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Venkateswara G Rao - One of the best experts on this subject based on the ideXlab platform.
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thermal post buckling analysis of slender columns using the concept of coupled Displacement Field
2010Co-Authors: R K Gupta, Jagadish Babu Gunda, Ranga G Janardhan, Venkateswara G RaoAbstract:Thermal post-buckling analysis of columns with an axially immovable ends is studied using the Rayleigh-Ritz (R-R) method, where the admissible Displacement functions are chosen based on the concept of coupled Displacement Field (CDF) criteria. Geometric non-linearity is considered using the von-Karman strain Displacement relations of the beam. Furthermore, the Displacement Fields derived from CDF criteria are used in an intuitive formulation, where the thermal post-buckling behavior can be predicted by using two parameters namely tension developed in the column and linear buckling load. An exhaustive set of column boundary conditions are considered namely classical such as hinged-hinged, clamped-clamped, clamped-hinged and non-classical such as clamped-guided and hinged-guided. Post-buckling analysis results are presented in the form of closed form expressions, where the ratio of post-buckling load to linear buckling load parameter is expressed as a function of central amplitude of the column for all the boundary conditions considered. The amount of non-linearity predicted using the present formulations (R-R method and intuitive method) based on the concept of coupled Displacement Field (CDF) criteria shows an excellent agreement with the available literature results for both classical and non-classical boundary conditions.
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fundamental frequency for large amplitude vibrations of uniform timoshenko beams with central point concentrated mass using coupled Displacement Field method
2006Co-Authors: Venkateswara G Rao, Meera K Saheb, Ranga G JanardhanAbstract:Abstract Complex structures used in many Fields of engineering are made up of simple structural elements like beams, plates, etc. These structural elements, sometimes carry concentrated point masses at discrete points, and when subjected to severe dynamic environment tend to vibrate with large amplitudes. Both the continuum and the finite-element solutions are available in the open literature to tackle this coupled nonlinear problem, without concentrated point masses with particular emphasis on the fundamental linear and nonlinear frequencies. However, for short beams and moderately thick plates, one has to consider the effects of shear deformation and rotary inertia to evaluate their fundamental linear and nonlinear frequencies. A commonly used method for obtaining the same is the energy method, or a finite-element analogue of the same. In this paper the authors used a coupled Displacement Field method where in the number of undetermined coefficients ‘2n’ existing in the classical energy method are reduced to ‘n’, which significantly simplifies the procedure to obtain the analytical solution. The large amplitude free vibration behaviour of the most commonly used uniform shear flexible hinged–hinged and clamped–clamped beams with central point concentrated masses is studied here. This study reveals some interesting aspects concerned with the problem considered. The numerical results in terms of the linear frequency parameter and the ratios of nonlinear to linear radian frequencies for the uniform with a central point concentrated mass are given in the digital form.
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thermal post buckling behaviour of laminated plates using a shear flexible element based on coupled Displacement Field
2003Co-Authors: Sita V Thankam, Venkateswara G Rao, Gajbir Singh, A K RathAbstract:Post buckling behaviour of rectangular laminated plates subjected to thermal loads is investigated in this paper. For this purpose, a four-node, lock-free, rectangular composite plate finite element having six degrees of freedom per node viz three translations, two bending rotations about x- and y-axes and a twist is developed. The element is based on a bicubic representation of the transverse Displacement Field. The Field descriptions for other variables are derived using equilibrium equations of strips along x- and y-axes of the plate. As a result Field descriptions involve material properties apart from the usual geometric variables. 3×3 Guass Quadrature formula is employed to compute the elemental matrices. Though an exact integration rule has been employed, the element is free of shear locking even in the extreme thin plate regimes. The effect of boundary conditions, aspect ratio, number of layers and lay-up sequence on the post-buckling behavior is studied in detail. The numerical examples solved herein reveal the possibility of secondary bifurcations from the primary post-buckling path.
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a2 node beam element based on coupled Displacement Field for buckling analysis of curved composite beams
2001Co-Authors: Joseph Wilfred, Gajbir Singh, Venkateswara G RaoAbstract:The present paper aims to explore an alternatice interpolation strategy for the assumed Displacement Fields in the finite element buckling analysis of straigth and curved composite beams. The elemental static equilibrium equations are employed to derive the alternate interpolation polynomials for the Displacement Fields. These polynomials are coupled by means of coefficients involving the generalized co-ordinates and geometrical and material properties of the element. The proposed interpolation scheme lead to an element, which is free from spurious constraints in the Euler's limit of slender beam behaviour, that is in-extensible bending, and hence exhibits no locking. The 2-node beam element having six engineering degrees of freedom per node is developed using this coupled Displacement Field. The accuracy and convergence characteristics of the element are shown to be independent of material lay-up and slenderness ratio. To establish the consistent performance of the element, several test problems over a wide range of slenderness ratio with straigth-to-deep arch configurations of isotropic/composite materials are considered.
J C Savage - One of the best experts on this subject based on the ideXlab platform.
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Displacement Field for an edge dislocation in a layered half space
1998Co-Authors: J C SavageAbstract:The Displacement Field for an edge dislocation in an Earth model consisting of a layer welded to a half-space of different material is found in the form of a Fourier integral following the method given by Weeks et al. [1968]. There are four elementary solutions to be considered: the dislocation is either in the half-space or the layer and the Burgers vector is either parallel or perpendicular to the layer. A general two-dimensional solution for a dip-slip faulting or dike injection (arbitrary dip) can be constructed from a superposition of these elementary solutions. Surface deformations have been calculated for an edge dislocation located at the interface with Burgers vector inclined 0°, 30°, 60°, and 90° to the interface for the case where the rigidity of the layer is half of that of the half-space and the Poisson ratios are the same. Those Displacement Fields have been compared to the Displacement Fields generated by similarly situated edge dislocations in a uniform half-space. The surface Displacement Field produced by the edge dislocation in the layered half-space is very similar to that produced by an edge dislocation at a different depth in a uniform half-space. In general, a low-modulus (high-modulus) layer causes the half-space equivalent dislocation to appear shallower (deeper) than the actual dislocation in the layered half-space.
A Armigliato - One of the best experts on this subject based on the ideXlab platform.
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method for determination of the Displacement Field in patterned nanostructures by tem cbed analysis of split high order laue zone line profiles
2007Co-Authors: Alessio Spessot, Stefano Frabboni, Roberte Balboni, A ArmigliatoAbstract:Summary A method to extract accurate information on the Displacement Field distribution from split high-order Laue zones lines in a convergent-beam electron diffraction pattern of nanostructures has been developed. Starting from two-dimensional many beam dynamical simulation of HOLZ patterns, we assembled a recursive procedure to reconstruct the Displacement Field in the investigated regions of the sample, based on the best fit of a parametrized model. This recursive procedure minimizes the differences between simulated and experimental patterns, taken in strained regions, by comparing the corresponding rocking curves of a number of high-order Laue zone reflections. Due to its sensitivity to small Displacement variations along the electron beam direction, this method is able to discriminate between different models, and can be also used to map a strain Field component in the specimen. We tested this method in a series of experimental convergent-beam electron diffraction patterns, taken in a shallow trench isolation structure. The method presented here is of general validity and, in principle, it can be applied to any sample where not negligible strain gradients along the beam direction are present.
Lars Benckert - One of the best experts on this subject based on the ideXlab platform.
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measurement of dynamic crack tip Displacement Field by speckle photography and interferometry
1993Co-Authors: J M Huntley, Lars BenckertAbstract:Abstract Speckle interferometry has been used to measure the transient Displacement Field around a crack due to stress wave loading. Double exposure interferograms are recorded with a pulsed ruby laser, and correlation fringes formed by spatial filtering of the developed film. A new technique is presented for reducing the noise level in spatially filtered speckle interferograms. Independent fringe patterns, obtained from one interferogram but with the filtering aperture sampling different regions of the Fourier transform plane, are digitised by a CCD camera and combined numerically. It is demonstrated that accurate analysis of fringe patterns by the Fourier transform method can be carried out, even if no carrier fringes are present. The measurements are compared with those obtained by speckle photography. Least-squares fitting of the theoretical Displacement Field is used to calculate the stress intensity factor at the crack tip as a function of time.
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measurement of dynamic crack tip Displacement Field by speckle photography and interferometry
1992Co-Authors: J M Huntley, Lars BenckertAbstract:Measurement of Dynamic Crack Tip Displacement Field by Speckle Photography and Interferometry
Erwan Pathier - One of the best experts on this subject based on the ideXlab platform.
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coseismic Displacement Field and slip distribution of the 2005 kashmir earthquake from sar amplitude image correlation and differential interferometry
2013Co-Authors: Yajing Yan, Virginie Pinel, Emmanuel Trouve, Erwan Pathier, Jonathan Perrin, Pascale Bascou, Francois JouanneAbstract:The coseismic surface Displacement Field and slip distribution at depth due to the Kashmir earthquake (Mw = 7.6, 2005) have been analysed by different authors using subpixel correlation of synthetic aperture radar (SAR) images and optical images, teleseismic analysis, GPS measurements, as well as in situ Field measurements. In this paper, first, we use 23 sets of measurement from subpixel correlation of SAR images and differential interferometry to retrieve the 3-D coseismic surface Displacement Field. The obtained horizontal and vertical components along the fault trace are then compared, respectively, to equivalent measurements obtained from subpixel correlation of two optical ASTER images and in situ Field measurements. Second, the coseismic fault geometry parameters and slip distribution at depth are estimated. In addition to the one segment slip model as reported in previous work, a two segments slip model that better fits the surface fault break is proposed. The improvement of the two segments slip model in interpreting the measured Displacement Field is highlighted through comparison of residuals of both slip models. Taking advantage of differential interferometry measurements that provide precise and continuous information in the far Field of the fault, firstly, a wedge thrust according to Bendick et al. to the Northwest of the main rupture built on our two segments model is tested. According to the obtained results, the residual of the two segments main rupture plus wedge thrust model is slightly smaller than the residual of the two segments model to the Northwest of the Balakot-Bagh fault. Secondly, we test the sensitivity of our slip model to the presence of slip along a decollement as evidenced by Jouanne et al. through post-seismic analysis. The results indicate that the estimations of the coseismic Displacement Field and slip distribution in this paper are not significantly biased by such post-seismic Displacement and that most coseismic Displacement is located on a ∼40° NE-dipping fault, as previously reported.
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Displacement Field and slip distribution of the 2005 kashmir earthquake from sar imagery
2006Co-Authors: Erwan Pathier, Eric J Fielding, Tim J Wright, R T Walker, Barry Parsons, Scott HensleyAbstract:[1] The 8th October 2005 Kashmir Earthquake Mw 7.6 involved primarily thrust motion on a NE-dipping fault. Sub-pixel correlation of ENVISAT SAR images gives the location of the 80 km-long fault trace (within 300–800 m) and a 3D surface Displacement Field with a sub-metric accuracy covering the whole epicentral area. The slip distribution inverted using elastic dislocation models indicates that slip occurs mainly in the upper 10 km, between the cities of Muzaffarabad and Balakot. The rupture reached the surface in several places. In the hanging wall, horizontal motions show rotation from pure thrust to oblique right-lateral motion that are not observed in the footwall. A segmentation of the fault near Muzaffarabad is also suggested. North of the city of Balakot, slip decreases dramatically, but a diffuse zone of mainly vertical surface Displacements, which could be post-seismic, exists further north, where most of the aftershocks occur, aligned along the NW-SE Indus-Kohistan Seismic Zone.
