JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III AEROSPACE VEHICLE STRUCTURES II Previous Question Paper (October - 2020 - R13)
Answer any five questions. All questions carry equal marks.
Main
Explain buckling waves in a simply supported flat plate.
Answer
When a simply supported flat plate is subjected to in-plane compressive loads, it remains flat until the load reaches a critical value, known as the buckling load. Beyond this point, the plate undergoes a bifurcation, forming a series of periodic buckling waves or half-sine waves in both the longitudinal and transverse directions. These waves represent the lowest energy configuration that satisfies the boundary conditions of zero displacement and zero bending moment at the simply supported edges.
Find the compression buckling stress for a sheet 10cm × 10cm × 3mm with all four edges simply supported, assuming Et = 55 GPa.
Answer
To calculate the compression buckling stress for a simply supported plate, we use the formula for the critical buckling stress:
Given parameters:
- Width (b) = 100 mm
- Thickness (t) = 3 mm
- Modulus (E) = 55 GPa = 55,000 MPa
- Aspect ratio (a/b) = 100/100 = 1
- Poisson's ratio (ν) = 0.3 (standard for metallic alloys)
For a square plate (aspect ratio = 1) with all edges simply supported, the buckling coefficient k is 4.0.
Substituting the values:
The compression buckling stress for the given plate is approximately 178.96 MPa.
Determine the buckling strength of a panel, comprising flat sheet and uniformly spaced Z-section stringers, a part of whose cross section is shown in Figure 1, under uniform compressive loads.
Answer
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Determine the shear flow distribution in the thin-walled Z-section shown in figure 2 due to a shear load Sy applied through the shear centre of the section.
Answer
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A beam having the cross-section shown in figure 3 is subjected to a bending moment of 1500 N-M in a vertical plane. Calculate the maximum direct stress due to bending stating the point at which it acts.
Answer
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Part of a wing section is in the form of the two-cell box shown in figure 4 in which the vertical spars are connected to the wing skin through angle sections all having a cross-sectional area of 300 mm2. 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.
Answer
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Find the position of the shear centre of the rectangular four boom beam section shown in figure 5. The booms carry only direct stresses but the skin is fully effective in carrying both shear and direct stress. The area of each boom is 100mm2.
Answer
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Derive the expression of the torsion bending constant for an open section beam fully built-in at one end.
Answer
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The fuselage section shown in Figure 6 is subjected to a bending moment of 100 kNm applied in the vertical plane of symmetry. If the section has been completely idealized into a combination of direct stress carrying booms and shear stress only carrying panels, determine the direct stress in each boom.
Answer
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