A two-dimensional flexible channel model of the vocal folds coupled with an unsteady one-dimensional flow model is presented for an analysis of the mechanism of phonation. The vocal fold is approximated by springs and dampers distributed in the main flow direction that are enveloped with an elastic cover. In order to approximate three-dimensional collision of the vocal folds using the two-dimensional model, threshold values for the glottal width are introduced. The numerical results show that the collision plays an important role in speech sound, especially for higher resonant frequency components, because it causes the source sound to include high-frequency components.
We have performed a simulation analysis of the pseudoelastic behavior of a NiTi shape memory alloy wire placed in air, subjected to tensile cyclic loads over a range of low strain rates. Thermomechanical interactions, such as energy dissipation, latent heat and heat transfer, are accounted for in a one-dimensional thermomechanical model based on the phase interaction energy function which was introduced in our previous analyses. The interaction energy function was numerically determined so as to make an analytical constitutive relationship fit available experimental stress-strain curves. Numerical results show that the loading strain rate is influential on changes in the stress-strain characteristics and the temperature of the wire. Good agreement between experiment and analysis was obtained, and the effectiveness of the thermomechanical model proposed here has been confirmed.
In our previous work we proposed a new concept of the control system in which vibrations of a partially magnetized thin beam are actively suppressed using electromagnetic forces induced by an electric current conducted through the beam. In this experimental study we will demonstrate the effectiveness of the electromagnetic force which plays a major role in our new vibration control system. As a partially magnetized beam is not available at the present moment, a magnetic field generated by a permanent magnet is used to control the motion of a thin elastic beam on which an electric current is conducted through an electric wire glued onto the beam's surface across its breadth. The objective of the present study is to examine if an actually induced electromagnetic force acting on the electric wire is effective in suppressing the beam's vibrations. A feedforward control analysis of the corresponding experiment is performed to confirm experimental results.
A Shear Actuated Fiber Composite (SAFC) concept is developed that may find application in structural actuation and health monitoring tasks. The fabrication aspects of SAFC are briefly discussed. A uniform field model is employed to study electro-elastic behavior of the SAFC. The composite actuator is modeled as a general laminate having seven layers, and the effective properties are evaluated further using shear deformation lamination theory. The geometric parameters such as fiber volume fraction, fiber thickness, and fiber orientation are considered, and their influence on the characteristics of SAFC is analyzed. It is observed that a higher fiber thickness may provide better shear actuation capability for the SAFC actuator; but conformability requirements bring a constraint on fiber thickness that needs to be optimized. A fiber volume content of 85—95% appears to provide a design envelope for the SAFC actuator. SAFC has shown a promising feature of simultaneously coupling both transverse shear strains, if the poled PZT fibers are oriented directionally. Therefore, SAFC can be used as a torsional actuator for developing electro-elastically tailored smart laminated or sandwich structures. It is also expected that the SAFC actuator may provide a better solution for active aeroelastic control applications, where torsion mode is critical.
The influence of actuator damage on the performance of closed loop vibration control is
numerically evaluated. Debonding is considered a damage mode and finite element
procedures are subsequently developed to introduce its effect on system matrices, namely
elastic and electro-elastic stiffness. A simple modelling scheme for multiple debonding is
proposed, which can also idealize multiple delamination in the host laminate.
Debonding in actuators in general has reduced their load carrying appreciably as
well as vibration control characteristics. Therefore, incorporating such a damage
mode in the control design as an uncertainty parameter would help to realize a
damage-tolerant active vibration control system. It is interesting to note that
debonding in actuators has influenced both active damping and active stiffening
effects.
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