• Steel and Composite Structures
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• v.13 no.1
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• pp.91-107
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• 2012

In this research, mechanical buckling of hybrid functionally graded plates is considered using a new four variable refined plate theory. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory presented is variationally consistent, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The plate properties are assumed to be varied through the thickness following a simple power law distribution in terms of volume fraction of material constituents. Governing equations are derived from the principle of minimum total potential energy. The closed-form solution of a simply supported rectangular plate subjected to in-plane loading has been obtained by using the Navier method. The effectiveness of the theories is brought out through illustrative examples.

• Journal of KSNVE
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• v.8 no.5
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• pp.974-980
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• 1998

The analysis of dynamic responses are carried out on several orthotropic systems due to transient line source. These include infinite and semi-infinite spaces. The media possess orthotropic or higher symmetry. The lode is in the form of a normal stress acting with parallel to symmetry axis on the plane of symmetry within the materials. The results are first derived for responses of infinite media due to a harmonic line source. Subsequently the results for semi-infinite are derived by using superposition of the solution in the infinite medium together with a scattered solution from the boundaries. The sum of both solutions has to satisfy stress free boundary conditions thereby leading to the complete solutions. Explicit splutions for the displacements due to transient line loads are then obtaind by using Cargniard-DeHoop contour.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.3
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• pp.69-76
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• 2004

Polishing a die that has free-form surfaces is a time-consuming and tedious job, and requires a considerable amount of high-precision skill. In order to reduce the polishing time and cope with the shortage of skilled workers, an automatic polishing robot system was developed. The polishing robot system is composed of two subsystems, a three-axis machining center and a two-axis polishing head. The machining center is controlled by a FANUC controller, and the polishing head by DSP controller. The system has five degrees of freedom and is able to keep the polishing tool normal to the die surface during operation. To easily operate the developed polishing robot system, this study developed an integrated operating program in the Windows environment. The program consists of five modules: a polishing data generation module, a code separation module, a polishing module, a graphic simulator module, and a teaching module. Also, the automatic teaching system was developed to easily obtain teaching data and it consists of a three dimensional joystick and a proximity sensor. Also, to evaluate the performance of the integrated operating program and the polishing robot system, polishing experiments of a die of shadow mask were carried out.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.292-304
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• 2005

In this paper we present the linearized equations of motion for a bicycle as a benchmark. The results obtained by pencil-and-paper and two programs are compared. The bicycle model we consider here consists of four rigid bodies, viz. a rear frame, a front frame being the front fork and handlebar assembly, a rear wheel and a front wheel, which are connected by revolute joints. The contact between the knife-edge wheels and the flat level surface is modelled by holonomic constraints in the normal direction and by non-holonomic constraints in the longitudinal and lateral direction. The rider is rigidly attached to the rear frame with hands free from the handlebar. This system has three degrees of freedom, the roll, the steer, and the forward speed. For the benchmark we consider the linearized equations for small perturbations of the upright steady forward motion. The entries of the matrices of these equations form the basis for comparison. Three diffrent kinds of methods to obtain the results are compared : pencil-and-paper, the numeric multibody dynamics program SPACAR, and the symbolic software system Auto Sim. Because the results of the three methods are the same within the machine round-off error, we assume that the results are correct and can be used as a bicycle dynamics benchmark.

• KIEAE Journal
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• v.13 no.1
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• pp.65-74
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• 2013

Recently, greenery system is frequently applied on buildings and artificial grounds to improve urban ecological functionality. Specifically, architectural greenery is also known as an architectural language that can meet the sustainable design concept of architects. Although the architectural greenery system can be optimized through an interdisciplinary approach between architecture, horticulture and landscape- architecture, there is a problem of communication on the ideal gap between them. Therefore, this study is expected to establish the comtemporary architecture as hi-tech and the organic architecture in internationalism. Moreover, it can analyze the case study on architectural greenery system designed by a Pritzker Prize winner who represents the comtemporary architectural trend. In this analysis, we calculate and compare the U-value of the free-form surface system based on the international standards: ISO and CIBSE etc. Moreover, we calculate a change of artificial soil transmittance respect on compounding ratio of the bottom ash and pearlite. In the case of California Academy of Science by Renzo Piano, total transmittance of the greenery system results in 48% of domestic thermal insulation standard in dry condition. This result will be used as a basic study to promote developing the advanced system based on the concept of consilience.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.123-123
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• 2000

Polishing a die that has free-form surfaces is a time-consuming and tedious job, and requires a considerable amount of high-precision skill. In order to reduce the polishing time and cope with the shortage of skilled workers, a user-friendly automatic polishing system was developed in this research. The polishing system with five degrees of freedom is able to keep the polishing tool normal to the die surface. The polishing system is controlled by a PC-NC controller. And, to easily onerate the developed polishing system, this stud)r developed a integrated program in the Windows environment. This program consists of 4 modules: polishing module, a graphic simulator, a polishing data generation module, and a teaching. Also, the automatic teaching system was developed to easily obtain a teaching data. The developed teaching system consists of a three dimensional joystick and a proximity sensor. In order to evaluate stability of the driving program and the leaching system, polishing experiments of the die of saddle shape were carried out.

• Advances in materials Research
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• v.8 no.3
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• pp.155-177
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• 2019

In this paper, a new displacement based high-order shear deformation theory is introduced for the static response of functionally graded sandwich plate with new definition of porosity distribution taking into account composition and the scheme of the sandwich plate. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory presented is variationally consistent, has strong similarity with classical plate theory in many aspects, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. Material properties of FGM layers are assumed to vary continuously across the plate thickness according to either power-law or sigmoid function in terms of the volume fractions of the constituents. The face layers are considered to be FG across each face thickness while the core is made of a ceramic homogeneous layer. Governing equations are derived from the principle of virtual displacements. The closed-form solution of a simply supported rectangular plate subjected to sinusoidal loading has been obtained by using the Navier method. Numerical results are presented to show the effect of the material distribution, the sandwich plate geometry and the porosity on the deflections and stresses of FG sandwich plates. The validity of the present theory is investigated by comparing some of the present results with other published results.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.723-735
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• 2019

This paper employs computational tools to investigate the cause of resistance reductions in calm water and waves of the sharp bow form compared to the blunt bow in 66,000 DWT bulk carriers. A more slender shape at the fore-shoulder without a bulbous bow is a prominent feature of the sharp bow. The blunt bow incorporates a bulbous shape. A two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved; and a realizable k-ε model has been applied for the turbulent closure. The free-surface is obtained by solving a VOF equation. The computational results have been validated with model tests carried out at a towing tank. The pressure component of resistance in the sharp bow is reduced by 8.9% in calm water, and 6.4-12.7% in regular head waves. The frictional components of resistance in the sharp and blunt bows are largely the same.

• International Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.10-16
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• 2016

A trigonometric Layerwise higher order shear deformation theory (TLHSDT) is developed and implemented for free vibration and buckling analysis of laminated composite and sandwich plates by analytical and finite element formulation. The present model assumes parabolic variation of out-plane stresses through the depth of the plate and also accomplish the zero transverse shear stresses over the surface of the plate. Thus a need of shear correction factor is obviated. The present zigzag model able to meet the transverse shear stress continuity and zigzag form of in-plane displacement continuity at the plate interfaces. Hence, botheration of shear correction coefficient is neglected. In the case of analytical method, the governing differential equation and boundary conditions are obtained from the principle of virtual work. For the finite element formulation, an efficient eight noded $C^0$ continuous isoparametric serendipity element is established and employed to examine the dynamic analysis. Like FSDT, the considered mathematical model possesses similar number of variables and which decides the present models computationally more effective. Several numerical predictions are carried out and results are compared with those of other existing numerical approaches.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.2
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• pp.169-177
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• 2018

Twisted rudder, twisted rudder with bulb, and twisted rudder with bulb and fin have been developed computationally for 3,000 TEU container ship through parametric study. The objective function is to minimize delivered power in model scale. Design variables are twisted angle, rudder bulb diameter and fin angle. The governing equation is Reynolds averaged Navier-Stokes equations in an unsteady turbulent flow and the Reynolds stress model applied for the turbulent closure. A double body model is used for the treatment of free-surface. The calculation was carried out in towing and self-propulsion conditions at design speed. The sliding mesh technique was employed to simulate the flow around the propeller. Form factor is obtained from the towing computation. Self-propulsion point is obtained from the self-propelled computations at two propeller rotating speeds. The delivered power due to the designed twisted rudder, twisted rudder with bulb, and twisted rudder with bulb and fin are reduced by 1.1%, 1.6%, and 2.0%, respectively.