Aircraft Engineering THE MONTHLY ORGAN OF THE AERONAUTICAL ENGINEERING PROFESSION VOL XXVII No 315 MAY 1955 plants and jet pipes. The introduction of methods, of which the accuracy can be known, for combining the effects of temperature N this issue we publish the last section of the present part of gradients and non-linear stress/strain laws may in time, and with D R J. H. ARGYRIS'S 'Energy Theorems and Structural Analysis'. It due notice taken of experience in the practical field, make possible a I may not be out of place to give some indication of the reasons for reduction in such factors of ignorance as have at present to be publishing a work of this length in the form of a series of articles, combined with factors of safety. Another factor which may lead particularly as some of our readers whose first interest is not in the towards this desirable end is the greater accuracy made possible by theory of structures may feel that a disproportionate amount of use of the automatic digital computer. The sheer physical problem of space has been devoted to it. Serial publication does mean that the carrying out the computing by the older methods, both in structural results of such work as D R ARGYRIS has been doing appear at the analysis and in flutter work, has in the past tended to reduce the earliest possible moment. Although the development of the theories number of stations chosen for iterative procedures. The computer, has been going on for some time, the manuscript of each published by the large factor by which it speeds up the process, makes possible section has only been assembled in its final form, and the illustra the use of a larger number of stations, with attendant increase in tions drawn, about a month to six weeks before the appearance of accuracy. The use of computers has, of course, been taken into the issue in which it has been published. This has meant that all account in the present work, and several of the examples have been concerned have had to work to a tight schedule, not least the author laid out for the computer, and use made of the matrix notation which and his small team, and it has left little time for the solution of the is suited to it. complex problems of type-setting with which our printers have had In flutter work it has often been found that the factor limiting the to deal. As a result of all this, we hope, the methods of structural accuracy of predictions most seriously was the doubtful aerodynamic analysis proposed will be available to the industry earlier than if derivatives. With introduction of temperature gradients into the publication had been delayed until the manuscript was complete, and analysis of structures, the effects of temperature on material prop the whole could be presented in book form. The series has aroused erties, and in particular on proof stress and the elastic moduli, have great interest, and we believe that it will have a considerable influence to be accurately determined. It is not without interest that these on the structural analysis of the next generation of aircraft. problems also have received the attention of our author's team, as As is our usual practice with a series of any length, we intend to was indicated in the paper by MESSRS THOMAS, KELSEY and ARGYRIS reprint the articles in a more coherent form as a monograph, and it entitled 'A Dynamic Method for Determining the Variation with is envisaged that this will eventually be issued in two volumes, the Temperature of the Elastic Moduli of some Aluminium Alloys'. This first containing that portion which is completed with the section in paper was presented to the Conference on Stresses due to Vibra this issue, i.e. Parts I and II. Arrangements for the publication of tions held at Reading last December, and organized by the Stress this volume are not yet complete, but it is hoped that copies will be Analysis Group of the Institute of Physics. A summary appeared in available later this year: in any case the details will be announced in our February issue, and it is hoped to publish a more extended AIRCRAFT ENGINEERING when they are known. The second volume paper on the same subject in the future. will probably consist of the projected Parts III and IV of the work, These questions of accuracy, and the thoroughness with which which will of course be published first in the journal in the same way calculations are carried out, are not without relevance to the findings as Parts I and II. of the Comet inquiry. It may fairly be said that one of the most important lessons learnt from the tragic experiences with this Scope and Applications aircraft is the importance of making full use of existing knowledge and theories in the design of aircraft, always provided of course that the As is shown in Part II, and as will also become evident in the parts theories have proved their worth. In the aircraft industry there is which are to follow, the methods developed have a great degree of becoming less and less room for the rule of thumb methods of generality, and are very suitable for application to problems involving traditional engineering practice, and the trend, which has long been temperature gradients and plasticity, and where conditions are other evident, for the closer integration of the work of the 'men of mathe wise likely to be non-linear and follow laws which have to be ex matics' with that of the engineers on the job seems certain to con pressed as arbitrary functions. The treatment of cases where tempera tinue. In so far as this trend is not accepted we run the risks of ture gradients are present is of immediate interest; such problems, as failing to predict troubles which it should have been possible to is well known, being very much in the minds of the designers of predict, or of building aircraft which are less economical or effi high-performance aircraft, where aerodynamic heating may be con cient than they should be. The engineer has a not unhealthy suspic siderable. Less spectacular, but of even wider significance at present, ion of the academic approach, but he cannot afford to ignore the is the situation where temperature gradients are imposed upon load- results of academic work. bearing structure by installations within it, most obviously power
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: May 1, 1955
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