This set of Machine Design Multiple Choice Questions & Answers (MCQs) focuses on “Shaft Design”.
1. While designing shaft on the basis of torsional rigidity, angle of twist is given by?
c) 292 Ml/Gd⁴
d) None of the mentioned
Explanation: θ=(180/π)xMl/GJ where J=πd⁴/32.
2. According to ASME code, maximum allowable shear stress is taken as X% of yield strength or Y% of ultimate strength.
a) X=30 Y=18
b) X=30 Y=30
c) X=18 Y=18
d) X=18 Y=30
Explanation: ASME Standard. The lesser value is taken among the two.
3. Does ASME Standard take into consideration shock and fatigue factors?
Explanation: Moment is multiplied by a number to consider these factors while designing the shaft.
The layout of a shaft supported on bearings at A & B is shown. Power is supplied by means of a vertical belt on pulley B which is then transmitted to pulley C carrying a horizontal belt. The angle of wrap is 180’ and coefficient of friction is 0.3. Maximum permissible tension in the rope is 3kN. The radius of pulley at B & C is 300mm and 150mm.
For questions 4-7, refer to figure 1.
4. Calculate the torque supplied to the shaft.
d) None of the listed
Explanation: M=(P₁-P₂)xR where P₁=3000N, P₂=P₁/e^(Coeff of friction x Angle of wrap).
5. Calculate the tension in the rope of pulley C.
a) 6778.3N and 7765.3N
b) 5948.15N and 2288.75N
c) 5468.4N ad 8678.3N
d) None of the listed
Explanation: (P₃-P₄)x150=549.3×1000 and P₃/P₄=2.6. Hence P₃=5948.15N and P₄=2288.75N.
6. If allowable shear stress in the shaft is 70N/mm² and torsional and bending moments are M=1185000N-mm and m=330000N-mm, find the diameter of the shaft.
7. If bending moment on point B in horizontal plate is M and in vertical plane is m, then the net bending moment at point B is?
Explanation: The two moments act perpendicularly to each other.
8. Calculate the shaft diameter on rigidity basis if torsional moment is 196000N-mm, length of shaft is 1000mm. Permissible angle of twist per meter is 0.5’ and take G=79300N/mm².
a) None of the listed
9. If yielding strength=400N/mm², the find the permissible shear stress according to ASME standards.
a) 72 N/mm²
b) 76 N/mm²
c) 268 N/mm²
d) 422 N/mm²
10. The stiffness of solid shaft is more than the stiffness of hollow shaft with same weight.
Explanation: Hollow shaft is more stiff.
11. The strength of hollow shaft is more than the strength of solid shaft of same weight.
Explanation: Outer fibers are more effective in resisting the applied moments. In hollow shafts material is removed and spread on a larger radius.
12. Solid shaft is costlier than hollow shaft of same weight.
Explanation: Hollow shaft cost is more as material is to be selectively emplaced.
13. Solid shafts are used in epicyclic gearboxes.
Explanation: In epicyclic gears, one shaft rotates inside other and hence hollow shafts are used.
14. Flexible shafts have ___ rigidity in torsion making them flexible.
c) Very high
d) Infinitely small
Explanation: Flexible shafts have high rigidity in torsion making then capable to transmit torque.
15. Flexible shafts have ______ rigidity in bending moment.
c) Very high
d) Extremely low
Explanation: Flexible shafts have low rigidity in bending moments making them flexible.
Sanfoundry Global Education & Learning Series – Machine Design.
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