JNTU
JNTU B.Tech III AEROSPACE VEHICLE STRUCTURES II Previous Question Paper (January/February - 2023 - R13)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
Explain the basic theory of thin plates.
Answer
The basic theory of thin plates, known as Kirchhoff-Love plate theory, assumes that the plate thickness is small compared to its lateral dimensions. It posits that a line initially normal to the mid-surface remains straight and normal to the deformed mid-surface, and that normal stress in the thickness direction is negligible.
What is the term flexural rigidity called in bending of thin plates and explain?
Answer
Flexural rigidity, denoted as D, represents the resistance of a plate to bending. It is defined by the formula:
where E is Young's modulus, t is plate thickness, and ν is Poisson's ratio. It acts similarly to the flexural rigidity EI in beam theory, scaling the relationship between bending moments and plate curvature.
Explain about Bredt–Batho theory and formula.
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Discuss about primary and secondary warping of thin-walled beams.
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Explain the effect of idealization on the analysis of open and closed section beams.
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Derive the equation to find out boom areas with neat sketches.
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Write a short note on loading discontinuities in beams?
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Discuss shear stress distributions of a closed section beam built in one end and subjected to bending.
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What is the function of wing ribs with neat sketches?
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Write about the cutouts in fuselage and wing with neat sketches.
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Part B
A plate 10mm thick is subjected to bending moments Mx equal to 10 Nm/mm and My equal to 5 Nm/mm. Find the maximum twisting moment per unit length in the plate and the direction of the planes on which this occurs.
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Determine the deflected form of the thin rectangular plate a×b is simply supported along its edges. It supports an in-plane tensile force Nx per unit length and carries a uniformly distributed load of intensity q0.
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A thin-walled beam has the cross-section shown in Figure 1. Determine the direct stress distribution produced by a hogging bending moment Mx.
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Calculate the position of the shear centre of the thin-walled unsymmetrical channel section shown in Figure 2.
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Part of a wing section is in the form of the two-cell box shown in Figure 3 in which the vertical spars are connected to the wing skin through angle sections all having a cross-sectional area of 300mm2. Idealize the section into an arrangement of direct stress carrying booms and shear stress only carrying panels suitable for resisting bending moments in a vertical plane. Position the booms at the spar/skin junctions.
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The thin-walled single cell beam shown in Figure 4 has been idealized into a combination of direct stress-carrying booms and shear-stress-only-carrying walls. If the section supports a vertical shear load of 10 kN acting in a vertical plane through booms 3 and 6, calculate the distribution of shear flow around the section. Boom areas: B1=B8=200 mm2, B2=B7=250 mm2, B3=B6=400 mm2, B4=B5=100 mm2.
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Derive the expression of the torsion bending constant for an open section beam fully built-in at one end.
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Explain the improvements of specific torsion bending strength in lipped Channel T-section over the un-lipped channel section.
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The wing section shown in Figure 5 has been idealized such that the booms carry all the direct stresses. If the wing section is subjected to a bending moment of 300 kNm applied in a vertical plane, calculate the direct stresses in the booms. Boom areas: B1 = B6 = 2580 mm2, B2 = B5 = 3880 mm2, B3 = B4 = 3230 mm2
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Find the shear flow in each web of the tapered beam shown in the Figure 6. Plot the distribution of axial load along each stiffening member when P1=20kN and P2 =10kN. All dimensions are in cm.
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