• 제목/요약/키워드: Cold-working

검색결과 325건 처리시간 0.026초

Experimental investigations on composite slabs to evaluate longitudinal shear strength

  • Saravanan, M.;Marimuthu, V.;Prabha, P.;Arul Jayachandran, S.;Datta, D.
    • Steel and Composite Structures
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    • 제13권5호
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    • pp.489-500
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    • 2012
  • Cold-formed steel profile sheets acting as decks have been popularly used in composite slab systems in steel structural works, since it acts as a working platform as well as formwork for concreting during construction stage and also as tension reinforcement for the concrete slab during service. In developing countries like India, this system of flooring is being increasingly used due to the innate advantage of these systems. Three modes of failure have been identified in composite slab such as flexural, vertical shear and longitudinal shear failure. Longitudinal shear failure is the one which is difficult to predict theoretically and therefore experimental methods suggested by Eurocode 4 (EC 4) of four point bending test is in practice throughout world. This paper presents such an experimental investigation on embossed profile sheet acting as a composite deck where in the longitudinal shear bond characteristics values are evaluated. Two stages, brittle and ductile phases were observed during the tests. The cyclic load appears to less effect on the ultimate shear strength of the composite slab.

내부 확산법으로 제조한 $Nb_{3}$ Sn초전도선의 세선화에 의한 유연성 조사 (Effect of wire diameters on superconducting and mechanical properties of internal tin processed $Nb_{3}$ Sn wires)

  • 하동우;오상수;이남진;하홍수;권영길;류강식;백홍구
    • 한국초전도저온공학회:학술대회논문집
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    • 한국초전도저온공학회 2001년도 학술대회 논문집
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    • pp.29-32
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    • 2001
  • Internal tin processed Nb$_3$Sn wires of intermediated worked state of were took from Mitsubishi and fabricated with various diameters ranging from 0.76 mm to 0.2 mm. These specimens were heat-treated at $460^{\circ}C$ for 70 h and at $570^{\circ}C$ for 100h to form bronze and at $700^{\circ}C$ for 100h to form Nb$_3$Sn compound. Bending strain Ic s of the wires were measured with various bending diameters ranging from flat to 76 mm. In order to investigate the sensitivity for strain, small diameters of wires were strain Ic at 6 T, 4.2 K. There were no breakage decrease during cold working to 0.2 mm of diameter and no decrease Jc to the diameter of 0.3 mm. The values of bending strain Ic of 0.2 mm and 0.3 mm diameters of the wires were not decreased at 76 mm of bending diameter.

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더미스터 온도센서를 이용한 나노유체의 대류열전달계수 측정 장치 (Measuring Apparatus for Convective Heat Transfer Coefficient of Nanofluids Using a Thermistor Temperature Sensor)

  • 이신표
    • 대한기계학회논문집B
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    • 제40권2호
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    • pp.103-110
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    • 2016
  • 나노유체의 대류열전달 성능을 평가하는 센서로서 가는 백금 열선이 많이 사용되었다. 그러나 센서의 강도가 약해서 취급에 주의가 필요하고 측정실험에서 센서에 대한 엄밀한 교정과정을 생략하거나 정밀도 높은 기구들을 사용하지 않으면 비현실적인 대류열전달계수가 얻어졌다. 본 연구에서는 백금 열선 대신 더미스터 센서를 채택한 새로운 나노유체 대류 성능 평가장치를 제안하였고 그 작동 원리를 자세히 설명하였다. 순수 엔진오일에 대한 두 센서의 비교 실험을 통하여 더미스터 센서의 실용적 장점을 확인할 수 있었다. 제안된 장치는 개발된 나노유체의 채택 여부를 판단하는 유용한 도구로 사용될 수 있을 것이다.

마이크로터빈의 새로운 점화 기법과 점화 인식 로직 개발 (New Ignition Method and Ignition Recognition Logic for a Microturbine)

  • 김기래;최영규;노민식
    • 제어로봇시스템학회논문지
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    • 제13권2호
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    • pp.179-186
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    • 2007
  • This paper presents new ignition method and ignition recognition logic for a microturbine. New ignition method is designed by constant speed control of a microturbine with pre-determined time during a ignition period. It make more accurate air-fuel ratio as well as give enough time to ignition system to have full performance under cold temperature. And ignition recognition logic is designed by observing output current change of inverter by generating output torque of a microturbine in the instant of ignition. For filtering a output torque current of inverter with high frequency, we applied a moving average method. So far, ignition recognition is usually implemented by measuring of exhausted gas temperature(EGT) of microturbine. The proposed logic can give more accurate judgement of ignition as well as keep a good working of starting system under out of order a temperature measuring system and biased initial value of EGT sensor. Finally, the two proposed logics are proved by field operating a microturbine under various conditions.

분리형 히트파이프식 열교환기에서 향류 및 병류유동에 따른 가동특성에 관한 연구 (A Study on the Operating Characteristics by Counter Flow and Parallel Flow in Separate Heat Pipe Exchanger)

  • 이기우;장기창;유성연
    • 에너지공학
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    • 제7권1호
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    • pp.44-56
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    • 1998
  • 분리형 히트파이프식 열교환기는 증발기와 응축기를 폐열원과 열풍이 필요한 곳에 분리설치하고 증기 및 액체의 연락관으로 두 열교환기를 연결하여 하나의 폐루프를 구성하고 증발기와 응축기의 설치 높이차에 의해 작동이 이루어지는 것이다. 따라서 고온 및 저온유체의 병류 및 향류의 혼합배치가 용이하다는 장점이 있으나, 고온유체의 온도가 높을 경우에는 포화증기의 압력이 높아져 파이프가 견딜 수 있는 사용한계를 초과하게 될 수 있다. 또한 너무 낮으면 증기의 비체적증가와 함께 유속의 증가로 압력손실이 커져 설치높이차를 크게 하던지 증기연락관의 직경을 크게 하여야 하는 문제가 발생할 수 있다. 따라서 설계과정에서 고온유체 및 저온유체의 온도, 유량 등이 정하여진 상태에서 병류 및 향류로 배치하는 경우에 분리형 히트파이프식 열교환기를 Lmtd방법으로 설계하고, 고온 및 저온유체의 온도 및 유량이 실제 운전과정에서 변화가능한 범위에 대해 Ntu 방법으로 열교환량,포화증기압력 및 압력손실에 따른 증발기와 응축기의 설치높이차 등에 대한 가동특성을 고찰하였다.

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항공기용 연료호스 제작시 최적 크림핑 직경에 관한 연구 (A Study on the Optimal Crimping Diameter of Aircraft Fuel Hoses in Manufacturing Process)

  • 전준영;김병탁
    • 동력기계공학회지
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    • 제18권1호
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    • pp.84-90
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    • 2014
  • The high pressure hoses are widely used for the vehicles, aircraft, and overall industries. The hose assembly is generally composed of a nipple, a socket and a hose with reinforcement layers to increase the tensile strength. To produce the hose assembly, crimping or swaging process is usually used to clamp its components to ensure the prevention of fluid leakage. Crimping is a cold-working technique to form a strong bond between the workpiece and a non-metallic component. The crimping stroke is a primary parameter to be determined in the metalworking process, and it plays an important role in hose performance. This study aims at investigating the optimal crimping stroke according to the size of aircraft high pressure hose by using MSC/MARC. It is supposed that the results can be useful to get the information about the crimping stroke in manufacturing process, even with the different size of a hose.

기관 폐열 회수를 위한 열교환기의 Baffle 길이 변경에 따른 성능 예측에 관한 수치 해석적 연구 (An Investigation on Flow and Structural Characteristics of Heat Exchanger in Rankine Steam Cycle for Co-generation System)

  • 류규현;김구성;이영훈;강석호;박기범
    • 신재생에너지
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    • 제9권4호
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    • pp.32-39
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    • 2013
  • A 2-loop waste heat recovery system with Rankine steam cycles for the improvement of fuel efficiency of gasoline vehicles has been investigated. A high temperature loop is used to recover waste heat from exhaust gas and a low temperature loop is used to recover waste heat from cold engine coolant. This paper has dealt with a layout of low temperature loop system, the review of the velocity contours through numerical analysis. According to the result of analysis, the designed heat exchanger. And comparing with flow analysis results, LT Boiler is safe to operation.

열처리에 따른 미세구조 변화가 Ti 판재의 부식특성에 미치는 영향 (The Effect of Microstructural Evolution on Corrosion Property of Ti Plate with Heat Treatment)

  • 김민규;이찬수;김태규;김혜성
    • 열처리공학회지
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    • 제31권1호
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    • pp.12-17
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    • 2018
  • We investigated the corrosion behavior of commercially pure cold working processed (CP)-Ti with coarse-grained (CG) microstructure heat-treated at $400^{\circ}C$ and $600^{\circ}C$, respectively. It is observed that corrosion resistance of as-received CP-Ti heat-treated at $400^{\circ}C$, at which recrystallization proceeds, is largely improved. Interestingly, the mechanical property of CP-Ti sample at $400^{\circ}C$ was scarcely deteriorated. It is attributed to the decrease of the defects such as strain variance and dislocation density. On the other hand, the annealing treatment at $600^{\circ}C$ of CP-Ti plate causes to grain growth with the noticeable reduction of mechanical property. Hence, it is considered that defect density such as strain and dislocation density is important microstructural parameter for the improvement of corrosion resistance. The introduction of proper annealing treatment can help to improve corrosion resistance without scarifying mechanical property of CP-Ti.

Development of Chain Conveyor-type Spinach Harvester

  • Jun H. J.;Hong J. T.;Choi Y.;Kim Y. K.
    • Agricultural and Biosystems Engineering
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    • 제5권2호
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    • pp.40-44
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    • 2004
  • This study was conducted to solve the problem of spinach harvesting done by manpower at the outdoor field during the cold winter season. Prototype spinach harvester was designed to dig, pick-up, and collect in a continuous operation for harvesting outdoor field-planted crawling type spinach. In the field test, two types of blades (Type A : angle of $150^{\circ}$, Type B : straight) were used for measuring the cutting loads of spinach and chain conveyor with lugs was used for picking up the root cut spinach. Prototype's vibrating blade reduced the digging power of the fixed blade by $46\%$. The loss was also very little ($0.7\%$) with a digging depth of 4 cm, an oscillation frequency of 748 rpm, and an oscillation distance of 33 mm. The working performance of the prototype spinach harvester was 38 hour/ha resulting to $96\%$ labor cost reduction compared to the conventional harvesting.

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$Ni_3$Al의 기계적합금화에 미치는 $Y_2O_3$ 첨가의 영향 (The Effect of $Y_2O_3$ Addition on the Mechanical Alloying of $Ni_3$Al)

  • 이상태
    • 한국분말재료학회지
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    • 제4권3호
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    • pp.205-213
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    • 1997
  • Mechanical alloying of $Ni_3Al$ and $Y_2O_3$ added ODS $Ni_3Al$ from elemental powders was investigated by the X-ray diffraction, differential scanning calorimeter, transmission electron microscopy and optical microscopy. The steady states of $Ni_3Al$ and ODS $Ni_3Al$ powders were reached after mechanical alloying with the condition of the ball-to-powder input ratio of 20:1 for 20 hours and 10 hours, respectively. The addition of nano-sized $Y_2O_3$ particles enhanced cold working and fracture, and subsequently accelerated MA of $Ni_3Al$ powders. DSC results of MAed $Ni_3Al$ powders showed four exothermic peaks at 14$0^{\circ}C$, 234$^{\circ}C$, 337$^{\circ}C$ and 385$^{\circ}C$. From the high temperature X-ray diffraction analysis, it was concluded that the peaks were resulted from the recovery solution of unalloyed Al in Ni, the formation of intermediate phase NiAl, and $LI_2$ ordering of MAed $Ni_3Al$ powders.

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