MCQs on Shaft Design
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.
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.
Does ASME Standard take into consideration shock and fatigue factors?
a) Yes b) No
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.
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).
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.
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.
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.
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
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
The stiffness of solid shaft is more than the stiffness of hollow shaft with same weight.
Explanation: Hollow shaft is more stiff.
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.
Solid shaft is costlier than hollow shaft of same weight.
Explanation: Hollow shaft cost is more as material is to be selectively emplaced.
Solid shafts are used in epicyclic gearboxes.
Explanation: In epicyclic gears, one shaft rotates inside other and hence hollow shafts are used.
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.
Flexible shafts have ______ rigidity in bending moment.
a) High b) Low c) Very high d) Extremely low
Explanation: Flexible shafts have low rigidity in bending moments making them flexible.