• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.5 s.176
• /
• pp.1261-1270
• /
• 2000

This paper is concerned with the development of a general model for predicting material damping in laminates based on the strain energy method. In this model, the effect of interlaminar stress on damping is taken into accounts along with those of in-plane extension/compression and in-plane shear. The model was verified by carrying out the damping measurements on $90^0$ unidirectional composite beams varying length and thickness. The analytical predictions were favorably compared with the experimental data. The transverse shear($$\sigma$_{yz}$) appears to have a considerable influence on the damping behaviors in $90^0$ unidirectional polymer composites. However, the other interlaminar stresses($$\sigma$_{xz}$, $$\sigma$_z$) were shown to have little impact on vibration damping in $90^0$ laminated composite beam.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.460-464
• /
• 1997

By the used of a similar numerical method as in the previous paper, the forming limit stain of coatedsheet metals is investigated in which the FEM is applied and J2G(J/sab 2/-Gotoh's corner theory) is utilized as the plasticity constitutive equation. Coated two-layer sheets and sheets bonded with dissimilar sheets on both surface planes are stetched in a plane-strain atate, with various work-hardening exponent n-values and thicknesses of each layer. Processes of shear-band formation in such composite sheets are clearly illustrated. It is concluded that, in the coated state, the higher limiting strain of one layer is reduced due to the lower limiting stain of the other layer and vice, and does not necessarily obey the rule of linear combination of the limiting stain of each layer weighted according thickness.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.778-782
• /
• 1996

By the use of a similar numerical method as that in the previous paper, the forming limit strain of bonded sheet metals is investigated, in which the FEM is applied and J2G(J2-Gotoh's corner theory) is utilized as the plasticity constitutive equation. Bonded two-layer sheets and sheets bonded with dissimilar sheets on both surface planes are stretched in a plane-strain state, with various work-hardening exponent n-values and thicknesses of each layer. Processes of shear-band formation in such composite sheets are clearly illustrated. It is concluded that, in the bonded state, the higher limiting strain of one layer is reduced due to the lower limiting strain of the other layer and vice versa, and does not necessarily obey the rule of linear combination of the limiting strain of each layer weighted according thickness.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.04a
• /
• pp.340-345
• /
• 2003

By the use of a similar numerical method as that in the previous paper, the forming limit strain by coating method of clad sheet metals is investigated, in which the FEM is applied and J2G(J2-Gotoh's corner theory) is utilized as the plasticity constitutive equation. Clad two-layer sheets and sheets bonded with dissimilar sheets on both surface planes are stretched in a plane-strain state, with various work-hardening exponent n-values and thicknesses of each layer. Processes of shear-band formation in such composite sheets are clearly illustrated. It is concluded that, in the clad state, the higher limiting strain of one layer is reduced due to the lower limiting strain of the other layer and vice versa, and does not necessarily obey the rule of linear combination of the limiting strain of each layer weighted according thickness.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.11
• /
• pp.1119-1125
• /
• 2009

The coupled fluid-structure interaction problem is analyzed using the theoretical method to investigate the coupled vibration characteristics of functionally graded material(FGM) cylindrical shells conveying an incompressible, inviscid fluid. Material properties are assumed to vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The steady flow of fluid is described by the classical potential flow theory. The motion of shell represented by the first order shear deformation theory(FSDT) to account for rotary inertia and transverse shear strains. The effect of internal fluid can be taken into consideration by imposing a relation between the fluid pressure and the radial displacement of the structure at the interface. Numerical examples are presented and compared with exiting results.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1992.04a
• /
• pp.89-93
• /
• 1992

We experimented cutting characteristics-cutting force, behavior of chip, surface roughness-under low temperature, which generated by liquid nitrogen(77K). The results obtained are as follows; 1) The workpice is became to-195 .deg. C in 5, minutes, and in cooled cutting, cutting force bycooled workpices is stronger than normal temperature condition. Chip thickness is decreasing comparative toN.C and shear angle in shear plane is in creasing. 2) Chip formation becomes long or short tubular chips in turning SXM440, SNCM21 steel, when cutting speed is low and cutting temperatre is cooled condition, but in the STS304 steel the variation of c formations isn't known to. 3) In C.C, surface roughness of workpices is better than N.C and found to make more the crat wearthan N.C 4) It is possible to detect the behavior of chip by monitoring the maximum amplitude of gai value of cutting force.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.585-590
• /
• 2003

It analyzed the reinforcement effect according to reinforced period for FREP. It found that reinforcement effect of P-Type that was reinforced during the usage decreased compared to I-Type that was reinforced before the usage. So when reinforcing a existing structure that is being used, it should consider the stress that is produced due to the fixed load. It evaluated bending and shear of RC reinforcing beam based on the test and analytical conditions of this study. It found that stress concentration was concentrated due to rapid change of bending rigidity in reinforced cutting part as a result of excessive reinforcement thickness of FREP. It resulted in rip-off failure. It means that it should evaluate the shear when designing reinforcement.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.7 s.94
• /
• pp.1686-1699
• /
• 1993

In this paper, the thermal buckling of thick composite angle-ply laminates subject to uniform temperature distribution is studied. For the plates of 4-edges simply supported condition and those of 4-edges clamped condition, the critical buckling temperatue is derived, using tile finite element method based on the shear deformation theory. The effects of lamination angle, layer number, laminate thickness, plate aspect ratio and boundary constraints upon the critical buckling temperature are presented.

• Steel and Composite Structures
• /
• v.28 no.3
• /
• pp.381-388
• /
• 2018

In this paper, forced vibration of micro cylindrical shell reinforced by functionally graded carbon nanotubes (FG-CNTs) is presented. The structure is subjected to transverse harmonic load and modeled by beam model. The size effects are considered based on strain gradient theory containing three small scale parameters. The mixture rule is used for obtaining the effective material properties of the structure. Based on sinusoidal shear deformation theory of beam, energy method and Hamilton's principle, the motion equations are derived. Applying differential quadrature method (DQM) and Newmark method, the frequency curves of the structure are plotted. The effect of different parameters including, CNTs volume percent and distribution type, boundary conditions, size effect and length to thickness ratio on the frequency curves of the structure is studied. Numerical results indicate that the dynamic deflection of the FGX-CNT-reinforced cylindrical is lower with respect to other type of CNT distribution.

• Earthquakes and Structures
• /
• v.18 no.4
• /
• pp.481-492
• /
• 2020

A New hyperbolic shear deformation theory is developed for the bending analysis of softcore and hardcore functionally graded sandwich beams. This theory satisfies the equilibrium conditions at the top and bottom faces of the sandwich beam and does not require the shear correction factor. The governing equations are derived from the principle of virtual work. Sandwich beams have functionally graded skins and two types of homogenous core (softcore and hardcore). The material properties of functionally graded skins are graded through the thickness according to the power-law distribution. The Navier solution is used to obtain the closed form solutions for simply supported FGM sandwich beams. The accuracy and effectiveness of proposed theory are verified by comparison with previous research. A detailed numerical study is carried out to examine the influence of the deflections, stresses, and sandwich beam type on the bending responses of functionally graded sandwich beams.