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Andrew P.F. Little

Bio: Andrew P.F. Little is an academic researcher from University of Portsmouth. The author has contributed to research in topics: Hydrostatic pressure & Buckling. The author has an hindex of 9, co-authored 22 publications receiving 198 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors describe experimental tests carried out on three ring-stiffened cones that were tested to destruction under external hydrostatic pressure, and provide a design chart using the results obtained from these three vessels, together with the results of six other vessels obtained from other tests.

33 citations

Journal ArticleDOI
01 Jun 2011-Strain
TL;DR: In this article, an experimental and an analytical investigation into the collapse of 44 circular cylindrical composite tubes under external hydrostatic pressure was carried out using a simple solution for isotropic materials, namely a well-known formula by ‘von Mises’.
Abstract: This paper describes an experimental and an analytical investigation into the collapse of 44 circular cylindrical composite tubes under external hydrostatic pressure. The results for 22 of these tubes were from a previous investigation and the results for a further 22 models are reported for the first time in this paper. The investigations concentrated on fibre-reinforced plastic tube specimens made from a mixture of three carbon and two E-glass fibre layers. The lay-up was 0°/ 90°/0°/90°/0; the carbon fibres were laid lengthwise (0°) and the E-glass fibres circumferentially (90°). The theoretical investigations were carried out using a simple solution for isotropic materials, namely a well-known formula by ‘von Mises’. The previous investigation also used a numerical solution based on ANSYS, but this was found to be rather disappointing. The experimental investigations showed that the composite specimens behaved similarly to isotropic materials previously tested, in that the short vessels collapsed through axisymmetric deformation while the longer tubes collapsed through non-symmetric bifurcation buckling. Furthermore, it was discovered that the specimens failed at changes of the composite lay-up due to the manufacturing process of these specimens. These changes seem to be the weak points of the specimens. For the theoretical investigations, two different types of material properties were used to analyse the composite. These were calculated properties derived from the properties of the single layers given by the manufacturer and also the experimentally obtained properties. Two different approaches were chosen for the investigation of the theoretical buckling pressures, of the previously analysed models, namely a program called ‘MisesNP’, based on a well-known formula by von Mises for single-layer isotropic materials, and two finite element analyses using the famous computer package called ‘ANSYS’. These latter analyses simulated the composite with a single-layer orthotrophic element (Shell93) and also with a multi-layer element (Shell99). The results from Shell93 and Shell99 agreed with each other but, in general, their predictions were higher than the analytical solution by von Mises. The von Mises solution agreed better than the finite element solutions for the longer vessels, which collapsed by elastic instability, particularly when the experimentally obtained material properties were used. Thus, it was concluded that the results obtained from the finite element analyses predicted ‘questionable’ buckling pressures. The report provides design charts by all approaches and material types, which allow the possibility of obtaining a ‘plastic knockdown factor’ for these vessels. The theoretical buckling pressures obtained using the computer programs MisesNP or ANSYS can then be divided by the plastic knockdown factor obtained from the design charts, to give the predicted buckling pressures. It is not known whether or not this method can be used for the design of very large vessels.

32 citations

Journal ArticleDOI
TL;DR: In this article, a carbon fiber corrugated circular cylinder was tested to destuction under external hydrostatic pressure, where the structure was modelled with several orthotropic axisymmetric thin-walled shell elements.

23 citations

01 Jan 2008
TL;DR: In this paper, the buckling of twelve thin-walled geometrically imperfect tubes, which were tested to destruction under uniform external hydrostatic pressure, was reported. But the theoretical analyses agreed with each other, they did not agree with the experimental data for the shorter tubes; this was because the shorter tube collapsed by inelastic instability due to initial geometrical imperfections of the tubes.
Abstract: The paper reports on the buckling of twelve thin-walled geometrically imperfect tubes, which were tested to destruction under uniform external hydrostatic pressure. The paper also reports on other similar tests to destruction, carried out on a large number of geometrically imperfect tubes. Theoretical studies were also carried out with well-known analytical solutions, together with a numerical solution using a finite element computer package, namely ANSYS. Whereas the theoretical analyses agreed with each other, they did not agree with the experimental data for the shorter tubes; this was because the shorter tubes collapsed by inelastic instability due to initial geometrical imperfections of the tubes. Exact analysis of slightly geometrically imperfect tubes, with random distribution has so far defied reliable theoretical solutions. However, the paper presents a design chart, which can cater for these geometrical imperfections. The design chart may also be suitable for large vessels such as submarines, off-shore drilling rigs, silos, etc. Circular cylinders under external pressure, often appear in the form of submarine pressure hulls, torpedoes, off-shore drilling rigs, silos, tunnels, immersed tubes, rockets, medical equipment, food cans, etc. Such vessels are good for resisting internal or external pressure, however under uniform external pressure they can collapse at a fraction of the pressure that will cause failure under internal pressure. Failure of these vessels under uniform external pressure is called non-symmetric bifurcation buckling or shell instability [1,2,3]. To improve the resistance of these vessels to the effects of uniform external pressure, the vessels are usually stiffened by ring stiffeners spaced at near equal distances apart. If, however, the ring stiffeners are not strong enough, the entire flank of the vessel can collapse bodily by a mode called general instability. Another mode of failure is known as axisymmetric deformation, where the cylinder implodes axisymmetrically, so that its cross-section keeps its circular form while collapsing. In this study, we will be concerned with elastic and inelastic shell instability; as such vessels can collapse at pressures of a fraction of that which cause the vessels to fail under internal

17 citations

Journal ArticleDOI
TL;DR: A system that uses a combination of techniques to suggest weld requirements for ships’ parts is proposed, which has distinguished between various parts, and programs have been generated to validate the approaches used.
Abstract: A system that uses a combination of techniques to suggest weld requirements for ships’ parts is proposed. These suggestions are evaluated, decisions are made and then weld parameters are sent to a program generator. New image capture methods are being combined with a decision-making system that uses multiple parallel artificial intelligence (AI) techniques. A pattern recognition system recognises shipbuilding parts using shape contour information. Fourier descriptors provide information and neural networks make decisions about shapes. The system has distinguished between various parts, and programs have been generated to validate the approaches used. The system has recently been improved by pre-processing using a simple and accurate corner finder in an edge-detected image.

17 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the eigenvalue buckling of functionally graded graphene platelets (GPLs) reinforced cylindrical shells consisting of multiple layers through finite element method (FEM) was determined by modified Halpin-Tsai model and rule of mixture.

130 citations

Journal ArticleDOI
22 Feb 2019-Sensors
TL;DR: This work verifies the state-of-the-art as it currently applies to eight digital domains: Autonomous vehicles and robotics; artificial intelligence; big data; virtual reality, augmented and mixed reality; internet of things; the cloud and edge computing; digital security; and 3D printing and additive engineering.
Abstract: Although maritime transport is the backbone of world commerce, its digitalization lags significantly behind when we consider some basic facts. This work verifies the state-of-the-art as it currently applies to eight digital domains: Autonomous vehicles and robotics; artificial intelligence; big data; virtual reality, augmented and mixed reality; internet of things; the cloud and edge computing; digital security; and 3D printing and additive engineering. It also provides insight into each of the three sectors into which this industry has been divided: Ship design and shipbuilding; shipping; and ports. The work, based on a systematic literature review, demonstrates that there are domains on which almost no formal study has been done thus far and concludes that there are major areas that require attention in terms of research. It also illustrates the increasing interest on the subject, arising from the necessity of raising the maritime transport industry to the same level of digitalization as other industries.

93 citations

Journal ArticleDOI
TL;DR: In this paper, a non-linear finite element model based on the arc length method was developed to evaluate the damage and failure in carbon fiber reinforced epoxy filament wound composite tubes.

76 citations