• Composite Materials and Engineering
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• v.3 no.3
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• pp.179-199
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• 2021

A simple solution for free vibration of cross-ply and angle-ply laminated composite plates in a thermal environment is investigated using a basic trigonometric shear deformation theory. By application of trigonometric four variable plate theory, the transverse displacement is subdivided into bending and shear components, the present theory's number of unknowns and governing equations is reduced, making it easier to use. Hamilton's Principle is extended to derive the equations of motion of the plates using Navier's double trigonometric series, a closed-form solution is obtained; the primary conclusion is that simple solution is obtained with good results accuracy when compared with previously published results, and the natural frequency will differ depending on, environment temperature, thickness ratio, and lamination angle, as well as the aspect ratio of the plate.

• Steel and Composite Structures
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• v.48 no.5
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• pp.583-597
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• 2023

This paper introduces a novel approach to multi-material topology optimization (MTO) targeting in-plane bi-directional functionally graded (IBFG) non-uniform thickness Reissner-Mindlin plates, employing an alternative active phase approach. The mathematical formulation integrates a first shear deformation theory (FSDT) to address compliance minimization as the objective function. Through an alternating active-phase algorithm in conjunction with the block Gauss-Seidel method, the study transforms a multi-phase topology optimization challenge with multi-volume fraction constraints into multiple binary phase sub-problems, each with a single volume fraction constraint. The investigation focuses on IBFG materials that incorporate adequate local bulk and shear moduli to enhance the precision of material interactions. Furthermore, the well-established mixed interpolation of tensorial components 4-node elements (MITC4) is harnessed to tackle shear-locking issues inherent in thin plate models. The study meticulously presents detailed mathematical formulations for IBFG plates in the MTO framework, underscored by numerous numerical examples demonstrating the method's efficiency and reliability.

• Steel and Composite Structures
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• v.45 no.1
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• pp.39-49
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• 2022

This research investigates a rotary disk with variable cross-section and incompressible hyperelastic material with functionally graded properties in large hyperelastic deformations. For this purpose, a power relation has been used to express the changes in cross-section and properties of hyperelastic material. So that (m) represents the changes in cross-section and (n) represents the manner of changes in material properties. The constants used for hyperelastic material have been obtained from experimental data. The obtained equations have been solved for different m, n, and (angular velocity) values, and the values of radial stresses, tangential stresses, and elongation have been compared. The results show that m and n have a significant impact on disk behavior, so the expected behavior of the disk can be obtained by an optimal selection of these two parameters.

• Advances in nano research
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• v.16 no.5
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• pp.489-500
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• 2024

This paper studies the free vibration analysis of the piezo-magneto-thermo-elastic FG nanobeam submerged in a fluid environment. The problem governed by the partial differential equations is determined by refined higher-order State Space Strain Gradient Theory (SSSGT). Hamilton's principle is applied to discretize the differential equation and transform it into a coupled Euler-Lagrange equation. Furthermore, the equations are solved analytically using Navier's solution technique to form stiffness, damping, and mass matrices. Also, the effects of nonlocal ceramic and metal parts over various parameters such as temperature, Magnetic potential and electric voltage on the free vibration are interpreted graphically. A comparison with existing published findings is performed to showcase the precision of the results.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.71-76
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• 1994

Eight singly reinforced high strength concrete beams were tested to investigate their flexural behavior. The variable is tensile steel raio. The test results are presented in terms of load-deformation behavior, ductility indexes, and cracking patterns. The flexural strengths obtained experimentally are compapred to the analytical results, and good agreements are obtained. The flexural design provisions of the ACI Building Code are found to be adequate to predict the strength of reinforced high-strength concrete beams.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.114-119
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• 1997

Natural vibration of the rotor system having multi-step cross-sections is analyzed. The rotary inertia and the shear deformation are considered. Torque is also included in order to simulate the power transmission system. The complex displacement and the variable separation are introduced. The exact solutions in uniform cross-section segment and the boundary conditions are used. Natural frequencies and mode shapes are obtained, especially the mode shapes are countinuous.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.239-243
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• 2003

A reducing bearing angle theory for bond of ribbed reinforcing bars to concrete is proposed to simulate experimental observation. Analytical expressions to determine bond strength for splitting and pullout failure are derived, where the bearing angle is a key variable. As bearing angle is reduced, splitting strength decreases and shearing strength increases. The proposed reducing bearing angle theory is effective to simulate damage of the deformed bar-concrete interface and understand bond mechanism of ribbed reinforcing steel in concrete structures.

• Structural Engineering and Mechanics
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• v.65 no.1
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• pp.111-120
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• 2018

This paper presents a new and simple solution for determining the natural frequencies of framed tube combined with shear-walls and tube-in-tube systems. The novelty of the presented approach is based on the bending moment function approximation instead of the mode shape function approximation. This novelty makes the presented solution very simpler and very shorter in the mathematical calculations process. The shear stiffness, flexural stiffness and mass per unit length of the structure are variable along the height. The effect of the structure weight on its natural frequencies is considered using a variable axial force. The effects of shear lag phenomena has been investigated on the natural frequencies of the structure. The whole structure is modeled by an equivalent non-prismatic shear-flexural cantilever beam under variable axial forces. The governing differential equation of motion is converted into a system of linear algebraic equations and the natural frequencies are calculated by determining a non-trivial solution for the system of equations. The accuracy of the proposed method is verified through several numerical examples and the results are compared with the literature.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.764-767
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• 2005

This paper deals with the flexural-torsional free vibrations of circular strip foundations with a variable breadth. The breadth of strip foundation varies with the linear functional fashion, which is symmetric about the mid-arc. Differential equations governing free vibrations of such foundations are derived, in which Winkler foundation is considered as the model of elastic soils. Effects of the rotatory and torsional inertias and shear deformation are included in the governing equations. Differential equations are numerically solved to calculate the natural frequencies. In the numerical examples, the free-free end constraint is considered. Effects of the rotatory and torsional inertias and shear parameter on the natural frequencies are reported. Parametric studies between frequency parameters and various system parameters are investigated.

• Design & Manufacturing
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• v.12 no.3
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• pp.60-65
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• 2018

The production of the automotive parts with the ultra high strength steel usually involves large amount of springback as well as fracture during the cold stamping process. Variable blank holding force(VBHF) can be used as one of the effective process parameters to reduce the springback amount with achieving better condition of formability. In this paper, VBHF with respect to the punch stroke is applied to the stamping process of the front side rear lower member for reducing the springback amount. From the analyses with constant blank holding force(CBHF), 24 kinds of VBHF conditions are utilized to investigate the springback tendency. It is noted that springback can be effectively reduced when BHF is increased near the bottom dead center because VBHF provides the tensile force to the blank with an adequate level of deformation without fracture.