• Steel and Composite Structures
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• v.45 no.4
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• pp.483-499
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• 2022

In present work, bending and free vibration studies are carried out on different kinds of sandwich FGM beams using recently proposed (Chakrabarty et al. 2011) C-0 finite element (FE) based higher-order zigzag theory (HOZT). The material gradation is assumed along the thickness direction of the beam. Power-law, exponential-law, and sigmoidal laws (Garg et al 2021c) are used during the present study. Virtual work principle is used for bending solutions and Hamilton's principle is applied for carrying out free vibration analysis as done by Chalak et al. 2014. Stress distribution across the thickness of the beam is also studied in detail. It is observed that the behavior of an unsymmetric beam is different from what is exhibited by a symmetric one. Several new results are also reported which will be useful in future studies.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4A
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• pp.207-215
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• 2012

Structural behavior of built-up compression members with unsymmetric connectors under buckling status has been studied through these experiments. When the distance between adjacent H-300 beams of built-up compression member is 2 m in length, and the H-300 beams are lengthened up to 30 m in length with three-10 m-H-beams by bolts and double arrayed, three specimen having each connector interval 4 m, 5 m, 6 m are experimented for evaluating buckling loads. The buckling loads from the experiments are compared with buckling loads of structural analysis using FEM and buckling loads of Timoshenko Eq. loads in order to figure out how the connectors' interval affects on longitudinal and lateral displacements, also strain of the built-up compression members as well. The result shows that the buckling loads tend to sharply decrease non-linearly according to connectors' interval increases. As well as that, the differences between experimental buckling loads and theoretical buckling loads and between experimental buckling loads and structural analyses buckling loads also have a tendency to be increased as the connector interval increases.

• Structural Engineering and Mechanics
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• v.7 no.2
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• pp.181-202
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• 1999

Dynamic response of axisymmetric arbitrary laminated composite cylindrical shell of finite length, using three-dimensional elasticity equations are studied. The shell is simply supported at both ends. The highly coupled partial differential equations are reduced to ordinary differential equations (ODE) with variable coefficients by means of trigonometric function expansion in axial direction. For cylindrical shell under dynamic load, the resulting differential equations are solved by Galerkin finite element method, In this solution, the continuity conditions between any two layer is satisfied. It is found that the difference between elasticity solution (ES) and higher order shear deformation theory (HSD) become higher for a symmetric laminations than their unsymmetric counterpart. That is due to the effect of bending-streching coupling. It is also found that due to the discontinuity of inplane stresses at the interface of the laminate, the slope of transverse normal and shear stresses aren't continuous across the interface. For free vibration analysis, through dividing each layer into thin laminas, the variable coefficients in ODE become constants and the resulting equations can be solved exactly. It is shown that the natural frequency of symmetric angle-ply are generally higher than their antisymmetric counterpart. Also the results are in good agreement with similar results found in literatures.

• Steel and Composite Structures
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• v.37 no.4
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• pp.405-418
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• 2020

The application of double-skin composite wall should meet different layout plans. However, most available research focused on the rectangular section with uniform axial compression. In this research, the structural behavior of double-skin composite wall with L section was studied. Due to the unsymmetric geometric characteristics, the considered loading condition combined the axial compression and biaxial bending. Five specimens were designed and tested under eccentric compression. The variables in the test included the width of the web wall, the truss spacing, the thickness of the steel faceplate, and the thickness of the web wall. The test results were discussed in terms of the load-displacement responses, buckling behavior, stiffness, ductility, strength utilization, strain distribution. Two modern codes were employed to predict the interaction between the axial compression and the biaxial bending. The method to calculate the available bending moment along the two directions was proposed. It was found that CECS 159:2004 offers more suitable results than AISC 360.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2758-2764
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• 2014

We demonstrated the synthesis of organic carbonates using alkyl/aryl 4,5-dichloro-6-oxopyridazine-1(6H)-carboxylates and alcohol in the presence of aluminum chloride. Alkyl/aryl 4,5-dichloro-6-oxopyridazine-1(6H)-carboxylates were reacted with alcohol in the presence of $AlCl_3$ in toluene at room temperature to afford the corresponding unsymmetric and symmetric organic carbonates in good to excellent yields. These are efficient and convenient processes. Alkyl/aryl 4,5-dichloro-6-oxopyridazine-1(6H)-carboxylates are solid, stable and non-toxic $CO_2/CO_2R$(Ar) source. It is noteworthy that the reaction is carry out under an ambient and acidic conditions, the easy-to prepare and readily available starting materials and the quantitative isolation of reusable 4,5-dichloropyridazin-3(2H)-one.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.247-252
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• 2008

This paper presents an active vibration control of cantilever beams under disturbances by a primary force. A direct velocity feedback control using a pair of PZT actuator and a velocity sensor is considered. Variation of the stability and performance with the locations of the sensor/actuator pair is investigated. It is found that the maximum gain varies with the locations of the sensor/actuator pair significantly. The maximum gain shows a symmetric distribution along the beam length with respect to the center point, although the boundary condition of the beam is unsymmetric. The control performance is affected by the location of the primary force as well as the location of the sensor/actuator pair. The active control system can more effectively reduce the vibration when the primary force is located close to the fixed boundary.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1000-1004
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• 1995

In the case of the external cylindrical grinding machine, the grinding mechanism can cause a wheel to vibrate due to a wheel cutter. This phenomena will bring about the unsymmetric wear up to high frequency without any relation of rotational speed. So far, when the grinding spindle is analyzed, it is assumed that a wheel is considered as lumped mass at the endof a beam. Nowadays, there is a tendency to use the wheel with a lsrge diameter or CBN wheel to achieve the high speed and accuracy grinding performance. Therefore, this kind of assumption is no longer valid. At the analysis of the grinding spindle, the parameter which dapends on the dynamic characteristics is a combination force between each part. For example, there is the tightness torque of a bolt and taper element in the grindle. In addition, the material property of the wheel can contribute the dynamic characteristics. This paper shows the mode participation of the shell mode of the wheel in the grindle and the dynamic characteristics according to the parameters which are the configuration of the flange and tightness torque of a bolt and taper. Modal parameter of the wheel, flange and the spindle can be extracted through frequency response function obtained by modal test. After that, by changing the tightness torque and kinds of wheel, we could accomplish the test in the whole combined grinding spindle. To perform modal analysis of vibration characteristics in the grinding spindle, we could develop the model of finite element method.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.136-140
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• 2002

High temperature fatigue crack growth behavior of P92 and STS 316L steel were investigated under four load conditions using CT type specimens. Loading and unloading times for the low wave forms were combinations of 1 sec. and 50 sec., which were two symmetric wave forms and two unsymmetric wave forms. Their behaviors are characterized using ΔK parameter. In STS 316L, Crack growth rate generally increases as frequency decreases. However, sensitivity of the loading rate to crack growth rate was fecund to be far greater than that of the unloading time. It is because as loading time increases, creep occurs at crack tip causing the crack growth rate to increase. However creep does not occur at the crack tip even if the unloading time is increased. In P92 steel, crack growth rate showed same behavior as in STS 316L. But the increase in loading or unloading time made almost no difference in crack growth rate, suggesting that no significant creep occurs in P92 steel even though loading time increases. After conducting high temperature tensile tests and comparing high temperature fatigue crack growth rates under various wave forms, it was proved that P92 steel has not only good high temperature properties but also improved, better high temperature fatigue properties than STS 316L.

• Structural Engineering and Mechanics
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• v.28 no.5
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• pp.495-514
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• 2008

In this paper, experimental and theoretical investigations of the effect of the mean moment on the response and collapse of circular thin-walled tubes subjected to cyclic bending are discussed. To highlight the influence of the mean moment effect, three different moment ratios r (minimum moment/ maximum moment) of -1, -0.5 and 0, respectively, were experimentally investigated. It has been found that the moment-curvature loop gradually shrinks with the number of cycles, and becomes stable after a few cycles for symmetric cyclic bending (r = -1). However, the moment-curvature loop exhibits ratcheting and increases with the number of cycles for unsymmetric cyclic bending (r = -0.5 or 0). In addition, although the three groups of tested specimens had three different moment ratios, when plotted in a log-log scale, three parallel straight lines describe the relationship between the controlled moment range and the number of cycles necessary to produce buckling. Finally, the endochronic theory combined with the principle of virtual work was used to simulate the relationship among the moment, curvature and ovalization of thin-walled tubes under cyclic bending. An empirical formulation was proposed for simulating the relationship between the moment range and the number of cycles necessary to produce buckling for thin-walled tubes subjected to cyclic bending with different moment ratios. The results of the experimental investigation and the simulation are in good agreement with each other.

• Bulletin of the Society of Naval Architects of Korea
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• v.24 no.3
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• pp.25-34
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• 1987

Whereas the finite element method is well established today, the boundary element method is a fairly recent development. Both are general-purpose methods for the solution of various structural analysis problem. The B.E.M has several potential advantages relative to the F.E.M. One of them is that the number of unknowns in algebraic system obtained by discretization is proportional to the number of boundary nodes. Anothor advantage is the ease of discretization and input data preparation. However, the B.E.M. always leads to a fully populated and unsymmetric system of equations. Even though the number of degree-of-freedom is reduced as compared with F.E.M, since nodes exist on the boundary only in the B.E.M, to follow that the effort to solve the equations can be greater. It has been shown also that the time spent in setting up the coefficient matrix is a significant and can, in some cases, be greater than the time required to solve the equation. Thus, one can naturally consider the idea that two methods should be coupled, then the advantages of both methods can be taken. And further, by using this coupling method the HATCH CORNER was analyzed to give initial design data.