Aluminium-Lithium (Al–Li) alloys have been of interest since the 1950s when they were first used on a military aircraft. Having lithium as the main alloying element in Al alloys is attractive since (i) each 1 wt% Li reduces the density by ~3% and increases modulus by ~5%, and (ii) high strengths can be achieved by precipitation-hardening. During the 1980s, extensive research and development was carried out on alloys with high lithium contents (>2 wt%≡~8 at%) such as AA 8090 (Al 2.4 Li 1.2 Cu 0.7 Mg 0.12 Zr) (wt%). The mechanical properties of these ‘second-generation’ Al–Li alloys, however, did not match those of conventional Al (-Zn)-Mg-Cu alloys, and the lower fracture toughness of these alloys (for equivalent strengths was a particular problem. Thus, 2nd generation Al–Li alloys did not see widespread use. The experience with 2nd generation Al–Li alloys led to the development of ‘3rd generation’ alloys with lower Li contents (0.75–1.7 wt%), and some of these alloys have a better overall balance of properties, including fracture toughness, than the best available conventional Al alloys. These 3rd generation Al–Li alloys should therefore see extensive use in future civil and military aircraft. This chapter on fracture toughness and fracture modes of aerospace Al–Li alloys outlines why fracture toughness is important for aerospace structures and components, and summarises testing procedures and terminologies in regard to plane-strain and plane-stress fracture toughness. The relationships between fracture toughness/fracture modes and microstructural features such as grain morphology, constituent particles, impurity phases, matrix precipitates, grain-boundary precipitates, and grain boundary segregation, are then discussed. Proposed explanations for the low fracture toughness of 2nd generation Al–Li alloys, associated with low-energy intergranular and transgranular shear fractures, are discussed in some depth, followed by a summary of the alloy-design principles behind the development of 3rd generation Al–Li alloys with a much improved resistance to low-energy fracture modes. Quantitative data for fracture toughness of 2nd and 3rd generation Al–Li alloys in comparison with conventional Al alloys are provided, showing that 3rd generation Al–Li alloys have outstanding combinations of toughness and strength combined with reduced densities. The superior toughness of 3rd generation Al–Li alloys compared with 2nd generation alloys is reflected in the differences in fracture-surface topography and fracture path. The chapter concludes with a summary of the current and proposed uses of 3rd generation Al–Li alloys in aircraft structures and components
The structural and engineering property requirements for widespread deployment of aluminium-lithium (Al-Li) alloys in aircraft are discussed, particularly with respect to commercial transport aircraft. The development of Al-Li alloys has been driven mainly by the fact that additions of lithium to aluminium alloys lowers the density and increases the elastic modulus, thereby offering the potential of significant weight savings with respect to conventional (non-lithium containing) alloys. The first use of Al-Li alloys in aircraft goes back to the late 1950s (alloy AA 2020) and mid-1960s (alloys 1420 and 1421). These materials are referred to as the 1st generation Al-Li alloys. Subsequently there have been two major development programmes resulting in the 2nd and 3rd generation alloys. Development of the 2nd generation alloys began in the 1970s and continued through the 1980s. Attempts were made to develop families of Al-Li alloys for widespread replacement of conventional alloys. Ultimately this was unsuccessful except for ‘niche’ applications. The failure to find widespread application was associated largely with the too-high lithium contents of the alloys (typically more than 2 wt%). This resulted in serious disadvantages, including mechanical property anisotropy, low short-transverse ductility and fracture toughness, and thermal instability. Development of the 3rd generation Al-Li alloys began in the late 1980s and is ongoing. These alloys have significantly reduced lithium contents (0.75 – 1.8 wt%) and there are other important compositional changes. Silver and zinc have been added for strength, and zinc improves the corrosion resistance; and manganese is added besides zirconium, which was already present in 2nd generation alloys, to control recrystallization and texture. These differences and improved knowledge about thermomechanical processing and heat-treatment have resulted in a family of alloys with significant property advantages covering all major structural areas and applications for transport aircraft.
Most aluminium-lithium (Al–Li) alloy fatigue crack growth (FCG) data have been obtained for 2nd generation alloys, specifically under constant amplitude (CA) and constant stress ratio (CR) loading, and for long/large cracks. These data show the alloys in a favourable light, but this FCG ‘advantage’ essentially disappears under realistic flight simulation loading, and is also absent for short/small cracks. Furthermore, the FCG advantage is due to inhomogeneous plastic deformation, which has undesirable consequences for other important properties. These consequences have greatly restricted the use of 2nd generation alloys in aerospace structures. FCG data for 3rd generation Al–Li alloys are becoming more available. Many of the issues associated with 2nd generation alloys have been eliminated or greatly alleviated as a result of several changes, including reduced Li contents and innovative thermomechanical processing. Consequently, the FCG behaviour of 3rd generation alloys is more similar to that of conventional alloys. Nevertheless, the 3rd generation alloys tend to have better FCG properties than equivalent conventional alloys; and these and other improvements have already led to many aircraft applications.
Aluminium-Lithium (Al–Li) alloys have been of interest since the 1950s when they were first used on a military aircraft. Having lithium as the main alloying element in Al alloys is attractive since (i) each 1 wt% Li reduces the density by ~3% and increases modulus by ~5%, and (ii) high strengths can be achieved by precipitation-hardening. During the 1980s, extensive research and development was carried out on alloys with high lithium contents (>2 wt%≡~8 at%) such as AA 8090 (Al 2.4 Li 1.2 Cu 0.7 Mg 0.12 Zr) (wt%). The mechanical properties of these ‘second-generation’ Al–Li alloys, however, did not match those of conventional Al (-Zn)-Mg-Cu alloys, and the lower fracture toughness of these alloys (for equivalent strengths was a particular problem. Thus, 2nd generation Al–Li alloys did not see widespread use. The experience with 2nd generation Al–Li alloys led to the development of ‘3rd generation’ alloys with lower Li contents (0.75–1.7 wt%), and some of these alloys have a better overall balance of properties, including fracture toughness, than the best available conventional Al alloys. These 3rd generation Al–Li alloys should therefore see extensive use in future civil and military aircraft. This chapter on fracture toughness and fracture modes of aerospace Al–Li alloys outlines why fracture toughness is important for aerospace structures and components, and summarises testing procedures and terminologies in regard to plane-strain and plane-stress fracture toughness. The relationships between fracture toughness/fracture modes and microstructural features such as grain morphology, constituent particles, impurity phases, matrix precipitates, grain-boundary precipitates, and grain boundary segregation, are then discussed. Proposed explanations for the low fracture toughness of 2nd generation Al–Li alloys, associated with low-energy intergranular and transgranular shear fractures, are discussed in some depth, followed by a summary of the alloy-design principles behind the development of 3rd generation Al–Li alloys with a much improved resistance to low-energy fracture modes. Quantitative data for fracture toughness of 2nd and 3rd generation Al–Li alloys in comparison with conventional Al alloys are provided, showing that 3rd generation Al–Li alloys have outstanding combinations of toughness and strength combined with reduced densities. The superior toughness of 3rd generation Al–Li alloys compared with 2nd generation alloys is reflected in the differences in fracture-surface topography and fracture path. The chapter concludes with a summary of the current and proposed uses of 3rd generation Al–Li alloys in aircraft structures and components
The structural and engineering property requirements for widespread deployment of aluminium-lithium (Al-Li) alloys in aircraft are discussed, particularly with respect to commercial transport aircraft. The development of Al-Li alloys has been driven mainly by the fact that additions of lithium to aluminium alloys lowers the density and increases the elastic modulus, thereby offering the potential of significant weight savings with respect to conventional (non-lithium containing) alloys. The first use of Al-Li alloys in aircraft goes back to the late 1950s (alloy AA 2020) and mid-1960s (alloys 1420 and 1421). These materials are referred to as the 1st generation Al-Li alloys. Subsequently there have been two major development programmes resulting in the 2nd and 3rd generation alloys. Development of the 2nd generation alloys began in the 1970s and continued through the 1980s. Attempts were made to develop families of Al-Li alloys for widespread replacement of conventional alloys. Ultimately this was unsuccessful except for ‘niche’ applications. The failure to find widespread application was associated largely with the too-high lithium contents of the alloys (typically more than 2 wt%). This resulted in serious disadvantages, including mechanical property anisotropy, low short-transverse ductility and fracture toughness, and thermal instability. Development of the 3rd generation Al-Li alloys began in the late 1980s and is ongoing. These alloys have significantly reduced lithium contents (0.75 – 1.8 wt%) and there are other important compositional changes. Silver and zinc have been added for strength, and zinc improves the corrosion resistance; and manganese is added besides zirconium, which was already present in 2nd generation alloys, to control recrystallization and texture. These differences and improved knowledge about thermomechanical processing and heat-treatment have resulted in a family of alloys with significant property advantages covering all major structural areas and applications for transport aircraft.
A dynasty of high ability and great charm, the Stuarts exerted a compelling fascination over their supporters and enemies alike. First published in 1991, this title assesses the influence of the Stuart mystique on the modern political and cultural identity of Scotland. Murray Pittock traces the Stuart myth from the days of Charles I to the modern Scottish National Party, and discusses both pro- and anti-Union propaganda. He provides a unique insight into the ‘radicalism’ of Scottish Jacobitism, contrasting this ‘Jacobitisim of the Left’ with the sentimental image constructed by the Victorians. Dealing with a subject of great relevance to modern British society, this reissue provides an extensive analysis of Scottish nationhood, the Stuart cult and Jacobite ideology. It will be of great interest to students of literature, history, and Scottish culture and politics.
The study of the biological effects of foreign chemicals (whether therapeutic drugs or chemicals present at work or in the environment) interests the biologist from a number of different and complementary viewpoints. Apart from the more obvious pharmacological and toxicological interest, the experimentalist often uses foreign chemicals to produce in experimental animals disease states similar to naturally occurring diseases, so that their pathogenetic mechanisms and therapy can be studied under controlled conditions. In addition - as Claude Bernard pointed out over a century ago - foreign chemicals can be employed as instruments to analyze the most delicate vital processes; much can be learned about the physiological processes themselves by a careful study of the mechanisms by which these are altered by chemicals. The field of heme and hemoproteins offers an example of the interplay of these different approaches. Their metabolism can be altered by therapeutic drugs and other foreign chemicals and this results in a variety of biological responses that transcend the boundaries of pharmacology into the confines of clinical medi cine, genetics, toxicology, biochemistry and physiology. In this book a multidisciplinary approach to the study of heme metabolism is presented including the effect of chemicals on heme metabolism in patients, the results of experimental work in the whole animal, as well as in vitro studies.
“Watchmakers and Clockmakers of the World” is a comprehensive reference book of the most notable makers of clocks and watches in the world at the time when this book was first published. It is presented as a series of lists, each containing different information pertaining to the industry and the main companies involved in the manufacture of timepieces. Contents Include: “Conventions Abbreviations”, “List of Names with Alternative Spellings”, “List of Watch and Clockmakers”, “List of Initials and Monograms”, “List of Place Names”, “Maps”, etc. Many vintage books such as this are increasingly scarce and expensive. It is with this in mind that we are republishing this volume now in an affordable, modern, high-quality edition complete with a specially-commissioned new introduction on clockmaking.
This book examines and analyses the relationship between the RAF, the Free French Movement and the French fighter pilots in WWII. A highly significant subject, this has been ignored by academics on both sides of the Channel. This ground-breaking study will fill a significant gap in the historiography of the War. Bennett's painstaking research has unearthed primary source material in both Britain and France including Squadron records, diaries, oral histories and memoirs. In the post-war period the idea of French pilots serving with the RAF seemed anachronistic to both sides. For the French nation the desire to draw a veil over the war years helped to obscure many aspects of the past, and for the British the idea of French pilots did not accord with the myths of "the Few" to whom so much was owed. Those French pilots who served had to make daring escapes. Classed as deserters they risked court martial and execution if caught. They would play a vital role on D-Day and the battle for control of the skies which followed.
Reprint of the original, first published in 1872. The publishing house Anatiposi publishes historical books as reprints. Due to their age, these books may have missing pages or inferior quality. Our aim is to preserve these books and make them available to the public so that they do not get lost.
Originally published in 1915, this book presents a detailed guide to the Hackness dialect then 'spoken by agriculturalists and their labourers on the Wolds and in the Dales of North-Eastern and Eastern Yorkshire'. The text is divided into two main parts, with the first analysing phonetic elements of the dialect and the second examining its grammatical structure and examples of usage. A bibliography and comprehensive glossary are also included. This book will be of value to anyone with an interest in local dialects and linguistics.
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