Hirakazu Kasuya

Buckling Strength of Composite Laminated Plates under Compressive Load.

Because of their high specific strength and stiffness, fiber-reinforced plastics have been used as structural members in various fields, and hence analysis of thin laminated structures is important. Postbuckling behaviors of thin laminated plates under uniaxial compression have been discussed by many researchers. However, little research has been performed on the secondary buckling phenomenon for thin laminated plate which occurs with further increase of load. In this paper, the stability condition of CFRP cross-ply laminated plates under uniaxial compression which are simply supported along four edges is determined, using the second variation of total potential energy. The necessity of secondary buckling is proven analytically, and the effects of various factors, such as number of layers, deflection pattern and average axial shortening, are clarified.

Postbuckling Stability Analysis of Composite Laminated Flat Plates with Initial Deflection under Biaxial Compression

Postbuckling Stability Analysis of Composite Laminated Flat Plates with Initial Deflection under Biaxial Compression Keiichi Nemoto1, Hirakazu Kasuya2, Hisao Kikugawa3 and Tooru Kohiga4, 1Department of Aerospace Engineering, The Yokohama Rubber Co., Ltd., Hiratsuka 2548601 2Department of Prime Mover Engineering, School of Engineering, Tokai University, Hiratsuka 2591292 3Department of Biomedical Engineering, School of Engineering, Tokai University, Hiratsuka 2591292 4Course of Mechanical Engineering, Graduate School of Engineering, Tokai University, Hiratsuka 2591292

Noncontact guide system for traveling elastic steel plates: vibration control performance for different guideway shapes

We have developed a noncontact guide system for a high-speed traveling elastic steel plate in which electromagnetic forces are applied by actuators at the edges of the plate to control its position. Recently, we have been examining a noncontact guide system, in which one of the loops of a belt-shaped thin steel plate is supported by a pulley, and another loop is guided without contact using electromagnets. It was confirmed experimentally that the loop shape of the thin steel plate changes with increasing traveling speed when no control is carried out. In this study, a basic examination of the technique for forming a guideway using electromagnets, in which the change in the uncontrolled loop shape is considered, was carried out. By comparing the results for guideways with several different shapes, the effect of the guideway shape on the vibration suppression performance of the steel plate was discussed experimentally. As a result, it was confirmed that the vibration suppression performance of the steel plate can be improved by adjusting the shape of the noncontact guide system that uses electromagnets to conform with that of the loop of the uncontrolled steel plate.

Electromagnetic levitation control system for a thin steel plate: optimal placement of permanent magnets for levitation assist using genetic algorithm

For thin steel plates, which are used in many industrial products including those of the automobile industry, we have proposed a magnetic levitation control system and confirmed its realization by means of a digital control experiment. However, the use of a limited number of electromagnets cannot suppress static deflection and high-order-mode elastic vibration, which are characteristics of a flexible magnetic material. To solve this problem, we have proposed a hybrid levitation control system for the thin steel plate using the magnetic force generated by permanent magnets, which have no operational costs, in the areas where the attractive force of the electromagnets is negligible. In this study, we attempt to determine the optimal placement of permanent magnets to reduce the deflection and elastic vibration of a thin steel plate under the generated magnetic field. To verify the usefulness of optimal placement of the permanent magnets, experiments concerning elastic vibration were performed on a magnetically levitated thin steel plate. As a result, it was confirmed that the control performance was improved by the optimal placement of the permanent magnets.

Effect of Lamination Constitution on Buckling of Angle-Ply Laminated Cylindrical Shells under Bending.

Advanced fiber-reinforced composite materials have been used for structural members, because of their high specific strength and stiffness. In general, laminated cylindrical shells behave differently from isotropic and homogeneous orthotropic cylinders due to the effect of lamination constitution associated with their anisotropy and unsymmetric lamination.In this paper, the effect of lamination constitution on the buckling stress of carbon fiber/epoxy (CFRP) angle-ply laminated cylindrical shells under bending is reported. The effect of various factors, such as stacking sequence, number of layers, lamination angle, dimension of cylinders, and buckling modes, on the buckling value are analyzed by assuming the buckling patterns which satisfy the Flugge-type equilibrium equations. It is clarified that the buckling stress is significantly affected by the effect of lamination constitution.

Dynamic Response of Composite Laminated Cylindrical Shells Subjected to Periodic External Pressure.

Advanced fiber-reinforced composite materials have been used for structural members because of their high specific strength and stiffness. A study is conducted on the stability of symmetric cross-ply laminated cylindrical shells under static and periodic external pressure of short duration. The cylindrical shell can withstand an impulsive load greater than the static buckling pressure if the loading duration is very short compared with the free vibration period of the laminated cylindrical shell in the first mode. The inevitability of dynamically unstable behaviors and the effects of various factors, such as load ratio, number of layers, stacking sequence, fundamental natural frequency, driving amplitude of the vibration and dynamic unstable mode, are analytically clarified.

Dynamic Response of Composite Laminated Cylindrical Shells Subjected to Axial Step Loading.

Advanced fiber-reinforced laminated composite materials have been used for structural members because of their high specific strength and stiffness. This paper deals with the problem of dynamic stability of laminated cylindrical shells subjected to axial step loading. First, the axially symmetric motion of the shell under the loading is determined. Subsequently, certain perturbations are superimposed on this motion, and their behavior in time is investigated. The symmetric state of motion of the shell is called stable if the perturbations remain bounded. The solutions for the prebuckling motion and the perturbated motion are obtained by the use of Galerkins method. The inevitability of dynamically unstable behaviors is proved analytically and the effects of various factors such as compressive load ratio, number of layers, dynamic unstable mode and dimension of cylinder are clarified.

Buckling of laminated composite cylindrical shells under external pressure.

In general, laminated composite structures exhibit some coupling effect due to anisotropy and unsymmetric lamination. Thus, when the number of layers is low, they behave quite differently from the homogeneous orthotropic ones.In the present paper, the coupling effect on buckling pressure in the cross-ply and angle-ply laminated cylindrical shells subjected to external pressure was discussed based on the analysis by use of the Donnell-type equilibrium equations. The effects due to various factors such as stacking sequence, number of layers, lamination angle and dimension of cylinder, on the buckling pressure were clarified analytically. The principal conclusions are summarized as follows.(1) As for the effect of number of layers with equal thickness, N, the buckling pressure decreased very much when N is small in both cross-ply and angle-ply laminates because of the variation of cross-ply ratio and the coupling effect, respectively.(2) As for the effect of lamination angle, θ, in angle-ply laminates, the buckling pressure was minimum at θ=0° and maximum at θ=90° in both symmetric and antisymmetric laminates.(3) The coupling effect of laminates disappeared rapidly with an increase of the number of layers and their mechanical behavior became similar to that of homogeneous orthotropic laminates.