JEPPIAAR ENGINEERING COLLEGEDEPARTMENT OF AERONAUTICAL ENGINEERING

AE 2254- AIRCRAFT STRUCTURES -IIMPORTANT QUESTIONS

UNIT IStatically determinate structures

1. Tabulate the member forces for the structure shown below:

2. Calculate the forces included in the members of the pin-jointed truss shown in figure. Show the values on a neat diagram of the truss. Mention clearly the nature of the forces (tension or compression) in each case.

3. Find the forces in all the members of a structure shown below.

UNIT IIStatically indeterminate structures

1. Evaluate the bending moment and shear force diagram of the beam as shown in figure below. What are the reactions at the supports?

2. State and prove Theorem of three moments.

3. Find out the support reactions and draw shear force and bending moment diagram for the figure shown below.

UNIT IIIEnergy methods

1. The external diameter of a hollow shaft is twice the internal diameter. It is subjected to pure torque and it attains a maximum shear stress ζ. Show that the strain energy stored per unit volume of the shaft is 5 ζ2/16C. such a shaft is required to transmit 5800kW at 120rpm with uniform torque, the maximum stress not exceeding 94MN/m2. Determine the Shaft diameters, the energy stored per m3. C=100GN/m2

2. Find an expression for the strain energy due to bending for a beam of length l simply supported at the ends and carrying a uniformly distributed load w/unit run over the whole of its span. The beam is of constant cross section throughout its length having flexural rigidity as EI.

3. A beam of length l is simply supported t its ends and carries a concentrated load 2W at its center; it has a rectangular cross-section breadth b, depth d. If C is the modulus of rigidity for the beam find Shear strain energy in the beam, deflection due to shear.

UNIT IV Columns

1. A hollow alloy tube 5m long with diameters 40mm and 25mm respectively was found to extend 6.4mm under a tensile load of 6 tons. Find the buckling load for the tube, when used as a strut with both the ends pinned. Also find the safe load on the tube, taking factor of safety as 4.

2. Find the Euler’s Crippling load for hollow cylindrical steel columns of 38 mm external diameter and 2.5 mm thick. Take length of the column as 2.3 m and hinged at its both ends. Take E = 205 KN/mm2. Also determine the crippling load by Rankin’s formula using fc = 335 KN/mm2 and = 1/7500.

3. Derive an expression for Euler’s formula when one end of the column is fixed and the other end hinged.

UNIT VFailure theory

1. A cylindrical drum 800 mm in diameter has to withstand an internal pressure of 1.6 N/mm2. Calculate the necessary wall thickness for a factor of safety of 3.5 if the criterion of failure is maximum strain energy and the elastic limit in pure tension is 287 N/mm2. Take Poisson’s ratio, 1/m = 0.3

2. A cross section of a shaft 100mm in diameter is subjected to a bending moment of 8 KN-m and a twisting moment of 12 KN-m. Find the direct stress which acting alone will make the shaft to store the maximum strain energy per unit volume. Take 1/m = 0.3

3. A rectangular block of material is subjected to a tensile stress of 110 N/mm2

on one plane and a tensile stress of 45 N/mm2 on a plane at right angles, together with shear stresses of 65 N/mm2 on the same planes, Find:(a) The direction of the principal planes(b) The magnitude of the principal stresses(c) The magnitude of the greatest shear stresses.