• Title/Summary/Keyword: elastic stress method

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The effect of bolt tightening methods and sequence on the performance of gasketed bolted flange joint assembly

  • Abid, Muhammad;Khan, Yasir Mehmood
    • Structural Engineering and Mechanics
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    • v.46 no.6
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    • pp.843-852
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    • 2013
  • This paper presents results of the effect of different bolt tightening sequences and methods on the performance of gasketed bolted flange joint using nonlinear finite element analysis. Bolt preload scatter due to elastic interactions, flange stress variation and bolt bending due to flange rotation and gasket contact stress variation is difficult to eliminate in torque control method i.e. tightening one bolt at a time. Although stretch control method (tightening more than one bolt at time) eradicates the bolt preload scatter, flange stress variation is relatively high. Flange joint's performance is compared to establish relative merits and demerits of both the methods and different bolt tightening sequences.

Elastic Modulus Measurement of Micro Gold Electroplating Structure (마이크로 금 전해 도금 구조물의 탄성계수 측정)

  • Kim, Duck-Hyun;Ahn, Yoo-Min;Baek, Chang-Wook;Kim, Yong-Kweon
    • Proceedings of the KIEE Conference
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    • 1998.07g
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    • pp.2530-2532
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    • 1998
  • Micro gold electroplating structure is fabricated by surface micromachining process. The made structure is clamped-clamped beam and its 1st natural frequency is measured by resonance method. In order to find residual stress, first natural frequency of beam which has tensile stress inside is analysed using Rayleigh's method. Elastic modulus and residual stress are estimated from the measured natural frequency.

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Evaluation of Mechanical Compressive Properties of Al-Si-Cu-Mg Alloy Foams Using Electrical Conductivity (전기전도도를 이용한 Al-Si-Cu-Mg 합금 품의 기계적 압축 특성 평가)

  • Lee, Chang-Hun;Kim, Am-Kee;Ha, San;Nahm, Seung-Hoon;Cho, Seong-Seock
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.377-381
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    • 2004
  • Electrical conductivity of Al-Si-Cu-Mg alloy foams of various density produced in powder metallurgical method has been measured using two probe electrical conductivity measurement method. Compressive mechanical properties such as elastic modulus and plastic plateau stress of foams were evaluated from electrical conductivity using power law relation and scaling laws of foam properties. Uni-axial compression test was also performed. Experimentally measured elastic modulus and plastic plateau stress were compared with the values evaluated from electrical conductivity. The computed values were in good agreement with the experimental result.

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Experimental study and calculation of laterally-prestressed confined concrete columns

  • Nematzadeh, Mahdi;Fazli, Saeed;Hajirasouliha, Iman
    • Steel and Composite Structures
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    • v.23 no.5
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    • pp.517-527
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    • 2017
  • In this paper, the effect of active confinement on the compressive behaviour of circular steel tube-confined concrete (STCC) and concrete-filled steel tube (CFST) columns is investigated. In STCC columns the axial load is only applied to the concrete core, while in CFST columns the load is carried by the whole composite section. A new method is introduced to apply confining pressure on fresh concrete by laterally prestressing steel tubes. In order to achieve different prestressing levels, short-term and long-term pressures are applied to the fresh concrete. Three groups of STCC and CFST specimens (passive, S-active and L-active groups) are tested under axial loads. The results including stress-strain relationships of composite column components, secant modulus of elasticity, and volumetric strain are presented and discussed. Based on the elastic-plastic theory, the behaviour of the steel tube is also analyzed during elastic, yielding, and strain hardening stages. The results show that using the proposed prestressing method can considerably improve the compressive behaviour of both STCC and CFST specimens, while increasing the prestressing level has insignificant effects. By applying prestressing, the linear range in the stress-strain curve of STCC specimens increases by almost twice as much, while the improvement is negligible in CFST specimens.

Development of Elastic-Plastic Fracture Analysis Program for Structural Elements under an Impact Loadings (충격하중을 받는 구조부재의 탄소성 파괴해석 프로그램 개발)

  • K.S. Kim;J.B. Park
    • Journal of the Society of Naval Architects of Korea
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    • v.35 no.1
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    • pp.61-71
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    • 1998
  • This paper describes a dynamic fracture behaviors of structural elements under elastic or elasto-plastic stress waves in two dimensional space. The governing equation of this problem has the type of hyperbolic partial differential equation, which consists of the equation of motions and incremental elasto-plastic constitutive equations. To solve this problem we introduce Zwas' method which is based on the finite difference method. Additionally, in order to deal with the dynamic behavior of elasto-plastic problems, an elasto-plastic loading path in the stress space is proposed to model the plastic yield phenomenon. Based on the result of this computation, the dynamic stress intensity factor at the crack tip of an elastic material is calculated, and the time history of a plastic zone of a elasto-plastic material is to be shown.

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Free vibration analysis of nonlocal viscoelastic nanobeam with holes and elastic foundations by Navier analytical method

  • Ola A. Siam;Rabab A. Shanab;Mohamed A. Eltaher;Norhan A. Mohamed
    • Advances in aircraft and spacecraft science
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    • v.10 no.3
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    • pp.257-279
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    • 2023
  • This manuscript is dedicated to deriving the closed form solutions of free vibration of viscoelastic nanobeam embedded in an elastic medium using nonlocal differential Eringen elasticity theory that not considered before. The kinematic displacements of Euler-Bernoulli and Timoshenko theories are developed to consider the thin nanobeam structure (i.e., zero shear strain/stress) and moderated thick nanobeam (with constant shear strain/stress). To consider the internal damping viscoelastic effect of the structure, Kelvin/Voigt constitutive relation is proposed. The perforation geometry is intended by uniform symmetric squared holes arranged array with equal space. The partial differential equations of motion and boundary conditions of viscoelastic perforated nonlocal nanobeam with elastic foundation are derived by Hamilton principle. Closed form solutions of damped and natural frequencies are evaluated explicitly and verified with prestigious studies. Parametric studies are performed to signify the impact of elastic foundation parameters, viscoelastic coefficients, nanoscale, supporting boundary conditions, and perforation geometry on the dynamic behavior. The closed form solutions can be implemented in the analysis of viscoelastic NEMS/MEMS with perforations and embedded in elastic medium.

Viscoelastic Stress Analysis of Adhesive-bonded Cylindrical by FEM (유한요소법을 이용한 원통체의 점탄성 응력 해석)

  • Park, Sung-Jin
    • Journal of the Society of Disaster Information
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    • v.15 no.2
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    • pp.259-267
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    • 2019
  • Purpose: In this paper adhesive-bonded cylindrical lap joints are analyzed by assuming that the adherends are elastic and the adhesive is linearly viscoelastic. Method: The distribution of the stresses in the adhensive is evaluated using the Finite Element Method. Nuverical examples for identical and different adherends bonded through a four parameter viscoelastic solid adhesive are illustrated. Results: The stress distribution in the adhesive layer with respect to time is shown. The stress distribution in the adhesive layer with respect to time is shown. The results are also shown that adherend thickness and elastic modulus give effect on the normalized stress. Conclusion: In this study, the stress distribution of the adhesive layer of the wrapped cylindrical body considering the viscoelasticity of the adhesive layer was numerically analyzed by using a four - element elastomer model.

An Evaluation of Residual Stress Redistribution in the Welding Residual Stress Field Caused by Fatigue Crack Propagation by Finite Element Method (용접잔류응력장에서 피로균열의 전파에 따른 잔류응력 재분포에 대한 해석적 평가)

  • Park, Eung-Joon;Kim, Eung-Joon
    • Journal of Welding and Joining
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    • v.26 no.6
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    • pp.92-96
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    • 2008
  • An investigation was performed to predict residual stress redistribution for the crack propagation initially through tensile residual stress field. The analytical method, which is based on Dugdale model by finite element analysis using elastic analysis method considering the superposition principle, was proposed to estimate the redistribution of residual stress caused by crack propagation. The various aspect of distribution of residual stress caused by crack propagation was examined based on the configuration change of specimen. The analysis results show that the aspect of redistribution of residual stress caused by crack propagation depends on the width of the specimen provided that the initial distribution of residual stress is identical.

Indentation Damage of Porous Alumina Ceramice

  • Ha, Jang-Hoon;Lee, Chul-Seung;Kim, Jong-Ho;Kim, Do-Kyung
    • Journal of the Korean Ceramic Society
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    • v.41 no.1
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    • pp.19-23
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    • 2004
  • The Hertzian indentation contact damage behavior of porous alumina with controlled pore shape was investigated by experiments. Porous alumina ceramics containing well-defined pore shape, size and distribution were prepared by incorporation of fugitive spherical starch. Porous alumina with isolated pore structure was prepared with porosity range up to 30%. The indentation stress-strain curves of porous alumina were constructed. Elastic modulus and yield stress can be obtained from the stress-strain relationship. Impulse excitation method for the measurement of elastic modulus was also conducted as well as Hertzian indentation and was confirmed as a useful tool to evaluate the elasticity of highly porous ceramics. Elastic modulus of the inter-connected pore structure is more sensitive to porosity than that of the isolated pore structure. When the specimen had isolated pore structure, higher yield point was obtained than it had inter-connected pore structure. This study proposed that the elastic modiulus of porous ceramics is strongly related to not only porosity, but also the structure of pore.

Residual Stress and Elastic Modulus of Y2O3 Coating Deposited by EB-PVD and its Effects on Surface Crack Formation

  • Kim, Dae-Min;Han, Yoon-Soo;Kim, Seongwon;Oh, Yoon-Suk;Lim, Dae-Soon;Kim, Hyung-Tae;Lee, Sung-Min
    • Journal of the Korean Ceramic Society
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    • v.52 no.6
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    • pp.410-416
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    • 2015
  • Recently, a new $Y_2O_3$ coating deposited using the EB-PVD method has been developed for erosion resistant applications in fluorocarbon plasma environments. In this study, surface crack formation in the $Y_2O_3$ coating has been analyzed in terms of residual stress and elastic modulus. The coating, deposited on silicon substrate at temperatures higher than $600^{\circ}C$, showed itself to be sound, without surface cracks. When the residual stress of the coating was measured using the Stoney formula, it was found to be considerably lower than the value calculated using the elastic modulus and thermal expansion coefficient of bulk $Y_2O_3$. In addition, amorphous $SiO_2$ and crystalline $Al_2O_3$ coatings were similarly prepared and their residual stresses were compared to the calculated values. From nano-indentation measurement, the elastic modulus of the $Y_2O_3$ coating in the direction parallel to the coating surface was found to be lower than that in the normal direction. The lower modulus in the parallel direction was confirmed independently using the load-deflection curves of a micro-cantilever made of $Y_2O_3$ coating and from the average residual stress-temperature curve of the coated sample. The elastic modulus in these experiments was around 33 ~ 35 GPa, which is much lower than that of a sintered bulk sample. Thus, this low elastic modulus, which may come from the columnar feather-like structure of the coating, contributed to decreasing the average residual tensile stress. Finally, in terms of toughness and thermal cycling stability, the implications of the lowered elastic modulus are discussed.