• 소성∙가공
• /
• 제6권4호
• /
• pp.279-290
• /
• 1997

The sectional forming analysis of stamping pocesses for aluminum alloy sheet metals was investigated. For the modeling of the anomalous behavior of aluminum alloy sheet. the Barlat's strain rate potential and Hill's 1990 non-quadratic yield theory with an isotropic hardening rule were employed. The rigid-viscoplastic FEM formulation which solves equilibrium equation for plane-strain stage with mesh-normal geometric constraints was derived. A new method to determine the Barlat's anisotropic coefficients was also suggested. To verify the validity of the formulation, the stretch and draw forming processes of a square cup were simulated.

• Structural Engineering and Mechanics
• /
• 제58권5호
• /
• pp.745-755
• /
• 2016

A three-dimensional finite element method is used for analysis of repairing cracks in plates with bonded composite patch in elastic and elastic plastic analysis. This study was performed in order to establish an analytical model of the J-integral for repair crack. This formulation of the J-integral to establish models of fatigue crack growth in repairing aircraft structures. The model was developed by interpolation of numerical results. The obtained results were compared with those calculated with the finite element method. It was found that our model gives a good agreement of the J-integral. The arrow shape reduces the J integral at the crack tip, which improves the repair efficiency.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제6권4호
• /
• pp.1000-1013
• /
• 2014

This paper presents some of the efforts by the authors towards numerical prediction of springing of ships. A time-domain Higher Order Boundary Element Method (HOBEM) based on cubic shape function is first presented to solve a complete second-order problem in terms of wave steepness and ship motions in a consistent manner. In order to avoid high order derivatives on the body surfaces, e.g. mj-terms, a new formulation of the Boundary Value Problem in a body-fixed coordinate system has been proposed instead of traditional formulation in inertial coordinate system. The local steady flow effects on the unsteady waves are taken into account. Double-body flow is used as the basis flow which is an appropriate approximation for ships with moderate forward speed. This numerical model was used to estimate the complete second order wave excitation of springing of a displacement ship at constant forward speeds.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
• /
• pp.53-59
• /
• 1998

A new algorithm using meshless particle method for the analysis of crack propagation problems is presented. The meshless particle method requires only a set of nodes and the description of boundaries in its formulation. The method is particulary useful for crack propagation problems due to the absence of any predefined element connectivity. Formulation procedures for the construction of displacement and shape functions are described. A numerical integration scheme and a strategy for the consideration of crack propagation are also described. Numerical examples show that the proposed method is very convenient and efficient in modeling crack problems and can guarantee the accuracy of solution in crack propagation analysis.

• 대한기계학회논문집
• /
• 제18권11호
• /
• pp.2871-2882
• /
• 1994

Two kinds of 4-node plane stress/strain finite elements are presented in this work. They are derived from the modified Hellinger-Reissner variational principle so as to employ the internal incompatible displacement and independent stress fields, or the incompatible displacement and strain fields. The introduced incompatible functions are selected to satisfy the constant strain condition. The elements are evaluated on several problems of bending and material incompressibility with regular and distorted elements. The results show that the new elements perform excellently in the calculation of deformation and stresses.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2002년도 가을 학술발표회 논문집
• /
• pp.443-450
• /
• 2002

It is known that the distribution of the active earth pressure against a translating rigid wall is not triangular, but nonlinear, due to arching effects in the backfill. In the present paper, a new formulation for calculating the active earth pressure on a rigid retaining wall undergoing horizontal translation is proposed. It takes into account the arching effects that occur in the backfill. In order to check the accuracy of the proposed formulation, the predictions from the equation are compared with both existing full-scale test results and values from existing equations. The comparisons between calculated and measured values show that the proposed equations satisfactorily predict both the earth pressure distribution and the total active earth force on the translating wall.

• Structural Engineering and Mechanics
• /
• 제36권4호
• /
• pp.421-445
• /
• 2010

In this paper the formulation of an efficient frame element applicable for nonlinear analysis of 3D reinforced concrete (RC) frames is outlined. Interaction between axial force and bending moment is considered by using the fibre element approach. Further, section warping, effect of normal and tangential forces on the torsional stiffness of section and second order geometrical nonlinearities are included in the model. The developed computer code is employed for nonlinear static analysis of RC sub-assemblages and a simple approach for extending the formulation to dynamic cases is presented. Dynamic progressive collapse assessment of RC space frames based on the alternate path method is undertaken and dynamic load factor (DLF) is estimated. Further, it is concluded that the torsional behaviour of reinforced concrete elements satisfying minimum standard requirements is not significant for the framed structures studied.

• Structural Engineering and Mechanics
• /
• 제5권6호
• /
• pp.743-754
• /
• 1997

A three-dimensional constitutive modeling for reinforced concrete is presented for finite element nonlinear analysis of reinforced concrete. The targets of interest to the authors are columns confined by lateral steel hoops, RC thin shells subjected to combined in-plane and out-of-plane actions and massive structures of three-dimensional (3D) extent in shear. The elasto-plastic and continuum fracture law is applied to pre-cracked solid concrete. For post cracking formulation, fixed multi-directional smeared crack model is adopted for RC domains of 3D geometry subjected to monotonic and reversed cyclic actions. The authors propose a new scheme of decomposing stress strain fields into sub-planes on which 2D constitutive laws can be applied. The proposed model for 3D reinforced concrete is experimentally verified in both member and structural levels under cyclic actions.

• Structural Engineering and Mechanics
• /
• 제55권4호
• /
• pp.815-837
• /
• 2015

A new family of structure-dependent integration methods is developed to enhance with desired numerical damping. This family method preserves the most important advantage of the structure-dependent integration method, which can integrate unconditional stability and explicit formulation together, and thus it is very computationally efficient. In addition, its numerical damping can be continuously controlled with a parameter. Consequently, it is best suited to solving an inertia-type problem, where the unimportant high frequency responses can be suppressed or even eliminated by the favorable numerical damping while the low frequency modes can be very accurately integrated.

• 약학회지
• /
• 제57권6호
• /
• pp.442-447
• /
• 2013

The aim of the present study was to improve commercial twice-a-day Acebrophylline formulation to once-a-day new formulation to improve patient compliances. To develop the double-layered tablet, the sustained release layer was prepared using Eudragit$^{(R)}$ L100-55 and Carnauba wax. The sustained release layer has shown delayed release rates in pH 1.2 which comparable to that of performed in pH 6.8 buffer. In the comparative pharmacokinetic study with commercialized Surfolase$^{(R)}$, the present double-layered Acebrophylline tablet has shown similar pharmacokinetic parameters of AUC, $C_{max}$ and $T_{max}$ values.