• Title/Summary/Keyword: Ratio of critical thickness

Search Result 176, Processing Time 0.022 seconds

Stability and vibration analysis of composite plates using spline finite strips with higher-order shear deformation

  • Akhras, G.;Li, W.
    • Structural Engineering and Mechanics
    • /
    • v.27 no.1
    • /
    • pp.1-16
    • /
    • 2007
  • In the present study, a spline finite strip with higher-order shear deformation is formulated for the stability and free vibration analysis of composite plates. The analysis is conducted based on Reddy's third-order shear deformation theory, Touratier's "Sine" model, Afaq's exponential model and Cho's higher-order zigzag laminate theory. Consequently, the shear correction coefficients are not required in the analysis, and an improved accuracy for thick laminates is achieved. The numerical results, based on different shear deformation theories, are presented in comparison with the three-dimensional elasticity solutions. The effects of length-to-thickness ratio, fibre orientation, and boundary conditions on the critical buckling loads and natural frequencies are investigated through numerical examples.

Buckling analysis of steel plates in composite structures with novel shape function

  • Qin, Ying;Luo, Ke-Rong;Yan, Xin
    • Steel and Composite Structures
    • /
    • v.35 no.3
    • /
    • pp.405-413
    • /
    • 2020
  • Current study on the buckling analysis of steel plate in composite structures normally focuses on applying finite element method to derive the buckling stress. However, it is time consuming, computationally complicated and tedious for general use in design by civil engineers. Therefore, in this study an analytical study is conducted to predict the buckling behavior of steel plates in composite structures. Hand calculation method was proposed based on energy principle. Novel buckling shapes with biquadratic functions along both loaded and unloaded direction were proposed to satisfy the boundary condition. Explicit solutions for predicting the critical local buckling stress of steel plate is obtained based on the Rayleigh-Ritz approach. The obtained results are compared with both experimental and numerical data. Good agreement has been achieved. Furthermore, the influences of key factors such as aspect ratio, width to thickness ratio, and elastic restraint stiffness on the local buckling performance are comprehensively discussed.

Numerical buckling temperature prediction of graded sandwich panel using higher order shear deformation theory under variable temperature loading

  • Sahoo, Brundaban;Sahoo, Bamadev;Sharma, Nitin;Mehar, Kulmani;Panda, Subrata Kumar
    • Smart Structures and Systems
    • /
    • v.26 no.5
    • /
    • pp.641-656
    • /
    • 2020
  • The finite element solutions of thermal buckling load values of the graded sandwich curved shell structure are reported in this research using a higher-order kinematic model including the shear deformation effect. The numerical buckling temperature has been computed using an in-house specialized code (MATLAB environment) prepared in the framework of the current mathematical formulation. In addition, the mathematical model includes the excess structural distortion under the influence of elevated environment via Green-Lagrange nonlinear strain. The corresponding eigenvalue equation has been solved to predict the critical buckling temperature of the graded sandwich structure. The numerical stability and the accuracy of the current solution have been confirmed by comparing with the available published results. Thereafter, the model is extended to bring out the influences of structural parameters i.e. the curvature ratio, core-face thickness ratio, support conditions, power-law indices and sandwich types on the thermal buckling behavior of graded sandwich curved shell panels.

Laser Weldability of Sheet steels for Tailored Blank Manufacturing(1) (테일러드 블랭크용 박판 강재의 레이저 용접성 (1))

  • 김기철
    • Journal of Welding and Joining
    • /
    • v.16 no.1
    • /
    • pp.77-87
    • /
    • 1998
  • This paper deals with the effect of laser welding parameters on the weld formation. Thin steels for automotive application were prepared so as to be welded with high power carbon dioxide laser system. Major process parameters were position of focus and travel speed. The effect of shielding gas was also discussed by employing the high speed photometry. Test results showed that the optimal position of focus varied in accordance with the joint configuration; bead-on-plate, butt or lap welding. It was recommended that the position of focus for the lap welding be located at slightly inner part of the material to be welded. In this case, however, it was noticeable that the weld penetration ratio, d/t$_{0}$ dropped drastically at the critical region. Results also demonstrated that both the bead width and penetration reduced as the travel speed increased. The penetration ratio showed two distinct regions; stabilized zone at the lower range of the travel spped and sudden drop zone at the higher range of travel speed. Lower limit of the penetration for acceptable weld was proved to be about 90% of the parent metal thickness based on the physical properties of the weld. Mixed gas application for both the shielding of molten metal and laser induced plasma control was recommended as far as the penetration was concerned.d.

  • PDF

A Study on Dynamic Characteristics of Gas Centered Swirl Coaxial Injector with Acoustic Excitation by Varying Momentum Flux Ratio (운동량 플럭스 비의 변화에 따른 기체 중심 스월 동축형 분사기의 기체 가진 동특성 연구)

  • Lee, Jungho;Park, Gujeong;Yoon, Youngbin
    • Journal of ILASS-Korea
    • /
    • v.20 no.3
    • /
    • pp.168-174
    • /
    • 2015
  • Combustion instability is critical problem in developing liquid rocket engine. There have been many efforts to solve this problem. In this study, the method was sought through the injector as part of these efforts to suppress combustion instability. If the injector can suppress the disturbance coming from the supply line as a kind of buffer it will serve to reduce combustion instability. Especially we target at gas propellant oscillation in gas-centered swirl coaxial injector. The phenomenon is simulated with acoustic excitation of speaker. The film thickness response at injector exit was measured by using a liquid film electrode. Also the response of spray to the disturbance was observed by high-speed photography. Gas-liquid momentum flux ratio and the frequency of feeding gas oscillation were changed to investigate the effect of these experimental parameters. The trend of response by varying these parameters and the cause of weak points was studied to suggest the better design of injector for suppressing combustion instability.

Dynamic Stability Analysis of Thick Plates with Varying Thickness and Concentrated Mass on Inhomogeneous Pasternak Foundation (비균질 Pasternak 지반에 놓인 집중질량을 갖는 변단면 후판의 동적안정해석)

  • Lee, Yong-Soo;Kim, Il-Jung
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.21 no.8
    • /
    • pp.698-707
    • /
    • 2011
  • This paper is to analyze the stability of the thick plate on inhomogeneous Pasternak foundation, with linearly varying thickness and concentrated mass by finite element method. To verify this finite element method, the results of natural frequencies and buckling stresses by the proposed method are compared with the existing solutions. The dynamic instability regions are decided by the dynamic stability analysis of the thick plate on inhomogeneous Pasternak foundation, with linearly varying thickness and concentrated mass. The non-dimensional Winkler foundation parameter is applied as 100, 1000 and non-dimensional shear foundation parameter is applied as 5. The tapered ratios are applied as 0.25 and 1.0, the ratios of concentrated mass to plate mass as 0.25 and 1.0, and the ratio of in-plane force to critical load as 0.4. As the result of numerical analysis of the thick plate on inhomogeneous Pasternak foundation for $u{\times}v=300cm{\times}300cm$ and $a{\times}b=600cm{\times}600cm$, instability areas of the thick plate which has the larger rigidity of inner area are farther from ${\beta}$-axis and narrower than those which has the larger rigidity of outer area.

Growth and dielectric Properties or $BaTiO_3/SrTiO_3$ oxide artificial superlattice deposited by pulsed laser deposition (PLD) (Pulsed laser depostion (PLD)법으로 증착된 $BaTiO_3/SrTiO_3$ 산화물 초격자의 성장 및 유전특성)

  • 김주호;김이준;정동근;김용성;이재찬
    • Journal of the Korean Vacuum Society
    • /
    • v.11 no.3
    • /
    • pp.166-170
    • /
    • 2002
  • Artificial $BaTiO_3$(BTO)/$SrTiO_3$(STO) oxide superlattice have been deposited on MgO (100) single crystal substrate by pulsed laser deposition(PLD) method. The stacking periodicity of BTO/STO superlattice structure was varied from $BTO_{1\;unit\; cell}/STO_{1\;unit\; cell}$ to $BTO_{125\;unit\; cell}/STO_{125 \;unit \;cell}$ thickness with the total thickness of 100 nm. The result of X-ray diffraction showed the characteristics of superlattice in the BTO/STO multilayer structure. we have also confirmed that there was no interdiffusion at the interface between BTO and STO layers by high resolution transmission electron microscopy(HRTEM). The dielectric constant of superlattice increased with decreasing stacking periodicity of the BTO/STO superlattice within the critical thickness. The dielectric constant of the BTO/STO superlattice reached a maximum i.e., 1230 at a stacking perioicity of $BTO_{2\;unit\; cell}/STO_{2\;unit\; cell}$ .

An experimental study on fatigue performance of cryogenic metallic materials for IMO type B tank

  • Lee, Jin-Sung;You, Won-Hyo;Yoo, Chang-Hyuk;Kim, Kyung-Su;Kim, Yooil
    • International Journal of Naval Architecture and Ocean Engineering
    • /
    • v.5 no.4
    • /
    • pp.580-597
    • /
    • 2013
  • Three materials SUS304, 9% Ni steel and Al 5083-O alloy, which are considered possible candidate for International Maritime Organization (IMO) type B Cargo Containment System, were studied. Monotonic tensile, fatigue, fatigue crack growth rate and Crack Tip Opening Displacement tests were carried out at room, intermediate low ($-100^{\circ}C$) and cryogenic ($-163^{\circ}C$) temperatures. The initial yield and tensile strengths of all materials tended to increase with decreasing temperature, whereas the change in elastic modulus was not as remarkable. The largest and smallest improvement ratio of the initial yield strengths due to a temperature reduction were observed in the SUS304 and Al 5083-O alloy, respectively. The fatigue strengths of the three materials increased with decreasing temperature. The largest increase in fatigue strength was observed in the Al 5083-O alloy, whereas the 9% Ni steel sample showed the smallest increase. In the fatigue crack growth rate test, SUS304 and Al 5083-O alloy showed a decrease in the crack propagation rate, due to decrease in temperature, but no visible improvement in da/dN was observed in the case of 9% Ni steel. In the Crack Tip Opening Displacement (CTOD) test, CTOD values were converted to critical crack length for the comparison with different thickness specimens. The critical crack length tended to decrease in the case of SUS304 and increase for the Al 5083-O alloy with decreasing temperature. In case of 9% Ni steel, change of critical crack length was not observed due to temperature decrease. In addition, the changing material properties according to the temperature of the LNG tank were analyzed according to the international code for the construction and equipment of ships carrying liquefied gases in bulk (IGC code) and the rules of classifications.

Static stability and of symmetric and sigmoid functionally graded beam under variable axial load

  • Melaibari, Ammar;Khoshaim, Ahmed B.;Mohamed, Salwa A.;Eltaher, Mohamed A.
    • Steel and Composite Structures
    • /
    • v.35 no.5
    • /
    • pp.671-685
    • /
    • 2020
  • This manuscript presents impacts of gradation of material functions and axial load functions on critical buckling loads and mode shapes of functionally graded (FG) thin and thick beams by using higher order shear deformation theory, for the first time. Volume fractions of metal and ceramic materials are assumed to be distributed through a beam thickness by both sigmoid law and symmetric power functions. Ceramic-metal-ceramic (CMC) and metal-ceramic-metal (MCM) symmetric distributions are proposed relative to mid-plane of the beam structure. The axial compressive load is depicted by constant, linear, and parabolic continuous functions through the axial direction. The equilibrium governing equations are derived by using Hamilton's principles. Numerical differential quadrature method (DQM) is developed to discretize the spatial domain and covert the governing variable coefficients differential equations and boundary conditions to system of algebraic equations. Algebraic equations are formed as a generalized matrix eigenvalue problem, that will be solved to get eigenvalues (buckling loads) and eigenvectors (mode shapes). The proposed model is verified with respectable published work. Numerical results depict influences of gradation function, gradation parameter, axial load function, slenderness ratio and boundary conditions on critical buckling loads and mode-shapes of FG beam structure. It is found that gradation types have different effects on the critical buckling. The proposed model can be effective in analysis and design of structure beam element subject to distributed axial compressive load, such as, spacecraft, nuclear structure, and naval structure.

Post-buckling Behaviour of Aluminium Alloys Rectangular Plate Considering the Initial Deflection Effect (초기 처짐 영향을 고려한 알루미늄 합금 사각형 판의 좌굴 후 거동)

  • Oh, Young-Cheol;Kang, Byoung-Mo;Ko, Jae-Yong
    • Journal of the Korean Society of Marine Environment & Safety
    • /
    • v.20 no.6
    • /
    • pp.738-745
    • /
    • 2014
  • In this paper, It is performing to the elastic and elasto-plastic large deformation series analysis using a numerical method for the initial deflection effect of the aluminum alloy rectangular plate in the elasto-plastic loading area patch loading size. It is assumed a boundary condition to be a simply supported condition and consider the initial deflection amplitude, aspect ratio. It examined the critical elastic buckling load and post-buckling behaviour of aluminium alloy A6082-T6 rectangular plate. It used a commercial program for the elastic and elasto-plastic deformation series analysis. If the initial deflection amplitude is smaller, the in-plane rigidity with increasing to load is reduced from the start and occurs significantly more increasing the amplitude. More higher the aspect ratio, the initial yield strength is gradually decreased, and the plate thickness thicker and occurs larger than the thin walled plate a reduction ratio of the initial yield strength of the patch loading size as 0.5.