• Title/Summary/Keyword: Combined Stress

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Stress Analysis of Truss Connection subjected to Moving Load Using Section Properties Factor (단면 수정계수를 이용한 이동 하중에 따른 트러스 연결부의 응력해석)

  • 이상호;배기훈
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2002.10a
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    • pp.354-361
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    • 2002
  • This paper propose section properties factor to generate stress history for fatigue analysis and safety inspection of steel bridge. A methodology is described for the computation of numerical stress histories in the steel truss bridge, caused by the vehicles using section properties factor. The global 3-D beam model of bridge is combined with the local shell model of selected details. Joint geometry is introduced by the local shell model. The global beam model takes the effects of joint rigidity and interaction of structural elements into account. Connection nodes in the global beam model correspond to the end cross-section centroids of the local shell model. Their displacements are interpreted as imposed deformations on the local shell model. The load cases fur the global model simulate the vertical unit force along the stringers. The load cases fer the local model are imposed unit deformations. Combining these, and applying vehicle loads, numerical stress histories are obtained. The method is illustrated by test load results of an existing bridge.

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A Study on the Optimal Shape Design Using Automatic Regridding and Design Element (자동 격자 생성법과 설계 요소를 이용한 형상 최적 설계에 관한 연구)

  • Kim, Ho-Ryong;Dan, Byung-Ju
    • Journal of the Korean Society for Precision Engineering
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    • v.10 no.3
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    • pp.87-96
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    • 1993
  • In this study, the peak stress of a fuillet in elastic structure was optimized to have minimum value by using quadratic isoparametric element. The method of auomatic gridding was also developed along with shape algorithm and design element technique was adopted in selecting design variables. The computer program developed was combined with the Hooke-Jeeves direct algorithm of optimization techniques in order to minimize the peak stress of the fillet. The imployment of design element technique significantly cut down computer time by the reduction in design variables, and the opitmum fillet shape with uniform minimum stress was obtained by varying design variables along x and y directions in improving the shape compared to other results. By using automatic gridding, in which Bezier surfaces and Coons surfaces of cubic interpolation were employed, the irregular boundary was removed resulting in smoother anbd more accurate fillet shape possessing uniform minimum stress.

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Engineering J-Integral Estimation for Internal Axial Surface Cracks in Cylinders (II) -Optimised Reference Stress Based Estimation- (실린더에 존재하는 축방향 표면균열에 대한 공학적 J-적분식 (II) - 최적참조응력에 기초한 방법-)

  • Kim, Jin-Su;Kim, Yun-Jae;Kim, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.11
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    • pp.2442-2449
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    • 2002
  • This paper provides an reference stress based J estimation equation fur cylinders with finite internal axial surface cracks under internal pressure. In part 1, the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-0) materials is proposed. In this paper, the developed CE/EPRI -type solutions ale then re-formulated based on the reference stress concept. Such a re-formulation provides a simpler equation for J. estimation are then further extended to combined internal pressure and bending. The proposed reference stress based J estimation equation is compared with elastic-plastic 3-D FE results using actual stress-strain data for a Type 304 stainless steel. Good agreement between the FE results and the proposed reference stress based J estimations provides confidence in the use of the proposed method to elastic -plastic fracture mechanics of pressurised piping.

The Effect of Welding Residual Stress on Whole Structure with T-Joint RHS

  • Rajesh S. R.;Bang H. S.;Kim H.
    • International Journal of Korean Welding Society
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    • v.5 no.1
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    • pp.60-65
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    • 2005
  • In the field of welding the mechanical behavior of a welded structure under consideration may be predicted via heat transfer and welding residual stress analysis. Usually such numerical analyses are limited to small regular mesh models or test specimens. Nevertheless, there is very few strength assessment of the whole structure that includes the effect of welded residual stress. The present work is based on the specialized finite element codes for the calculation of nonlinear heat transfer details and residual stress including the external load on the welded RHS (Rectangular Hollow Section) T-joint connections of the whole structure. First the thermal history of the combined fillet and butt-welded T-joint equal width cold-formed RHS are calculated using nonlinear finite element analysis (FEA) considering the quarter model of the joint. Then using this thermal history the residual stress around the joints has been evaluated. To validity the FEA result, the calculated residual stresses were compared with the available experimental results. The residual stress obtained from the quarter model is mapped to the full model and then to the whole structure model using FEM codes. The results from the FEM codes were exported to the commercial package for visualization and further analysis applying loads and boundary conditions on the whole structure. The residual stress redistribution along with the external applied load is examined computationally.

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Fast analytical estimation of the influence zone depth, its numerical verification and FEM accuracy testing

  • Kuklik, Pavel;Broucek, Miroslav;Kopackova, Marie
    • Structural Engineering and Mechanics
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    • v.33 no.5
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    • pp.635-647
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    • 2009
  • For the calculation of foundation settlement it is recommended to take into account so called influence zone inside the subsoil bellow the foundation structure. Influence zone inside the subsoil is the region where the load has a substantial influence on the deformation of the soil skeleton. The soil skeleton is pre-consolidated or over consolidated due to the original geostatic stress state. An excavation changes the original geostatic stress state and it creates the space for the load transferred from upper structure. The theory of elastic layer in Westergard manner is selected for the vertical stress calculation. The depth of influence zone is calculated from the equality of the original geostatic stress and the new geostatic stress due to excavation combined with the vertical stress from the upper structure. Two close formulas are presented for the influence zone calculation. Using ADINA code we carried out several numerical examples to verify the proposed analytical formulas and to enhance their use in civil engineering practice. Otherwise, the FEM code accuracy can be control.

Celecoxib-mediated activation of endoplasmic reticulum stress induces de novo ceramide biosynthesis and apoptosis in hepatoma HepG2 cells

  • Maeng, Hyo Jin;Song, Jae-Hwi;Kim, Goon-Tae;Song, Yoo-Jeong;Lee, Kangpa;Kim, Jae-Young;Park, Tae-Sik
    • BMB Reports
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    • v.50 no.3
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    • pp.144-149
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    • 2017
  • Ceramides are the major sphingolipid metabolites involved in cell survival and apoptosis. When HepG2 hepatoma cells were treated with celecoxib, the expression of the genes in de novo sphingolipid biosynthesis and sphingomyelinase pathway was upregulated and cellular ceramide was elevated. In addition, celecoxib induced endoplasmic reticulum (ER) stress in a time-dependent manner. SPTLC2, a subunit of serine palmitoyltransferase, was overexpressed by adenovirus. Adenoviral overexpression of SPTLC2 (AdSPTLC2) decreased cell viability of HEK293 and HepG2 cells. In addition, AdSPTLC2 induced apoptosis via the caspase-dependent apoptotic pathway and elevated cellular ceramide, sphingoid bases, and dihydroceramide. However, overexpression of SPTLC2 did not induce ER stress. Collectively, celecoxib activates de novo sphingolipid biosynthesis and the combined effects of elevated ceramide and transcriptional activation of ER stress induce apoptosis. However, activation of de novo sphingolipid biosynthesis does not activate ER stress in hepatoma cells and is distinct from the celecoxib-mediated activation of ER stress.

Early Stage Growth Structure and Stress Relaxation of CoCrPt Thin Films on Spherically Modulated Polymer Surface

  • Kim, Sa-Rah;Jeong, Jun-Ho;Shin, Sung-Chul;Son, Vo Thanh;Jeon, Bo-Geon;Kim, Cheol-Gi;Jeong, Jong-Ryul
    • Journal of Magnetics
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    • v.15 no.1
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    • pp.12-16
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    • 2010
  • Combined study of in-situ stress measurements and atomic force microscopy (AFM) revealed drastic stress relaxation in the CoCrPt and PS(styrene)-PVP(vinyl pyridine) polymer hybrid structure that was closely related to the growth structure of the film. We have observed not only no large initial growth stress at the initial stages of film growth but also twice smaller stress in magnitude with opposite sign in the CoCrPt/PS-PVP/Si sample. The microstructural studies using AFM at the various film growth stages revealed that the film growth structure plays an important role in the stress relaxation mechanism of CoCrPt films on a corrugated polymer surface.

New Engineering J and COD Estimation Method for Circumferential Through-Wall Cracked Pipes-Combined Tension and Bending Load (원주방향 관통균열이 존재하는 배관의 새로운 J-적분 및 COD 계산식-인장하중과 굽힘모멘트가 동시에 작용하는 경우)

  • Huh, Nam-Su;Kim, Yun-Jae;Kim, Young-Jin
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.7
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    • pp.85-90
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    • 2001
  • In order to apply the Leak-Before-Break(LBB)concept to nuclear piping, accurate estimation of J-integral and crack opening displacement(COD) is essential for complex loading, such as combined tension and bending. This paper proposes a new engineering method to estimate J-integral and the COD for circumferential through-wall cracked pipes subject to combined tension and bending loading. The proposed method to estimate the COD is validated against three published pipe test data, generated from a monotonically increasing bending load with a constant internal pressure, which shows excellent agreements.

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A high-order analytical method for thick composite tubes

  • Sarvestani, Hamidreza Yazdani;Hojjati, Mehdi
    • Steel and Composite Structures
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    • v.21 no.4
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    • pp.755-773
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    • 2016
  • In the present paper, a new high-order simple-input analytical method is used to study thick laminated composite straight tubes subjected to combined axial force, torque and bending moment. The most general displacement field of elasticity for an arbitrary laminated composite straight tube is obtained to analytically calculate stresses under combined loadings based on a layerwise method. The accuracy of the proposed method is subsequently verified by comparing the numerical results obtained using the proposed method with finite element method (FEM) and experimental data. The results show good corresponded. The proposed method provides advantages in terms of computational time compared to FEM.

Characterization and Application of DLC Films Produced by New Combined PVD-CVD Technique

  • Chekan, N.M.;Kim, S.W.;Akula, I.P.;Jhee, T.G.
    • Journal of the Korean Society for Heat Treatment
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    • v.23 no.2
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    • pp.75-82
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    • 2010
  • A new advanced combined PVD/CVD technique of DLC film deposition has been developed. Deposition of a DLC film was carried out using a pulsed carbon arc discharge in vapor hydrocarbon atmosphere. The arc plasma enhancing CVD process promotes dramatic increase in the deposition rate and decrease of compressive stress as well as improvement of film thickness uniformity compared to that obtained with a single PVD pulsed arc process. The optical spectroscopy investigation reveals great increase in radiating components of $C_2$ Swan system molecular bands due to acetylene molecules decomposition. AFM, Raman spectroscopy, XPS and nano-indentation were used to characterize DLC films. The method ensures obtaining a new superhard DLC nano-material for deposition of protective coatings onto various industrial products including those used in medicine.