Non-Linear Buckling Analysis of Axially Loaded Column with Non-Prismatic I-Section

In order to use material efficiently, non-prismatic column sections are frequently employed. Tapered-web column cross-sections are commonly used, and design guides of such sections are available. In this study, various web-and-flange-tapered column sections were analysed numerically using finite element method to obtain each buckling load assuming the material as elastic-perfectly plastic material. For each non-prismatic column, the analysis was also performed assuming the column is prismatic using average cross-section with the same length and boundary conditions. Buckling load of the prismatic columns were obtained using equation provided by AISC 360-16. This study proposes a multiplier that can be applied to the buckling load of a prismatic column with an average cross-section to acquire the buckling load of the corresponding non-prismatic column. The multiplier proposed in this study depends on three variables, namely the depth tapered ratio, width tapered ratio, and slenderness ratio of the prismatic section. The equation that uses those three variables to obtain the multiplier is obtained using regression of the finite element results with a coefficient of determination of 0.96

Abatement of particulate-laden SO2 in tapered bubble column with internals

The performance of particulate-laden SO2 scrubbing in a modified tapered bubble column with internals is reported in this article. The presence of particles improved the particulate-laden SO2 removal efficiency to about 15% that was elucidated by the facilitated adsorptive mass transport. Experimentation revealed that nearly 100% removal efficiency of particulate-laden SO2 was achievable without any additives or pretreatment under certain operating condition of the scrubber. An empirical correlation was developed to predict the performance of the modified tapered scrubber. Experimental values fitted excellently well with the predicted values through the correlation (within ±5% deviation). The performance of the modified tapered bubble scrubber with column internals has been found to be better than a tapered bubble column without any internals

A Nestable Tapered Column Concept for Large Space Structures

A structural element concept is described which permits achievement of weight critical payloads for space shuttle. These columns are highly efficient structural members which could be the basic building elements for very large, space truss structures. Parametric results are presented which show that untapered cylindrical columns result in volume limited payloads on the space shuttle and that nestable, tapered columns easily eliminate this problem. It is recognized that the tapered column concept belongs to a class of structures which must be assembled in orbit. However, analytical results are presented which indicate that the gain in the amount of structure placed in orbit per launch, is great enough that such a concept should be considered in future systems studies of very large space structures

Tapered laminate designs for new non-crimp fabric architectures

Non-Crimp Fabric (NCF) materials are now available in a range of areal weights and layer architectures, including 0/45, 0/−45, 45/−45 and 0/90, which correspond to the standard ply orientations employed in traditional UD material lay-ups. The benefit of NCF material is generally associated with increased deposition rate, but this advantage may be offset by reduced design freedoms when a specific form of mechanical coupling behaviour is required, layer terminations must be introduced and/or thermal warping distortion eliminated. This article investigates the extent to which new NCF architectures can be tailored to achieve warp free tapered laminates with mechanical Extension-Shearing Bending-Twisting coupling, by single axis (longitudinal) deposition of all ply angles; thus avoiding ply discontinuities that may be introduce in large component manufacture. Lamination parameter design spaces are used to demonstrate the extent of the feasible solutions both before and after applying a laminate tapering scheme

A Two-Ply Termination Strategy For Mechanically Coupled Tapered Laminates

Tapered designs are currently certified only for balanced and symmetric laminate construction, despite the severe design constraint that 1 angle-ply termination requires a further 3 angle-ply terminations: two terminations to maintain balanced construction and a further two terminations to maintain symmetry. This constraint is often violated in practice, leading to localised thermal warping; the effects of which have yet to be quantified.<p></p> An obvious, but somewhat controversial strategy for ‘thin laminate’ designs, with traditional uni-directional (UD) material, is to adopt unbalanced and/or nonsymmetric stacking sequence configurations to fully exploit the available design space, particularly where tapered designs are a requirement. This extended design space has previously been shown to contain warp-free laminates with either fully uncoupled mechanical properties or with Extension-Shearing and/or BendingTwisting coupling behaviour.<p></p> Extension-Shearing coupling, which arises in unbalanced construction, can be exploited to produce bending-twisting deformation in aircraft wing-box structures when top and bottom skins have identical bias fibre alignment, but equally, this can be eliminated with opposing bias fibre alignment. Bending-Twisting coupling, which is generally present in symmetric laminate construction, results in weaker compression buckling strength compared to the equivalent fully uncoupled laminate (with matching stiffness properties), but with potentially stronger shear buckling strength.<p></p> Recent studies on Extension-Shearing and Bending-Twisting coupled laminates have provided useful insight into the available design space for tapered laminates with single angle-ply or cross-ply terminations. Similar tailoring strategies are now applied to unconventional tapered laminate designs (i.e. those free from the ubiquitous symmetric and balanced, or un-balanced, design constraint) with two-ply terminations, to investigate the extent to which angleply layers can be terminated without introducing Extension-Shearing coupling, or the extent to which angle- and cross-ply combinations can be terminated to tailor or maintain Extension-Shearing throughout the tapered laminate. Consideration is also given to the potential effectiveness of introducing tailored mechanical coupling through ply terminations, e.g. to induce bending-twisting coupling in a wing-tip or winglet, using Extension-Shearing coupling at the laminate level, whilst maintaining fully uncoupled laminate behaviour in the tapered skins elsewhere in the wing-box

Lightweight structural columns

Lightweight half-lengths of columns for truss structures are described. The columns are adapted for nestable storage and transport to facilitate fabrication of large area truss structures at a remote site and particularly adaptable for space applications

Broadband light coupling to dielectric slot waveguides with tapered plasmonic nanoantennas

We propose and theoretically verify an efficient mechanism of broadband coupling between incident light and on-chip dielectric slot waveguide by employing a tapered plasmonic nanoantenna. Nanoantenna receives free space radiation and couples it to a dielectric slot waveguide with the efficiency of up to 20% in a broad spectral range, having a small footprint as compared with the currently used narrowband dielectric grating couplers. We argue that the frequency selective properties of such nanoantennas also allow for using them as ultrasmall on-chip multiplexer/demultiplexer devices

Advanced optimal extraction for the Spitzer/IRS

We present new advances in the spectral extraction of point-like sources adapted to the Infrared Spectrograph onboard the Spitzer Space Telescope. For the first time, we created a super-sampled point spread function of the low-resolution modules. We describe how to use the point spread function to perform optimal extraction of a single source and of multiple sources within the slit. We also examine the case of the optimal extraction of one or several sources with a complex background. The new algorithms are gathered in a plugin called Adopt which is part of the SMART data analysis software.Comment: Accepted for publication in PAS

Numerical investigation of controlling interfacial instabilities in non-standard Hele-Shaw configurations

Viscous fingering experiments in Hele-Shaw cells lead to striking pattern formations which have been the subject of intense focus among the physics and applied mathematics community for many years. In recent times, much attention has been devoted to devising strategies for controlling such patterns and reducing the growth of the interfacial fingers. We continue this research by reporting on numerical simulations, based on the level set method, of a generalised Hele-Shaw model for which the geometry of the Hele-Shaw cell is altered. First, we investigate how imposing constant and time-dependent injection rates in a Hele-Shaw cell that is either standard, tapered or rotating can be used to reduce the development of viscous fingering when an inviscid fluid is injected into a viscous fluid over a finite time period. We perform a series of numerical experiments comparing the effectiveness of each strategy to determine how these non-standard Hele-Shaw configurations influence the morphological features of the inviscid-viscous fluid interface. Tapering plates in either converging or diverging directions leads to reduced metrics of viscous fingering at the final time when compared to the standard parallel configuration, especially with carefully chosen injection rates; for the rotating plate case, the effect is even more dramatic, with sufficiently large rotation rates completely stabilising the interface. Next, we illustrate how the number of non-splitting fingers can be controlled by injecting the inviscid fluid at a time-dependent rate while increasing the gap between the plates. Simulations compare well with previous experimental results for various injection rates and geometric configurations. Further, we demonstrate how the fully nonlinear dynamics of the problem affect the number of fingers that emerge and how well this number agrees with predictions from linear stability analysis