Rr322102-aircraft-structures-ii

Set No. 1

Code No: RR322102

III B.Tech Supplimentary Examinations, Aug/Sep 2008 AIRCRAFT STRUCTURES-II (Aeronautical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. Find the centroid and M.I. about both centroided axes. Also find the Major and Minor principal M.I. for the unsymmetrical Z section. Shown in figure 1. [16]

Figure 1 2. A channel section is subjected to a shear of 20kN. Determine the shear flow at points B,C,D and plot the shear flow variation throughout the cross-section. Also calculate the resultant force in each region of the cross-section. Shown in figure 2. [16]

Figure 2 3. Locate ShearCentre. Shown in figure 3.

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Set No. 1

Code No: RR322102

Figure 3 4. Two cell Aluminum structure is subjected to external torque T = 20 N-m. Determine the shear flow and angle of twist, if the max. Shear Stress is 40mpa. G =26 MPa. All dimensions are in mm. Shown in figure 4. [16]

Figure 4 5. Explain the procedure of finding shear flow in symmetric closed section, and location of shear centre for both single and multicell sections. [16] 6. A sheet panel is 75 - 230- 1.3 mm size. Consider all sides as simply supported. Determine the buckling load if the normal compressive load is applied normal to the 75mm sides. Do so for 3 different materials (a) Al alloy 70 75 -T6 (b) Magnesium HK31A (c) Titanium Ti-8Mn.

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7. For the beam shown in Figure 7, plot the axial loads in the flanges and stiffeners and flanges. Compute flange-bending moments and load per mm on all rivets. [16]

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Set No. 1

Code No: RR322102

Figure 7 8. Write short notes on the following: (a) shear lag (b) torsion of thin walled members. ⋆⋆⋆⋆⋆

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Set No. 2

Code No: RR322102

III B.Tech Supplimentary Examinations, Aug/Sep 2008 AIRCRAFT STRUCTURES-II (Aeronautical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. An axial compressive load P is acting at pt A ⊥ Lr to yz plane. Derive the Equation for bending stress at the four perpendicular. Corners and specify the nature of stresses. Identify the location for Max. tensile and compressive stresses. Shown in figure 1. [16]

Figure 1 2. Determine the shear flow and shear force for the section shown in figure 2.

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Figure 2 3. Determine Shear Centre. Shown in figure 3.

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Set No. 2

Code No: RR322102

Figure 3 4. A hollow thin wall torsion member is shown in figure 4. With uniform thickness and subjected to torque T. Derive the equation for torque and angle of twist in all the compartments. Also show that walls BC, CD, FC are Stress-free. [16]

Figure 4 5. Explain the procedure of finding shear flow in symmetric closed section, and location of shear centre for both single and multicell sections. [16] 6. Stiffener of flange member is an extrusion of 7075-T6 Aluminum alloy. Skin and web sheets are 7075-T6 Aluminum alloy. Thickness of skin is 0.9 mm and thickness of stiffener is 1.3 mm. Skin is fastened to stiffener by two rows of 3.2mm diameter rivets of brazier head type space 22mm apart. The web is attached to the stiffener by one row of 5mm diameter rivets spaced 25mm apart. Determine the effective skin area and total compressive load that the unit can carry. Shown in figure 6.[16]

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Set No. 2

Code No: RR322102

Figure 6 7. The beam shown in the Figure 7. Is assumed to have a pure tension field web. Plot the axial loads in the stiffeners and flanges. Assume angle of tension diagonal α = 45. [16]

Figure 7 8. Write short notes on the following: (a) shear lag (b) torsion of thin walled members. ⋆⋆⋆⋆⋆

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Set No. 3

Code No: RR322102

III B.Tech Supplimentary Examinations, Aug/Sep 2008 AIRCRAFT STRUCTURES-II (Aeronautical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. Show that, if a solid rectangular beam is bent by a couple applied in a plane containing one diagonal of the rectangular cross-section, the neutral axis will lie along the other diagonal. [16] 2. Derive the equation for shear flow in unsymmetrical section about the axis with the help of a neat sketch. [16] 3. Determine the location shear centre of the thin walked channel section. Shown in figure 3. [16]

Figure 3 4. A thin walled-box beam section of 2a x a x t is to be compared with circular section of diameter ‘a’. Find the thickness t so that the two sections have. Shown in figure 4 and figure 4. [16]

Figure 4

Figure 4 (a) The same maximum stress for the same torque 1 of 2

Set No. 3

Code No: RR322102 (b) The same stiffness.

5. Explain the procedure of finding shear flow in symmetric closed section, and location of shear centre for both single and multicell sections. [16] 6. A sheet panel 125mm - 320mm - 12mm has all edges simply supported. The panel is subjected to compression loads, which produce compressive stresses of 1700 N/cm2 applied normal to 125mm side. Will the sheet buckle under the given load system if made of Al alloy 2024-73 material. What is the margin of safety? [16] 7. What are the various types of wing structures? Show the construction with different types of stringers and web? [16] 8. Write short notes on the following: (a) stress concentrations (b) Effect of stress concentrations o wings and fuselage. ⋆⋆⋆⋆⋆

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Set No. 4

Code No: RR322102

III B.Tech Supplimentary Examinations, Aug/Sep 2008 AIRCRAFT STRUCTURES-II (Aeronautical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. Derive the Equation for bending stress for the beam show above figure1. Locate the orientation of the NA. Plot the Variation of the bending stress. [16]

Figure 1 2. Define shear flow? Explain the concept of shear flow in thin walled beams with the help of a neat sketch. [16] 3. Determine the Shear Centre of the thin walled section thickness t is constant. Shown in figure 3. [16]

Figure 3

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Set No. 4

Code No: RR322102

4. Derive the Bredt- Batho formula related to torsion. What are the assumptions made? [16] 5. A thin walled Box beam is use in the support structure of an aeroplane wing. Locate its shear centre. Shown in figure 5. [16]

Figure 5 6. Find crippling stress for the angle sections shown in figure 6 and 6. Using Gerard’s method.

Figure 6

Figure 6 (a) 2024 T3 Aluminum alloy (b) 7075-76 Aluminum alloy (All dimensions are in mm).

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7. What is shear flow in structural elements? Explain shear flow in wing and fuselage and sketch the variation? [16] 8. Write short notes on the following: (a) Effective walls and ineffective walls 2 of 3

Set No. 4

Code No: RR322102 (b) Sheet wrinkling.

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