On probabilistic aspects in the dynamic degradation of ductile materials

Dynamic loadings produce high stress waves leading to the spallation of ductile materials such as aluminum, copper, magnesium or tantalum. The main mechanism used herein to explain the change of the number of cavities with the stress rate is nucleation inhibition, as induced by the growth of already nucleated cavities. The dependence of the spall strength and critical time with the loading rate is investigated in the framework of a probabilistic model. The present approach, which explains previous experimental findings on the strain-rate dependence of the spall strength, is applied to analyze experimental data on tantalum.Comment: 28 pages, 13 figures, 3 table

Superconducting electromagnetic launch system for civil aircraft

This paper considers the feasibility of different superconducting technologies for electromagnetic launch (EML) to assist civil aircraft take-off. EML has the potential of reducing the required runway length by increasing aircraft acceleration. Expensive airport extensions to face constant air traffic growth could be avoided by allowing large aircraft to operate from short runways at small airports. The new system positively affects total aircraft noise and exhaust emissions near airports and improves overall aircraft efficiency through reducing engine design constraints. Superconducting Linear Synchronous Motors (SCLSMs) can be exploited to deliver the required take-off thrust with electromagnetic performance that cannot be easily achieved by conventional electrical machines. The sizing procedure of a SCLSM able to launch A320 in weight is presented. Electromagnetic and thermal aspects of the machine are taken into account including the modelling of ac losses in superconductors and thermal insulation. The metallic high temperature superconductor (HTS) magnesium diboride (MgB2) is used and operated at 20 K, the boiling temperature of liquid hydrogen. With modern manufacturing technology, multifilament MgB2 wires appear to be the most cost-effective solution for this application. Finally the impact of the cryocooler efficiency on the machine performance is evaluated

Thermal design of linear induction and synchronous motor for electromagnetic launch of civil aircraft

The engine size of modern passenger transport aircraft is principally determined by take-off conditions, since initial acceleration requires maximum engine power. An elec¬tromagnetic launch (EML) system could provide some or all of the energy required at takeoff so that the aircraft engine power requirement and fuel consumption may be significantly reduced. So far, EML for aircraft has been adopted only for military applications to replace steam catapults on the deck of aircraft carriers. This paper will describe the potential application of EML to propel civil aircraft on the runways of modern air¬ports. A comparison of synchronous and asynchronous electrical motor systems designed to launch an A320-200 sized aircraft is presented. The paper also describes a solution of the transient heat transfer problem applied to the conductive components of EML systems

Electromagnetic launch systems for civil aircraft assisted take-off

This paper considers the feasibility of different technologies for an electromagnetic launcher to assist civil aircraft take-off. This method is investigated to reduce the power required from the engines during initial acceleration. Assisted launch has the potential of reducing the required runway length, reducing noise near airports and improving overall aircraft efficiency through reducing engine thrust requirements. The research compares two possible linear motor topologies which may be efficaciously used for this application. The comparison is made on results from both analytical and finite element analysis (FEA)

Design study and scaled experiment of induction and synchronous motor for civil application of electromagnetic aircraft launch system

The engine size of modern passenger transport aircraft is principally determined by take-off conditions, since initial acceleration requires maximum engine power. An Electromagnetic Launch (EML) system could provide some or all of the energy required at the launch stage so that the aircraft engine power requirement and fuel consumption may be significantly reduced. So far, EML for aircraft has been adopted only for military applications to replace steam catapults on the deck of aircraft carriers. This paper will describe the application of EML to propel civil aircraft on the runways of modern airports. A comparison of synchronous and asynchronous electrical motor systems designed to launch an A320-200 will be presented. The paper will present the solution of the transient heat transfer problem of EML systems and the respective design limitations of a civil aircraft launcher under rated current density. The experimental setup that will serve for future validation is introduced

Analyse et optimisation du comportement en fatigue des réservoirs d'hydrogène gazeux de type III = Analysis and optimisation of the fatigue lifetime of hydrogen high pressure tanks

National audienceLa présente étude explicite une méthode de dimensionnement d'un réservoir d'hydrogène haute pression soit 700 bar. Ce type de réservoir est composé d'un liner métallique et d'un renfort en composite. Un bon dimensionnement est nécessaire pour l'utilisation de ce type de réservoir en toute sécurité dans la mesure où des problèmes de fatigue apparaissent lorsque la structure est soumise à des hautes pressions de façon répétée

Reducing weight and fuel consumption of civil aircraft by electromagnetic launch

Electromagnetic launch systems have been proposed for military applications to accelerate jet planes on aircraft carriers. This paper proposes the implementation of similar technology to aid civil aircraft take-off, which can provide significant economic, environmental and technical benefits. Assisted launch has the potential of reducing on ground noise and emissions near airports and improving overall aircraft efficiency through reducing engine thrust requirements. This paper presents a take-off performance analysis for an Airbus A320-200 taking off with and without the assistance of the electromagnetic catapult. Assisted take-off allows for a significant reduction in take-off field length, giving more capacity with existing airport footprints and reducing the necessary footprint of new airports, which will both reduce costs and increase the number of suitable sites. The electromagnetic catapult may allow the installation of smaller engines with lower rated thrust. The consequent fuel consumption and operational cost reduction is estimated. The potential of reducing the aircraft operational costs and the runway length required make electromagnetic launch system an attractive solution to the air traffic growth in busy airports

The effects of pushback delays on airport ground movement

With the constant increase in air traffic, airports are facing capacity problems. Optimisation methods for specific airport processes are starting to be increasingly utilised by many large airports. However, many processes do happen in parallel, and maximising the potential benefits will require a more complex optimisation model, which can consider multiple processes simultaneously and take into account the detailed complexities of the processes where necessary, rather than using more abstract models. This paper focuses on one of these complexities, which is usually ignored in ground movement planning; showing the importance of the pushback process in the routing process. It investigates whether taking the pushback process into consideration can result in the prediction of delays that would otherwise pass unnoticed. Having an accurate model for the pushback process is important for this and identifying all of the delays that may occur can lead to more accurate and realistic models that can then be used in the decision making process for ground movement operations. After testing two different routing methods with a more detailed pushback process, we found that many of the delays are not predicted if the pushback process is not explicitly modelled. Having a more precise model, with accurate movements of aircraft is very important for any integrated model and will allow ground movement models to be of use in more reliable integrated decision making systems at airports. Minimising these delays can help airports increase their capacity and become more environmentally friendly

The importance of considering pushback time and arrivals when routing departures on the ground at airports

With the constant increase in air traffic, airports are facing capacity problems. Many airports are increasingly interested in utilising optimisation methods for specific airport processes. However, many such processes do happen in parallel, and maximising the potential benefits will require a complex optimisation model. A model which considers multiple processes simultaneously and the detailed complexities of the processes, rather than using more abstract models. This paper investigates how the arriving aircraft can affect the routing process and whether the pushback process can result into different types of delays. Furthermore, aircraft are routed backwards, starting from the destination in order to be at the runway on time and to respect the departure sequence. After testing our model with and without the arriving aircraft we found that arriving aircraft can indeed produce a lot of delays. Such delays would otherwise pass unnoticed as they result to departing aircraft choose different paths or pushback earlier so they be at the runway on time. Having an accurate model for the pushback process is important in order to understand in depth how the pushback process affects the other processes that happen in parallel. Furthermore, it led to more accurate and realistic model, which may assist the decision making process for ground movement operations and thereby help airports increase their capacity and become more environmentally friendly

The effects of pushback delays on airport ground movement

With the constant increase in air traffic, airports are facing capacity problems. Optimisation methods for specific airport processes are starting to be increasingly utilised by many large airports. However, many processes do happen in parallel, and maximising the potential benefits will require a more complex optimisation model, which can consider multiple processes simultaneously and take into account the detailed complexities of the processes where necessary, rather than using more abstract models. This paper focuses on one of these complexities, which is usually ignored in ground movement planning; showing the importance of the pushback process in the routing process. It investigates whether taking the pushback process into consideration can result in the prediction of delays that would otherwise pass unnoticed. Having an accurate model for the pushback process is important for this and identifying all of the delays that may occur can lead to more accurate and realistic models that can then be used in the decision making process for ground movement operations. After testing two different routing methods with a more detailed pushback process, we found that many of the delays are not predicted if the pushback process is not explicitly modelled. Having a more precise model, with accurate movements of aircraft is very important for any integrated model and will allow ground movement models to be of use in more reliable integrated decision making systems at airports. Minimising these delays can help airports increase their capacity and become more environmentally friendly