251,569 research outputs found
Finite element formulation for linear thermoviscoelastic materials
Report presents the finite difference equations in time and finite element matrix equations in space for general linear thermovisoelastic problems. The equations are derived for a general three-dimensional body but are applicable to one- and two-dimensional configurations with minor changes
An analysis of performance estimation methods for aircraft
Measurements and analytical extrapolation validity in predicting full scale flight performance from model wind tunnel test
Magic Wavelengths for Terahertz Clock Transitions
Magic wavelengths for laser trapping of boson isotopes of alkaline-earth Sr,
Ca and Mg atoms are investigated while considering terahertz clock transitions
between the metastable triplet states. Our
calculation shows that magic wavelengths of trapping laser do exist. This
result is important because those metastable states have already been used to
realize accurate clocks in the terahertz frequency domain. Detailed discussions
for magic wavelength for terahertz clock transitions are given in this paper.Comment: 7 page
Lyapunov functions and the exact differential equation
Liapunov functions and exact differential equatio
Lyapunov functions for a class of Nth order nonlinear differential equations
Sequential development of quadratic polynomial into Liapunov function for nonlinear differential equation
Lyapunov functions from auxiliary exact differential equations
Use of auxiliary differential equations derived from nonlinear differential equations to find Lyapunov functio
Off-axis impact of unidirectional composites with cracks: Dynamic stress intensification
The dynamic response of unidirectional composites under off axis (angle loading) impact is analyzed by assuming that the composite contains an initial flaw in the matrix material. The analytical method utilizes Fourier transform for the space variable and Laplace transform for the time variable. The off axis impact is separated into two parts, one being symmetric and the other skew-symmetric with reference to the crack plane. Transient boundary conditions of normal and shear tractions are applied to a crack embedded in the matrix of the unidirectional composite. The two boundary conditions are solved independently and the results superimposed. Mathematically, these conditions reduce the problem to a system of dual integral equations which are solved in the Laplace transform plane for the transformation of the dynamic stress intensity factor. The time inversion is carried out numerically for various combinations of the material properties of the composite and the results are displayed graphically
Sudden bending of cracked laminates
A dynamic approximate laminated plate theory is developed with emphasis placed on obtaining effective solution for the crack configuration where the 1/square root of r stress singularity and the condition of plane strain are preserved. The radial distance r is measured from the crack edge. The results obtained show that the crack moment intensity tends to decrease as the crack length to laminate plate thickness is increased. Hence, a laminated plate has the desirable feature of stabilizing a through crack as it increases its length at constant load. Also, the level of the average load intensity transmitted to a through crack can be reduced by making the inner layers to be stiffer than the outer layers. The present theory, although approximate, is useful for analyzing laminate failure to crack propagation under dynamic load conditions
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