Showing papers in "Aeronautical Journal in 1955"
TL;DR: In this article, it is shown that free vibration cannot be treated satisfactorily unless the definition of hysteretic damping is widened in some way to cover nonharmonic motion.
Abstract: This paper is the first of a series of three which are concerned with the subject of “ hysteretic damping.” This type of damping, in a simple system with one degree of freedom, is like the familiar “ viscous damping ” in that it implies a resisting force which is in phase with velocity; but it is unlike viscous damping in that the magnitude of the force is not proportional to the velocity but to the displacement. When a system has n degrees of freedom, hysteretic damping implies that damping forces exist which are proportional to relative displacement but which are in phase with relative velocity. From a physical standpoint, hysteretic damping may give a better representation of the facts when the damping arises from the internal friction of solid materials. On the side of theory, it raises considerations which it is the purpose of these three papers to elucidate. It may be said, at the outset, that the notion of hysteretic damping raises no great mathematical difficulty; on the contrary, a main reason for presenting the theory is that it appears to allow of a much simpler discussion (than does viscous damping) of the nature of steady damped oscillation of systems having n degrees of freedom. In the first paper, the purpose is discussed of mathematical theories of damping in vibration theory. It is concluded that the theory of “ hysteretic damping ” is a useful one since it provides an alternative to the fiction of “ viscous ” damping while retaining the mathematical linearity of equations of motion. The word “ hysteretic” is proposed for use in this sense instead of the previously used adjective, namely “ structural.” “ Complex damping ” is related to hysteretic damping in a way which is explained. The theory is given for forced oscillations of a system with one degree of freedom. It is shown that free vibration cannot be treated satisfactorily unless the definition of hysteretic damping is widened in some way to cover non-harmonic motion.
86 citations
TL;DR: In this paper, a theory of wrinkling in Sandwich Construction is presented in two parts, in which the thickness of the core is regarded as finite and the analysis is extended to the case where the face is supported by a sufficiently thick or a semi-infinite medium.
Abstract: In this paper a theory of wrinkling in Sandwich Construction is presented in two parts. In the first part, the thickness of the core is regarded as finite. The wrinkling stress is given by a simple square root formula consisting of the Young's moduli of the materials and the ratio of the thickness of the face and core. In the second part of the theory the same procedure is followed, with the main difference that shearing stresses in the core are also considered, and the analysis is extended to the case where the face is supported by a sufficiently thick or a semi-infinite medium. The result for the wrinkling stress is a cubic root formula which consists of the moduli of the materials but indirectly depends upon the geometry of the structure; this formula is valid only if the ratio of the thickness of the core and the face is greater than or at least equal to the ratio of the width of the marginal zone of distortions in the core, and the thickness of the face. The width of the zone is also useful as the criterion which discriminates between the two cases of buckling as envisaged in this paper. The theory is compared with the previous works, and also with the test results already available. The selection of the experimental data comprises steel, aluminium alloy and Papreg (laminated paper plastic) as the face; and onazote, cellular cellulose acetate, granulated cork, sponge rubber and expanded formvar as the core materials over a wide range of core-face thickness ratio. The agreement between the theory and the tests is satisfactory.
34 citations
TL;DR: A FLIER'S WORLD as discussed by the authors is a book written by a one-time research pilot and instructor, well known in the U.S.A. for his aeronautical articles in Harpers and Life.
Abstract: A FLIER'S WORLD. Wolfgang Langewiesche. Hodder & Stoughton, London, 1954. 255 pp. Illustrated. 12s. 6d. Written by a one-time research pilot and instructor, well known in the U.S.A. for his aeronautical articles in Harpers and Life, this book aptly conveys an impression of a pilot's viewpoint of sky, land and sea. Not only has Wolfgang Langewiesche the trick of explaining difficult things in simple phrases, but he conveys the sense of flight in terms which every one who has flown will instantly recognise are true, and which equally well will hold the attention of non-flying readers. Indeed the couple of alltoo-brief sections dealing with piloting comprise one of the best attempts so far made at recapturing the sense of the subtly combined reactions of body and mind which arise in the strange, fascinating, time-measured volumetric world of those who sit at the controls of an aeroplane. \" Explanations are supposed to be dull to give, even duller to receive. Don't you believe it. There's a little electric spark that jumps somewhere inside you the moment you really understand something,\" writes the author, and for the non-technical reader the spark should continue to jump throughout the book, for it ranges widely across the world of flight. It is a pity, however, that Langewiesche did not bother to rewrite the chapter \" How fast can we fly?\" for although he explains very excellently the hazards of stability and control as sonic speeds are approached, nevertheless it is sadly dated because the problem is presented as unresolved. In fact the author is a little naughty, for he is well aware of the imperfection and explains in a footnote that the chapter was originally printed as an article just after the Second World War— at which period many will remember it as remarkably informative and illuminating. Nevertheless, all that he has written of shock-wave effects remains perfectly valid— if incomplete. Opening sections of the book offer simplified and interesting explanations of aerodynamic phenomena, after which \" what makes the weather \" continues to sustain the fascination and leads to description of the world seen with an airman's eye. Written throughout with considerable perception this book is recommended to all who have more than a passing interest in flight—and, in particular, flying from the pilot's seat rather than in the cabin of an airliner. Langewiesche is a genius at painless teaching.—HARALD PENROSE.
27 citations
TL;DR: In this paper, it is shown that aircraft may experience bumpiness which the pilot would describe as moderate or severe, at altitudes up to at least 40,000 feet, thus including altitude bands where commercial jet aircraft will be flying during the next few years, and the requirement is for the aircraft commander to be supplied with sufficient information to enable him to avoid such turbulence, or to provide him with adequate warning so that crew and passengers can be properly prepared for it.
Abstract: How much is known about high altitude clear air turbulence? Sufficient to show that aircraft may, with little or no warning, experience bumpiness which the pilot would describe as “ moderate ” or, on occasions, “ severe,” at altitudes up to at least 40,000 feet, thus including altitude bands where commercial jet aircraft will be flying during the next few years. The phenomenon, therefore, is of significance to airline operators and the requirement is for the aircraft commander to be supplied with sufficient information to enable him to avoid such turbulence, or to provide him with adequate warning so that crew and passengers can be properly prepared for it. This does not imply that there is evidence to suppose that clear air turbulence may be of such severity as to affect the safety of a flight. It is important, however, to take good care of the passengers and their comfort is an essential consideration.
17 citations
TL;DR: In the year 1954, the Attinello flap in the United States marked the introduction of one form of boundary layer control as an engineering and practical reality as discussed by the authors, which was the first practical application of boundary-layer control for aircraft.
Abstract: It has almost become a tradition in recent years to begin a paper on boundary layer by paying a tribute to the great Prandtl and his famous paper in which he introduced the conception of boundary layer into Fluid Dynamics. The year 1954 is, however, not only memorable to mark the passing of fifty years since Prandtl's classical demonstration of the effect of boundary layer suction on the flow pattern around a cylinder; it is also memorable because in 1954 most convincing demonstrations of practical applications of boundary layer control for aircraft have taken place. I am referring, in particular, to the demonstrations with the Attinello flap in the United States which mark the introduction of one form of boundary layer control as an engineering and practical reality.
15 citations
TL;DR: Timoshenko's Vibration problems in engineering as discussed by the authors is a classic text on the subject of non-linear vibration and has been extensively revised and improved over the last few decades.
Abstract: VIBRATION PROBLEMS IN ENGINEERING (Third Edition). S. P. Timoshenko (with the collaboration of D. H. Young). D. Van Nostrand, New York, 1955. 468 pp. Diagrams. 65s. Those who are interested in the subject of mechanical vibration are fortunate in that there are a few very fine books indeed to which they can turn in times of need or distress. Of these, Timoshenko's Vibration Problems in Engineering is an oustanding example. \" It is in Timoshenko \" is a comforting assertion in vibration theory, implying that it (whatever \" i t \" is) will be set out in an understandable form in a book which is probably familiar already to the reader. In preparing this (the third) edition, Professor Timoshenko has been assisted by Professor D. H. Young. These writers have set out to make the book more up to date without simply adding new material and so increasing its bulk. The result is, in the main, very successful. Chapter I deals with systems having one degree of freedom and it has been thoroughly revised both in content and arrangement. Perhaps the most striking change lies in the increased emphasis that has been placed upon transient vibration; both analytical and graphical treatments of it are discussed. A considerable number of problems have been added. The subject of non-linear vibration is dealt with in Chapter II and this portion of the book has been considerably enlarged. Of the new material, two important topics have been dealt with particularly well—namely the phaseplane-displacement technique of Jacobsen and the application of Ritz's method to non-linear systems; this latter is treated without the use of variational methods. Obviously, one cannot expect anything like a thorough treatment of such an enormous subject as non-linear vibration in a single chapter of a book of this sort. Therefore it is desirable that the treatment should be carefully sign-posted with references, not only to original papers, but to modern books on the subject. The reviewer feels that, in this respect, more might be done by way of improvement. For instance, the powerful phase-plane methods have received a rather scanty treatment in the text which could more easily be adopted if reference had been made to the book by Andronow and Chaikin (Theory of Oscillations, Princeton University Press). The previous edition of this book has served, and served well, both as a textbook and as a reference book. In the reviewer's opinion, the present one is, in one respect, somewhat more of a work of reference and has a slightly diminished value for teaching purposes. This view is expressed with some trepidation; it may not be shared by others and, indeed, some may well feel that, for the very same reason, precisely the reverse is true. The question arises in Chapters III and IV which are concerned with twoand n-degree-of-freedom systems respectively; they do not differ greatly from previous editions save in one important respect. Lagrangian methods have been dropped. This is because it is thought that the equations of motion of vibrating systems are best set up by the more familiar principle of D'Alembert. That may or may not be so; but it is surely not the whole story. The main attraction of Lagrange's method is that it permits one to impart generality to vibration theory through the discussion of inertia and stability coefficients as a class. That is not what the practising engineer is usually after—for him, Lagrange's equations are merely a means of setting up differential equations and it is true that he can generally dispense with them for this purpose. Lagrange's equations are most useful when the engineer thinks of the theory of vibration in general terms and if he does not do this in a university, it is not at all likely that he will acquire the ability to do so later. If Chapters III and IV are the cause of some slight misgivings, Chapter V (the last) more than compensates for this. This chapter deals with elastic bodies and is 165 pages long. It has been thoroughly revised and amplified; for instance, there is now a treatment of coupled bending and torsional vibration of beams. Finally, the Appendix of the second edition (which deals with vibration measuring instruments) has been left out. It has certainly dated. In reviewing this book, the previous edition has been taken as the standard of comparison. The new one is undoubtedly an improvement upon the old. And the old has long been accepted as one of the best and most important on the subject of vibration. This is a very fine book indeed.—R. E. D. BISHOP.
12 citations
TL;DR: It will be shown how these calculations may be modified to deal with the corresponding structure with discontinuities, which for this reason will be referred to as the “modified” structure.
Abstract: A structure with cut–outs or other discontinuities is generally considered to be more difficult to analyse than a similar structure without such features, although it is in fact less redundant. This is largely due to the special conditions which have to be introduced to allow for these discontinuities, tending to make the calculations less adaptable to routine computation . Another and very practical reason is that it is sometimes fairly easy to—dare we say it?—make a reasonable guess at the load distribution in a structure without cut–outs, whereas a much more critical approach is necessary for the treatment of structural discontinuities. Be that as it may, it will be assumed here that the structure without discontinuities, which will henceforth be termed the “original” structure, can be analysed exactly, in the sense that all the effective redundancies are taken into account. It will now be shown how these calculations may be modified to deal with the corresponding structure with discontinuities, which for this reason will be referred to as the “modified” structure.
8 citations
TL;DR: In this article, the aerodynamic characteristics of airframes are expressed as aerodynamic transfer functions, giving the relationships between input and output for each of the three separate planes of motion, roll, pitch, and yaw.
Abstract: The aerodynamic characteristics of airframes are expressed as aerodynamic transfer functions, giving the relationships between input and output for each of the three separate planes of motion, roll, pitch, and yaw. By assuming no cross-coupling between planes and linear aerodynamics, and by making certain other assumptions, which apply particularly to conventional airframes with fixed wings and rear controls, relatively simple approximate algebraic transfer functions giving the relationships between the control surface deflection (the input) and any airframe motion (the output), are obtained. The open loop aerodynamic transfer functions thus obtained are used as part of the auto-pilot block diagram, in which the performance of other components, such as actuators, instruments and electrical networks, are also expressed in transfer function form. The aerodynamic transfer functions are useful in auto-pilot evolution and synthesis in that they aid selection of the airframe motions to be measured, modified, and fed back to close the auto-pilot loop. For mathematical assessment of closed loop performance and stability, open loop transient and frequency responses are used, and curves of airframe responses are plotted in linear, logarithmic and polar form by standard methods from the aerodynamic transfer functions. Some methods of using these curves, which follow the general lines adopted in servo-mechanism and electronic amplifier design, are explained briefly. Analogue computers are frequently used when the computations to be made are so complicated as to need the use of a computing machine. The aerodynamic transfer functions then form one block of the simulator set-up, and on larger computers the more exact form, including any non-linearities and cross-coupling effects, can be used.
7 citations
TL;DR: In this paper, the problem of the buckling under bi-axial compression is considered for flat rectangular isotropic plates with simple edge conditions and no lateral restraint, and a buckling stress coefficient is plotted against the side ratio for various conditions of edge restraint and a known compression or tension on the sides of the plate.
Abstract: The problem of the buckling under bi-axial compression is considered for flat rectangular isotropic plates with simple edge conditions and no lateral restraint. The buckling stress coefficient is plotted against the side ratio for various conditions of edge restraint and a known compression or tension on the sides of the plate. It is found that there is some reduction in the buckling stress if the sides of the plate are subjected to compressive stresses and, conversely, there is an increase for tensile stresses. Furthermore, for plates with large side ratios, there is a rapid decrease of the spanwise buckling stress as the chordwise compressive stress approaches its appropriate Euler instability value.
7 citations
TL;DR: The present paper attempts to summarise the problems which now arise and to give some idea of the progress which has been made in the intervening years as discussed by the authors, but it is difficult to compare the two works.
Abstract: Some five years ago the author was privileged to deliver a Section Lecture to the Royal Aeronautical Society on the subject of reheat. The present paper attempts to summarise the problems which now arise and to give some idea of the progress which has been made in the intervening years. In 1949, reheat was in its infancy in Great Britain. A certain amount of progress had been made in the United States but the information from that source was scanty and vague. Tests at the National Gas Turbine Establishment (N.G.T.E.) had given some engine data but this was in the nature of preliminary information only and was by no means complete. In fact the majority of the problems which now beset us were then completely unknown or were considered unimportant. The N.G.T.E. work was valuable, however, in that it demonstrated the practicability of reheat, although at the time the comments of many who saw this and other schemes in operation were somewhat sceptical and definitely unflattering.
7 citations
TL;DR: It involves as few arithmetical manipulations as does the most rapid method of pivotal condensation currently used, and is easier than any other known method to learn and to remember.
Abstract: A new method for evaluating determinants or matrices is given; it is rather tedious to describe and awkward to prove, but is very easy to use. The chief advantages this method is believed to possess are: (i) It involves as few arithmetical manipulations as does the most rapid method of pivotal condensation currently used. (ii) It is easier than any other known method to learn and to remember. (iii) It can be adapted to routine computation, in such a way as to minimise the likelihood of error. (iv) A digital computor can readily be programmed to use it.
TL;DR: The main disadvantages of large airfields, both for military and for civil aviation, soon become obvious: (i) The enormous expenditure in either case; for military aviation this expenditure has to be approved, but it is at the expense of the production of actual aircraft, like Ugolin who ate his children so that they would not be fatherless; and (ii) The lack of flexibility of air forces operating from fixed bases, thus reducing their efficiency.
Abstract: As technical progress has improved the airborne performance of aircraft, so the difficulties associated with their take-off and landing have increased. The grass airfields which were still commonplace at the end of the Second World War have now developed into complex arrangements of concrete runways of up to three kilometres (two miles) long, taxiways, dispersal areas, and so on. The main disadvantages of these large airfields, both for military and for civil aviation, soon become obvious: — (i) The enormous expenditure in either case; for military aviation this expenditure has to be approved, but it is at the expense of the production of actual aircraft—like Ugolin who ate his children so that they would not be fatherless; for civil aviation, the high cost of airfield construction has hampered the development of aviation in the remote areas where it would be of particular use in raising the standard of living. (ii) The lack of flexibility of air forces operating from fixed bases, thus reducing their efficiency. (iii) The increase in vulnerability as destructive weapons become more highly perfected.
TL;DR: In this paper, the effect of temperature discontinuities on the pressure conditions in the exhaust pipes and cylinders of two-stroke cycle engines, both models and running engines, was investigated.
Abstract: The laws of reflection of pressure waves at temperature discontinuities are well known. Of particular interest is the effect of temperature discontinuities on the pressure conditions in the exhaust pipes and cylinders of two-stroke cycle engines, both models and running engines. Model experiments are usually performed at low temperatures with the cylinder release temperature and exhaust pipe temperatures of the same order; under these conditions the reverse type of temperature phenomenon occurs to that in running engines with excess scavenge air. In the case of a model during the exhaust blowdown the gas from the cylinder reaches the exhaust pipe with a greater density than that of the gas initially in the exhaust pipe.
TL;DR: In this paper, the authors suggest that there can be little progress in air safety without the assimilation of human engineering data by investigators and the Industry alike, and make some suggestions for possible future developments of technique.
Abstract: Attention is confined to civil aviation and the present scope of investigating procedures is outlined on a world-wide basis. Deficiencies in these procedures are noted and some suggestions are made for possible future developments of technique. In particular it is suggested that there can be little progress in air safety without the assimilation of “ human engineering data” by investigators and the Industry alike. Opinions expressed are entirely personal to the author and are not associated in any way with the official views of The British Aviation Insurance Co. Ltd.
TL;DR: It is gratifying to learn from Mr. Nicholls (May 1955, p. 364) that he is favourably impressed with the exponential function and it is to be hoped that he, and others interested in stress-strain relationships, may find it to be of practical value as discussed by the authors.
Abstract: It is gratifying to learn from Mr. Nicholls (May 1955, p. 364) that he is favourably impressed with the exponential function, and it is to be hoped that he, and others interested in stress-strain relationships, may find it to be of practical value. While the modifications which he suggests are quite legitimate, they tend to mask the essential simplicity of the function. It would be difficult to obtain the asymptotic stress from his first equation. The second can be easily solved for strain, but the converse process is complicated by the fact that the current stress appears both inside and outside the exponential. It is surely much more straightforward, and infinitely quicker, to plot the stress-strain curve from the proof stress data and analyse it in the normal way.
TL;DR: The structural problems introduced by the kinetic heating of high speed aircraft require a radical extension of what has hitherto been regarded as the normal domain of structural theory as mentioned in this paper, and the structural analysis of high-speed aircraft cannot be regarded as a selfcontained subject which merely provides basic data for the structural worker.
Abstract: The structural problems introduced by the kinetic heating of high speed aircraft require a radical extension of what has hitherto been regarded as the normal domain of structural theory. Aerodynamics, for example, cannot be regarded as a self-contained subject which merely provides basic data for the structural worker. Certain aspects of aerodynamic theory, particularly the mode of heat generation, have to be considered simultaneously with the structural problem. Thermodynamics and metallurgy are still more closely integrated with structural theory. The laws of heat transfer, and the variation of material properties with temperature, are both essential factors in the structural analysis.
TL;DR: This lecture intends in this lecture to discuss ways in which it thinks analogue computing can be of assistance to aeronautics in the future, and is less concerned with how analogue computors are built, than with how they are used, and in fact, what circumstances justify using them at all.
Abstract: I intend in this lecture to discuss tlie ways in which I think analogue computing can be of assistance to aeronautics in the future. I shall therefore be less concerned with how they are built, than with how they are used, and in fact, what circumstances justify using them at all. Up to a few years ago the only large computors were analogue ones, so the user had no choice, but when the automatic digital computor became established as a practical machine (and even before) there were many people to suggest that the analogue was obsolete. This view is now less widely held, even by makers and designers of digital machines, and reviews of aeronautical computing aids have usually found some place for the analogue computor, without establishing any general principles on which the choice has been made, except, perhaps, to suggest that the accuracy required is the criterion. I shall start by describing three of the types of computor most commonly used in aeronautics, the “ response simulator,” the “ electrolytic tank” and the “network analyser” and use these to illustrate the particular properties of analogue computing.
TL;DR: In this paper, an expression for the theoretical pressure distribution due to small incidence on a slender elliptic half-cone in uniform motion was derived, and it was shown that this distribution is additive to the zero incidence pressure distribution.
Abstract: The slender–body solution for the flow about low aspect–ratio wings of non–zero thickness yields a pressure distribution which is valid in the vicinity of the leading edge and therefore suitable for comparison with measured distributions. In this note an expression is derived for the theoretical pressure distribution, due to small incidence, on a slender elliptic half–cone in uniform motion. It is shown that this distribution is additive to the zero incidence pressure distribution. A comparison with some low speed measurements shows qualitative agreement. The method can be simply extended to other bodies of elliptic cross section.
TL;DR: In this paper, the collapse strength of a simple integral panel under uniform end compression is discussed firstly as a problem of interconnected flat plates, and secondly in terms of the torsional stability of the stiffeners.
Abstract: Summary: The local instability of a simple type of integral panel under uniform end compression is discussed firstly as a problem of interconnected flat plates, and secondly in terms of the torsional stability of the stiffeners. It is found that the second method under–estimates the “true” local buckling stress. This conclusion is in conflict with earlier work by Yusuff on closer study it is found that Yusuff's analysis involves two important assumptions which are generally unjustifiable. It is suggested that the collapse strength of a short compressed panel may be estimated with reasonable accuracy from a knowledge of the initial local buckling stress and the proof stress of the material of the panel.
TL;DR: In this article, the optimum sectional dimensions for long thin walled cells of circular, semi-circular, rectangular and triangular shapes and uniform wall thickness have been derived for failure by local buckling and a limit on the twisting deformation of the cells.
Abstract: The minimum weight approach to structural design was introduced by F. R. Shanley with reference to narrow and wide columns and shells subjected to bending, and was later dealt with more comprehensively in a book by the same author. This was further extended to structures like tapered round thin-walled columns and frames. In this paper expressions giving optimum sectional dimensions for long thin walled cells of circular, semi–circular, rectangular and triangular shapes and uniform wall thickness have been derived. The design criteria used to obtain the minimum necessary conditions are (1) failure by local buckling and (2) a limit on the twisting deformation of the cells. Working curves from which the optimum sectional dimensions can be read for given torque and limiting twist have been plotted. And finally, a method of approach to the problem of combined bending and torsion has also been indicated.
TL;DR: In this article, the fatigue strength of magnesium alloy ZW2 (2 per cent. zinc, 0·65 percent. zirconium) in sheet form was investigated and direct stress fatigue determinations were made on small round test pieces machined from ¾ in. thick plate.
Abstract: The work reported in this Note originally formed part of a comprehensive investigation into the fatigue strength of magnesium alloy ZW2 (2 per cent. zinc, 0·65 per cent. zirconium) in sheet form. The major portion of the programme was eventually cancelled but the tests herein described are sufficiently self-contained to be repotted by themselves. Direct stress fatigue determinations were made on small round test pieces machined from ¾ in. thick plate, at mean stresses of 0, 4,000, 8,000 and 13,000 lb./in. 2 . Static and rotating bar fatigue tests were also made.
TL;DR: The paper by A.C.Nicholls in the October 1954 Journal as discussed by the authors describes two empirical equations neither of which possesses the first essential of an acceptable strain hardening function, namely that the stress attained in a preliminary straining operation shall become explicitly the threshold stress at which subsequent deformation begins.
Abstract: The Paper by A.C.Nicholls in the October 1954 Journal (p. 724) describes two empirical equations neither of which possesses the first essential of an acceptable strain hardening function, namely that the stress attained in a preliminary straining operation shall become explicitly the threshold stress at which subsequent deformation begins. Eight years of study and the analysis of hundreds of published curves have convinced me that the exponential function put forward in 1948 faithfully reflects the strain hardening process. Far from being empirical, it can readily be deduced from a few simple and credible assumptions, and has counterparts in many branches of physics.
TL;DR: The work described in this article was undertaken under a Ministry of Supply Contract to investigate the fatigue strength of certain materials where the expected endurance in use was less than the range of values usually examined in fatigue testing.
Abstract: The work described was undertaken under a Ministry of Supply Contract to investigate the fatigue strength of certain materials where the expected endurance in use was less than the range of values usually examined in fatigue testing. The material was supplied in the form of a 6 ft. x 3 ft. x 1/4 in. sheet of aluminium alloy MG5. Tensile test pieces having a parallel length one inch wide by 4 1/2 in. long were taken in both directions from two diagonally opposite corners of the sheet. Later, similar longitudinal test pieces were taken from areas near the other two corners. The plane bending fatigue test pieces were of the form shown in Fig. 1 and were all cut in the longitudinal direction. The waisted test portion was polished on the edges, the original sheet surface being retained on the faces. Steel plates were clamped to the ends of the test pieces by bolts passing through the holes in order to localise the strain in the test portion as much as possible.
TL;DR: The theory of stress concentration is such a fascinating study that the whole lecture could be most happily devoted to discussion of the stress distribution round all sorts of special boundaries as discussed by the authors. But the most detailed knowledge of elastic stress distribution is of little value unless we can be sure how the stresses computed will be reflected in the actual strength of the part.
Abstract: The theory of stress concentration is such a fascinating study that the whole of this lecture could be most happily devoted to discussion of the stress distribution round all sorts of special boundaries. At the same time the most detailed knowledge of elastic stress distribution is of little value unless we can be sure how the stresses computed will be reflected in the actual strength of the part. For that reason this paper is divided into three sections: the first deals with certain moderately simple cases of stress and load concentration and shows how the stress analysis is confirmed by static and fatigue tests: the second describes some investigations of special two–dimensional boundaries and indicates, some fairly general theoretical conclusions which can be drawn: in the third I shall try to review the possible reasons why, in practice, the best found conclusions are not always borne out.
TL;DR: Mitchell's aircraft included, in the civil transport field, the Sea Eagle of 1923, which opened air services to the Channel Islands, the unique "Air Yacht" of 1929 and the very advanced 75,000 lb., 174 ft. span, six-engined, 40-passenger commercial flying boat of 1930 (Fig. 1), the contract for which was unfortunately cancelled as an economy measure in January 1932 after work was well advanced as discussed by the authors.
Abstract: Reginald J. Mitchell of Supermarines—a North Staffordshireman, like myself, and, in the words of Joe Smith, “ a practical engineer possessed of an abundance of plain, straightforward common sense; a man of drive and genius”—will go down to history as among the most inspired of those who had the good fortune to live and work in Aviation's pioneering days. During the short span of his active designing and engineering life—for the 16 years between 1920 and 1936—he produced 24 different aircraft types, so brilliantly and affectionately discussed by the great Joe Smith in his foundation Mitchell Memorial Lecture in January 1954. Mitchell's aircraft included, in the civil transport field, the “ Sea Eagle ” of 1923, which opened air services to the Channel Islands, the unique “Air Yacht” of 1929 and the very advanced 75,000 lb., 174 ft. span, six-engined, 40-passenger commercial flying boat of 1930 (Fig. 1), the contract for which was unfortunately cancelled as an economy measure in January 1932 after work was well advanced.
TL;DR: In this article, the authors presented approximate solutions for the lowest critical buckling load of an isosceles triangular plate loaded with collocation, where the base of the triangle is simply supported and the other equal edges are clamped.
Abstract: Approximate Solutions obtained by the method of collocation are presented for the lowest critical buckling load of an isosceles triangular plate loaded as shown in Fig. 1. Also, the fundamental frequency is given. The base of the triangle is simply supported and the other equal edges are clamped. The usual assumptions regarding the bending of thin plates are made. The governing differential equation for the plate loaded as shown in Fig. 1 is 1 where D is the plate stiffness, N is axial load per unit length, w is deflection, positive downward, and the quantities a and h are dimensions shown in Fig.1.
TL;DR: In this article, the forces on planing plates and Vee wedges were investigated in the U.S.A. for the first time, and the results showed that planing surfaces can be used for the design of flying-boats.
Abstract: During the past few years numerous developments in the hydrodynamic design of flying-boats have been brought about mainly by systematic model research. Although Germany deserves the credit for initiating research on the forces on planing plates and Vee wedges, we are indebted to various estabhshments in the U.S.A. for the multiplicity of data on both flying-boats and simple planing surfaces, which are now available.
TL;DR: Oberth's plans and ideas for a space station are described in detail in this paper, where the reader is taken out further into space and time, and he learns why future generations will probably be better morally and thereby qualify to live in space in dwelling wheels.
Abstract: Although the following quotation (page 123) refers to Oberth's plans and ideas for a space station they offer, I think, the key to the whole book. \" Finally a word about the seriousness of these ideas. Every time after a lecture a voice is raised ' I bet he doesn't believe all that himself.' Sometimes it is Aunt Anne who having left her kitchen hopes to be well entertained with space travel, sometimes it is even the well known expert who hasn't had the time to look into these things. \" W h y this remarkable view? Space travel is a technical undertaking as worthy as any other. It follows on air travel so logically that you have to be malicious not to see and admit it, and the problems are not so great that one could not solve them. \" This is what I set out to demonstrate.\" After a few pages on how to prepare men for space the author introduces rather nicely in the second chapter the conservation of momentum and gives his proposal for a three stage satellite rocket. In the third chapter he deals with the space suit in considerable detail, even allowing the space man to wipe his nose. Chapter 4, space station, is not so detailed. He concentrates more on showing what could be done with such a station. A sparkling fight follows for the author's favourite child, the space mirror. After a sketchy account of electric space ships (Chapter 6) he designs the moon car (Chapter 7) apparently his second best favourite. It stands on one long leg, can travel on the surface, and jump. Finally the reader is taken out further into space and time, and he learns why future generations will probably be better morally and thereby qualify to live in space in dwelling wheels.
TL;DR: In this paper, a growing interest on the part of aeronautical engineers in forgings of large size, for three main reasons: certain types of forgings will naturally need to be bigger as the aircraft itself becomes bigger; more composite structures are being replaced by single components made as forgings; and there is an increasing use of complex units machined directly from blocks of metal which are too big in at least one dimension to be made as extrusions or rolled plate.
Abstract: Today there is growing interest on the part of aeronautical engineers in forgings of large size, for three main reasons. Certain types of forgings will naturally need to be bigger as the aircraft itself becomes bigger; more composite structures are being replaced by single components made as forgings; and there is an increasing use of complex units machined directly from blocks of metal which are too big in at least one dimension to be made as extrusions or rolled plate. It is with these larger forgings that we are mainly concerned. Their production presents many serious problems. It is reasonable to hope that some of these will be overcome as experience grows and techniques are improved but others seem to be inherent in the materials used and must be appreciated at the design stage of the component if fully satisfactory service is to be obtained.
TL;DR: The author describes what had been done already in Canada during the earlier years of this century to give some feeling for the accomplishments in aeronautical research in my Country during the past ten years.
Abstract: With the exception, possibly, of the detective thriller most stories are best enjoyed by starting at the beginning. My story is no exception and, if i am to give you some feeling for the accomplishments in aeronautical research in my Country during the past ten years, I must refer briefly to what had been done already in Canada during the earlier years of this century.