Buckling load reduction for stiffened panels due to cutouts in ribs

In aerospace structures it is common to find stiffened panels with transverse supporting structures, e.g. wing ribs or fuselage frames. Incorporating cutouts into these supporting structures to allow the stringers to pass through freely considerably reduces the buckling load of the panels. It is shown that a minor modification in the fabrication of the stiffened panel gives most of the advantages of cutouts while still giving a buckling load close to that of a panel with no cutouts

Design of structures by a splitting method

A simplified method for the design of multi-spar wing boxes is presented. In typical multi-spar wing boxes the spars divide the boxes into cells. In the method presented these are analyzed individually, with adjacent cells taking their share of the stiffnesses of the common spar wall. This splitting method yields a design method that is computationally much quicker than designing a complete wing box, because each cell is considered separately from the others, except for linking between their design variables. The critical buckling load factor of the assembled structure when designed in this way will usually exceed the design load factor and otherwise will be equal to it, i.e. the design is guaranteed to be conservative

Buckling and vibration of stiffened panels or single plates with clamped ends

An efficient method for the buckling and vibration analysis of plates or stiffened panels with clamped ends is presented. The method uses Lagrangian multipliers to couple sinusoidal modes with appropriate half-wavelengths of response, thereby enforcing the end conditions at discrete point supports. Clamped ends can usually be modelled accurately using only a few point supports, while arguments from symmetry often enable some of the required end conditions to be satisfied without explicitly applying constraints. In such cases few half-wavelengths are needed to obtain excellent accuracy. Solutions obtained for the simple limiting case of single plates are exact or within 1% of the classical or other reported solutions. Solutions obtained for stiffened panels are in close agreement with those obtained using finite element analysis

Addressing decision making for remanufacturing operations and design-for-remanufacture

Remanufacturing is a process of returning a used product to at least original equipment manufacturer original performance specification from the customers' perspective and giving the resultant product a warranty that is at least equal to that of a newly manufactured equivalent. This paper explains the need to combine ecological concerns and economic growth and the significance of remanufacturing in this. Using the experience of an international aero-engine manufacturer it discusses the impact of the need for sustainable manufacturing on organisational business models. It explains some key decision-making issues that hinder remanufacturing and suggests effective solutions. It presents a peer-validated, high-level design guideline to assist decision-making in design in order to support remanufacturing. The design guide was developed in the UK through the analysis of selections of products during case studies and workshops involving remanufacturing and conventional manufacturing practitioners as well as academics. It is one of the initial stages in the development of a robust design for remanufacture guideline

Gravitation and inertia; a rearrangement of vacuum in gravity

We address the gravitation and inertia in the framework of 'general gauge principle', which accounts for 'gravitation gauge group' generated by hidden local internal symmetry implemented on the flat space. We connect this group to nonlinear realization of the Lie group of 'distortion' of local internal properties of six-dimensional flat space, which is assumed as a toy model underlying four-dimensional Minkowski space. The agreement between proposed gravitational theory and available observational verifications is satisfactory. We construct relativistic field theory of inertia and derive the relativistic law of inertia. This theory furnishes justification for introduction of the Principle of Equivalence. We address the rearrangement of vacuum state in gravity resulting from these ideas.Comment: 17 pages, no figures, revtex4, Accepted for publication in Astrophys. Space Sc

Optimum design and testing of a postbuckled stiffened panel

The efficient, industrially used, linear elastic preliminary design software VICONOPT is employed to design a stiffened panel with a post-buckled reserve of strength. The initial buckling mode is a local skin mode in longitudinal compression with allowance being made for the effects of an initial overall imperfection. The resulting panel has been analyzed using the non-linear FE package ABAQUS and four laboratory specimens have been tested to failure. The similarity of the experimental failure with the VICONOPT and ABAQUS predictions suggests that VICONOPT can give a satisfactory preliminary design. While neither model matches completely the boundary conditions found in a real aircraft compression panel, it is suggested that the VICONOPT model may be a better representation than either the ABAQUS model or the experimental tests

Constraining spacetime torsion with LAGEOS

We compute the corrections to the orbital Lense-Thirring effect (or frame-dragging) in the presence of spacetime torsion. We derive the equations of motion of a test body in the gravitational field of a rotating axisymmetric massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi. We calculate the secular variations of the longitudes of the node and of the pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be used to constrain torsion parameters. We report the experimental constraints obtained using both the nodes and perigee measurements of the orbital Lense-Thirring effect. This makes LAGEOS and Gravity Probe B (GPB) complementary frame-dragging and torsion experiments, since they constrain three different combinations of torsion parameters

Evidence for short range orbital order in paramagnetic insulating (Al,V)_2O_3

The local structure of (Al_0.06V_0.94)_2O_3 in the paramagnetic insulating (PI) and antiferromagnetically ordered insulating (AFI) phase has been investigated using hard and soft x-ray absorption techniques. It is shown that: 1) on a local scale, the symmetry of the vanadium sites in both the PI and the AFI phase is the same; and 2) the vanadium 3d - oxygen 2p hybridization, as gauged by the oxygen 1s absorption edge, is the same for both phases, but distinctly different from the paramagnetic metallic phase of pure V_2O_3. These findings can be understood in the context of a recently proposed model which relates the long range monoclinic distortion of the antiferromagnetically ordered state to orbital ordering, if orbital short range order in the PI phase is assumed. The measured anisotropy of the x-ray absorption spectra is discussed in relation to spin-polarized density functional calculations.Comment: 8 pages, 5 figure