• 대한기계학회논문집A
• /
• 제21권2호
• /
• pp.288-296
• /
• 1997

Curved beam elements with two nodes based on shallow beam geometry and strain interpolations are employed in eigenvalue analysis. In these elements, the displacement interpolation functions and mass matrices are consistent with strain fields. To assess the quality of the element mass matrix in free vibration problems, several numerical experiments are performed. In these analysis, both the inconsistent mass matrices using linear displacement interpolation function and the consistent mass matrices are used to show the difference. The numerical results demonstrate that the accuracy is closely related to the property of the mass matrix as well as that of the stiffness matrix and that the mass matrix consistent with strain fields is very beneficial to eigenvalue analysis. Also, it is proved that the strain based elements are very efficient in a wide range of element aspect ratios and curvature properties.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제4권3호
• /
• pp.313-321
• /
• 2012

Vibration analysis of a thin-walled structure can be performed with a consistent mass matrix determined by the shape functions of all degrees of freedom (d.o.f.) used for construction of conventional stiffness matrix, or with a lumped mass matrix. In similar way stability of a structure can be analysed with consistent geometric stiffness matrix or geometric stiffness matrix with lumped buckling load, related only to the rotational d.o.f. Recently, the simplified mass matrix is constructed employing shape functions of in-plane displacements for plate deflection. In this paper the same approach is used for construction of simplified geometric stiffness matrix. Beam element, and triangular and rectangular plate element are considered. Application of the new geometric stiffness is illustrated in the case of simply supported beam and square plate. The same problems are solved with consistent and lumped geometric stiffness matrix, and the obtained results are compared with the analytical solution. Also, a combination of simplified and lumped geometric stiffness matrix is analysed in order to increase accuracy of stability analysis.

• Structural Engineering and Mechanics
• /
• 제7권3호
• /
• pp.259-276
• /
• 1999

An analytical solution for the shape functions of a beam segment supported on a generalized two-parameter elastic foundation is derived. The solution is general, and is not restricted to a particular range of magnitudes of the foundation parameters. The exact shape functions can be utilized to derive exact analytic expressions for the coefficients of the element stiffness matrix, work equivalent nodal forces for arbitrary transverse loads and coefficients of the consistent mass and geometrical stiffness matrices. As illustration, each distinct coefficient of the element stiffness matrix is compared with its conventional counterpart for a beam segment supported by no foundation at all for the entire range of foundation parameters.

• Journal of Mechanical Science and Technology
• /
• 제18권12호
• /
• pp.2125-2136
• /
• 2004

In this paper, a numerical application algorithm for applying the CFAM (Consistent Fluid Added Mass) matrix for a core seismic analysis is developed and applied to the 7-ducts core system to investigate the fluid effects on the dynamic characteristics and the seismic time history responses. To this end, three cases such as the in-air condition, the in-water condition without the fluid coupling terms, and the in-water condition with the fluid coupling terms are considered in this paper. From modal analysis, the core duct assemblies revealed strongly coupled out-of-phase vibration modes unlike the other cases with the fluid coupling terms considered. From the results of the seismic time history analysis, it was also verified that the fluid coupling terms in the CFAM matrix can significantly affect the impact responses and the seismic displacement responses of the ducts.

• Bulletin of the Korean Chemical Society
• /
• 제35권12호
• /
• pp.3482-3488
• /
• 2014

Matrix-induced mass bias and its effect on the accuracy of isotope ratio measurements have been examined for a quadrupole-based inductively coupled plasma-mass spectrometer (Q ICP-MS). Matrix-induced mass bias effect was directly proportional to % mass difference, and its magnitude varied for element and nebulizer flow rate. For a given element and conditions in a day, the effect was consistent. The isotope ratio of Cd106/Cd114 under $200{\mu}g\;g^{-1}$ U matrix deviated from the natural value significantly by 3.5%. When Cd 111 and Cd114 were used for the quantification of Cd with isotope dilution (ID) method, the average of differences between the calculated and measured concentrations was -0.034% for samples without matrix ($0.076{\mu}g\;g^{-1}$ to $0.21{\mu}g\;g^{-1}$ for the period of 6 months). However, the error was as large as 1.5% for samples with $200{\mu}g\;g^{-1}$ U. The error in ID caused by matrix could be larger when larger mass difference isotopes are used.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집A
• /
• pp.655-660
• /
• 2000

This paper presents the construction of consistent coefficient matrix elements for jointed structures using the reduction of flexibility and mass matrices. The reduced flexibility coefficient matrix hat little structural complexity than Guyan's stiffness matrix reduction since the only element of the original matrix, corresponding to the selected nodal degrees of freedom, contributes. The proposed method was applied to building equivalent coefficient matrices for a clamp jointed structure in finite element modal analysis of a cantilevered beam. The theoretical analysis results were compared with those experimental modal analysis, Comparison of both shows good agreement each other.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 2003년도 추계학술발표대회 요약집
• /
• pp.476.1-476.1
• /
• 2003

• 대한기계학회논문집A
• /
• 제30권1호
• /
• pp.18-25
• /
• 2006

The purpose of this research work is to demonstrate a successful application of hybrid-mixed formulation and nodeless degrees of freedom in developing a very accurate in-plane curved beam element for free vibration analysis. To resolve the numerical difficulties due to the spurious constraints, the present element, based on the Hellinger-Reissner variational principle and considering the effect of shear deformation, employed consistent stress parameters corresponding to cubic displacement polynomials with additional nodeless degrees. The stress parameters were eliminated by the stationary condition, and the nodeless degrees were condensed by Guyan Reduction. Several numerical examples indicated that the property of the mass matrix as well as that of the stiffness matrix have a great effect on the numerical performance. The element with consistent mass matrix produced best results on convergence and accuracy in the numerical analysis of Eigenvalue problems. Also, the higher-order mixed curved beam element showed a superior numerical behavior for the free vibration analyses.

• 소음진동
• /
• 제6권3호
• /
• pp.287-296
• /
• 1996

A virtual work form of flexible multibody dynamic formulation with rotary inertia has been derived. For the analysis of large flexible multibody systems, deformation modal coordinates have been employed to represent coupled motion between gross and vibrational motion. For the efficient evaluation of the entries in the mass matrix, a flexible body has been treated as a collection of mass points. The rotary inertia was generated from the consistent mass matrix in a finite element model. Deformation mode shapes were obtained from finite element analysis. Bending and twisting vibration analyses of a cantilever have been carried out to see rotary inertia effects. A space flexible robot simulation has been also carried out to show effectiveness of the proposed formulation. This formulation is effective to the model that consists of beam, plate, or shell element that contains rotational degree of freedom at the nodal point. It is also effective to the flexible body model to which a large lumped rotary inertia is attached.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2008년도 정기 학술대회
• /
• pp.190-196
• /
• 2008

The dynamical rotor system is investigated through the derivation and formulations of the dynamic equation of the rotating system in terms of both inertial and fixed frame of the system as well as quaternion. The investigation is aimed at analyzing the dynamical rotating system precession speed. The resulting equations of motion consist of the consistent mass matrix and gyroscopic matrix. The formulation shows its features and difference between its linearity and nonlinearity.