• Title/Summary/Keyword: Critical Load

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Development of Elastic-Plastic Fracture Mechanics Evaluation Program for Leak-Before-Break Analysis of Nuclear Piping (원전 배관 파단전누설 평가를 위한 탄소성 파괴역학 평가 프로그램 개발)

  • Park, Jun-Geun;Huh, Nam-Su;Kim, Ye-Ji;Lee, Sang-Min
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.16 no.2
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    • pp.35-46
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    • 2020
  • In this paper, a fracture mechanics evaluation system which can be used to assess the leak-before-break (LBB) of nuclear piping is developed. Existing solutions for calculating the fracture mechanics parameters (J-integral and crack opening displacement) required for LBB evaluation were firstly presented. Then a module for calculating J-integral and COD was developed, with an additional module for predicting the critical load based on the crack driving force diagram to finally develop a fracture mechanics evaluation system. To confirm the validity of the proposed evaluation system, finite element (FE) analysis was performed, and the FE J-integral and COD results were compared with prediction results using the J-integral and COD estimations program. Furthermore, the critical load assessment module was verified by comparing the actual pipe test results (Battelle test data) with prediction results using the proposed program.

An Approximate Method for the Buckling Analysis of a Composite Lattice Rectangular Plate

  • Kim, Yongha;Kim, Pyunghwa;Kim, Hiyeop;Park, Jungsun
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.3
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    • pp.450-466
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    • 2017
  • This paper defines the modified effective membrane stiffness, bending stiffness considering the directionally dependent mechanical properties and mode shape function of a composite lattice rectangular plate, which is assumed to be a Kirchhoff-Love plate. It subsequently presents an approximate method of conducting a buckling analysis of the composite lattice rectangular plate with various boundary conditions under uniform compression using the Ritz method. This method considers the coupled buckling mode as well as the global and local buckling modes. The validity of the present method is verified by comparing the results of the finite element analysis. In addition, this paper performs a parametric analysis to investigate the effects of the design parameters on the critical load and buckling mode shape of the composite lattice rectangular plate based on the present method. The results allow a database to be obtained on the buckling characteristics of composite lattice rectangular plates. Consequently, it is concluded that the present method which facilitates the calculation of the critical load and buckling mode shape according to the design parameters as well as the parametric analysis are very useful not only because of their structural design but also because of the buckling analysis of composite lattice structures.

Rayleigh-Ritz procedure for determination of the critical load of tapered columns

  • Marques, Liliana;Da Silva, Luis Simoes;Rebelo, Carlos
    • Steel and Composite Structures
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    • v.16 no.1
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    • pp.45-58
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    • 2014
  • EC3 provides several methodologies for the stability verification of members and frames. However, when dealing with the verification of non-uniform members in general, with tapered cross-section, irregular distribution of restraints, non-linear axis, castellated, etc., several difficulties are noted. Because there are yet no guidelines to overcome any of these issues, safety verification is conservative. In recent research from the authors of this paper, an Ayrton-Perry based procedure was proposed for the flexural buckling verification of web-tapered columns. However, in order to apply this procedure, Linear Buckling Analysis (LBA) of the tapered column must be performed for determination of the critical load. Because tapered members should lead to efficient structural solutions, it is therefore of major importance to provide simple and accurate formula for determination of the critical axial force of tapered columns. In this paper, firstly, the fourth order differential equation for non-uniform columns is derived. For the particular case of simply supported web-tapered columns subject to in-plane buckling, the Rayleigh-Ritz method is applied. Finally, and followed by a numerical parametric study, a formula for determination of the critical axial force of simply supported linearly web-tapered columns buckling in plane is proposed leading to differences up to 8% relatively to the LBA model.

A frictionless contact problem for two elastic layers supported by a Winkler foundation

  • Birinci, Ahmet;Erdol, Ragip
    • Structural Engineering and Mechanics
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    • v.15 no.3
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    • pp.331-344
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    • 2003
  • The plane contact problem for two infinite elastic layers whose elastic constants and heights are different is considered. The layers lying on a Winkler foundation are acted upon by symmetrical distributed loads whose lengths are 2a applied to the upper layer and uniform vertical body forces due to the effect of gravity in the layers. It is assumed that the contact between two elastic layers is frictionless and that only compressive normal tractions can be transmitted through the interface. The contact along the interface will be continuous if the value of the load factor, ${\lambda}$, is less than a critical value. However, interface separation takes place if it exceeds this critical value. First, the problem of continuous contact is solved and the value of the critical load factor, ${\lambda}_{cr}$, is determined. Then, the discontinuous contact problem is formulated in terms of a singular integral equation. Numerical solutions for contact stress distribution, the size of the separation areas, critical load factor and separation distance, and vertical displacement in the separation zone are given for various dimensionless quantities and distributed loads.

Wear Behavior of TiN Coatings Deposited on High Speed Steel and Alloy Tool Steel (TiN 코팅된 고속도강과 합금공구강의 마멸거동)

  • 김석삼;서창민;박준목
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.3
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    • pp.705-712
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    • 1995
  • The wear characteristics and wear mechanisms in TiN coating deposited on high speed steel and alloy tool steel by ion plating were investigated. Pin on V-block wear tester was used for a wear test method. The specimen was composed of three kinds of high speed steel and alloy tool steel which had different hardness by changing the heat treating condition. Three kinds of coating thickness were also applied to each specimen. Microscopic observation of worn surfaces was made by SEM. The scratch test of coating surface by the ion plating showed that critical load to break the coating interface was greater than 50N. The critical load increased with both substrate hardness and coating thickness. The wear resistance of TiN coated high speed steel became 10 times greater than that of non-coated ones. SEM observation showed that leading edge of contact was compressive and trailing edge was under maximum tensile stress and then surface cracking broke out perpendicular to sliding direction.

Evaluation on Tensile Properties and Fracture Toughness of Glass Fiber/Aluminum Hybrid Laminates (유리섬유/알루미늄 혼성 적층판의 인장특성과 파괴인성 평가)

  • Woo Sung-Choong;Choi Nak-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.6
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    • pp.876-888
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    • 2005
  • Tensile properties and fracture toughness of monolithic aluminum, fiber reinforced plastics and glass fiber/aluminum hybrid laminates under tensile loads have been investigated using plain coupon and single-edge-notched specimens. Elastic modulus and ultimate tensile strength of GFMLs showed different characteristic behaviors according to the Al kind, fiber orientation and composition ratio. Fracture, toughness of A-GFML-UD which was determined by the evaluation of $K_{IC}$ and $G_{IC}$ based on critical load was similar to that of GFRP-UD and was much higher than monolithic Al. Therefore, A-GFML-UD presented superior fracture toughness as well as prominent damage tolerance in comparison to its constituent Al. By separating Al sheet from GFMLs after the test, optical microscope observation of fracture zone of GFRP layer in the vicinity of crack tip revealed that crack advance of GFMLs depended on the orientation of fiber layer as well as Al/fiber composition ratio.

Study on stability and design guidelines for the combined system of scaffolds and shores

  • Peng, Jui-Lin;Wang, Chung-Sheng;Wang, Shu-Hong;Chan, Siu-Lai
    • Steel and Composite Structures
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    • v.35 no.3
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    • pp.385-404
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    • 2020
  • Since the scaffold is composed of modular members, the total height of multi-story scaffolds does not often meet with the headroom of construction buildings. At this time, other supporting members need to be set up on the top of scaffolds. However, the mechanical behaviors of the combined system of scaffolds and other supporting members have seldom been discussed. This study explores the stability of the combined system of scaffolds and shores. The loading tests conducted in the laboratory show that the critical load of the combined system of two-story scaffolds and wooden shores is about half that of the three-story scaffold system with the same height. In the failure of both the "scaffold system" and the "combined system of scaffolds and shores' after loading, the deformation mainly occurs in the in-plane direction of the scaffold. The outdoor loading test shows that no failure occurs on any members when the combined system fails. Instead, the whole system buckles and then collapses. In addition, the top formwork of the combined system can achieve the effect of lateral support reinforcement with small lateral support forces in the outdoor loading test. This study proposes the preliminary design guidelines for the scaffolding structural design.

Contact Damage and Strength Degradation of Yttria doped Tetragonal Zirconia Polycrystal (Y$_2$O$_3$ 를 첨가한 정방정 지르코니아에서의 접촉손상 및 강도저하)

  • 정연길;최성철
    • Journal of the Korean Ceramic Society
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    • v.35 no.5
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    • pp.429-436
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    • 1998
  • The mechanical properties and damage mode of {{{{ {Y}_{2 } {O}_{3} }}-doped tetragonal (Y-TZP) can-didated as biomaterials were performed under indentation stress-strain curve critical load for yield and cracking strength degradation and fatigue behavior with Hertzian indentation tests. This material shows the brittle behavior which is confirmed by indentation stress-strain response. The critical load for cracking(Pc) is much higher than that for yields (Py) indicating crack resistance Strength were strongly dependant on contact area and there were no degradation when the indenter size was ${\gamma}$=3.18 mm suggesting that Y-TZP should be highly damage tolerant to the blunt contacts. Multi-cycle contact were found to be innocuous up to {{{{ {10 }^{6 } }} cycles at 500N and {{{{ {10 }^{5 } }} cycles at 1000N in water. On the other hand contacts at {{{{ {10 }^{6 } }} cycles at 1000 N in water did show some signs of incipient degradation. By contrast contacts with Vickers indenter pro-duced substantial strength losses at much lower loads suggesting that the mechanical integrity of this ma-terial would be compromised by inadvertent sharp contacts.

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On Beck's column with shear and compressibility

  • Cveticanin, L.J.;Atanackovic, T.M.
    • Structural Engineering and Mechanics
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    • v.6 no.7
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    • pp.747-756
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    • 1998
  • In this paper the influence of rotary inertia, shear and compressibility on the value of the critical force for the Beck's column is analyzed. The constitutive equation is of Engesser's type. As a result, the critical load parameter for which instability of flutter type occurs is calculated for several values of the column's parameters.

Reinforced Concrete Flat plates Under Combined In-plane and Out-of-plane Loads (바닥하중 및 면내압축력을 받는 플렛 플에이트 슬래브)

  • 박홍근;김의회;홍성걸
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.424-429
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    • 1998
  • Numerical studies are performed to investigate the behavior of flat plates under combined in-plane and out-of-plane loads. The numerical model is verified by comparison with experiments for plates simply supported on four edges. Through study on different load combination and loading sequence, the critical load condition that governs the strength of the flat plate is determined. Parametric studies are performed to investigate the buckling coefficient and the effective flexural rigidity so that the moment magnification method is applicable to the flat plates.

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