1,720,988 research outputs found
Aeroelastic response and stability analysis of composite rotor blades in forward flight
No full textThe aeroelastic phenomena of a composite rotor blade are investigated using a finite element method. The aeroelastic equations of motion of the rotor blade are formulated using a large deflection-type beam model that has no artificial restrictions on the magnitudes of displacements and rotations due to the degree of nonlinearity. The sectional elastic constants of a composite box beam including warping deformations are determined from the refined cross-sectional finite element method. The nonlinear, periodic blade steady response is obtained using a time finite clement method on full finite element equation. The aeroelastic stability of a rotor blade is investigated by linearizing the dynamics of the rotor blade about the nonlinear equilibrium position. Numerical results of the steady equilibrium deflections and the aeroelastic modal damping are presented fur various configurations of composite rotor blades and are compared with those obtained from a previously published modal analysis using a moderate deflection-type beam theory. (C) 2001 Published by Elsevier Science Ltd
TRANSITION BEHAVIOR OF DEFORMATION MODE FROM SHEARING TO LOOPING IN AL-LI SINGLE-CRYSTALS
No full textThe transition behaviour of deformation mode from particle shearing to looping has been investigated in the Al-Li alloy single crystals using optical microscopy, transmission electron microscopy and mechanical testing. The observation of slip-line morphology and of dislocation structures indicated the occurrence of a transition of deformation mode from particle shearing to bypassing by Orowan looping. The loop size measurements suggested that the critical loop size is close to the average planar particle size at the onset of the peak-ageing condition. The antiphase boundary energy is calculated to be about 0.100Jm(-2) from the analysis of this transition behaviour. This is smaller than that expected from the observed dislocation pair spacings. The similar analysis of ageing curves of polycrystals containing Zr tends to show a higher antiphase boundary energy. This is because the peak-ageing condition appears relatively rapidly owing to a bimodal size distribution of delta' particles in these crystals. The dislocation pair spacings decrease, during the early stage of ageing, with an increase in particle sizes in agreement with the theory
NONCONTACT TEMPERATURE MEASUREMENT IN MICROLITER-SIZED VOLUMES USING FLUORESCENT-LABELED DNA OLIGOMERS
No full textX112728sciescopu
STATIC AND DYNAMIC ANALYSIS OF COMPOSITE BOX BEAMS USING LARGE DEFLECTION THEORY
No full textThe static and dynamic behavior of composite box beams is investigated using a large deflection beam theory. The finite element equations of motion for beams undergoing arbitrary large displacements and rotations, but small strains, are obtained from Hamilton's principle. The importance of non-classical structural phenomena is systematically investigated for composite box beams. The sectional elastic constants including warping deformations have been determined from the refined cross-sectional finite element method. The effects of fiber orientations and stacking sequences on the static deformation and vibration characteristics have been investigated. Numerical results are compared with the previously published experimental and theoretical results. The present results are proved to be very accurate
Influence of nanobubbles on the bending of microcantilevers
No full textYoung's equation, which is commonly used for determining the contact angle of liquid drops on a solid surface, ignores the vertical component of the surface energy. Although this force is extremely small and its effect on the solid can be ignored, it plays a significant role for flexible surfaces such as microcantilevers. A gold-coated silicon microcantilever and a dodecanethiol coated silicon microcantilever were used to detect real-time formation of nanobubbles on their surfaces when exposed to air-rich water. As air nanobubbles form on the surfaces of the cantilever, the cantilever undergoes bending, and we relate this to the vertical component of surface energy in Young's equation. This implies that the vertical component of the surface tension should be considered for flexible solid surfaces, and the formation of nanobubbles should be avoided when cantilevers are used as sensors to avoid artifacts. (c) 2006 American Institute of Physics.open111721sciescopu
MODAL ANALYSIS OF MICROCANTILEVER SENSORS WITH ENVIRONMENTAL DAMPING
No full textThe vibration response of microcantilevers to simple harmonic base motion is formulated in terms of base motion plus modal responses relative to the moving base frame. Environmental damping is evaluated. The analysis gives the frequency responses of the first four modes and shows that the phase angle of each mode relative to the moving base frame is constant but that the phase angle of the absolute motion varies along the length of cantilevers. This finding is verified with experimental data. Phase changes along cantilevers depend on frequency ratios and the magnitude of environmental damping. Experimental data are used to establish damping factors, and phase angles are measured experimentally and compared with theoretical predictions. (C) 2005 American Institute of Physics.open112537sciescopu
Air plasma coupled with antibody-conjugated nanoparticles: a new weapon against cancer
No full textAmbient air plasmas have been known to kill cancer cells. To enhance selectivity we have used antibody-conjugated nanoparticles. We achieved five times enhancement of melanoma cell death over the case of the plasma alone by using an air plasma with gold nanoparticles bound to anti-FAK antibodies. Our results show that this new interdisciplinary technique has enormous potential for use as a complement to conventional therapies.X11113sciescopu
Refined aeroelastic analysis of hingeless rotor blades in hover
No full textThe aeroelastic response and stability of hingeless rotor blades in hover are investigated using both refined structural and aerodynamic models, Finite elements based on a large deflection-type beam theory are used for structural analysis, Although the strain components in the beam element are assumed to be small compared to unity, no kinematical limitations are imposed on the magnitude of displacements and rotations, A three-dimensional aerodynamic model including compressibility effect, which is a thin lifting-surface theory based on the unsteady vortex lattice method, is applied to evaluate the aerodynamic loads, A thin lifting-surface and its wake are represented by a number of the quadrilateral vortex-ring elements, The wake geometry is prescribed from the known generalized equations, numerical results of the steady-state deflections and the stability for the stiff in-plane rotor blade are presented, It is found that the three-dimensional aerodynamic tip-relief, unsteady wake dynamics, and compressibility effects, not predicted in the two-dimensional strip theory, play an important role in the hingeless rotor aeroelastic analysis in hover
Quantitative Analysis of Elasitic Properties of Al-Li Alloys Using Ultrasonic Velocity Measurement and TEM
No full text- …
