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The lateral buckling analysis of cold-formed thin walled beams subjected to pure bending moments has been performed. The critical buckling loads are estimated based an optimization criteria. The estimated critical buckling stresses are compared with the published results, they show excellent agreement. The effect of the beam length, radius and thickness of the flanges and the length of the extended open flanges, on the critical buckling stresses have been studied for several combinations of the geometric parameters of the beam. Among the three beams, the critical buckling moments for the beam with the extended open flanges are found to be the maximum. However, considering the material and manufacturing costs, beams with rounded cross section are efficient in resisting the buckling loads. [ABSTRACT FROM AUTHOR]

Abstract: The newly developed p-M diagram provides a means for readily evaluating the collapse and/or buckling load of pressure equipment with external flaws simultaneously subjected to internal pressure, p and external bending moment, M due to earthquake, etc. In this paper, some FEAs for large diameter vessels with an external flaw were conducted under (1) pure external bending moment, and (2) subjected simultaneously to both internal pressure and external bending moment, in order to determine the plastic collapse load by applying the twice-elastic slope (TES) as recommended by the ASME and to determine the buckling load. The p-M line adopted in the Ibaraki FFS rule based on the measured yield stress indicates that the safety margin for the TES loads at the LTA is about 1.2–1.8, and 1.5–2.0 for the buckling loads. The Ibaraki FFS rule that prevents buckling by applying Donnell''s equation of FS=2 can assure adequate levels of integrity and safety. [Copyright &y& Elsevier]

Abstract: In finite element methods that are based on position and slope coordinates, a representation of axial and bending deformation by means of an elastic line approach has become popular. Such beam and plate formulations based on the so-called absolute nodal coordinate formulation have not yet been verified sufficiently enough with respect to analytical results or classical nonlinear rod theories. Examining the existing planar absolute nodal coordinate element, which uses a curvature proportional bending strain expression, it turns out that the deformation does not fully agree with the solution of the geometrically exact theory and, even more serious, the normal force is incorrect. A correction based on the classical ideas of the extensible elastica and geometrically exact theories is applied and a consistent strain energy and bending moment relations are derived. The strain energy of the solid finite element formulation of the absolute nodal coordinate beam is based on the St. Venant–Kirchhoff material: therefore, the strain energy is derived for the latter case and compared to classical nonlinear rod theories. The error in the original absolute nodal coordinate formulation is documented by numerical examples. The numerical example of a large deformation cantilever beam shows that the normal force is incorrect when using the previous approach, while a perfect agreement between the absolute nodal coordinate formulation and the extensible elastica can be gained when applying the proposed modifications. The numerical examples show a very good agreement of reference analytical and numerical solutions with the solutions of the proposed beam formulation for the case of large deformation pre-curved static and dynamic problems, including buckling and eigenvalue analysis. The resulting beam formulation does not employ rotational degrees of freedom and therefore has advantages compared to classical beam elements regarding energy-momentum conservation. [Copyright &y& Elsevier]

The trend for aeroengines with increasing thrust capacities requires the development of shaft technology to deal with this greater power transmission, while still restricting their dimensions and weight. Thin-walled designs can assist in achieving this objective, but are limited by their torsional collapse behaviour. By improving the understanding of the torsional buckling behaviour of shafts, this will enable improved shaft designs able to deal with the increase load capacities required. Until recently the prediction of buckling failures of such thin-walled shafts was by empirical and theoretical equations, which are, in general, unnecessarily conservative. A previous publication described the development and validation of an accurate and versatile finite element-based analysis technique for predicting the torsional buckling behaviour of thin-walled shafts. Although for a typical aeroengine drive shaft the dominant loading mode, under normal conditions, is torsion, aeroengine drive shafts will also experience bending and axial loading. The aim of this paper is to prove that the previously developed finite element buckling methodology can be used for buckling analyses of shafts under combined load situations. This paper presents validation cases for which experimental test results are compared with the results of finite element analyses, under various loading modes; it shows that the behaviour of shafts under combined loads can be accurately predicted using the finite element method. [ABSTRACT FROM AUTHOR]