11-06-2013, 01:03 PM
SEMESTER EXAMINATIONS FOR EXPERIMENTAL STRESS ANALYSIS
EXPERIMENTAL STRESS.pdf (Size: 47.88 KB / Downloads: 24)
Answer any five questions
All questions carry equal marks
1.a) Derive the equilibrium equations for a 3D elastic body.
b) If a displacement field is described as follows,
u = (-3x2y + 7y2x2 + 6xy) and v = (6xy2 +8yx3 – y2)
Determine the strain components ∈x, ∈y, and γxy at the point x =2, y = -3.
2.a) Outline the two methods which can be used to compensate for temperature induced apparent strains in semiconductor strain gauges.
b) The strain sensitivity of most metallic alloys is about 2. What portion of this sensitivity is due to dimension changes in the conductor? What portion is due to changes in the number of free electrons and their mobility?
3.a) Briefly describe the difference between direct and frequency modulation recording.
b) Four strain gauges are mounted on a steel tension specimen having a cross sectional area of 6 mm2 to produce a load cell. If two of the gauges are mounted in the axial direction and the other two in the transverse direction, and if the gauge factor for all gauges is 2.05. What gauge factor should be dialed into a manual null balance strain indicator so that it will give a direct reading of the load P applied to the tension load cell?
4.a) What are the primary disadvantages of the brittle coating method?
b) What is the significance of uncracked areas of the brittle coating field at the conduction of brittle coating test? Comment on the advisability of using servo – controlled loading methods for brittle coating testing.
5.a) Describe the mechanism of formation of Moire fringes.
b) Explain the displacement field approach to moiré fringe analysis.
6. Derive the equations for light passing through a stressed model in a plane polariscope with the polarizer and analyzer are in parallel positions. Under what condition does extinction (I = 0) occur?
7.a) Explain in detail different techniques for locking deformations in the loaded model.
b) Describe the applications of the Frozen Stress Method.
8.a) Discuss the procedure to be used to install a coating on a panel with an elliptical hole.
b) Specify a coating i.e., material and thickness, to use for the analysis of the following (E = 200 GPa, μ = 0.30) Structures
i) A curved beam where maximum stress is 150 MPa
ii) A cylindrical shell with radius 1500 mm and wall thickness 15 mm subjected to a pressure of 5 MPa.