• Journal of Mechanical Science and Technology
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• 제18권11호
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• pp.1891-1899
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• 2004

The characteristics of dynamic systems subjected to multiple linear constraints are determined by considering the constrained effects. Although there have been many researches to investigate the dynamic characteristics of constrained systems, most of them depend on numerical analysis like Lagrange multipliers method. In 1992, Udwadia and Kalaba presented an explicit form to describe the motion for constrained discrete systems. Starting from the method, this study determines the dynamic characteristics of the systems to have positive semidefinite mass matrix and the continuous systems. And this study presents a closed form to calculate frequency response matrix for constrained systems subjected to harmonic forces. The proposed methods that do not depend on any numerical schemes take more generalized forms than other research results.

• 오토저널
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• 제5권3호
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• pp.45-55
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• 1983

This paper discussed about Application Technique of Numerical Methods for large structure. The dynamic behaviours of a vehicle were investigated through finite element modelling. After dividing a vehicle body into three substructures, Basic Mass System was composed of 60 flexual modes which was obtained from the dynamic characteristics of each substructure using Modal Synthesis Method. Engine, transmission and rear axle, etc. were added to Basic Mass Model, consequently Full Mass System was constructed by 72 degree of freedoms. Full Mass System was analyzed over the frequency range 0.5-50.0 Hz under the loading conditions which were Stationary Gaussian Random Process. Results and discussions provided the guidelines to eliminate resonances among the parts and to improve the Ride Quality. The Absorbed Power was used as a standard to determine the Ride Quality. The RMS value of driver's vertical acceleration was obtained 0.423g from the basic model and 0.415g from the modified model.

• Structural Engineering and Mechanics
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• 제39권3호
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• pp.399-410
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• 2011

Base isolation, having quite simple contents, aims to protect the buildings from earthquake-induced damages by installing structural components having low horizontal stiffness between substructure and superstructure. In this study, an appropriate base isolation system for 2-D reinforced concrete frame is investigated. For different structural heights, the structural systems of 2, 3 and 4 bays are modeled by applying base isolation systems and results are compared with conventional structural systems. 1999 Marmara earthquake data is used for applying the model by time history method in SAP2000 package. Results of various parameters such as base shear force, structure drift ratio, structure period and superstructure acceleration are discussed for all models.

• Interaction and multiscale mechanics
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• 제1권4호
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• pp.423-435
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• 2008

This paper employs the reproducing kernel (RK) approximation for evaluation of field theory-based incompatibility tensor in a polycrystalline plasticity simulation. The modulation patterns, which is interpreted as mimicking geometrical-type dislocation substructures, are obtained based on the proposed method. Comparisons are made using FEM and RK based approximation methods among different support sizes and other evaluation conditions of the strain gradients. It is demonstrated that the evolution of the modulation patterns needs to be accurately calculated at each time step to yield a correct physical interpretation. The effect of the higher order strain derivative processing zone on the predicted modulation patterns is also discussed.

• Structural Engineering and Mechanics
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• 제24권1호
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• pp.91-105
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• 2006

In this paper, post-earthquake capacity evaluation method of reinforced concrete buildings was studied. Substructure pseudo-dynamic test and static loading test of first story column in a four-story R/C building was carried out in order to investigate the validity of the evaluation method proposed in the Damage Assessment Guideline (JBDPA 2001). In pseudo-dynamic test, different levels of damage were induced in the specimens by pre-loading, and input levels of seismic motion, at which the specimens reached to the ultimate stage, were examined. From the experimental result, no significant difference in damage levels such as residual crack width between the specimens under static and pseudo-dynamic loading was found. It is shown that the seismic capacity reduction factors ${\eta}$ can provide a reasonable estimation of post-earthquake seismic capacity of R/C buildings suffered earthquakes.

• 대한기계학회논문집A
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• 제25권3호
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• pp.495-501
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• 2001

In this paper, a new technique which models the joints characteristics through reduction of DOFs of structures with joints using component mode synthesis (CMS) method is proposed. Bolt joints are modeled by mass-spring systems. Also generalized mass and stiffness matrices for this models are introduced. Because bolt joints have influence on eigenvalues of structures, exact eigenvalues from modal test are used. The results show that the behaviors of structures with bolt joints depend to a large extent on the translational DOFs and not on rotational DOFs of mass and stiffness matrices of bolts. Furthermore it is confirmed that lumped mass-spring systems as models of bolt joints are effective models considering the facts that joint characteristics converged to constant values in some iterations and eignevalues from proposed method are in good agreement with ones from modal test.

• 대한기계학회논문집A
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• 제25권4호
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• pp.555-563
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• 2001

Support dynamics are often important in rotordynamic analyses. It may well happen in real situation of machines such as centrifugal pumps or turbines operating on flexible structure. This paper presents the applications of the impedance coupling method and the improved rotor model for including the support effects on the interaction with the rotor. The impedance coupling techniques are based on the FRFs of each substructure. Its dynamic stiffness matrix can be assembled to generate the system matrix, which satisfy the constraint conditions in the connection coordinates. And, the improved rotor uses the simplified spring-mass models as support properties. The equivalent support models are directly incorporated into the finite element rotor model. To verify the suggested analytical procedures, the results are compared to those of the pump system.

• 소음진동
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• 제10권4호
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• pp.648-654
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• 2000

A procedure to determine the realizable optimal positions of rigid supports is suggested to get a maximum fundamental natural frequency. a measured frequency response function based substructure-coupling technique is used to model the supported structure. The optimization procedure carries out the eigenvalue sensitivity analysis with respect to the stiffness of supports. As a result of such stiffness optimization, the optimal rigid-support positions are shown to be determined by choosing the position of the largest stiffness. The optimally determined support conditions are verified to satisfy the eigenvalue limit theorem. To demonstrate the effectiveness of the proposed method, the optimal support positions of a plate model are investigated. Experimental results indicate that the proposed method can effectively find out the optimal support conditions of the structure just based on the measured frequency response functions without any use of numerical model of the structure.

• 한국자동차공학회논문집
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• 제17권1호
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• pp.64-71
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• 2009

The development of more safe recliners is an important issue in the automotive industry. However, the development of new recliners is costly and take much time because it is typically based on experimental evaluation using prototypes. This study presents the evaluation of rear crashworthiness for round recliner using finite element method. That reduces the number of repeating test and gives an information about stiffness. To evaluate rear crashworthiness, the FMVSS 301 simulation and pendulum impact simulation were performed. The load path on two simulations was observed and compared each other in this paper. Also stress, strain and internal energy was compared. It is attempted the tooth strength simulation using a substructure option on PAM-CRASH.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권12호
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• pp.527-531
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• 2005

Because of increasing demand for safety of the power transformer, the seismic qualification process in accordance with the standard of IEEE Std 693-1997 is essentially required by customer. Dynamic analysis method and static analysis method were used to qualify the seismic withstanding of the power transformer at high seismic level. Maximum stress was detected at the connection between the main structure and appendages, and maximum displacement was detected at the point of appendage's end tip. Load path and substructure system can be considered as important elements to prevent over stress and over displacement.