• 한국소음진동공학회논문집
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• 제12권2호
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• pp.116-123
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• 2002

Applying a general coupled lateral and torsional vibration finite element model of gear pair element, this paper intends to look into in detail the coupled lateral and torsional vibration characteristics of a turbo-chiller rotor bearing system, having a bull-pinion speed increasing gear. Investigations have been carried out systematically by comparing the uncoupled and coupled natural frequencies and their mode shapes upon varying the gear mesh stiffness with considerations on rotating speeds, and also by comparing the strain energies of lateral and torsional vibration modes. Results hale shown that some modes may hale the coupled lateral and torsional mode characteristics as the gear mesh stiffness Increases over a certain value, and moreover that their associated dominant modes may be different from their initial modes, j.e., a certain dominant mode may change from an initial torsional one to a lateral one or from an initial lateral one to a torsional one.

• Structural Engineering and Mechanics
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• 제49권2호
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• pp.147-161
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• 2014

In this paper a nonlinear finite element analysis model is established for cold-formed steel zed-section purlins subjected to uplift loading. In the model, the lateral and rotational restraints provided by the sheeting to the purlin are simplified as a lateral rigid restraint imposed at the upper flange-web junction and a rotational spring restraint applied at the mid of the upper flange where the sheeting is fixed. The analyses are performed by considering both geometrical and material nonlinearities. The influences of the rotational spring stiffness and initial geometrical imperfections on the uplift loading capacity of the purlin are investigated numerically. It is found that the rotational spring stiffness has significant influence on the purlin performance. However, the influence of the initial geometric imperfections on the purlin performance is found only in purlins of medium or long length with no or low rotational spring stiffness.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.624-629
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• 2008

When TBM excavates a tunnel, existing concrete lining segments are used as supporting structures for driving force. Axial stress on the lining segments are apt to be large in case of direct driving force. However, it drastically decline as it is farther and father from TBM and later, it tends to converge after a certain point. Such tendencies show similar results of finite element analysis. At the initial intervals, the values of finite element analysis are larger, while at the later intervals, the actual stress values are larger. It concludes that such tendencies are attributable to that the concrete lining segments have partially burst and cracked in the axial direction at the initial intervals. And differences of stresses at the later intervals are created by the changed plasticity of ground and the friction on the external sides of the lining segments.

• 한국해양공학회지
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• 제22권5호
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• pp.94-99
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• 2008

Three types of salt resistant concrete beams reinforced with glass fiber reinforced polymer-ribbed bars (GFRP-ribbed bars) were selected, and their applicable properties were investigated with the goal of improving the problem of capacity deterioration in marine structures due to sea water corrosion. In this study, the structural behaviors were similar to RC beams in relation to the development of the strength and stiffness up to the generation of the initial crack. After the growth of this initial crack, the structural properties decreased owing to a sudden loss of bond strength. Also these beams showed the trends of brittle failure. As a result, it was confirmed that a GFS beam replaced with Fly Ash (20%) and Silica Fume (5%) has the best application as a marine structural element.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권6호
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• pp.247-253
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• 2003

A novel finite element mesh regeneration method is presented for 3D shape optimization of electromagnetic devices. The method has its theoretical basis in the structural deformation of an elastic body. When the shape of the electromagnetic devices changes during the optimization process, a proper 3D finite element mesh can be easily obtained using the method from the initial mesh. For real engineering problems, the method guarantees a smooth shape with proper mesh quality, and maintains the same mesh topology as the initial mesh. Application of the optimum design of an electromagnetic shielding plate shows the effectiveness of the presented method.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.127-130
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• 2002

Vibration analysis of rotating blade is the main purpose of the present study. In this study, general formulation is performed for rotating shell structures including the centrifugal force, Coriolis acceleration and initial twist. Furthermore, simplified equations are derived for the case of an open cylindrical shell. Based on the concept of degenerated shell element with the Reisser-Mindlin's assumptions, the finite element method is adopted for solving the problems. In addition, it is investigated the effect of the stacking sequence of the composites on the vibration characteristics of the blade. The results are summarized for the various parameters such as the speed of rotation and pre-twist of the blade. Also, present results are compared with the previous works and experimental data.

• 한국생산제조학회지
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• 제18권3호
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• pp.321-327
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• 2009

This paper studied the influences of the main design parameter-the expansion angle and the material properties of the self-expansion anterior cruciate ligament fixation device on the contact condition with the bone and the initial stability of the device. Using finite element analysis, the stress distributions of the ring part of the device and the wall of the bone tunnel were calculated. And the micro-migration of the device by the pull-out force was calculated. From the analysis results, it was found that when designing the self-expansion type anterior cruciate ligament fixation device, it is desirable to use the material having higher Young's modulus and to design the fixation device that all wedges uniformly maintain contact with bone to obtain initial stability after operation.

• Design & Manufacturing
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• 제6권1호
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• pp.45-51
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• 2012

The main goal of this paper is to establish an interference tolerance for determining optimal amount of clearance in the shaft-bearing system supported by radial ball bearings. The 2-D frictional contact model was employed for the FE analysis between the shaft and the inner raceway. Several examples were simulated using different material properties for the solid shaft. Efforts were focused on the deformation applied in the radial direction to select suitable bearings. The analysis results showed that the initial axial preload applied on the bearings plays a significant role to reduce bearing fatigue life. The proposed design parameters obtained by numerical simulations can approximately predict a rate of bearing life reduction as a function of shaft diameter ratio. This analysis can also be used to calculate the optimal initial radial clearance in order to obtain a shaft-bearing system design for high accuracy and long life.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.570-575
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• 2002

Servo performance of a disk drive is greatly affected by the mechanical resonance frequencies of the head gimbal assembly (HSA). It is important factor to allow broader bandwidths for servo system in improving overall drive performance. In this paper, an optimal design for ODD suspension is attempted to increase resonance frequencies in tracking direction. Initial model was designed and the design parameter was defined to the model. The mode frequency variation for the change of design parameter was observed by modal analysis using the finite element method(FEM). The sensitivity matrix was calculated from the observed data and so through sensitivity analysis, an optimized ODD suspension was designed to have the higher resonant frequency than the initial model.

• 대한기계학회논문집A
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• 제28권9호
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• pp.1337-1343
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• 2004

Shape optimization was performed to obtain a precise shape of cutouts including the internal shape of cutouts in a laminated composite plate by three dimensional modeling using solid element. Volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. It makes Tsai-Hill failure index at each element uniform in laminated composites under the predetermined volume a designer requires. Shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study; (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminate composite, (2) The optimal shapes of the various load conditions and cutouts were obtained, (3) The maximum Tsai-Hill failure indices of the optimal shapes were remarkably reduced comparing with those of the initial shapes.