Processing math: 100%
  • Title/Summary/Keyword: Thermal-mechanical Fatigue

Search Result 293, Processing Time 0.022 seconds

A Study on the Local Inhomogeneous Structure of Al 7050 Forged Part (Al 7050 단조품의 국부적 불균일 조직 형성에 대한 연구)

  • 이정환;김대용;김재곤;이상용;이영선;전승문;이명건
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1995.06a
    • /
    • pp.81-90
    • /
    • 1995
  • Age hardenable aluminum alloys show high specific strength, good thermal and electrical conductivity as well as lightness, and are typical aircraft materials. High fatigue strength and good resistancy against stress corrosion cracking are also important for aircraft aluminum alloys. Al alloy 7050 has been developed to meet the above mentioned requirements and the use of this alloy as forged aircraft part becomes more important. However, forged 7050 parts showed undersirable structures such as severe local grain coarsening in surface area and unproper metal flow that is degrading mechanical properties. In this paper, microstructural aspects of die forging in the Al alloy 7050 are investigated. Also suggested are the optimal forging conditions for microstructural control of Al alloy 7050.

A Study on the Local Grain Coarsening in Surface of Al 7050 Forged Part (Al 7050 단조품 표면의 입도성장층 방지에 관한 연구)

  • Lee, Jeong-Hwan;Lee, Sang-Yong;Lee, Yeong-Seon
    • 연구논문집
    • /
    • s.26
    • /
    • pp.113-120
    • /
    • 1996
  • Age hardenable aluminium alloys show high specific strength, good thermal and electrical conductivity as well as lightness, and are typical aircraft materials. High fatigue strength and good resistancy against stress corrosion cracking are also important for aircraft aluminium alloys. Al alloy 7050 has been developed to meet the above mentioned requirements and the use of this alloy as forged aircraft part becomes more important. However, forged 7050 parts showed undersiable structures such as severe local grain coarsening in surface area and unproper metal flow that is degrading mechanical properties. In this paper, microstructural aspects of die forging in the Al alloy 7050 are investigated. Also suggested are the optimal forging conditions for microstructural control of Al alloy 7050.

  • PDF

A study on deformation and strength of polymer composites using automobiles (자동차용 폴리머 복합재료의 변형과 강도에 관한 연구)

  • Shin, Je-Hoon;Lim, Jae-Kyoo;Park, Han-Ju
    • Proceedings of the KSME Conference
    • /
    • 2000.11a
    • /
    • pp.238-243
    • /
    • 2000
  • The effect of the temperature, the fatigue and the test speed on DEN(double edged notch) specimen which was made by the pp-rubber composites during fracture was stuied. DEN specimen was made on PP-rubber composites through the injection molding. With increasing temperature the fracture strength is linearly decrease and the fracture energy is first increase by 0C and after that decrease. In the same temperature the fracture strength during increasing the notch radius is hardly increase. The fracture behaviour at low and high test speed is different entirely. At high test speed plastic region is small and fracture behaviour was seen to brittle fracture tendency. The deformation mechanism of polypropylene-rubber composites during fracture was studied by SEM fractography. A strong plastic deformation of the matrix material ahead of the notch/crack occured. The deformation seem to be enhanced by a thermal blunting of the notch/crack.

  • PDF

Lead-free Solder Alloys (무연솔더합금)

  • 이호영
    • Journal of Surface Science and Engineering
    • /
    • v.35 no.4
    • /
    • pp.218-231
    • /
    • 2002
  • As the environmental regulation worldwide emerges, most notably in Europe and Japan, the elimination of Pb usage in electronic assemblies has been an important issue for microelectronics assembly due to the inherent toxicity of Pb. This has provided an impetus towards the development of Pb-free solders. A major factor affecting alloy selection is the melting point, since this will have a major impact on the other polymeric materials used in microelectronic assembly and encapsulation. Other important manufacturing issues are cost, availability, and wetting characteristics. Reliability related properties include mechanical strength, fatigue resistance, coefficient of thermal expansion and reactivity with substrate. In this article, Pb-free solder alloys have been proposed so far have been reviewed and are summarized.

A Study on the Reheat Crack around Welded Joint of Pressusre Vessel with 21/4Cr-1Mo Steel (21/4Cr-1Mo강 압력용기 Nozzle 용접이음부의 재열균열에 관한 연구)

  • Bang, Han Seo;Kim, Jong Myeong
    • Journal of Welding and Joining
    • /
    • v.18 no.2
    • /
    • pp.227-227
    • /
    • 2000
  • Pressure vessels usually consist of main body and pipes which are connected with the main body. And as joining method of such main body and pipes, welding is carried out. After welding, welding residual stresses inevitably occur around welded joints. As residual stresses act harmfully on fatigue strength, corrosion and buckling strength of structure, PWHT is carried out for the purpose of removing the residual stress. But, during PWHT process, 2 ¼Cr-1Mo steels are frequently apt to generate reheat crack. For this reason, it is strongly needed to analyze and examine the mechanical behavior of welded joints before and after PWHT process. So, in this study, welded nozzle parts of pressure vessel where reheat cracks frequently occur are selected for examining the mechanism of crack-occurrence. (Received December 2, 1999)

A Study on the Reheat Crack around Welded Joint of Pressure Vessel with 214Cr1Mo Steel (214Cr1Mo강 압력용기 Nozzle 용접이음부의 재열균열에 관한 연구)

  • 방한서;김종명
    • Journal of Welding and Joining
    • /
    • v.18 no.2
    • /
    • pp.100-104
    • /
    • 2000
  • Pressure vessels usually consist of main body and pipes which are connected with the main body. And as joining method of such main body and pipes, welding is carried out. After welding, welding residual stresses inevitably occur around welded joints. As residual stresses act harmfully on fatigue strength, corrosion and buckling strength of structure, PWHT is carried out for the purpose of removing the residual stress. But, during PWHT process, 214Cr1Mo steels are frequently apt to generate reheat crack. For this reason, it is strongly needed to analyze and examine the mechanical behavior of welded joints before and after PWHT process. So, in this study, welded nozzle parts of pressure vessel where reheat cracks frequently occur are selected for examining the mechanism of crack-occurrence.

  • PDF

Tool Condition Monitoring with Non-contacting Sensors in Inconel 718 Milling Processes (비접촉센서를 이용한 Inconel 718 밀링가공에서 공구상태 감시)

  • Choi, Yong-Ki;Hwang, Moon-Chang;Kim, Young-Jun;Park, Kwang-Hwi;Koo, Joon-Young;Kim, Jeong-Suk
    • Journal of the Korean Society of Manufacturing Technology Engineers
    • /
    • v.25 no.6
    • /
    • pp.445-451
    • /
    • 2016
  • The Inconel 718 alloy is a well-known super-heat-resistant alloy and a difficult-to-cut material. Inconel 718 with excellent corrosion and heat resistance is used in harsh environments. However, the heat generated is not released owing to excellent physical properties, making processes (e.g., adhesion and thermal fatigue) difficult. Tool condition monitoring in machining is significant in reducing manufacturing costs. The cutting tool is easily broken and worn because of the material properties of Inconel 718. Therefore, tool management is required to improve tool life and machinability. This study proposes a method of predicting the tool wear with non-contacting sensors (e.g., IR thermometer for measuring the cutting temperature and a microphone for measuring the sound pressure level in machining). The cutting temperature and sound pressure fluctuation according to the tool condition and cutting force are analyzed using experimental data. This experiment verifies the effectiveness of the non-contact measurement signals in tool condition monitoring.

The Evaluation of Mechanical Property of X20CrMoV12.1 Boiler Tube Steels (X20CrMoV12.1강의 열화에 따른 기계적특성 평가)

  • Kim, B.S.;Lee, S.H.;Kim, D.S.;Jung, N.G.
    • Journal of Power System Engineering
    • /
    • v.8 no.3
    • /
    • pp.18-22
    • /
    • 2004
  • Boiler is one of the most important utilities providing steam to turbine in order to supply mechanical energy in thermal power plant. It is composed of thousands of tubes for high efficient heat transfer. The material for boiler tubes is used in such high temperature and pressure condition as 540C, 22MPa. The boiler tube material is required to resist creep damage, fatigue cracking, and corrosion damages. 2.25%Cr-1Mo steel is used for conventional boiler tubes, and austenitenite stainless steel is used for higher temperature boiler tubes. But the temperature and pressure of steam in power plant became higher for high plant efficiency. So, the property of boiler tube material must be upgaded to fit the plant property. Several boiler tube material was developed to fit such conditions. X20CrMoV12.1 steel is also developed in 1980's and used for superheater and reheater tubes in supercritical boilers. The material has martensite microstructures which is difficult to evaluate the degradation. In this thesis, degrade the X20CrMoV12.1 steel at high temperatures in electric furnace, and evaluate hardness with Vickers hardness tester and strengths with Indentation tester.

  • PDF

The Development of KOGAS Membrane for LNG Storage Tank (LNG 저장탱크용 KOGAS 멤브레인 개발)

  • Oh, Byoung-Taek;Kim, Young-Kyun;Yoon, Ihn-Soo;Seo, Heung-Seok;Hong, Seong-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.26 no.6
    • /
    • pp.1203-1208
    • /
    • 2002
  • LNG demand has been rapidly increasing in Korea for a variety of reasons including stable supply, non-polluting, and high combustion efficiency characteristics. As a result the construction and expansion of LNG storage facilities have been continuing at a vigorous pace. Korea Gas Corp. (KOGAS) has developed the design technology of the LNG storage tank. One of the most important structural core element of the LNG storage tank is the membrane, made by stainless steel. The membrane to be applied inside of LNG storage tank is provided with corrugations to absorb thermal contraction and expansion caused by LNG temperature. Analytical results have been performed to investigate the strength of the membrane and the reaction farce at the anchor point. Experimental studies are performed to investigate the deformation and strength of the membrane which is designed by Kogas. All experiments are conducted on the basis of RPIS, and we found the results are fully satisfied with the RPIS.

A Study on the Development of Friction Hinge with Automatic Closed Function (자동 닫힘 기능을 갖는 마찰힌지 개발에 관한 연구)

  • Ye, Sang-Don;Min, Byeong-Hyeon
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.13 no.1
    • /
    • pp.107-114
    • /
    • 2014
  • A friction hinge system which moves without power was designed and developed using the principle of friction force, which is caused by interference between the inner diameter of a silicon cap and the outer diameter of a cylindrical roller bearing with one-way rotation in a counterclockwise direction. The system was applied to the lid of buffet ware, which moved up by external force and moved down by gravitational force. However, design conditions which included a rotation angle of the hinge of more than 80 degrees and a closing time of more than 20 seconds were required when the lid of the buffet ware closed due to gravitational force. The design safety of the friction hinge body connected to the lid of the buffet ware from the hinge system was checked on the basis of structural, fatigue and thermal analyses. The material of the shaft, cap and flange among the hinge elements was changed to polyethylene from steel to reduce the weight of the friction hinge system. An injection molding simulation was performed and injection molds of the shaft, cap and flange were created. The weight of the hinge system was decreased from 805g to 219g.