Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You and Your Team.

Learn More →

Foreign Research Progress

Foreign Research Progress 292 AIRCRAFT ENGINEERIN G October, 1942 Translation s issued by the N.A.C.A. sions for the static and dynamic stresses of air­ pressure on th e cylinde r walls), axia l force in th e large Technical Memorandum No. 997. Deter­ screw blade roots ar e evolved. They, in combination cylinder, and lastly, shear in the large cylinder. mination of the Bending and Buckling Effect wit h the fatigue strength diagram of the employed Th e discussion of these three load cases enables in the Stress Analysis of Shell Structures material , afford for each engine power one certain general conclusions concerning the behaviour of Accessible from one side only. By A. Dose. operating point by which the state of stress serving th e ring stressed by the shell forces and affords ("Untersuchungen zur Erfassung des Bie- as a basis for the design of the root is defined. numerical data for the most important load cate­ Different stress cases must be analyzed, depending gories (obtainable from the computed by super­ gungs- bzw. Beulungseinflusses bei Span- upon the vibration tendency of engine and use of position). The quantitative results are illustrated nungsmessungen an nur einseitig zugäng- airscrew. The solution affords an insight into the in Figs. 12, 14 and 15, and condensed in simple lichen Schalenkonstruktionen." Luftfahrtfor- possible introduction of different size classes of approximat e formulae through (4·9), (6·2), and airscrew. schung, Vol. 18, Nos. 2-3, March 29, 1941, (7·8). Qualitatively, it can be stated that, on wings which do not depart excessively from the pp. 95-101.) plane , th e moment M about th e normal axis (hence Technical Memorandum No. 1002. Con­ Th e present report describes a device for ascer­ tha t of th e three moments which is othe r than zero tribution to the Ideal Efficiency of Screw taining the bending and buckling effect in stress even on a perfectly straight wing) remains th e para­ measurement s on shell structures accessible from Propellers. By Wilhelm Hoff. ("Bermer- moun t stress ; and not until there is a very appre­ one side only. Beginning with a discussion of the ciable three-dimensional curvature (when the ratio kungen zum idealen Wirkungsgrad von Schrau- relationship between flexural strain and certain b/a of th e cylinder radii approaches 1) do the two benpropellern." Luftfahrtforschung, Vol. 18, parameters , the respective errors of th e test method othe r components of th e three-dimensional moment No. 4, April 22, 1941, pp . 114-21.) for great or variable skin curvature within the test vector, the bending moment M and the torque rang e are analyzed and illustrated by specimen M become perceptible. Since M , as the graphs Th e stipulation of best thrust distribution is T 2 examples. indicate , varies but little with Î=b/a if suitable applied to th e annula r elements of th e airscrew with reference quantities are chosen, rings for "small " infinitely many blades in frictionless, incompressible openings can be computed as straight rings with Technical Memorandum No. 998. Inertia flow and an ideal jet propulsion system derived ver y good approximation. possessing hyperbolic angular velocity distribution of Dynamic Pressure Arrays. By Hans along th e blade radius an d combining th e advantage Th e (closed) ring is statically indeterminate. It Weidemann. ("Zur Trägheit von Staudruck- of uniform thrust distribution over th e section with effectively evades an excessive stress induced by anlagen." Luftfahrtforschung, Vol. 17, No. 7, minimu m slipstream an d rotation losses. Thi s system insufficient torsional stiffness by responding to the Jul y 20 , 1940, pp . 211-215.) is then compared with an airscrew possessing the load largely with bending moments M —still, on sam e angular velocity at all blade elements an d the rings fully ineffective in torsion, it is recommended Ther e is a certain time lag in dynamic pressure best possible thrust distribution secured by means tha t the existence of the shear stresses within changes before they are visible to the pilot on the of an induced efficiency varying uniformly over the permissible limits be confirmed by approximating indicato r dial. This lag depends upon the size of radius . Lastly , th e case of th e lightly loaded airscrew wit h th e help of the cited empirical formulas. th e employed tubing and the characteristics of the also is discussed. Th e three explored load distributions are three indicating instrument. A new mathematical term column loads for the unstiffened cylindrical shell; "pneumati c time constant," which depends only henc e they create in the undisturbed shell a pure on th e dimensions of th e tubin g and of th e indicator, Technical Memorandum No. 1003. The membran e stress attitude. The calculation is pre­ enables the comparison of different dynamic pres­ Resistance Coefficient of Commercial Round dicated on th e assumptio n tha t this membran e stress sure arrays. The pneumatic time constant is an Wire Grids. By B. Eckert and F. Pflüger. attitud e is not materially disturbed by the clastic indication of th e inertia of a dynami c pressure array. interference effect between th e stiffener opening and ("Bestimmung der Widerstandsbeiwerte hand- th e skin. This assumption is me t in th e "extreme " elsüblicher Runddrahtsiebe." Luftfahrtfor­ Technical Memorandum No. 999. Stress case of a very stiff ring an d a thin-wall shell without schung, Vol. 18, No. 4, April 22, 1941, Analysis of Circular Frames. By H. Fahlbusch frames (or with frames located at some distance pp. 142-46.) from the opening). For the frameless shell would and W. Wegner. ("Berechnung der Bean- hav e to attempt to terminate the "interference Th e resistance coefficients of commercial types of spruchnung kreisförmiger Ringspante." Luft­ loads " returned by the ring through cross stresses roun d wire grids were examined for the purpose of fahrtforschung, Vol. 18, No. 4, April 22, 1941, an d bending moments ; since these do not become obtainin g the necessary data on supercharger test pp . 122-27.) large in th e thin shell and are also damped quickly stand s for throttling th e inducted air t o a pressure an y "aid " of the shell for the ring can manifest Th e stresses in circular frames of constant bending corresponding to a desired air density. The meas­ itself merely in the formation of a small effective stiffness, as encountered in thin-wall shells, are urement s of the coefficients ranged up t o Reynolds border zone which takes nothing essential away investigated from the point of view of finite depth number s of 1,000. In th e arrangemen t of tw o grids from the ring. in tandem, which was necessary in order to obtain of sectional area of frame. The solution is carried I n the opposite extreme case (not discussed here) high resistance coefficients, the relationship of the ou t for four fundamental load conditions. The of a ring rigid in strain bu t flexible in bending and of coefficients with th e solidity, tha t is mesh density, metho d is illustrated on a worked out example. a shell closed all around by closely placed stiff of grid, was found to be accompanied by a further frames or curved floors—"egg surface"—the state relationship with th e mutual spacing of th e individ­ Technical Memorandum No. 1,000. The of stress and strain is utterly different. Shell and ual grids. Temperature of Unheated Bodies in a High- ring ar e for the most par t subject to diaphragm and axial stresses, and stressed in bending solely by the Speed Gas Stream. By E. Eckert and W. Technical Memorandum No. 1004. Statics constrained stresses due to the incompatibility of Weise. ("Die Temperatur unbeheizter Körper of Circular-Ring Stiffeners for Monocoque th e form changes. The case is of little practical in einem Gasstrom hoher Geschwindigkeit.' concern, since structural reasons usually call for Fuselages. By W. Stioda. ("Zur Statik von Forschung auf dent Gebiete des Ingenieurwesens, rings which are far from ineffective in bending. Kreisringspanten in Flugzeugdruckkabinen." Th e true shell lies between the two extremes. Vol. 12, No . 1, Jan.-Feb. 1941, pp . 40-50.) Luftfahrtforschung, Vol. 18, No. 6, June 30, If the ring is distinctly rigid in bending and the Th e present report deals with temperature meas­ shell is either thick-walled or forms an egg surface, 1941 , pp . 214-222. ) urement s on cylinders of 0.2 t o 3 millimetres diam­ a complicated elastic interference effect results Fo r circular-ring stiffeners in monocoque fuselages ete r in longitudinal and transverse air flow a t speeds which defies calculation and must be ascertained th e bending moments, axial forces, and shear forces of 100 to 300 metres per second. Within the ex­ experimentally . The present solution supplies the unde r the action of applied external forces or a plored test range, that is, the probable laminar- basis for such experiments by enabling th e estima­ momen t are accurately computed by known boundary-laye r region, th e temperature of cylinders tion of the maximum bending stresses to be ex­ methods . Circular-ring stiffeners with variable i n axial flow is practically independent of th e speed pecte d through the determination of their upper moment s of inertia are likewise considered. In an d in good agreement with Pohlhausen's theoretical limit. comparison with the step-by-step and partially values ; whereas, in transverse flow, cylinders of graphical procedure, the one here described is a certain diameter manifest a close relationship with (As the N.A.C.A. Technical Memoranda are not mor e accurate and at the same time a simpler speed, the ratio of the temperature above the air obtainable in England, the Editor will be glad to method . of th e body t o the adiabatic stagnation temperature lend his copy of any of them to readers who wish to first decreases with using speed and then rises again borrow them. In most instances, the copy of from a Mach number of 0.6. The importance of Technical Memorandum No. 1005. The Luftfahrtforschung containing the original German thi s "specific temperature" of the body for heat- article is also available on loan if required.) Stresses in Stiffener Openings. By K. transfer studies a t high speed is discussed. Marguerre. ("Spannungen in Ausschnittver- steifungen." Luftfahrtforschung, Vol. 18, No. Technical Memorandum No. I,OOI. The Books Received 7, July 19, 1941, pp . 253-61.) Design of Propeller Blade Roots. By G. Fundamental s of Vibration Study. By R. G. As th e initial step in th e analysis of stress distribu­ Cordes. ("Bemessung von Luftschrauben- Manley. 128 pages, illustrated. [Chapman & tion in thre e dimensionally curved rings (as employed flügelfüssen." Luftfahrtforschung, Vol. 18, Hall , 13s. 6d.] a s stiffeners in stressed skin aircraft designs) th e ring No . 4, April 22 , 1941, pp . 128-34.) Th e Machine Shop Yearbook and Production (Fig. 1) formed by the intersection of two circular Engineers ' Manual. Edited by H. C. Town. cylinder s is explored for three categories of load ; Predicated on the assumption of certain normal 558 pages, illustrated. [Paul Elek, 25s.] tension in both cylinders (produced by hydrostatic conditions for engine and airscrew, simple expres­ http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

Foreign Research Progress

Aircraft Engineering and Aerospace Technology , Volume 14 (10): 1 – Oct 1, 1942

Loading next page...
 
/lp/emerald-publishing/foreign-research-progress-Se5Bao0HdK
Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb030952
Publisher site
See Article on Publisher Site

Abstract

292 AIRCRAFT ENGINEERIN G October, 1942 Translation s issued by the N.A.C.A. sions for the static and dynamic stresses of air­ pressure on th e cylinde r walls), axia l force in th e large Technical Memorandum No. 997. Deter­ screw blade roots ar e evolved. They, in combination cylinder, and lastly, shear in the large cylinder. mination of the Bending and Buckling Effect wit h the fatigue strength diagram of the employed Th e discussion of these three load cases enables in the Stress Analysis of Shell Structures material , afford for each engine power one certain general conclusions concerning the behaviour of Accessible from one side only. By A. Dose. operating point by which the state of stress serving th e ring stressed by the shell forces and affords ("Untersuchungen zur Erfassung des Bie- as a basis for the design of the root is defined. numerical data for the most important load cate­ Different stress cases must be analyzed, depending gories (obtainable from the computed by super­ gungs- bzw. Beulungseinflusses bei Span- upon the vibration tendency of engine and use of position). The quantitative results are illustrated nungsmessungen an nur einseitig zugäng- airscrew. The solution affords an insight into the in Figs. 12, 14 and 15, and condensed in simple lichen Schalenkonstruktionen." Luftfahrtfor- possible introduction of different size classes of approximat e formulae through (4·9), (6·2), and airscrew. schung, Vol. 18, Nos. 2-3, March 29, 1941, (7·8). Qualitatively, it can be stated that, on wings which do not depart excessively from the pp. 95-101.) plane , th e moment M about th e normal axis (hence Technical Memorandum No. 1002. Con­ Th e present report describes a device for ascer­ tha t of th e three moments which is othe r than zero tribution to the Ideal Efficiency of Screw taining the bending and buckling effect in stress even on a perfectly straight wing) remains th e para­ measurement s on shell structures accessible from Propellers. By Wilhelm Hoff. ("Bermer- moun t stress ; and not until there is a very appre­ one side only. Beginning with a discussion of the ciable three-dimensional curvature (when the ratio kungen zum idealen Wirkungsgrad von Schrau- relationship between flexural strain and certain b/a of th e cylinder radii approaches 1) do the two benpropellern." Luftfahrtforschung, Vol. 18, parameters , the respective errors of th e test method othe r components of th e three-dimensional moment No. 4, April 22, 1941, pp . 114-21.) for great or variable skin curvature within the test vector, the bending moment M and the torque rang e are analyzed and illustrated by specimen M become perceptible. Since M , as the graphs Th e stipulation of best thrust distribution is T 2 examples. indicate , varies but little with Î=b/a if suitable applied to th e annula r elements of th e airscrew with reference quantities are chosen, rings for "small " infinitely many blades in frictionless, incompressible openings can be computed as straight rings with Technical Memorandum No. 998. Inertia flow and an ideal jet propulsion system derived ver y good approximation. possessing hyperbolic angular velocity distribution of Dynamic Pressure Arrays. By Hans along th e blade radius an d combining th e advantage Th e (closed) ring is statically indeterminate. It Weidemann. ("Zur Trägheit von Staudruck- of uniform thrust distribution over th e section with effectively evades an excessive stress induced by anlagen." Luftfahrtforschung, Vol. 17, No. 7, minimu m slipstream an d rotation losses. Thi s system insufficient torsional stiffness by responding to the Jul y 20 , 1940, pp . 211-215.) is then compared with an airscrew possessing the load largely with bending moments M —still, on sam e angular velocity at all blade elements an d the rings fully ineffective in torsion, it is recommended Ther e is a certain time lag in dynamic pressure best possible thrust distribution secured by means tha t the existence of the shear stresses within changes before they are visible to the pilot on the of an induced efficiency varying uniformly over the permissible limits be confirmed by approximating indicato r dial. This lag depends upon the size of radius . Lastly , th e case of th e lightly loaded airscrew wit h th e help of the cited empirical formulas. th e employed tubing and the characteristics of the also is discussed. Th e three explored load distributions are three indicating instrument. A new mathematical term column loads for the unstiffened cylindrical shell; "pneumati c time constant," which depends only henc e they create in the undisturbed shell a pure on th e dimensions of th e tubin g and of th e indicator, Technical Memorandum No. 1003. The membran e stress attitude. The calculation is pre­ enables the comparison of different dynamic pres­ Resistance Coefficient of Commercial Round dicated on th e assumptio n tha t this membran e stress sure arrays. The pneumatic time constant is an Wire Grids. By B. Eckert and F. Pflüger. attitud e is not materially disturbed by the clastic indication of th e inertia of a dynami c pressure array. interference effect between th e stiffener opening and ("Bestimmung der Widerstandsbeiwerte hand- th e skin. This assumption is me t in th e "extreme " elsüblicher Runddrahtsiebe." Luftfahrtfor­ Technical Memorandum No. 999. Stress case of a very stiff ring an d a thin-wall shell without schung, Vol. 18, No. 4, April 22, 1941, Analysis of Circular Frames. By H. Fahlbusch frames (or with frames located at some distance pp. 142-46.) from the opening). For the frameless shell would and W. Wegner. ("Berechnung der Bean- hav e to attempt to terminate the "interference Th e resistance coefficients of commercial types of spruchnung kreisförmiger Ringspante." Luft­ loads " returned by the ring through cross stresses roun d wire grids were examined for the purpose of fahrtforschung, Vol. 18, No. 4, April 22, 1941, an d bending moments ; since these do not become obtainin g the necessary data on supercharger test pp . 122-27.) large in th e thin shell and are also damped quickly stand s for throttling th e inducted air t o a pressure an y "aid " of the shell for the ring can manifest Th e stresses in circular frames of constant bending corresponding to a desired air density. The meas­ itself merely in the formation of a small effective stiffness, as encountered in thin-wall shells, are urement s of the coefficients ranged up t o Reynolds border zone which takes nothing essential away investigated from the point of view of finite depth number s of 1,000. In th e arrangemen t of tw o grids from the ring. in tandem, which was necessary in order to obtain of sectional area of frame. The solution is carried I n the opposite extreme case (not discussed here) high resistance coefficients, the relationship of the ou t for four fundamental load conditions. The of a ring rigid in strain bu t flexible in bending and of coefficients with th e solidity, tha t is mesh density, metho d is illustrated on a worked out example. a shell closed all around by closely placed stiff of grid, was found to be accompanied by a further frames or curved floors—"egg surface"—the state relationship with th e mutual spacing of th e individ­ Technical Memorandum No. 1,000. The of stress and strain is utterly different. Shell and ual grids. Temperature of Unheated Bodies in a High- ring ar e for the most par t subject to diaphragm and axial stresses, and stressed in bending solely by the Speed Gas Stream. By E. Eckert and W. Technical Memorandum No. 1004. Statics constrained stresses due to the incompatibility of Weise. ("Die Temperatur unbeheizter Körper of Circular-Ring Stiffeners for Monocoque th e form changes. The case is of little practical in einem Gasstrom hoher Geschwindigkeit.' concern, since structural reasons usually call for Fuselages. By W. Stioda. ("Zur Statik von Forschung auf dent Gebiete des Ingenieurwesens, rings which are far from ineffective in bending. Kreisringspanten in Flugzeugdruckkabinen." Th e true shell lies between the two extremes. Vol. 12, No . 1, Jan.-Feb. 1941, pp . 40-50.) Luftfahrtforschung, Vol. 18, No. 6, June 30, If the ring is distinctly rigid in bending and the Th e present report deals with temperature meas­ shell is either thick-walled or forms an egg surface, 1941 , pp . 214-222. ) urement s on cylinders of 0.2 t o 3 millimetres diam­ a complicated elastic interference effect results Fo r circular-ring stiffeners in monocoque fuselages ete r in longitudinal and transverse air flow a t speeds which defies calculation and must be ascertained th e bending moments, axial forces, and shear forces of 100 to 300 metres per second. Within the ex­ experimentally . The present solution supplies the unde r the action of applied external forces or a plored test range, that is, the probable laminar- basis for such experiments by enabling th e estima­ momen t are accurately computed by known boundary-laye r region, th e temperature of cylinders tion of the maximum bending stresses to be ex­ methods . Circular-ring stiffeners with variable i n axial flow is practically independent of th e speed pecte d through the determination of their upper moment s of inertia are likewise considered. In an d in good agreement with Pohlhausen's theoretical limit. comparison with the step-by-step and partially values ; whereas, in transverse flow, cylinders of graphical procedure, the one here described is a certain diameter manifest a close relationship with (As the N.A.C.A. Technical Memoranda are not mor e accurate and at the same time a simpler speed, the ratio of the temperature above the air obtainable in England, the Editor will be glad to method . of th e body t o the adiabatic stagnation temperature lend his copy of any of them to readers who wish to first decreases with using speed and then rises again borrow them. In most instances, the copy of from a Mach number of 0.6. The importance of Technical Memorandum No. 1005. The Luftfahrtforschung containing the original German thi s "specific temperature" of the body for heat- article is also available on loan if required.) Stresses in Stiffener Openings. By K. transfer studies a t high speed is discussed. Marguerre. ("Spannungen in Ausschnittver- steifungen." Luftfahrtforschung, Vol. 18, No. Technical Memorandum No. I,OOI. The Books Received 7, July 19, 1941, pp . 253-61.) Design of Propeller Blade Roots. By G. Fundamental s of Vibration Study. By R. G. As th e initial step in th e analysis of stress distribu­ Cordes. ("Bemessung von Luftschrauben- Manley. 128 pages, illustrated. [Chapman & tion in thre e dimensionally curved rings (as employed flügelfüssen." Luftfahrtforschung, Vol. 18, Hall , 13s. 6d.] a s stiffeners in stressed skin aircraft designs) th e ring No . 4, April 22 , 1941, pp . 128-34.) Th e Machine Shop Yearbook and Production (Fig. 1) formed by the intersection of two circular Engineers ' Manual. Edited by H. C. Town. cylinder s is explored for three categories of load ; Predicated on the assumption of certain normal 558 pages, illustrated. [Paul Elek, 25s.] tension in both cylinders (produced by hydrostatic conditions for engine and airscrew, simple expres­

Journal

Aircraft Engineering and Aerospace TechnologyEmerald Publishing

Published: Oct 1, 1942

There are no references for this article.