• Title/Summary/Keyword: Bending

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Effects of Induction Heat Bending Process on Microstructure and Corrosion Properties of ASME SA312 Gr.TP304 Stainless Steel Pipes

  • Kim, Nam In;Kim, Young Sik;Kim, Kyung Soo;Chang, Hyun Young;Park, Heung Bae;Sung, Gi Ho
    • Corrosion Science and Technology
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    • v.14 no.3
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    • pp.120-126
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    • 2015
  • The usage of bending products recently have increased since many industries such as automobile, aerospace, shipbuilding, and chemical plants need the application of pipings. Bending process is one of the inevitable steps to fabricate the facilities. Induction heat bending is composed of compressive bending process by local heating and cooling. This work focused on the effect of induction heat bending process on the properties of ASME SA312 Gr. TP304 stainless steel pipes. Tests were performed for base metal and bended area including extrados, intrados, crown up, and down parts. Microstructure was analyzed using an optical microscope and SEM. In order to determine intergranular corrosion resistance, Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) test and ASTM A262 practice A and C tests were done. Every specimen revealed non-metallic inclusion free under the criteria of 1.5i of the standard and the induction heat bending process did not affect the non-metallic inclusion in the alloys. Also, all the bended specimens had finer grain size than ASTM grain size number 5 corresponding to the grain sizes of the base metal and thus the grain size of the pipe bended by induction heat bending process is acceptable. Hardness of transition start, bend, and transition end areas of ASME SA312 TP304 stainless steel was a little higher than that of base metal. Intergranular corrosion behavior was determined by ASTM A262 practice A and C and DL-EPR test, and respectively step structure, corrosion rate under 0.3 mm/y, and Degree of Sensitization (DOS) of 0.001~0.075% were obtained. That is, the induction heat bending process didn't affect the intergranular corrosion behavior of ASME SA312 TP304 stainless steel.

Electrical Reliability of ITO Film on Flexible Substrate During bending Deformations and Bending Fatigue (유연 기판상 ITO 전극의 굽힘변형 및 굽힘피로에 따른 전기적 신뢰성 연구)

  • Seol, Jea-Geun;Kim, Byoung-Joon
    • Journal of the Microelectronics and Packaging Society
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    • v.24 no.4
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    • pp.47-52
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    • 2017
  • Recently, a great attention has been paid to the mechanical behavior of ITO (Indium Tin Oxide) film, which is widely used in current smart devices due to its excellent electrical properties and transparency. In this study, the reliability of ITO thin films on flexible substrates was investigated using bending test and bending fatigue test. According to the relative position of ITO and substrate, the experiment was conducted on both outer and inner bending conditions. Inner bending condition exhibited superior electrical stability compared to outer bending test. The electrical resistance during outer bending fatigue test significantly increased compared to that in the inner bending fatigue. The crack nucleation and propagation differs according to the stress state and they have a great influence on the electrical resistance. The crack morphologies were observed by scanning electron microscopy.

Bending performance evaluation of high strength and seismic purpose reinforcing bars (고강도 및 내진용 철근의 굽힘성능 평가)

  • Kim, Hee-Dong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.9
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    • pp.492-498
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    • 2017
  • This study examined the bending performance of high strength and seismic purpose reinforcing bars experimentally with various parameters. For the experimental approach on the bending performance, the specimens were prepared with parameters, such as steel grades, diameters of reinforcing bars, and bending angles of reinforcing bars. Tensile strength tests on the reinforcing bars, the bending tests and re-bending tests, and the second tensile strength tests on the re-bended reinforcing bars were conducted. According to the test results on high strength and seismic purpose reinforcing bars, defects did not appear when the yield strength of the reinforcing bar was 500 MPa or less and the diameter was D13 or less, even when the first bending process was performed with a $135^{\circ}$ bending angle and a $2d_b$ inner radius. The bending performance decreased asthe strength and diameter of the reinforcing bars was increased. In addition, there was no significant difference between the general reinforcing bars and seismic purpose-reinforcing bars.

A Study on Bending Fatigue Strength of One Side Fillet Welded T-Joint by SM 490A steel (Sm 490A강으로 제작된 T형 편면용접이음재의 굽힘피로강동에 관한 연구)

  • 엄동석;강성원;이태훈;이해우;조수형
    • Journal of Welding and Joining
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    • v.16 no.5
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    • pp.134-141
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    • 1998
  • In this study, a fillet size for bending fatigue strength of one side fillet welded T-joint, used in box type girder and other welding structure, was investigated by bending fatigue test with or without edge preparation and burn through, with variation of joint shape. As a result, the following conclusions were obtained. (1) In one side fillet welded T-joint, the larger the leg length, the greater the bending fatigue strength. The increase in bending fatigue strength. (2) One side filet welded T-joint with edge preparation showed higher bending fatigue strength than that with twofold-large leg length and without edge preparation. (3) In one side fillet welded T-joint without edge preparation, both manual welding and automatic welding were carried out with same condition. In this case, automatic welding shoed deeper penetration and more increased horizontal leg length than manual welding, so that automatic welding offers grater bending fatigue strength. (4) For one side fillet welded T-joint without edge preparation, the ratio(h/t) of the leg length (h) and the main plate thickness (t) in which toe crack can occur was 1.2 over. (5) In one side fillet welded T-joint with edge preparation, the burn through led to reduced bending fatigue strength. However, this bending fatigue strength was higher than that of one side fillet welded T-joint without edge preparation and with a larger leg length.

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Evaluation of Performance of CFRP Sheet Reinforcement on RC Members Subjected to Axial Load and Flexural Moment (축력과 휨 모멘트를 받는 RC 부재의 CFRP 시트 보강에 따른 성능 평가)

  • Bae, Chan Young;Lee, Ji Hyeong;Kim, Sang Woo;Kim, Jin Sup
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.43 no.5
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    • pp.567-576
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    • 2023
  • In general, RC beam members are designed as flexural members, considering only the bending load. However, in actual buildings, axial and bending load are simultaneously applied due to the continuity between members. As a result, the bending strength of the RC beam member increases, but the displacement decreases, and cracks are mainly concentrated in the center of the beam. Therefore, in this study, the bending performance of both normal and strengthened RC beam using carbon fiber sheets subjected to combined axial and bending load was experimentally evaluated. The carbon fiber sheets were wrapped around the middle of the specimens, and axial and bending load were applied simultaneously to the beams. The magnitude of the axial force and the effects of carbon fiber sheet reinforcement on the deformed shape, bending strength, deflection, and ductility of the RC beams were analyzed. The results show that as the applied axial force increased, the maximum bending strength increased, but the ductility decreased 64%. The bending strength of the strengthened beams increased up to 27%, the maximum deflection decreased around 8% and the ductility increased by up to 43%.

Bending behavior of shape memory alloy bar and its application of seismic restrainers for bridges (형상기억합금의 휨거동 및 교량변위제어장치적용 연구)

  • Choi, Eun-Soo;Park, Joo-Nam;Kim, Hak-Soo;Lee, Do-Hyung
    • Journal of the Earthquake Engineering Society of Korea
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    • v.11 no.5
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    • pp.23-32
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    • 2007
  • The goal of this study is to perform several bending tests on a shape memory alloy bar and to analyze the characteristics of the bending behavior. The other goal is to verify the seismic performance of an SMA bar bending application. Single and double bending tests were conducted with varying loading speeds and maximum displacement. The loading and the unloading stiffness were estimated from the force-displacement curves and the equivalent damping ratio of each test was also assessed. In single bending, the SMA bar showed the stiffness hardening after the displacement of 32 mm. It is assumed that this phenomenon is due to the stress-induced-martensite hardening. The increasing loading speed did not influence on the stiffness of the single bending SMA bar. The stiffness of the double bending bar is about 5 times of that of the single bending. This study introduced a seismic application of SMA bending bars as seismic restrainers for bridges and showed its practicality. SMA bars in bending are used for seismic restrainers in a three-span-simply-supported bridge. They showed the effectiveness to reduce the responses of the bridge and the applicability for a seismic restrainer. The significance of this study is to provide basic knowledge of SMA bending and its seismic applications.

Finite Element Inverse Analysis of the Cylindrical Cup Deep Drawing Process Considering Bending History (굽힘이력을 고려한 원형컵 딥드로잉공정의 유한요소역해석)

  • Huh, J.;Yoon, J.H.;Bao, Y.D.;Huh, H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2007.05a
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    • pp.340-343
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    • 2007
  • This paper introduces a new approach to consider the bending history in finite element inverse analysis of the cylindrical cup drawing. A modified membrane element is adopted to add the bending-unbending energy to the total plastic energy on the bending-unbending region predicted from the geometry of the final shape and tools. The algorithm suggested was applied to a cylindrical cup deep drawing process. The blank shape and the distribution of the thickness strain are compared with those obtained from incremental finite element analysis. The comparison demonstrates the algorithm proposed reduces the difference between the results from inverse analysis and those from incremental analysis when the bending history is considered.

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Optimization of Bending Process for the Fabrication of Ultra Precision Metallic Bipolar Plate for Molten Carbonate Fuel Cell (용융탄산염 연료전지용 초정밀 금속분리판 제작을 위한 굽힘 공정 최적화)

  • Lee, C.H.;Ryu, S.M.;Yang, D.Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.10a
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    • pp.345-348
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    • 2008
  • Metallic bipolar plate for molten carbonate fuel cell(MCFC) is composed of the shielded slot plate and the center plate. Among these, the center plate plays an important role in gas sealing. Therefore, manufacturing of the center plate is considered one of the key issues in MCFC. The center plate is manufactured by bending process. In bending process, springback and recoiling are two main problems. The aim of this article is to optimize the bending process of the center plate regardless of springback and recoiling. To achieve this goal, we proposed the punch having step to reduce springback and recoiling. Using finite element method and $L_9$ orthogonal array, we determined the main factors in the center plate bending process. And we found the optimal bending process condition for the MCFC center plate.

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The Fatigue Behavior and Delamination Properties in Fiber Reinforced Aramid Laminates -Case (I) : AFRP/Al Laminates-

  • Song, Sam-Hong;Kim, Cheol-Woong
    • Journal of Mechanical Science and Technology
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    • v.17 no.3
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    • pp.343-349
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    • 2003
  • The fuselage-wing intersection suffers from the cyclic bending moment of variable amplitude. Therefore, the influence of cyclic bending moment on the delamination and the fatigue crack propagation behavior in AFRP/Al laminate of fuselage-wing was investigated in this study. The cyclic bending moment fatigue test in AFRP/Al laminate was performed with five levels of bending moment. The shape and size of the delamination Lone formed along the fatigue crack between aluminum sheet and aramid fiber-adhesive layer were measured by an ultrasonic C-scan. The relationships between da/dN and ΔK, between the cyclic bending moment and the delamination zone size, and between the fiber bridging behavior and the delamination zone were studied. As results, fiber failures were not observed in the delamination zone in this study, the fiber bridging modification factor increases and the fatigue crack growth rate decrease and the shape of delamination zone is semi-elliptic with the contour decreasing non-linearly toward the crack tip.

The Study on the Fatigue Life Prediction on Wheels through CAE (CAE를 이용한 자동차용 휠(wheel)의 피로수명 예측기법 연구)

  • 김만섭;고길주;김정헌;양창근;김관묵
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.2
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    • pp.117-122
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    • 2004
  • The fatigue life in wheels was predicted by simulating the experimental method using Finite-Element analysis. Based on a high frequency fatigue property, calculations of the stresses in wheels were performed by simulating the rotating bending fatigue test. Wheels made of an aluminum alloy(A356.2) were tested using a bending fatigue tester. Results from bending fatigue test showed a linear correlation between bending moment and stress amplitude. Consequently, Finite-Element calculations were performed by a linear analysis. In order to find stress-cycles curves, spoke parts of wheel were tested using a rotary bending fatigue tester. Also, highly accurate Finite-Element analysis requires regression lines and confidence intervals from these results. In conclusion, if the fatigue data related to the material and manufacturing procedure are reliable, the prediction on fatigue lift in wheels can be carried out with high accuracy.