• Title/Summary/Keyword: Cold-working

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A Study on fatigue Properties with Different Edge Margin for Hole Expansion Plate (홀 확장된 판재의 에지마진 변화에 따른 피로특성 연구)

  • Lee, Joon-Hyun;Lee, Dong-Suk;Lee, Hwan-Woo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.11
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    • pp.2383-2389
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    • 2002
  • This paper describes an experimental study on fatigue life extension by using cold working process in fastener hole of aircraft structure. Cold working process was applied for A12024-7351 specimens by considering the effect of edge margin on fatigue life. It is generally recognized that cold working process offers a protective zone around fastener hole of aluminum aircraft structure due to the residual compressive stresses which lead to retardation of crack growth. Thus this process provides the beneficial effect of increasing the fatigue life of the component. there by decreasing maintenance costs. It has also been successfully incorporated into damage tolerance and structural integrity programs. Cold working specimens were tested at constant amplitude peak cyclic stresses. Fatigue life of cold working specimen compared with that of specimen fabricated with base material. The increase of fatigue life for cold working specimen is discussed by both considering the effect of residual compressive stresses measured by X-ray diffraction technique and quantitative effect of edge margin.

Feasibility Analysis of Simulation on the Mechanical Properties of Neutron Irradiated Austenitic Stainless Steels by Cold-working (냉간가공을 통한 중성자조사된 오스테나이트 스테인리스강의 기계적물성 모사 타당성 분석)

  • Kim, Jin Weon;Kim, Yun Jae
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.15 no.2
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    • pp.9-18
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    • 2019
  • The objective of this study is to investigate the feasibility of simulating the mechanical properties of irradiatied austenitic stainless steels by cold-working. In this study, the tensile properties, cyclic hardening behaviors and fracture toughness of cold-worked TP316L stainless steel were compared with those of austenitic stainless steels irradiated by neutrons. It showed that cold-working can properly simulate the increase in strength and the decrease in ductility and fracture resistance of austenitic stainless steels by neutron irradiation, even though it could not perfectly simulate the microstructures of irradiated austenitic stainless steels. Also, cold-working can appropriately simulate the hardening behaviors of neutron irradiated austenitic stainless steels under monotonic and cyclic loading conditions.

Effect of Cold Working on the Tensile Strength of Fe-26Mn-4Co-2Al Damping Alloy (Fe-26Mn-4Co-2Al 제진합금의 인장강도에 미치는 냉간가공의 영향)

  • Kang, Chang-Yong;Kim, Seong-Hwi;Jeong, Gyu-Seong
    • Journal of Power System Engineering
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    • v.20 no.6
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    • pp.46-50
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    • 2016
  • This study was carried out to investigate the effect of cold working on the tensile strength of Fe-26Mn-4Co-2Al damping alloy. ${\alpha}^{\prime}$ and ${\varepsilon}$-martensite were formed by cold working, and martensite was formed with the specific direction and surface relief. With the increasing degree of cold rolling, volume fraction of ${\alpha}^{\prime}$-martensite was increased, whereas the volume fraction of ${\varepsilon}$-martensite was decreased after rising to maximum value at specific lever of cold rolling. Tensile strength was linearly increased with an increasing of degree of cold rolling. Tensile strength was strongly affected to the volume fraction of ${\varepsilon}$-martensite formed by cold working, but the effect of volume fraction of ${\varepsilon}$-martensite on the tensile strength was not observed.

Effect of Cold Working on Tensile and Charpy Impact Properties of a High-Nitrogen Fe-18Mn-18Cr-0.61N Austenitic Steel (오스테나이트계 Fe-18Mn-18Cr-0.61N 고질소강의 인장 및 충격 특성에 미치는 냉간 가공의 영향)

  • Lee, S.Y.;Lee, S.I.;Hwang, B.
    • Journal of the Korean Society for Heat Treatment
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    • v.27 no.3
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    • pp.121-126
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    • 2014
  • High-nitrogen Fe-18Mn-18Cr-N austenitic steels with higher yield strength have been recently developed and used for generator retaining rings because they have non-magnetic, high strength, high ductility, and good corrosion resistance. In the present study, a high-nitrogen Fe-18Mn-18Cr-0.61N austenitic steel was fabricated and then tensile and Charpy impact tests were conducted on them in order to investigate the effect of cold working on the mechanical properties. Although the yield and tensile strengths usually increased with cold working, the ductility and impact toughness significantly decreased after cold working. On the other hand, the high-nitrogen austenitic steel exhibited a ductile-brittle transition due to unusual brittle fracture at low temperatures despite having a face-centered cubic structure. The ductile-brittle transition temperature obtained from Charpy impact tests could be remarkably increased by $60^{\circ}C$ after 20% cold working because of the enhanced cleavage-like brittle fracture.

A Study on Effects of the Residual Stresses Around Cold Working Hole of the Aircraft Structure (항공기 구조물의 체결용 HOLE을 COLD WORKING 할때 생성되는 잔류응력의 영향연구)

  • 강수준;최청호
    • Journal of the Korea Institute of Military Science and Technology
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    • v.2 no.1
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    • pp.101-109
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    • 1999
  • The objective of this research is to study effects of the residual stresses on the crack growth and the life of the structure, caused by cold working around the hole of the aircraft structure which will be jointed by rivets and bolts, etc. The compensated Morrow's equation, by experimental data from the materials AL7075-T6 and AL2024-T3, is suggested to calculate the values of the fatigue life prediction of the structure. Also, the compensated Forman's equation, by experimental data from a material AL7075-T6, is suggested to calculate the values of the crack growth prediction of the structure. It is founded that the calculated values from the suggested equations are almost close to the known values of the fatigue life prediction and the crack growth prediction. It is shown that this paper, associated with an initial research on the effects of residual stresses around hole, gives a direction to study the problem at the aircraft maintenance field.

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IMPROVEMENT OF FATIGUE LIFE IN POST-WELD COLD WORKED ALUMINUM RESISTANT SPOT WELDS

  • Kim, D.;Blake, D.M.;Ryu, S.J.;Lim, B.S.
    • International Journal of Automotive Technology
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    • v.7 no.5
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    • pp.579-584
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    • 2006
  • Aluminum Resistance Spot Weld(Al RSW) is an enabling technology for body assembly of low mass fraction vehicles. Due to the unreliable durability of spot-welded joints, applications of Al RSW are limited. This study presents experimental investigation on the use of a post-weld cold working process to improve the fatigue strength of Al RSW. The post-weld cold working process includes special shaped indenters that are pressed or driven into the structure to induce compressive residual stresses. The mechanical properties of the post-weld cold worked Al RSW were investigated, including the experimental results of fatigue and micro-hardness tests. Comparisons of the mechanical properties and qualitative results between the as-welded RSW specimens and the post-weld cold worked RSW specimens are discussed. The post-weld cold worked Al RSW samples had an increase in both microhardness and fatigue life.

Orientation dependence of GM-type pulse tube refrigerator (GM형 맥동관 냉동기의 저온부 경사도에 따른 냉각 성능 특성 연구)

  • Ko, Jun-Seok;Kim, Hyo-Bong;Park, Seong-Je;Hong, Yong-Ju;Yeom, Han-Kil;Lee, Chung-Soo;Kang, In-Su;Koh, Deuk-Yong
    • Progress in Superconductivity and Cryogenics
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    • v.14 no.3
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    • pp.48-52
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    • 2012
  • This paper describes experimental study on the orientation dependence of GM-type pulse tube refrigerator with helium and neon as working gas. A pulse tube refrigerator generates refrigeration work with gas expansion by gas displacer in the pulse tube. The pulse tube is only filled with working gas and there exists secondary flow due to large temperature difference between cold-end and warm-end. The stability of secondary flow is affected by orientation of cold-head and thus cooling performance is deteriorated by gas mixing due to secondary flow. In this study, a single stage GM-type pulse tube with orifice valve as a phase control device is fabricated and tested. The fabricated pulse tube refrigerator is tested with two different working gases of helium and neon. First, optimal valve opening and operating frequency are determined with experimental results of no-load test. And then, the variation of no-load temperature as orientation angle of cold-head is measured for two different working gases. Effect of orientation dependence of cold-head as working gas is discussed with experimental results.

A study on working limit of cold forging of carbon steel (냉간단조에 있어서 탄소강의 가공한계에 관한 연구)

  • Jae, Jin-Soo;Kang, Jong-Hun;Kang, Seong-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.7
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    • pp.1081-1088
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    • 1997
  • The purpose of this work is to investigate the working limit of carbon steel and forging condition of cold forging. The fracture criteria which was proposed by Oyane and Osakada was used. Compression test, hardness study and tension test by Oyane's creteria, microstructure study by Osakada's were carried out. The results were compared with each other. It was found that working limit on compressive hydrostatic stress is increased in comparison with that of tensile stress field and can be forecasted the fracture limit of closed cold forging.

A Study on the Efficiency Improvement of the Power Generation Process Using New Working Fluids Composed of Methane, Ethylene, Ethane, and Propane and the Cold Heat Contained in the Liquefied Natural Gas (메탄, 에틸렌, 에탄 및 프로판으로 구성된 새로운 작동 유체와 액화 천연가스의 냉열을 활용한 발전 공정의 효율 향상에 대한 연구)

  • JUNGHO CHO
    • Journal of Hydrogen and New Energy
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    • v.35 no.3
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    • pp.318-323
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    • 2024
  • In this paper, computer modeling works have been performed for the power generation Rankine cycle using new working fluids and liquefied natural gas (LNG) cold heat. PRO/II with PROVISION released January 2023 from AVEVA company was used, and Peng-Robinson equation of the state model with Twu's alpha function was selected for the modeling of the power generation cycle. Optimal working fluid composition was determined to maximize LNG cold heat to increase power generation efficiency and net power production.