• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.280-289
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• 2005

A single degree of freedom system and transmissibility are key concepts in many problems of vibration isolation. In order to apply this approach, however, several assumptions must be satisfied, which are often not realistic. For examples, in practical systems, vibration transmissions at multi-point with multi-degree of freedom(translational and rotational DOF) take place and mobilities or impedances of receiver structures cannot be ignored any more especially over high frequency range. Therefore, a multi-dimensional treatment is required for accurate estimation of dynamic behavior of the system. In this paper, an approach using vibrational power flow is introduced to deal with analysis of multi-dimensional vibration isolation system in a more practical way and in aspects of vibration isolations and vibration path analysis. Procedures of this approach and some results of research for vibrational power path analysis with rotational terms included are presented. Difficulties in this method are also discussed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.4
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• pp.475-484
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• 2000

In this paper, new additional nonconforming modes for the improvement of bending behavior in the distorted 8 node hexahedral element and their effective modification method are studied. The rotational degrees of freedom are introduced by using a functional in which the rotations are independent variables. In an element formulation, the same interpolations are used in displacement and rotation fields, but nonconforming modes we applied only in displacement fields. To verify the developed element various numerical tests are carried out and test results show good behavior.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.360-362
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• 2006

This paper proposes a new track-following control method using disturbance observer with the freedom of gain and frequency adaptation in optical disk drive system. Recent ODDs use smaller track pits, higher rotation speed and broader rotational speed variations to increase the data capacity and data transfer rate. This cause the degradation of track-following performance by increasing the disturbance of the rotary system. In this paper, we discussed on a DOB structure that efficiently attenuate the disturbance without effecting the overall feedback loop characteristics on CLV type ODD which uses a higher and broader range of rotational speed. DOB structure uses two band pass filter. We analyzed the track-following performance sensitivity on rotational frequency variance and gain changes. This analysis is done on a computer simulation environment and actual ODD product.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.185-191
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• 2001

In many papers, the powertrain system generally has been madeled as one-dimensional torque model. One-dimensional powertrain model may calculate the torque correctly but it does not consider the non-rotational degrees-of-freedom of the powertrain components and the interaction of these degrees-of-freedom with the vehicle body frame and suspension. To consider the non-rotational degrees of freedom, the differential is modeled as a three-dimensional rigid body in this paper. A constant velocity joint is newly formulated and a relative constraint is also formulated to model the motion transfer due to gear ratio of the differential. Implementing the proposed powertrain system in the multibody model, more detail dynamic responses can be obtained. Obtained outputs such as reaction torques on the constant velocity joint and reaction forces on the rack can be useful data in the design of a powertrain.

• Journal of Korean Association for Spatial Structures
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• v.4 no.4 s.14
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• pp.85-89
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• 2004

A frame element embedded normal to a shear wall or slab (shell element) is common in the structural systems. In that case there is a need for a membrane or shell element to have a normal rotation degree of freedom at each node in order to have a good result of stresses. Even if Many other people studied this area, All man, Cook and Sabir are representative investigators in this area. In this research paper, Sabir's methods of vertex rotation stiffness matrix in a membrane element are studied. New stiffness of vertex rotation are proposed by taking advantage of beam stiffness theory. Rectangular elements stiffness with rotational degree of freedom are compared in accuracy ratio each other.

• Structural Engineering and Mechanics
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• v.54 no.4
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• pp.711-723
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• 2015

This study investigates the identification of added mass and its location in the glass fiber reinforced polymer (GFRP) beam structures. The main emphasis of this paper is to ascertain the importance of inclusion of rotational degrees of freedom (dofs) in the introduction of added mass or damage identification. Two identification indices that include the rotational dofs have been introduced in this paper: the modal force index (MFI) and the modal rotational curvature index (MRCI). The MFI amplifies damage signature using undamaged numerical stiffness matrix which is related to changes in the altered mode shapes from the original mode shapes. The MRCI is obtained by using a higher derivative of rotational mode shapes. Experimental and numerical results are compared with the existing methods leading to a conclusion that the contributions of the rotational modes play a key role in the identification of added mass. The authors believe that the similar results are likely in the case of damage identification also.

• Journal of Korean Association for Spatial Structures
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• v.5 no.3 s.17
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• pp.7-13
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• 2005

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.234-241
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• 1999

In this study, an improved 8-node flat shell element is presented for the analysis of shell structure, by combining 8-node membrane element with drilling degree-of-freedom and 8-node plate bending element based on the recently presented technique. Firstly, 8-node membrane element designated as CLM8 is presented in this paper. The element has drilling degree-of.freedom in addition to transitional degree-of-freedom. Therefore the element possesses 3 degrees-of-freedom per each node which as well as the improvement of the element behavior, permits an easy connection to other element with rotational degree-of -freedom. Secondly. 8-node flat shell element was composed by adding 8-node Mindlin plate bending element to the membrane element. The behavior of the introduced plate bending element is further improved by combined use of nonconforming displacement modes, selectively reduced integration scheme and assumed shear strain fields. The element passes in the patch test, doesn't show spurious mechanism and doesn't produce shear locking phenomena. Finally, Numerical examples are presented to show the performance of flat shell element developed in the present study.

• Journal of KSNVE
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• v.5 no.4
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• pp.503-514
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• 1995

In the case of performing experimental modal analysis(EMA) and finite- element analysis(EFA) for a whole structure of automotive body that is composed of many complex parts, a trouble may arise from the calculation time, the capacity of memory in computers and the experimental conditions, etc. In this paper, for the vibrational analysis of automotive body model, the efficient modal synthesis method by means of dividing the whole structure into two parts and performing EMA and FEA for each part is studied. In addition, the method based on Lagrange interpolation is proposed for approximating rotational degrees-of-freedom information and linking FEA with EMA. In result, by measuring translational degrees-of-freedom information of only few points and adopting only few modes, the linking method based on Lagrange interpolation turned out to be efficient and accurate in the low frequency range.

• Journal of the Korean Ceramic Society
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• v.44 no.8
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• pp.412-418
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• 2007

The atomic scale details of the melting of solid argon were monitored with the aid of molecular dynamics simulations. The potential energy distribution is substantially disturbed by an increase in the interatomic distance and the random of set distance from the lattice points, with increasing temperature. The potential energy barriers between the lattice points decrease in magnitude with the temperature. Eventually, at the melting point, these barriers can be overcome by atoms that are excited with the entropy gain acquired when the atoms obtain rotational freedom in their atomic motion, and the rotational freedom leads to the collapse of the crystal structure. Furthermore, it was found that the surface of crystals plays an important role in the melting process: the surface eliminates the barrier for the nucleation of the liquid phase and facilitates the melting process. Moreover, the atomic structure of the surface varies with increasing temperature, first via surface roughening and then, before the bulk melts, via surface melting.