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1 - 10 of 28
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(2001)Journal ArticleThe March 2001 issue of MARENSA’s newsletter, Seaspace, carried the following report: ‘It is understood that HMAS Brisbane and HMAS Anzac competed recently in a sharp sprint over a three-mile course. Anzac had hoped that a quick engagement of gas turbine power would get them first to the finish line, but Brisbane’s 35-year-old boilers and steam turbines responded promptly to full throttle and the old girl showed she still had an unequalled turn of speed. It has been reported that she reached 32 knots on one minute from a standing start.’ Having no experience with the acceleration of naval vessels, reaching 32 knots in one minute from a standing start sounded very quick to me. With interest aroused, I pulled out my copy of Lackenby’s (1952) paper and did the following calculations to check whether the claim was reasonable:
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(1998)Journal ArticleA recent publication says that the primary spelling of the word for the depth of water required to float a ship is draught, with draft as the secondary spelling. A survey of thirty practising naval architects was made to check the claim, and found that a large majority of Australian-educated naval architects spell it draft. The overall results are interesting and are given here.
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(1998)Journal ArticleThe two types of marine hydrometer commonly used by naval architects and surveyors measure two distinct, but related, properties. The properties have different units and are used for different purposes. Some users may not be aware of the two types of hydrometer, the properties measured, or the errors which can significantly affect the end result. The relationships between the measured properties are discussed, together with the specific applications of the two types of hydrometer. The conversion of measurements made on one type of hydrometer to the other type is given, with examples of the conversions. Application of the principles presented here will prevent confusion and ensure the use, rather than abuse, of the two types of marine hydrometer.
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(2001)Journal ArticleThe influence of fore-and-aft asymmetry of a ship is known to be ignored in the classic thin-ship theory for resistance. In the current work, a more sophisticated approach is utilized in which the sinkage and trim are accounted for within the framework of the same theory. It is shown that the enhanced computer program correctly predicts that vessels with the centre of buoyancy forward of midships suffer a greater sinkage. In addition, the trim is relatively more by the bow. Finally, it is demonstrated that the inclusion of the effects of sinkage and trim in the analysis results in a slightly increased resistance for vessels with the centre of buoyancy forward of midships, in keeping with the experimental evidence.
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(2008)Journal ArticleAbstract This paper demonstrates the application of a new multiaxial creep damage model developed by the authors to predict the failure time of components made of service aged 2.25%Cr-1%Mo, 0.5%Cr-0.5%Mo-0.25%V low alloy steels, titanium and nickel-based superalloys. The model accounts for the tertiary creep behaviour and assumes the creep damage is related to the internal energy absorbed by the material. The authors argue that the model is the most appropriate for characterizing gross creep damage from a macroscopic point of view because it takes into accounts both the multiaxial internal deformation and loading. The verification and application of the model are demonstrated by applying it to the Bridgman notched bars for which the experimental data are available. The predicted failure times by the model are compared with the experimental results and those obtained from the reference stress method. The results show that the proposed model is capable of predicting failure times of the components made of the above-mentioned materials with an accuracy of 2.2% or better. Also, it is shown that the model predicts the creep failure times of the components more accurately than the reference stress method.
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(2008)Journal ArticleAbstract. Boilers in power, refinery and chemical processing plants contain extensive range of tube bends. Tube bends are manufactured by bending a straight-section tube. As a result, the cross-section of a tube bend becomes oval. Using the finite element analysis (FEA) and artificial neural network (ANN), the paper presents the relationships between the plastic collapse pressures and tube bend dimensions with various degrees of ovality. It is found that as ovality increases the plastic collapse pressure decreases. Also, the reduction of plastic collapse pressure with ovality is small for a thick tube bend when compared with that for a thin tube bend.
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(2014)Journal ArticlePull-through failure of bolted joints in composites is due to the relatively low through-thickness properties of laminated materials. Recently it has been identified that pull-through failure also plays an important role in the ultimate bearing load and total energy absorption of bolted joints, especially under dynamic conditions. It has been previously found that bolted joints loaded in bearing exhibit rate sensitivity whereas bolts loaded in pull-through experience very little sensitivity, for nearly identical joint configurations. The primary focus of this paper was to use explicit finite element simulation of pull-through failure to shed light on discrepancies between experimentally observed rate sensitivity for seemingly similar tests. The paper uses the stacked-shell modelling approach to efficiently model the interaction of delamination and ply failure under the complex dynamic load state. The results of the simulation indicated that the properties of the interface susceptible to loading rate sensitivity, Mode I and II strain energy release rates (SERR), did not have a great effect on the overall joint response; despite the prevalence of delamination during the failure process. A weak relationship between Mode II SERR and joint response was discovered which was consistent with experimental observations.
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(2002)Journal ArticleStriations and roughness on workpiece surfaces produced by abrasive waterjet (AWJ) have been the most persistent problems that stand in the way of wider applications of the technology in industry. This paper presents the an experimental investigation on the impact of using nozzle oscillation cutting technique in minimising or reducing these AWJ cut surface irregularities. The technique was used for cutting ductile materials, i.e. mild steel and aluminium, at various traverse speeds, oscillation angles and frequencies of oscillation. The results show that by oscillating the nozzle during cutting, the improvement in surface finish as measured by center-line average Ra can be obtained by as much as 30%.
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Optimization of Cutting Conditions for Single Pass Turning Operations Using a Deterministic Approach(2002)Journal ArticleAn optimization analysis, strategy and CAM software for the selection of economic cutting conditions in single pass turning operations are presented using a deterministic approach. The optimization is based on criteria typified by the maximum production rate and includes a host of practical constraints. It is shown that the deterministic optimization approach involving mathematical analyses of constrained economic trends and graphical representation on the feed-speed domain provides a clearly defined strategy that not only provides a unique global optimum solution, but also the software that is suitable for on-line CAM applications. A numerical study has verified the developed optimization strategies and software and shown the economic benefits of using optimization
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(2001)Journal ArticleA model is presented which predicts the chip flow direction in turning operations with nose radius tools under oblique cutting conditions. Only the tool cutting edge geometry and the cutting conditions (feed and depth of cut) are required to implement the model. An experimental study has verified the chip flow model and shown that the model’s predictions are in good agreement with the experimental results.