• 대한기계학회논문집
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• 제15권2호
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• pp.404-412
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• 1991

In the design of high speed machinery, designers must consider the problem of possible structural failure due to excessive dynamically varying stresses, which are induced by the varying external loads and internal inertia forces, in the links of the mechanism. A study of the dynamically induced stresses would indicate what values of the minimum permissible fatigue strength should be for safe mechanism operation. This paper investigates the nature of the stress fluctuation in high speed mechanism on the basis of the effects of both the loads and the friction. The latter is apt to be neglected in the usual analysis in spite of the fact that it is always generated in the operating machinery. The analysis is performed on the coupler of the slider-crank mechanism for illustrative purposes and the results are expressed in a non-dimensional form for design applications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
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• pp.35-37
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• 1993

This paper shows that the presence of constant impedance loads and induction motors in power system's loading contents can lead to transient voltage instabilities during normal system manipulations such as switchings. The abnormal induction motor characteristics during system transients which initiate the voltage instabilities are illustrated. The influence of motor and network parameters, such as motor inertia mechanical load quantity and nature on the severity of the voltage instability are studied.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.198-201
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• 2002

It has been well-blown that sandwich structures are efficient to resist bending loads by increasing the moment of inertia of the panel. However, the accurate theoretical prediction of failure load and its optimization of sandwich beams for strength under concentrated loads were so complicated. Moreover, the appropriate selection of the variables, such as face thickness, core density and core thickness of the sandwich beam with many theories has continuously researched to satisfy for the given strength to weight structural requirement. There will be interesting to investigate the effect of those variables with its optimization for the load resistance.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.949-954
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• 2006

The purpose of this paper is to investigate the stability of tapered columns with clamped one end and carrying a tip mass of rotatory inertia with translational elastic support at the other end. The linearly tapered columns with the solid rectangular cross-section is adopted as the column taper. The differential equation governing free vibrations of such Beck columns is derived using the Bernoulli-Euler beam theory. Both the divergence and flutter critical loads are calculated from the load-frequency curves which are obtained by solving the differential equation. The critical loads are presented as functions of various non-dimensional system parameters: the taper type, the subtangential parameter, mass ratio and spring stiffness.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.3-10
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• 1999

One of the important considerations in designing a machine tool is the durability. In this study, a durability estimation systems for horizontal machining centers is developed to evaluate the effects of structural specification and driving conditions on the durability. All loads such as weights, inertia forces, cutting force and so on, are automatically transferred from the upper elements to the lower elements by the force flows which can be derived from the structural code of horizontal machining centers. And the external loads applied to the motion elements such as bearings, LM guides, ball screws and so on, are determined by the equilibrium conditions of force and moment. Especially, the durability of horizontal machining center is estimated based on the lifes of motion elements operating under the desired driving conditions.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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• pp.460-465
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• 2000

In this study, a durability estimation system of turning centers is developed to systematically evaluate the effects of structural specification and testing condition on the durability. All loads such as weights, inertia forces, cutting force and so on, are automatically transferred from the upper elements to the lower elements by the force flow which can be derived from the structural code of turning center. And the external loads applying to the moving and rolling elements are determined by using the equilibrium conditions of force and moment. Especially, the durability of turning center is estimated based on the lifes of moving and rolling elements under the required testing condition.

• 전기학회논문지P
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• 제67권4호
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• pp.208-213
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• 2018

In this paper, we studied the control strategy of applying STATCOM(static synchronous compensator) to mitigate the FIDVR(fault induced delayed voltage recovery) phenomenon. The proportion of motor loads is gradually increasing which might affect power system stability. Excessive reactive power consumption by the stall of the motor loads causes FIDVR phenomenon. In addition, the low inertia of the small HVAC(heating, ventilation and air conditioner) unit will not separate itself in the event of a contingency, causing system instability. For this reason, we have developed a control strategy that utilizes STATCOM efficiently through static and dynamic analysis. Case studies on a Korean power system have validated the performance of the proposed scheme under severe contingency scenarios. The results have verified that the proposed strategy can effectively mitigate FIDVR and improve the stability and reliability of the system.

• 대한기계학회논문집A
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• 제36권5호
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• pp.497-504
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• 2012

모바일하버는 해상에서 컨테이너 상하역 작업을 하는 새로운 해상물류 시스템이다. 모바일하버용크레인과 같이 해상에서 작업하는 대형 구조물은 파도에 의해 발생하는 지지부의 운동으로 관성력의 영향을 크게 받는다. 따라서 구조물의 안전성에 대한 정확한 검증이 요구되며, 생산 비용을 줄이기 위해 경량화가 매우 중요하다. 이런 요구조건을 위해 동적 응답 최적설계를 수행한다. 등가정하중법은 동하중을 등가정하중으로 변환한 후, 정적 응답 최적화기법을 사용하여 문제를 해결하는 동적 응답 최적설계 방법이다. 지지부의 움직임을 고려한 등가정하중법을 제안하고, 제안한 방법으로 모바일하버용 크레인을 최적화한다.

• 해양환경안전학회지
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• 제18권6호
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• pp.577-583
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• 2012

부유구조물은 해양에서 다양한 외력을 경험하게 되며 특히, 파랑하중은 구조물의 설계에 결정적인 지배인자로 간주되고 있다. 이런 구조물은 파장과 크기의 상대적 관계로 소형구조물, 대형구조물 등으로 구분될 수 있으며 전통적으로 소형구조물은 회절발생이 없는 것으로 가정하며 대형구조물은 회절 작용에 따른 관성력만을 고려하여 파랑하중을 산출한다. 따라서 이 연구에서는 해양과 강, 호수 등에서 주로 사용되고 있는 정사각형 부유구조물을 이용하여 동유체력과 구조응답의 상관관계를 파악하여 장방형 부유구조물의 안전성에 대한 영향을 검토하였다.

• Geomechanics and Engineering
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• 제14권1호
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• pp.19-27
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• 2018

It follows from the basic principles of mechanics of deformable solids relating to the strength, stability and propagation of elastic waves that the Earth's inner core cannot exist in the form of a spherical structure in the assumed thermobaric conditions and calculation values of physico-mechanical parameters. Pressure level reaches a value that is significantly greater than the theoretical limit of medium strength in the model approximations at the surface of the sphere of the inner core. On the other hand, equilibrium state of the sphere is unstable on the geometric forming at much lower loads under the influence of the "dead" surface loads. In case of the action of "follower" loads, the assumed pressure value on the surface of the sphere is comparable with the value of the critical load of "internal" instability. In these cases, due to the instability of the equilibrium state, propagation of homogeneous deformations becomes uneven in the sphere. Moreover, the elastic waves with actual velocity cannot propagate in such conditions in solid medium. Violation of these fundamental conditions of mechanics required in determining the physical and mechanical properties of the medium should be taken into account in the integrated interpretations of seismic and laboratory (experimental) data. In this case, application of the linear theory of elasticity and elastic waves does not ensure the reliability of results on the structure and composition of the Earth's core despite compliance with the required integral conditions on the mass, moment of inertia and natural oscillations of the Earth.