• Title/Summary/Keyword: autofrettage process

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Development of an Automated Design System of a Large Pressure Vessel using the Steel, 34CrMo4 (강재(34CrMo4)를 사용한 대형 고압가스 용기의 설계 자동화 시스템 개발)

  • Kim, Ji-Hoon;Kim, Eui-Soo;Kim, Chul;Choi, Jae-Chan
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.8
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    • pp.21-29
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    • 2003
  • This paper describes a research work on the development of computer-aided design system for deep drawing & ironing of a high pressure vessel. An approach to the system is based on the knowledge-based rules. Knowledge for the system is formulated from plasticity theories, handbook, experimental results and empirical knowledge of field experts. An attempt is made to link programs incorporating a number of expert design rules with the process variables obtained by commercial FEM software, DEFORM and ANSYS, to form a useful package. It is composed of five main modules, which are calculation of product thickness, input, production feasibility check, process planning, and autofrettage process modules and two submodules, which are folding check and process variable verification submodules. Programs for the system have been written in AutoLISP on the AutoCAD 2000 using personal computer. The developed system makes it possible to design and manufacture large high pressure vessel requiring D.D.I. process more efficiently.

The Overstrain of Thick-Walled Cylinders Considering the Bauschinger Effect Facto. (BEF)

  • Ghorbanpour, A.;Loghman, A.;Khademizadeh, H.;Moradi, M.
    • Journal of Mechanical Science and Technology
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    • v.17 no.4
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    • pp.477-483
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    • 2003
  • An independent kinematic hardening material model in which the reverse yielding point is defined by the Bauschinger effect factor (BEF) , has been defined for stainless steel SUS 304. The material model and the BEF are obtained experimentally and represented mathematically as continuous functions of effective plastic strain. The material model has been incorporated in a non-linear stress analysis for the prediction of reverse yielding in thick-walled cylinders during the autofrettage process of these vessels. Residual stress distributions of the independent kinematic hardening material model at the onset of reverse yielding are compared with residual stresses of an isotropic hardening model showing the significant effect of the BEF on reverse yielding predictions. Critical pressures of direct and reverse yielding are obtained for the most commonly used cylinders and a range of permissible internal pressures for an efficient autofrettaged process is recommended.

A Study on the Residual Stress Evaluation of Autofrettaged SCM440 High Strength Steel (자긴가공된 SCM440 고강도강의 잔류응력평가에 관한 연구)

  • Kim, Jae-Hoon;Shim, Woo-Sung;Yoon, Young-Kwen;Lee, Young-Shin;Cha, Ki-Up;Hong, Suck-Kyun
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.4
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    • pp.39-45
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    • 2010
  • Thick-walled cylinders, such as a cannon or nuclear reactor, are autofrettaged to induce advantageous residual stresses into pressure vessels and to increase operating pressure and the fatigue lifetimes. As the autofrettage level increases, the magnitude of compressive residual stress at the bore also increases. The purpose of the present paper is to predict the accurate residual stress of SCM440 high strength steel using the Kendall model which was adopted by ASME Code. Hydraulic pressure process was applied in the inner part and thick-walled cylinders were autofrettaged up to 30% overstrain levels. Electro polishing on the surface of autofrettage specimen was performed to get more accurate residual stress. Residual stresses were measured by X-ray diffraction method. The autofrettage surface which was plastically deformed analyzed using a scanning electron microscope(SEM). Although there were some differences in measured residual stress and numerical results, it has a tendency to agree comparatively with each other.

An Integrated CAD/CAM System for CNG Pressure Vessel Manufactured by Deep Drawing and Ironing Operation

  • Park, Joon-Hong;Kim, Chul;Park, Jae-Chan
    • Journal of Mechanical Science and Technology
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    • v.18 no.6
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    • pp.904-914
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    • 2004
  • The fiber reinforced composite material is widely used in the multi-industrial field because of their high specific modulus and specific strength. It has two main merits which are to cut down energy by reducing weight and to prevent explosive damage proceeding to the sudden bursting which is generated by the pressure leakage condition. Therefore, Pressure vessels using this composite material can be applied in the field such as defence industry and aerospace industry. In this paper, for nonlinear finite element analysis of E-glass/epoxy filament winding of composite vessel subjected to internal pressure, the standard interpretation model is developed by using the ANSYS with AutoLISP and ANSYS APDL languages, general commercial software, which is verified as useful characteristic of the solution. Among the modules of the system, both the process planning module for carrying out the process planning of filament wound composite pressure vessel and the autofrettage process module for obtaining higher residual stress will minimize trial and error and reduce the period for developing new products. The system can serve as a valuable system for experts and as a dependable training aid for beginners.

DIMENSIONAL CHANGES AND REDISTRIBUTION OF RESID¬UAL STRESSES DUE TO INNER LAYER REMOVAL OF RESID¬UALLY STRESSED CYLINDRICAL COMPONENTS (잔류응력이 내재하는 원통형 부품의 내면 가공에 따른 치수 변화와 잔류 응력의 재분포)

  • S.H.Shin
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.5
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    • pp.522-526
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    • 1997
  • 잔류 응력이 존재하는 부품의 가공 시에는 잔류 응력 상태가 새로운 평형 상태를 이루기 위해 재 분포되며 이는 가공 자체에 따른 변형 이와의 부가적 변형을 초래한다. 고도의 정밀도를 요하는 가공에는 이러한 잔류 응력에 의한 부가적 변형을 고려하여야 하며, 가공 후의 잔류 응력의 재 분포 상태는 가공 후 부품의 물질적 성능을 결정하는데 중요한 요소이므로 이를 예측할 수 있어야 한다. 본 연구에서는 잔류 응력에 의한 부가적 치수 변화를 고려한 가공 후의 부품의 내경 및 두께와 잔류 응력의 재 분포를 예측할 수 있는 이론적 수식을 제시하고 유한요소법에 의한 시뮬레이션의 결과와 비교하였다. 초기 잔류 응력의 분포는 autofrettage process에 의해 유도되었다.

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A Study on the Residual Stress and Microstructure of Autofrettaged SCM440 High Strength Steel (자긴가공된 SCM440 고강도강의 잔류응력 및 미세구조 분석에 관한 연구)

  • Kim, J.H.;Shim, W.S.;Lee, Y.S.;Cha, K.U.;Hong, S.K.
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.311-316
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    • 2008
  • Thick-walled cylinders, such as a cannon or nuclear reactor, are autofrettaged to induce advantageous residual stresses into pressure vessels and to increase operating pressure and the fatigue lifetimes. As the autofrettage level increases, the magnitude of compressive residual stress at the bore also increases. The purpose of the present paper is to predict the accurate residual stress of SCM440 high strength steel using the Kendall model which was adopted by ASME Code. Hydraulic pressure process was applied and thick-walled cylinders were autofrettaged up to 30% overstrain levels. Electro polishing was performed to get more accurate data. Residual stresses were measured by X-ray diffraction method. The autofrettaged surface which was plastically deformed analyzed using a scanning electron microscope(SEM). Although there were some differences in measured residual stress and numerical, there is a tendency to agree.

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Study of Improvement in Fatigue Life of Fuel Injection Pipe of Common Rail System (커먼레일 시스템 연료분사관의 피로수명 개선에 관한 연구)

  • Song, Se Arm;Bae, Jun Ho;Jung, Sung Yuen;Kim, Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.8
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    • pp.991-998
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    • 2013
  • The fuel injection pipe of a common rail system used in a clean diesel vehicle plays a role in supplying fuel from a rail to the injector of each cylinder connecting the engine under a repeated internal pressure. The fuel injection pressure is increased to over 200 MPa for satisfying EU emission standards and improving fuel efficiency, and a heading process and an autofrettage process are required for preventing folding defects and improving fatigue life. In this study, the flow stress and SN data of the material of the pipe are obtained through a tensile test and a fatigue test. The heading process for checking the folding defects of pipe ends is performed by using FEA. Furthermore, the optimal design of the autofrettage process for improving fatigue life considering not only the compressive residual stresses of the inner surface but also the tensile residual stresses of the outer surfaces of the pipe under the repeated internal pressure is performed by using FEA. To verify the process design, fatigue analysis for the autofrettaged pipe is performed.

Optimal Design for CNG Composite Pressure Vessel Using Basalt Fiber (현무암 섬유를이용한 CNG 복합재 압력용기의 최적설계)

  • Jang, Hyo Seong;Bae, Jun Ho;Kim, Chul
    • Journal of the Korean Society for Precision Engineering
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    • v.32 no.3
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    • pp.269-277
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    • 2015
  • Compressed natural gas (CNG) composite vessels for vehicles have been generally made of 34CrMo4 for a inner liner part and E-glass/epoxy for a composite layer part. But, there is a problem of material loss of CNG composite vessels used in vehicles due to the design of excessive thickness of the liner. And, light weight of the CNG composite vessel is required for improving fuel efficiency. In this study, optimal design for CNG composite pressure vessel was performed by using basalt fiber, which is the environment-friendly material having a good mechanical strength. The optimal thickness of each part (inner liner and composite layer) was determined by theoretical analysis and FEA for satisfying structural safety and lightweight of the vessel. Also, for improving fatigue life, optimal autofrettage pressure was derived from FEA results.

Finite Element Analysis on the Strength Safety of a Fuel Tank for Highly Compressed Gas Vehicle (초고압가스 차량용 연료탱크의 강도안전성에 관한 유한요소해석)

  • Kim, Chung-Kyun;Kim, Do-Hyun
    • Journal of the Korean Institute of Gas
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    • v.13 no.6
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    • pp.29-33
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    • 2009
  • In this study, the strength safety of a composite fuel tank which is fabricated by an aluminum liner of Al6061-T6 materials and composite layers of carbon/epoxy-glass/epoxy composites has been analyzed by using a finite element analysis technique. In order to enhance the durability of the composite fuel tank, an autofrettage process was used and compressed natural gas was supplied to the prestressed fuel tank. The FEM computed results on the stress safety of autofrettaged gas tanks were compared with a criterion of design safety of US DOT-CFFC and Korean Standard. The FEM computed results indicated that the stress safety of autofrettaged fuels tanks shows instability at the dome zone and uniform stability at the parallel body, which provide an evaluation data for a strength safety of autofrettaged composite fuel tanks. The computed results show that the stress safety of 9.2 liter composite fuel tanks satisfied the safety criteria of four evaluation items, which are provided by US DOT-CFFC and KS and indicated a safe design.

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