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Aviation History
1937
1937 - 2367.PDF
AUGUST 26, 1937 SUPPLEMENT TO FLIGHT THE AIRCRAFT ENGINEER 10 KMV M 06 04 02 N. ..9i o« S V V \V \\ \ FIG.4 — k, f e NQ 10 0-8 0-6 0-4 0-2 Va (0 '0-9 H* S ^0-7 *& / / / / r y li 1 7 f i t -TV 12 10 0-8 04 M a / / / f I // v,. V V r ,/• ',' 7^ ' b/ fl Ob 0-7 0-8 10 FIG. 5 — kTv 1-0 0-8 06 04 0 2 lb M 1-2 l-U M 0 6 04 0-2 0 / I / /; '/ // // /, 71/, ^< ^ / /, / • ^ 7 f\ A f 7, 1 / / I & T 1 / / /. / P" 0-7 0 8 FIG. 8 —k. I e M*' KP;^ •2^ ^6 Fl /a G. 7- kT H \ \ It 2 FIG.6-k, I e FIG.9 CONCLUSION. Summarising, the loads applied to the stringer consist of a. End load due to pure bending. b. End load due to longitudinal component of the diagonal tension field. c. Bending loads in radial and tangential directions due to the transverse component of the diagonal tension field. The loads applied to the rings consist mainly of normal and tangential concentrated loads at the intersection of stringer and ring. Further secondary loads may be present, but for preliminary calculations these loads should suffice to give a rational basis. The author is indebted to Mr. I. J. Gerard, since many of the ideas included in this paper are the outcome of conversations with him. Appendix. (i) Direct Shear. Fig. (9) represents a portion of a thin shell of thickness t subjected to a vertical shear load V. In order to determine the distribution of shear stress round the shell consider the equilibrium of a small element ABCD whose position is defined by the co-ordinates x, y, z. Its position is further defined by the distance / between the element and a convenient reference point P, measured round the surface of the shell (P and the element at x, y, z, lying in the same vertical plane). Summing the forces acting on AB CD in the Oz direction, due to bending stresses p and shear stresses ,, gives : lp lz lq The plane Oxz may be taken to be the neutral surface of the shell when subjected to bending in the plane Oyz. Now if I is the second moment of area of the transverse section of the shell about the Ox axis, and M is the bending moment at a section distant z from the origin, M p=-f~ -y and = V iz Tip TJM y " TJT = Y ' 1= iq Vy "* W T~ Vy Integrating equation (1) gives V f q = — — .1 ydl+q. (1) (2) P - (P + ^. a*) (q+ ig.diy ill t. J)z = o where q0 is the shear at / = o. Equation (1) gives the rate of change of shear stress round the section and (2) gives the shear stress at any point whose position is defined by I (or x.y.z). The shear stress q is now assumed to be resisted by diagonal tension fields disposed at 450 to the Oz direction. The tensile stress is given by : Ft = 2t. The component of the F( stress in the Oxy plane is given by F = F*/2 .-. F = q.
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