3,524 research outputs found
Optimum design of co-cured steel-composite tubular single lap joints under axial load
No full textIn this paper, an optimum design method for co-cured steel-composite tubular single lap joints under axial load is proposed based on a failure model which incorporates the nonlinear mechanical behavior of the steel adherend and the failure mode of joints such as composite adherend failure and steel adherend failure. The design parameters considered were the test temperature, the stacking sequence of the composite adherends, the thickness ratio of the steel adherend to the composite adherend, and the existence of scarf in the steel adherend. Stress analysis of the cocured steel-composite tubular single lap joints was performed considering the nonlinear mechanical behavior of the steel adherend, and the fabrication residual thermal stress and thermal degradation of the composite adherend. The method developed may be employed in the joining of hybrid composite structures such as golf clubs and automotive composite propeller shafts in which a carbon/epoxy shaft has normally been bonded to a metal shaft with epoxy adhesives
Modelling of electromagnetic excitation forces of small induction motor for vibration and noise analysis
No full textThe authors present a simple method for calculating electromagnetic excitation forces in the airgap between stator and rotor of a five horse power three-phase squirrel cage induction motor, which are significantly responsible for the noise and vibration in the high frequency range under operating conditions. The method proposed adopts the classical transformer model to represent the electromagnetic circuit in the motor and takes into account skew of the rotor slot and fluctuations of the permeance due to rotor rotations in estimating the electromagnetic excitation forces at each tooth of the stator. The effects of rotor eccentricity and slot opening on the excitation forces are then analysed. Estimated electromagnetic forces are compared with measurements obtained by placing a flux-detecting coil on a stator tooth. The capabilities of the method are illustrated
Prediction of the tensile load capability of co-cured steel-composite tubular single lap joints considering thermal degradation
No full textCo-cured joints composed of composite and steel structures are realized by the excess resin extracted during cure of composite prepreg and the coupling pressure due to residual thermal stresses generated by the difference of coefficients of thermal expansion between the two materials. Although the excess resin from the composite prepreg is less dependent on the environmental temperature compared to conventional epoxy adhesives in which rubber is added to strengthen toughness, the coupling pressure is much dependent on the environmental temperature. In this study, the tensile load capability of co-cured joints composed of carbon fiber epoxy composite and steel adherends was experimentally investigated with respect to the stacking sequence of the composite and the environmental temperature. Also, the stress distributions in the composite were calculated by finite element method, from which the failure index of the composite adherend was calculated considering thermal degradation of the composite. The co-cured steel-composite tubular single lap joint under tensile loads might be applied to hybrid structures such as golf clubs and automotive composite propeller shafts which have a conventional adhesively-bonded joint by epoxy adhesives with fillers between a carbon/epoxy shaft and a metal shaft
Manufacturing of co-cured composite aluminum shafts with compression during co-curing operation to reduce residual thermal stresses
No full textShafts made of carbon fiber composite have higher fundamental bending natural frequency when the stacking angle of fiber is close to zero from the axial direction compared to that of metals such as aluminum and steel, which is an important property for power transmission shafts. However, the small stacking angle not only reduces the torque transmission capability of composite shafts but also makes the joining of composite shafts to other materials difficult. If a shaft is made of both carbon fiber composite and metal such as aluminum, the bending natural frequency as well as the torque transmission capability of the shaft can be increased: the carbon fiber composite increases the bending natural frequency and the aluminum increases the torque transmission capability. In this paper, a hybrid shaft was manufactured by co-curing carbon fiber epoxy composite to an aluminum shaft to increase the bending natural frequency and damping without reducing the torque transmission capability of the shaft. In order to reduce the residual thermal stress at the interface of the two materials, the aluminum shaft was compressed by giving a compressive preload during co-curing operation. From the fatigue test and finite element analysis of the co-cured hybrid shafts, it was found that the compression by a preload increased the torque transmission capability of the hybrid shafts
A methodology of constructing a decision path for IT investment
No full textInformation Technology (IT) may be used for organizational efficiency, but should also be flexible to adapt to the rapidly changing competitive business environment. In competitive business circumstances, management continually asks: (1) How flexible must the firm be in investing in IT in order to meet unknown business needs in the future? At the same time, how efficient must the firm be in order to meet current business needs?; (2) How well must the firm align its business strategy with IT investment in order for it to support its strategic goals?; (3) how to construct a decision path for IT investments with respect to flexibility, efficiency and alignment between business strategy and IT investments? Although many researchers have struggled to answer these questions, they generally provide no means for incorporating these factors into the rr investment decision process. This paper suggests a method that identifies the degree of flexibility required (alpha -value), and accounts for and incorporates the alpha -value in making IT investments. The proposed method is based on a product development method called Quality Function Deployment (QFD). It will be applied to a real case of the "H-company" in Korea to validate and evaluate the proposed methodology. (C) 2000 Elsevier Science B.V. All rights reserved
Analysis of Perilune Altitude Optimal Lunar Landing Trajectory
No full textMinistry of Education, Science and
Technolog
Modeling of Electromagnetic Excitation Forces of an Induction Motor for Vibration and Noise Analysis
No full text
Modeling of Electromagnetic Excitation Forces of an Induction Motor for Vibration and Noise Analysis
No full text- …
