• Smart Structures and Systems
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• v.25 no.6
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• pp.693-705
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• 2020

In the current investigation, large amplitude free vibration behavior of shallow curved pipes (tubes) made of functionally graded materials is investigated. Properties of the tube are distributed across the radius of the tube and are obtained by means of a power law function. It is also assumed that all thermo-mechanical properties are temperature dependent. The governing equations of the tube are obtained using a higher order shear deformation tube theory, where the traction free boundary conditions are satisfied on the top and bottom surfaces of the tube. The von Kármán type of geometrical non-linearity is included into the formulation to consider the large displacements and small strains. Uniform temperature elevation of the tube is also included into the formulation. For the case of tubes which are simply supported in flexure and axially immovable, the governing equations are solved using the two-step perturbation technique. Closed form expressions are provided to obtain the small and large amplitude fundamental natural frequencies of the FGM shallow curved tubes in thermal environment. Numerical results are given to explore the effects of thermal environment, radius ratio, and length to thickness ratio of the tube on the fundamental linear and non-linear frequencies.

• Corrosion Science and Technology
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• v.2 no.6
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• pp.266-271
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• 2003

Safety diagnosis of various structural components and facilities is indispensable for preventing catastrophic failure of material by time-dependent and environment accelerating degradation. Also, this diagnosis of operating components should be done periodically for safe maintenance and economical repair. However, conventional standard methods for mechanical properties have the problems of bulky specimen, destructive procedure and complex procedure of specimen sampling. So, a non-destructive and simple mechanical testing method using small specimen is needed. Therefore, an advanced indentation technique was developed as a potential method for non-destructive testing of in-field structures. This technique measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation such as yield strength, tensile strength and work-hardening index. In this paper, we characterized the tensile properties including yield and tensile strengths of the V-modified Cr-Mo steels in petro-chemical and thermo-electrical plants. And also, the effects of hydrogen-assisted degradation of the V-modified Cr-Mo steels were analyzed in terms of work-hardening index and yield ratio.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.395-400
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• 2017

Hydraulic test was conducted to evaluate the structural strength of valve exposed to high pressure environment during combustion progress. For the proof pressure, 1.05 times higher pressure than MEOP was applied in the hydraulic test. Two units of valves were used in the hydraulic test. The result for measured strain of the valve dependent on the pressurization conditions during the test were verified comparing with the results for the finite element analysis. Observing the difference between the results for the finite element analysis and the hydraulic test, the difference was within 20% error and the plastic deformation was not generated.

• Structural Engineering and Mechanics
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• v.3 no.2
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• pp.121-133
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• 1995

It is well known that two-dimensional simplified third-order theories satisfy the layer interface continuity of transverse shear strains, thus these theories violate the continuity of transverse shear stresses when two consecutive layers differ either in fibre orientation or material. The third-order theories considered herein involve four/or five dependent unknowns in the displacement field and satisfy the condition of vanishing of transverse shear stresses at the bounding planes of the plate. The objective of this investigation is to examine (i) the flexural response prediction accuracy of these third-order theories compared to exact elasticity solution (ii) the effect of layer interface continuity conditions on the flexural response. To investigate the effect of layer interface continuity conditions, three-dimensional elasticity solutions are developed by enforcing the continuity of different combinations of transverse stresses and/or strains at the layer interfaces. Three dimensional twenty node solid finite element (having three translational displacements as degrees of freedom) without the imposition of any of the conditions on the transverse stresses and strains is also employed for the flexural analysis of the laminated plates for the purposes of comparison with the above theories. These shear deformation theories and elasticity approaches in terms of accuracy, adequacy and applicability are examined through extensive numerical examples.

• Steel and Composite Structures
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• v.10 no.4
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• pp.361-371
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• 2010

Enhancement in the seismic buckling capacity of steel tanks caused by the addition of fiber reinforced polymers (FRP) retrofit layers attached to the outer walls of the steel tank is investigated. Three-dimensional non-linear finite element modeling is utilized to perform such analysis considering non linear material properties and non-linear large deformation large strain analysis. FRP composites which possess high stiffness and high failure strength are used to reduce the steel hoop stress and consequently improve the tank capacity. A number of tanks with varying dimensions and shell thicknesses are examined using FRP composites added in symmetric layers attached to the outer surface of the steel shell. The FRP shows its effectiveness in carrying part of the hoop stresses along with the steel before steel yielding. Following steel yielding, the FRP restrains the outward bulging of the tank and continues to resist higher hoop stresses. The percentage improvement in the ultimate base moment capacity of the tank due to the addition of more FRP layers is shown to be as high as 60% for some tanks. The percentage of increase in the tank moment capacity is shown to be dependent on the ratio of the shell thickness to the tank radius (t/R). Finally a new methodology has been explained to calculate the location of Elephant foot buckling and consequently the best location of FRP application.

• Transactions of Materials Processing
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• v.7 no.6
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• pp.570-574
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• 1998

The texture evolution during deep drawing of AA1050 sheets was experimentally investigated and the lattice rotation rate was predicted using rate sensitive model with full constraints boundary conditions. The measured textures are dependent on the amount of the flange deformation and the initial crystal orientations. In the specimen parallel to RD the initial crystal orientations and the D component rotated toward the Cu component and the initial crystal orientations along the $\alpha$ fiber rotated toward the G {1 1 0}<0 0 1> and P {1 1 0} <1 1 1> components during deep drawing. In the specimen parallel to $45{\circ}$ with respect to RD the initial crystal orientations around the D component rotated about ND and the initial crystal orientations along the ${\alpha}$ fiber also rotated toward the (1 1 0) [2 3] and (1 1 0)[2 7] components about ND. In the specimen parallel to TD. the initial crystal orientations around the D component rotated toward the rotated cube and the initial crystal orientations along the ${\alpha}$ fiber rotated toward the {1 1 0} <1 1 3> component.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.220-223
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• 2008

Large curved plate blocks are widely used to construct hull structure in shipbuilding industry. Most curved plates are manufactured by using manual method called as line heating that use deformation caused by residual stress after local heating along a line which is perpendicular to the curvature direction. However, its working environment is poor and its formability is totally dependent on an experienced technician. In view of that, multi-point dieless forming (MDF) technology that use reconfigurable punch arrays instead of one piece die is proposed in this study. The MDF process is based on a concept of equivalent die surface made by numbers of punches which has round tip at the end of it. In this study, numerical simulation for common curvature type such as saddle shape was carried out. In addition, experiments in the plate forming process were also conducted to compare with the numerical results in view of final configuration. Consequently, it was noted that the proposed dieless forming method has considerable feasibility to substitute the new process for conventional manual method.

• Journal of Fashion Business
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• v.9 no.6
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• pp.86-100
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• 2005

This paper has examined how ugliness has aesthetically been portrayed in modern make-up. In the past, ugliness was regarded as an antonym of beauty, but it recently plays a role on part of beauty, as independent portion of art. It was Schegel who initially maintained the view. According to his theory, ugliness represents interesting things including suffering reality, shock, attention, humor, surprises brought by distort and deformation. Hegel had a different view on it. As for him, he had the notion that ugliness was the opposite to beauty and that it had to be dependent in art, he argued that art was subordinate to philosophy, and that it was just nostalgia for the past, not representing reality, therefore, it could not be a foothold in contemporary art. In this context, some images of ugliness can be classified accordingly to Schegel's view deteste, decadence and androgynous can be fallen into a category describing reality; fetish, kitsch and grotesque can be included in interesting things. There is no fine line between the two. There are sometimes things they have in common. They mutually draw attentions by distancing themselves from general images of beauty, or making many changes and distorts in its part, using unique materials, unprecedented attempts of colors which result in creative and shocking images. Attempts made in ugly images in modern art are widening its concept to depicting reality on the body of human beings, also creating its new definition, playing a major role in independent part of modern art, not in the past way like wearing make-up on the face to make it look better.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.73-80
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• 2013

The dynamic characteristics of west coast sand were investigated in order to evaluate the design properties of the offshore wind turbine foundations to be constructed in the West Sea. Torsional shear tests were performed at different confining pressures and densities on specimens constituted by the dry fluviation method. The strain-dependent shear modulus and damping curves were obtained, together with modulus degradation curves. The results show that the confining pressure is more influential on the dynamic characteristics of the sand than the density. It was also found that the dynamic curves from this study were similar to those proposed by others. The modulus degradation ratio $G/G_{1st}$ varies slightly at a small strain level, but increases significantly once beyond the intermediate strain level.

• Advances in nano research
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• v.5 no.2
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• pp.69-97
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• 2017

In this study, nonlinear response of laminated functionally graded carbon nanotube reinforced composite (FG-CNTRC) plate under low-velocity impact based on the Eshelby-Mori-Tanaka approach in thermal conditions is studied. The governing equations are derived based on higher-order shear deformation plate theory (HSDT) under von $K\acute{a}rm\acute{a}n$ geometrical nonlinearity assumptions. The finite element method with 15 DOF at each node and Newmark's numerical integration method is applied to solve the governing equations. Four types of distributions of the uniaxially aligned reinforcement material through the thickness of the plates are considered. Material properties of the CNT and matrix are assumed to be temperature dependent. Contact force between the impactor and the laminated plate is obtained with the aid of the modified nonlinear Hertzian contact law models. In the numerical example, the effect of layup (stacking sequence) and lamination angle as well as the effect of temperature variations, distribution of CNTs, volume fraction of the CNTs, the mass and the velocity of the impactor in a constant energy level and boundary conditions on the impact response of the CNTRC laminated plates are investigated in details.