53204-mt----experimental Stress Analysis

NR

Code No: 53204/MT

M.Tech. – II Semester Regular Examinations, September, 2008 EXPERIMENTAL STRESS ANALYSIS (Machine Design) Time: 3hours

Max. Marks:60 Answer any FIVE questions All questions carry equal marks ---

1.a) b)

2.a) b) 3.a)

b) 4.a) b) 5.a) b)

Explain clearly what do you understand by: i) Plane stress problem ii) Plain strain problem. Given the displacement field: u = x 4 + 3x 2 y 2 + x + y + 2 z 3 + 4 v = xy + 2 y 3 + y 2 z + z 2 + 1 w = x 2 + xy + 2 yz + zx + y 2 + 2 z 2 + 2 Compute the associated strain at the point (2, 2, 2). Derive an expression for the gauge factor of an electrical resistance strain gauge. Describe with sketches wise type and foil type electrical resistance strain gauges. For recording strain-time curves explain when the following recording devices are used. i) Oscillograph ii) Cathod ray oscilloscope. With the help of a sketch explain the operating principle of a lightwriting oscillograph. State the advantages and limitations of the brittle coating method of experimental stress analysis. Discuss briefly the factors affecting the behaviour of stress coat. Explain Moire method of whole field strain analysis. Briefly discuss the advantages of Moire fringe technique. Contd…2

Code No: 53204/MT

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6.a)

Discuss the requirements of an ideal photoelastic model material for two dimensional photo elasticity. b) Discuss the effect of a stressed photoelastic model in a plane Polariscope.

7.a) b)

Explain briefly the shear difference method in three dimensions. Write a note on slicing a model and interpretation of the resulting fringe pattern in three dimensional photo elasticity.

8.

Write i) ii) iii) iv)

short notes on the following: Bire fringent coatings Fringe order determination in birefringent coatings Cross sensitivity of an electrical resistance strain gauge. Isochrometic and Isoclinics. *****