MCQ on design of Shaft machine design mechanical engineering

 MCQ on design of Shaft machine design mechanical engineering 

Which property is not required for shaft materials? (a) High shear and tensile strength (b) Good machinability (c) High fatigue strength (d) Good castability
Solution D

The design of shafts made of brittle materials is based on

(a)	Guest's theory
(b)	Rankine's theory
(c)	St Venant's theory
(d)	VonMises theory Solution B

When a shaft is subjected to a twisting moment, every cross-section of the shaft will be under

(a)	tensile stress
(b)	compressive stress
(c)	shear stress
(d)	bending stress

 Solution A

The product of the tangential force acting on the shaft and its distance from the axis of the shaft (i.e. the radius of the shaft) is known as

(a)	bending moment
(b)	twisting moment
(c)	torsional rigidity
(d)	flexural rigidity

 Solution B

The standard length of the shaft is

(a)	5 m
(b)	6 m
(c)	7 m
(d)	all of these Solution D

In power transmission equation, P=2πNT/60×1000

(a)	P is in kw and T is the maximum torque
(b)	P is in NM/sec and T is the maximum torque
(c)	P is in NM/sec and T is mean torque
(d)	P is in kw and T is mean torque

 Solution D

A shaft revolving at ω rad / s transmits torque (T) in N-m. The power developed is

(a)	T.ω watts
(b)	2πTω watts
(c)	2πTω/75 watts
(d)	2πTω/4500 watts Solution D

When the shaft is subjected to pure bending moment, the bending stress is given by?

(a)	32M/πd3
(b)	16M/πd3
(c)	8M/πd3
(d)	None of the listed  Solution A

 Which of the following act on shafts?

(a)	Torsional moment
(b)	Bending Moment
(c)	Both torsional and bending
(d)	None of the mentioned Solution C

A circular shaft can transmit a torque of 5 kN-m. If the torque is reduced to 4 kN-m, then the maximum value of bending moment that can be applied to the shaft is

(a)	1 kN-m
(b)	2 kN-m
(c)	3 kN-m
(d)	4 kN-m  Solution C

The angle of twist of shaft is

(a)	directly proportional to (shaft diameter)2
(b)	inversely proportional to (shaft diameter)2
(c)	directly proportional to (shaft diameter)4
(d)	inversely proportional to (shaft diameter)4  Solution D

Which of following statement is correct, for the two shafts connected in parallel?

(a)	Torque in each shaft is the same
(b)	Shear stress in each shaft is the same
(c)	The angle of twist of each shaft is the same
(d)	Torsional stiffness of each shaft is the same

 Solution C

A shaft is subjected to fluctuating loads for which the normal torque (T) and bending moment (M) are 1000 N-m and 500 N-m respectively. If the combined shock and fatigue factor for bending is 1.5 and combined shock and fatigue factor for torsion is 2, then the equivalent twisting moment for the shaft is

A. 2000 N-m

B. 2050 N-m

C. 2100 N-m

D. 2136 N-m

Answer: Option D 

Solution

$\text{T}=1000N-m,M=500N-m$

$T_e=\sqrt{(k_{M}M{)}^2+(k_{T}T{)}^2}$

$k_M=1.5,k_T=2$
$T_e=2136N-m$

A shaft is subjected to fluctuating loads with nominal torque of 1500 N-m and a bending moment of 2000 N-m respectively. If the combined shock and fatigue factors for bending and torsion are 2.0 and 1.5 respectively then the equivalent torque is  

A. 4589.5 N-m

B. 4050 N-m

C. 2400 N-m

D. 4136 N-m

Answer: Option A

Solution

$\text{T}=1500N-m,M=2000N-m$

$T_e=\sqrt{(k_{M}M{)}^2+(k_{T}T{)}^2}$

$k_M=2,k_T=1.5$

$T_e=4589.4N-m$

A shaft is subjected to a maximum bending stress of 80 N/mm2 and maximum shearing stress equal to 30 N/mm2 at a particular section. If the yield point in tension of the material is 280 N/mm2 and the maximum shear stress theory of failure is used, then the factor of safety obtained will be

A. 2.5

B. 2.8

C. 3.0

D. 3.5

Answer: Option B 

sigma 1  = √(sigma b)² + 4(tou)²

= √ 80² + 4(30)² = 100

For maximum shear stress = {sigma 1- sigma 2}/2

={100-0}/2 = 50

=tmax = (fos)/2*fos

So Factor Of safety = Yield stress/ 2 tmax
=280N/mm²/100N/mm²
=2.8