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NOVEMBER 2008 MAIN EXAMINATION

SUBJECT NAME: STRENGTH OF MATERIALS II

CODE: SMT211T/SMT101T

DURATION: 3 HOURS

TOTAL MARKS: 100

FULL MARKS: 100

SPECIAL REQUIREMENTS:NON-PROGRAMMABLE POCKET CALCULATORS

INSTRUCTIONS TO CANDIDATES: ANSWER ALL THE QUESTIONS

NUMBER OF PAGES (COVER PAGE INCLUDED) : 3+ APPENDIX

COURSE:

ND: ENGINEERING : MECHANICAL

FIRST EXAMINER:

DA DESAI

SECOND EXAMINER:

MODERATOR:

FM MASHILE

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a) Determine the average bearing pressure b between the angle bracket and the bolts.

b) Determine the average shear stress avg in the bolts. Disregard friction between

the bracket and the column./15/

QUESTION 4

A steel shaft ABCD has a total length of 540 mm consisting of AB = 150 mm;

BC = 150 mm and CD = 240 mm. AB is hollow with inside and outside diameters of 30 mm

and 40 mm respectively, BC and CD are solid and the diameter of BC = 40 mm. Calculate:

a) the diameter of CD if the torsional stiffness of CD is equal to that of AB.

b) the total angle of twist if the compound shaft is subjected to a torque of 500 N.m.

G = 80 GPa.

/15/QUESTION 5

A thin steel cylinder, 400 mm in diameter, with closed ends is rotated at a speed of

5 000 r/min about a longitudinal axis through its center. If it is simultaneously subjected to

an internal pressure of 4 MPa, calculate the thickness of the cylinder assuming that themaximum allowable tensile stress is limited to 170 MPa. The density of steel is 7.8 Mg/m3.

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QUESTION 6

The beam ABCDEF is loaded as shown in the figure below:

a) Determine the reactions at B and E; 4

b) Draw the Shear Force diagram; 2

c) Draw the Bending Moment diagram; 6d) Find the maximum Bending Moment and its position from A; 4

e) Determine the point(s) of contraflexure. 4

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QUESTION 7

A composite spring has two close-coiled helical springs connected in series. One spring ismade of steel and the other of bronze, both with a mean coil diameter of 35 mm and a wire

diameter of 4 mm.

a) If the deflection of both springs is to be the same, calculate the ratio between the numberof coils in each spring.

b) the greatest load that can be carried by this composite spring if the maximum allowable

stresses are 240 MPa and 180 MPa in the steel and bronze respectively.

Gsteel = 80 GPa and Gbronze = 40 GPa. .

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TOTAL MARKS [100]

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