JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III Year AEROSPACE VEHICLE STRUCTURES- II Previous Question Paper (May - 2018 - R13)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b, c as sub questions.
PART - A
State the principle of the stationary value of the total complementary energy
Answer
The principle of the stationary value of the total complementary energy states that for a linearly elastic structure in equilibrium under given loads, the actual state of stress is that which makes the total complementary energy stationary with respect to all statically admissible variations of the stress field.
What are the boundary conditions for a plate with one built-in edge and other edges are free for solving the bending of thin plate problems?
Answer
For a plate with one built-in (clamped) edge at x=0, the boundary conditions are: deflection w=0 and slope dw/dx=0. For the free edges, the bending moment M and the effective shear force (Kirchhoff shear) V must be zero.
What do you mean by unsymmetrical bending?
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Write the conditions for zero warping of beam subjected to torsion.
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Write the principal assumptions for structural idealization.
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Derive the expressions for boom areas of an idealized panel.
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Write the expression for a beam is axially unconstrained and loaded by a pure torque T the rate of twist is constant along the beam.
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What is torsion-bending constant for torsion of an arbitrary section beam?
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Distinguish between monocoque and semi monocoque fuselage.
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What are the various structural elements used in airplane wings? Explain their role with respect to different types of loads.
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PART - B
Explain the difference in the buckling behaviour of solid and thin walled columns.
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A column of length lm has the cross-section shown in Figure 1. If the ends of the column are pinned and free to warp, calculate its buckling load; E = 70000 N/mm2, G = 30000 N/mm2.
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A plate 10 mm thick is subjected to bending moments Mx equal to 10 N-m/mm and My equal to 5 N-m/mm. Calculate the maximum direct stresses in the plate.
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Derive the Bredt-Batho formula related to torsion. What are the assumptions made?
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Determine the direct stress distribution in the thin-walled Z-section shown in figure 2, produced by a positive bending moment Mx.
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Idealize the box section shown in figure 3 into an arrangement of direct stress carrying booms positioned at the four corners and panels which are assumed to carry only shear stresses. Hence determine the distance of the shear centre from the left-hand web.
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Calculate the deflection of the free end of a cantilever 2000mm long having a channel section identical to that in figure 4 and supporting a vertical, upward load of 4.8 kN acting through the shear centre of the section. The effective direct stress carrying thickness of the skin is zero while its actual thickness is 1 mm. Young’s modulus E and the shear modulus G are 70000 and 30000 N/mm2, respectively.
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Define shear lag and write the equilibrium equations with free body diagrams for six-boom beam subjected to a shear load.
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Derive the expression for total torque of I-section beam subjected to torsion.
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An axially symmetric beam has the thin-walled cross-section shown in figure 5. If the thickness t is constant throughout and making the usual assumptions for a thin-walled cross-section, show that the torsion bending constant ΓR calculated about the shear centre S is
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The central cell of a wing has the idealized section shown in figure 6. If the lift and drag loads on the wing produce bending moments of −120 000Nm and −30 000Nm, respectively at the section shown, calculate the direct stresses in the booms. Neglect axial constraint effects and assume that the lift and drag vectors are in vertical and horizontal planes.
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The fuselage of a light passenger carrying aircraft has the circular cross-section and the cross-sectional area of each stringer is 100 mm2 and the vertical distances given in figure 7, are to the mid-line of the section wall at the corresponding stringer position. If the fuselage is subjected to a bending moment of 200 kN-m applied in the vertical plan of symmetry, at this section, calculate the direct stress distribution.
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