution for pressurizer nozzle of Kori nuclear power plant was predicted using FE analysis, which consideded safe end. As a result, existing residual stress profile was redistributed and residual stress of inner surface was decreased specially. It means that safe end should be considered to reduce conservatism when estimating the piping system.

Stress Distributions at the Dissimilar Metal Weld of Safety Injection Nozzles According to Safe-end Length and SMW Thickness (안전단 길이 및 동종금속용접부 두께 변화에 따른 안전주입노즐 이종금속용접부의 응력분포)

  • Kim, Tae-Jin;Jeong, Woo-Chul;Huh, Nam-Su
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.10
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    • pp.979-984
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    • 2015
  • In the present paper, we evaluate the effects of the safe-end length and thickness of the similar metal weld (SMW) of safety injection nozzles on stress distributions at the dissimilar metal weld (DMW). For this evaluation, we carry out detailed 2-D axisymmetric finite element analyses by considering four different values of the safe-end length and four different values of the thickness of SMW. Based on the results obtained, we found that the SMW thickness affects the axial stresses at the center of the DMW for the shorter safe-end length; on the other hand, it does not affect the hoop stresses. In terms of the safe-end length, the values of the axial and hoop stresses at the inner surface of the DMW center increase as the safe-end length increases. In particular, for the cases considered in the present study, the stress distributions at the DMW center can be categorized according to certain values of safe-end length.

Safe Margin beyond Dens Tips to Ventral Dura in Anterior Odontoid Screw Fixation : Analysis of Three-Dimensional Computed Tomography Scan of Odontoid Process

  • Sung, Min-Jae;Kim, Kyoung-Tae;Hwang, Jeong-Hyun;Sung, Joo-Kyung;Cho, Dae-Chul
    • Journal of Korean Neurosurgical Society
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    • v.61 no.4
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    • pp.503-508
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    • 2018
  • Objective : Anterior odontoid screw fixation is a safe and effective method for the treatment of odontoid fractures. The surgical technique is recommended for perforation of the apical cortex of the dens by the lag screw. However, overpenetration of the apical cortex may lead to potentially serious complications such as damages of adjacent vascular and neural structures. The purpose of this study was to assess the role of three-dimensional computed tomography (CT) scan to evaluate the safe margin beyond dens tip to ventral dura for anterior odontoid screw fixation. Methods : We retrospectively analyzed the three-dimensional CT scans of the cervical spines in 55 consecutive patients at our trauma center. The patients included 38 males and 17 females aged between 22 and 73 years (mean age${\pm}$standard deviation, $45.8{\pm}14.2years$). Using sagittal images of 3-dimensional CT scan, the safe margins beyond dens tip to ventral dura as well as the appropriate screw length were measured. Results : The mean width of the apical dens tip was $9.6{\pm}1.1mm$. The mean lengths from the screw entry point to the apical dens tip and posterior end of dens tip were $39.2{\pm}2.6mm$ and $36.6{\pm}2.4mm$. The safe margin beyond apical dens tip to ventral dura was $7.7{\pm}1.7mm$. However, the safe margin beyond the posterior end of dens tip to ventral dura was decreased to $2.1{\pm}3.2mm$, which was statistically significant (p<0.01). There were no significant differences of safe margins beyond dens tip to ventral dura with patient gender and age. Conclusion : Extension by several millimeters beyond the dens tip is safe, if the trajectory of anterior odontoid screw is targeted at the apical dens tip. However, if the trajectory of the screw is targeted to the posterior end of dens tip, extension beyond dens tip may lead to damage immediately adjacent to the vental dura mater.

KOMPSAT-2 AOCS Control Mode & Power Safe Mode Design

  • Rhee, Seung-Wu;Kim, Hak-Jung;Lee, Joo-Jin
    • International Journal of Aeronautical and Space Sciences
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    • v.6 no.1
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    • pp.77-88
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    • 2005
  • KOMPSAT-2 is the second Korean earth observation satellite after KOMPSAT-l: the 1 meter GSD cartographic capability and planning to launch at the end of 2005 by ROKOT launch vehicle. The dedicated AOCS operational modes are designed for KOMPSAT-2 based on KOMPSAT-l experience All of AOCS operational modes requires gyro information. To compensate this drawback, Power Safe Mode is designed and implemented. Successfully AOCS on-board software is developed and extensively verified through a nonlinear simulation process. The simulation results of Power Safe Mode and Science Fine Submode are provided to demonstrate its functionality as well as its performance.

Vibration characteristics test of two types bogie frame of a freight car on Kyeungbu line (경부선을 주행하는 두 종류의 화차 대차프레임의 진동특성시험 및 진동증가 원인파악에 관한 연구)

  • 홍재성;함영삼;백영남;오택열
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.1323-1326
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    • 2004
  • A bogie frame of welded type have some problems. Some end beam has cracked. The cracks have profound influence on the safe freight service. The bogie consists of a frame, suspensions, brakes and wheel sets. Various analyses including a numerical simulation using a finite element method, a static load test, a fatigue test, and running test should be carried out to design the bogie. However cracks have been found at some end beams of the bogies mounted on the freight cars running with the high speed. The cracks of the end beam results in deterioration of the brake performance and the running safety. Numerical simulations and dynamic tests are carried out to figure out the causes of cracks in the existing bogie, and the vibrational characteristics of the improved bogie are compared with those of the conventional one. In this reports, the vibration characteristics were dealed with the most pressing matters for the solution of the end beam crack.

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Integrity evaluation of the welded structure bogie for the railway freight car (철도화차용 용접구조대차의 건전성평가에 관한 연구)

  • Hong J.S.;Ham Y.S.;Chung H.C.;Paik Y.N.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.361-364
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    • 2005
  • Some bogie frames manufactured in 1999, 2000 year have the fatal problem. Three or four years later, the cracked end beam among them have discovered in 2002, 2003 year. The crack situation of the end beam have a bad effect on brake system. In that case, the cars would be in danger of derailment. To improve the end beam, a research of covering the whole field of welded type bogie frame was started. Main line real tests were performed at Young-Dong line. The stress of main positions for bogie frame was measured. Also up-down direction and left-right direction vibration acceleration of the bogie frame were measured. At this time the tests were performed for the three types bogie. The test result concludes that the crack cause of the end beam is not brake load but vibration at running mainly. It is estimated that the life of the improved car which end beam reinforced is safe within the car permitted life(25 years). The improvement methods of the end beam are presented by construction modification, parts modification. The integrity evaluation is inspected by analysis the real line test results, the improvement methods of the end beam.

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Results of Tracheal Resection with End-to-end Anastomosis (기관절제술후 기관 단단문합술 치험 결과)

  • Shin Dong-Jin;Cho Woo-Jin;Baek Sungkuk;Woo Jeong Su;Kwon Soon-Young;Jung Kwang-Yoon
    • Korean Journal of Bronchoesophagology
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    • v.10 no.1
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    • pp.41-45
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    • 2004
  • Tracheostomy and endotracheal intubation are often performed in patients with acute and chronic respiratory failure. Recently, the incidence of iatrogenic tracheal stenosis has increased. Tracheal resection and end-to-end anastomosis would be one of the most physiologic treatment options for severe tracheal stenosis. Also, this treatment can be applied to the management of trachea invaded by thyroid cancer and tracheal neoplasm. The authors aimed to analyze the outcomes of end-to-end anastomosis of trachea following segmental resection in tracheal stenosis and tracheal invasion of cancer that we have recently experienced. Materials and methods Authors retrospectively studied 19 cases treated by tracheal resection with end-to-end anastomosis between Feburuary 1996 and January 2003. 12 patients had tracheal stenosis, 6 patients had tracheal invasion by thryroid cancer and 1 patient had tracheal cancer. We analyzed the direct causes of tracheal stenosis, preoperative vocal cord function, operation technique, early and delayed postoperative complications, and the outcome of end-to-end anastomois. Result Decannulation without significant aspiration was achieved in 16 cases($89.5\%$). A 27 year-old man could not be decannulated because of restenosis. A 62 year-old woman could not be decannulated because of bilateral vocal cord palsy. Conclusion End-to-end anastomosis is a safe and effective surgical method for tracheal stenosis. Case selection for end-to-end anastomosis and preservation of recurrent laryngeal nerve during operation is very important.

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A Round-Robin Analysis of Temperature and Residual Stresses in Dissimilar Metal Weld (이종금속용접부 온도 및 잔류응력의 라운드로빈 해석)

  • Song, Min-Sup;Kang, Sun-Ye;Park, June-Soo;Sohn, Gap-Heon
    • Proceedings of the KSME Conference
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    • pp.85-87
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    • 2008
  • DMWs are common feature of the PWR in the welded connections between carbon steel and stainless steel piping. The nickel-based weld metal, Alloy 82/182, is used for welding the dissimilar metals and is known to be susceptible to PWSCC. A round-robin program has been implemented to benchmark the numerical simulation of the transient temperature and weld residual stresses in the DMWs. To solve the round-robin problem related to Pressurizer Safety & Relief nozzle, the thermal elasto-plastic analysis is performed in the DMW by using the FEM. The welding includes both the DMW of the nozzle to safe-end and the SMW of the safe-end and piping. Major results of the analyses are discussed: The axial and circumferential residual stresses are found to be -88MPa(225MPa) and -38MPa(293MPa) on the inner surface of the DMW; where the values in parenthesis are the residual stresses after the DMW. Thermo-mechanical interaction by the SMW has a significant effect on the residual stress fields in the DMW.

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