• Geomechanics and Engineering
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• 제1권2호
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• pp.121-142
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• 2009

The paper deals with the applications of spectral finite element method to the dynamic analysis of framed foundations supporting high speed machines. Comparative performance of approximate dynamic stiffness methods formulated using static stiffness and lumped or consistent or average mass matrices with the exact spectral finite element for a three dimensional Euler-Bernoulli beam element is presented. The convergence of response computed using mode superposition method with the appropriate dynamic stiffness method as the number of modes increase is illustrated. Frequency proportional discretisation level required for mode superposition and approximate dynamic stiffness methods is outlined. It is reiterated that the results of exact dynamic stiffness method are invariant with reference to the discretisation level. The Eigen-frequencies of the system are evaluated using William-Wittrick algorithm and Sturm number generation in the $LDL^T$ decomposition of the real part of the dynamic stiffness matrix, as they cannot be explicitly evaluated. Major's method for dynamic analysis of machine supporting structures is modified and the plane frames are replaced with springs of exact dynamic stiffness and dynamically flexible longitudinal frames. Results of the analysis are compared with exact values. The possible simplifications that could be introduced for a typical machine induced excitation on a framed structure are illustrated and the developed program is modified to account for dynamic constraint equations with a master slave degree of freedom (DOF) option.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.55-65
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• 2009

This study is objected by analyzing whether it is applied to the analysis model considering the track stiffness or not when the railway bridge is designed or reviewed for the dynamic stability. It is performed that the analysis model is verified by comparing the field test result with the analysis result. Also, The dynamic response of railway bridge through the existing analysis model is compared with the analysis model considered the track stiffness. In addition, it is performed by analyzing the model considering the stiffness of concrete track. Therefore, this study is suggested that the design of railway bridge apply to the existing analysis model considering the mass of track and the dynamic stability review of railway bridge apply to it considered the stiffness & mass of track. Also, it is suggested that the stiffness of concrete slab on the bridge must consider when it is designed or checked over the dynamic stability.

• 한국정밀공학회지
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• 제16권12호
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• pp.99-108
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• 1999

A four-degree-of-freedom non-linear model with time varying mesh stiffness has been developed for the dynamic analysis of spur gear trains. The model includes a spur gear pair, two shafts, two inertias representing load and prime mover. In the model, developed several factors such as time varying mesh stiffness and damping, separation of teeth, teeth collision, various gear errors and profile modifications have been considered. Two computer programs are developed to calculate stiffness of a gear pair and transmission error and the dynamic analysis of modeled system using time integration method. Dynamic tooth and mesh forces, dynamic factors are calculated. Numerical examples have been given, which shows the time varying mesh stiffness ha a significant effect upon the dynamic tooth force and torsional vibrations.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.249-255
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• 2010

Ballasted track is under the circumstance of repetition of deterioration and recovery. Track deterioration is presented as track irregularity or settlement, and dynamic force subjected to track is one of major cause of the deterioration. The dynamic force is determined from the dynamic interaction between track and vehicle. Rail-pad stiffness is one of the factor affects track dynamic property. In this study, the relationship between rail-pad stiffness and track settlement was investigated. Dynamic forces according to various rail-pad stiffness was obtained from the dynamic vehicle-track interaction analysis using DARTS-NL. Track settlement was calculated by substitution the dynamic forces into various formulas for track settlement. From the result of analysis, it was known that the track settlement is increased about 6% when the rail-pad stiffness rise about twice. And this result leads that there is only a little relationship between rail-pad stiffness and track settlement.

• 한국생산제조학회지
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• 제21권1호
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• pp.130-136
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• 2012

Dynamic as well as static and geometric design parameters such as inertia, tooth profile, backlash and clearance can be directly considered via multi-body dynamic analysis along with contact analysis. However, it is time consuming to use finite elements for the consideration of the tooth flexibility in the multi-body dynamic analysis of gears. A computationally efficient procedure, so called, Gear Stiffness Module, is suggested to resolve this calculation time issue. The characteristics of gear tooth compliance are discussed and rotational stiffness element concept for the Gear Stiffness Module is presented. Transmission error analyses for a spur gear system are carried out to validate the reliability and efficiency of the module. Compared with the finite element model, the Gear Stiffness Module yields considerably similar results and takes only 3% of calculation time.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.760-763
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• 2003

This study proposed the analysis of damage defection due to the change of the stiffness of structure by using the original and modified dynamic characteristics. The method is applied to examples of a cantilever and 3 degree of freedom by modifying the stiffness. The predicted damage detections are in good agreement with these from the structural reanalysis using the modified stiffness.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.994-995
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• 2014

Supporting stiffness of seats is an important component affecting dynamic characteristics cognized by a passenger. To analyze dynamic characteristic of a seat for vehicles operating on various road conditions, the seat vibration from road irregularity should be understood and compared. In this study, the seat is analyzed as distributed supporting system. The dynamic stiffness is measured using masses. The characteristic of the seats is analyzed by measuring distributed dynamic stiffness. The distributed dynamic stiffness of the seat is estimated on various locations and the effects of each component such as spatial distribution, compression level and vibration amplitude are analyzed. The influence of seat cover, elastic support and flexible polyurethane foam on the measured stiffness was analyzed.

• 한국전산구조공학회논문집
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• 제23권2호
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• pp.165-173
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• 2010

본 논문에서는 비동질 탄성무한공간에 대한 비례경계유한요소법의 동적강도행렬을 해석적으로 유도하였다. 해석영역의 비동질성은 비동질파라메터를 지수로 하는 멱함수로 고려하였다. 동적강도행렬은 진동수영역에서 다항식으로 점근전개한 후, 방사조건을 만족시키도록 하여 각 다항식의 계수를 구하는 과정을 통하여 유도되었다. 얻어진 동적강도행렬의 타당성을 검증하기 위해 정확해가 알려져 있는 대표적인 문제에 대하여 비동질파라메터의 값을 변화시키면서 수치해석을 수행하였다. 그 결과 유도된 동적강도행렬이 비동질공간에 대한 특성을 적절하게 반영하는 것으로 나타났다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.102-106
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• 2003

An experimental modal analysis and dynamic stiffness evaluation of a moving body structure of a high speed machining center are presented in this paper. The natural frequencies and corresponding modes, and dynamic compliance of a moving body structure of high speed machining center are investigated by using F.E.M., hydraulic exciter test, and impulse hammer test. The lowest three natural frequencies were found to be 56.6 Hz, 112.7 Hz, and 142.7 Hz by FEA respectively, while those were 55 Hz, 112 Hz, 131 Hz by experimental analysis. Furthermore, both computed and measured absolute dynamic compliances of the moving body structure in iso-direction showed good agreement especially at the first two mode frequencies. With our experimental data, the dynamic characteristics of the machining center can be exploited to get a new development of structural dynamic design and modification.

• 한국공작기계학회논문집
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• 제12권6호
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• pp.50-55
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• 2003

This study proposed the analysis of damage detection due to the change of the stiffness of structure by using the original and modified dynamic characteristics. The present approach allows the use of composite data which consist of eigenvalues and eigenvectors. The suggested method is applied to examples of a cantilever and 3 degree of freedom system by modifying the stiffness. The predicted damage detections are in good agreement with these from the structural reanalysis using the modified stiffness.