• Computers and Concrete
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• v.34 no.5
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• pp.591-609
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• 2024

Two novel laminate constitutive equations (LCE) for the static analysis of anisotropic shells are presented and implemented in this work. The LCE, developed for both two-dimensional (2D) and three-dimensional (3D) analysis, are more general than those obtained using the Kirchhoff-Love (K-L) equations, Reissner-Minddlin (R-M) type models, refined 2D/3D models, and some general anisotropic doubly-curved shell theories. Our study presents a 2D LCE model that accounts for classical mechanical couplings based on previous models plus additional couplings including extensional-twisting-shearing, extensional-twisting, Gauss bending-twisting-shearing, and Gauss bending-shearing mechanical couplings related to the third fundamental, or Gauss tensor. Moreover, the developed 3D LCE model accounts for all 2D mechanical couplings cited above plus additional mechanical couplings due to the section warping tensor, which arises from the stretching-through-the-thickness variable. These mechanical couplings are pertinent to the optimal design of a composite and are often disregarded in various static and dynamic analysis studies. Neglecting these new mechanical couplings in the design and analysis of laminated composite shells (LCS) can result in significant errors, from both physical and mechanical viewpoint. As such, we recommend employing new complete constitutive relations that integrate these pertinent mechanical couplings for the aforementioned study. Based on our analysis of the impact of additional couplings, we have developed several mathematical formulations that address several challenges encountered in laminated shell theory. As we increase the shell's thickness ratio, our research examines the effects of these couplings on mechanical behavior, buckling shape, critical buckling pressure, and failure analysis through computational modelling and various tests. The examination of the thickness ratio of composite shells illustrates the contrast between our newly developed LCE and some existing LCE as the shells increase in thickness.

• Journal of Mechanical Science and Technology
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• v.16 no.4
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• pp.512-521
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• 2002

The flap-lag-torsion coupled aeroelastic behavior of a hingeless rotor blade with composite flexures in hovering flight has been investigated by using the finite element method. The quasisteady strip theory with dynamic inflow effects is used to obtain the aerodynamic loads acting on the blade. The governing differential equations of motion undergoing moderately large displacements and rotations are derived using the Hamilton's principle. The flexures used in the present model are composed of two composite plates which are rigidly attached together. The lead-lag flexure is located inboard of the flap flexure. A mixed warping model that combines the St. Versant torsion and the Vlasov torsion is developed to describe the twist behavior of the composite flexure. Numerical simulations are carried out to correlate the present results with experimental test data and also to identify the effects of structural couplings of the composite flexures on the aeroelastic stability of the blade. The prediction results agree well with other experimental data. The effects of elastic couplings such as pitch-flap, pitch-lag, and flap-lag couplings on the stability behavior of the composite blades are also investigated.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.379-384
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• 2008

This paper examines permanent magnet eddy current couplings and brakes. Specifically, the effect of permanent magnet magnetization patterns on the magnetic field and force production is investigated. The eddy current couplings and brakes employ high energy-product neodymium-iron-boron (NdFeB) permanent magnets that act on iron-backed copper drums to provide torque transfer from motor to load without mechanical contact. A 2-dimensional finite element modeling is performed to predict the electromagnetic behavior and the torque-speed characteristics of permanent magnet type eddy current couplings and brakes under constant speed operation.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.215-218
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• 1999

A general structural model, which is an extension of the Vlassov theory, is developed for the analysis of composite rotor blades with elastic couplings. A comprehensive analysis applicable to both thick-and thin-walled composite beams, which can have either open- or closed profile is formulated. The theory accounts for the effects of elastic couplings, shell wall thickness, and transverse shear deformations. A semi-complementary energy functional is used to account for the shear stress distribution in the shell wall. The bending and torsion related warpings and the shear correction factors are obtained in closed form as part of the analysis. The resulting first order shear deformation theory describes the beam kinematics in terms of the axial, flap and lag bending, flap and lag shear, torsion and torsion-warping deformations. The theory is validated against experimental results for various cross-section beams with elastic couplings.

• Journal of Magnetics
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• v.21 no.1
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• pp.110-114
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• 2016

Magnetic couplings are widely used in various industrial applications because they can transmit magnetic force without any mechanical contact. In addition, linear couplings have many advantages. For example, they do not need to convert rotary motion to linear motion. This paper shows an analytical analysis of tubular type linear magnetic couplings (TLMCs) with a Halbach array magnetized permanent magnet (PM). An analytical method for magnetic fields owing to PMs is performed by using magnetic vector potential as well as Poisson and Laplace equations. Then, the magnetic force is calculated by using the Maxwell stress tensor. The analytical analysis results were compared with finite element method (FEM) results. In addition, we predicted the magnetic force characteristic according to design parameters such as the iron core thickness, inner PM thickness to -outer PM thickness ratio, PM segment ratio of the axial magnetized PM segment and radial magnetized PM segment, and various pole numbers.

• Journal of Magnetics
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• v.20 no.3
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• pp.273-283
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• 2015

In this study, we propose an analytical model for studying magnetic fields in radial-flux permanent-magnet eddy-current couplings by considering the effects of slots and iron-core protrusions on the eddy currents. We focus on the analytical prediction of the air-gap field by considering the influence of eddy currents induced in conducting bars. In the proposed model, the permanent magnet region is treated as the source of a time-varying magnetic field and the moving-conductor eddy current problem is solved based on the resolution of time-harmonic Helmholtz equations. The spatial harmonics in the air gap and in slots, as well as the time harmonics are all considered in the analytical calculation. Based on the proposed field model, the electromagnetic torque is computed by using the Maxwell stress tensor method. Nonlinear finite element analysis is performed to validate the analytical model. The proposed model can be used for permanent-magnet eddy-current couplings with any slot-pole combination.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.04a
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• pp.165-172
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• 1993

A non-linear mathematical model has been developed for the dynamic analysis of the reactor internals. The model includes a lumped mass and stiffness with non-linear members such as gap-spring. As hydrodynamic couplings have also been considered in the model, the effect of fluid/structure interaction between internals components due to their immersion in a confining fluid can be studied for the dynamic response analysis. The reactor internals responses for seismic and pipe break excitations have been calculated for the case of with-and without-hydrodynamic couplings.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.354-362
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• 1995

The finite element modeling is used to study the buckling and postbuckling behavior of composite laminates with an embedded delamination. Degenerated shell element and rigid beam element are utilized for the finite element modeling. In the nonlinear finite element formulation, the updated Lagrangian description method based on the second Piola-Kirchhoff stress tensor and the Green strain tensor is used. The buckling and postbuckling behavior of composite laminates with a delamination are investigated for various delamination sizes, stacking sequences, and boundary conditions. It is shown that the buckling load and postbuckling behavior of composite laminates depend on the buckling model which is determined by the delamination size, stacking sequence and boundary condition. Also, results show that introduction of couplings can reduce greatly the buckling load.

• Structural Engineering and Mechanics
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• v.62 no.1
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• pp.33-42
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• 2017

We present in this paper a finite element formulation for nonlinear torsional analysis of 3D beams with arbitrary composite cross-sections. Since the proposed formulation employs a continuum mechanics based beam element with kinematics enriched by the extended St. Venant solutions, it can precisely account higher order warping effect and its 3D couplings. We propose a numerical procedure to calculate the extended St. Venant equation and the twisting center of an arbitrary composite cross-section simultaneously. The accuracy and efficiency of the proposed formulation are thoroughly investigated through representative numerical examples.

• Tribology and Lubricants
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• v.28 no.3
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• pp.124-129
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• 2012

The prediction of fretting wear is a significant issue for the design of contacting mechanical components such as flexible couplings and splines, jointed structures and so on. In our earlier study, we developed a numerical model to predict the fretting wear using boundary element method. The developed algorithm needs experimental fretting wear coefficients and friction coefficients between two moving materials to get more reliable results. In this study, therefore, we demonstrated the measurement method of the fretting wear coefficients and friction coefficients using disk on plate tribometer with piazo actuator and gap sensor. For four different material combinations, the fretting wear coefficients and friction coefficients are acquired through the fretting wear experiment and the analysis of the measured values. Thess results are useful to predict the quantative fretting wear rate in the developed algorithm.