1. Weldments in fabricated steel beams are designed for

1. 1. bending stresses at the flange

   
   
   

   2. shear stresses in transverse plane

   
   
   

   3. combination of bending and shear

   
   
   

   4. none of these because in fabricated beams welds not to get stressed

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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2. A hydrodynamic Journal bearing is subjected to 2000 N load at a rotational speed of 2000 rpm. Both bearing bore diameter and length are 40 mm. If radial clearance is 20 mm and bearing is lubricated with an oil having viscosity 0.03 Pa.s, the Sommerfeld number of the bearing is __________.

1. 1. 0.6

   
   
   

   2. 0.8

   
   
   

   3. 8.0

   
   
   

   4. 6.0

   
   
   

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1. View Hint View Answer Discuss in Forum

   S =		r		²	μDs
   		c			P

   
   d = 40 mm ⇒ r = 20 mm
   c = 20 μm ⇒ c = 20 × 10^–3mm
   μ = 0.03 PaS ⇒ μ = 0.03 × 1^–6MPa.S
   D_s = 2000 rpm ⇒ D_s = 2000/60 rps
   

   P =	p	=	2000	= 1.25 MPa
   	1 × d		40 × 40

   
   

   S =		20		²	×	0.03 × 10-6 × 2000/60	= 0.8
   		20 × 10-3				1.25

   Correct Option: B

   S =		r		²	μDs
   		c			P

   
   d = 40 mm ⇒ r = 20 mm
   c = 20 μm ⇒ c = 20 × 10^–3mm
   μ = 0.03 PaS ⇒ μ = 0.03 × 1^–6MPa.S
   D_s = 2000 rpm ⇒ D_s = 2000/60 rps
   

   P =	p	=	2000	= 1.25 MPa
   	1 × d		40 × 40

   
   

   S =		20		²	×	0.03 × 10-6 × 2000/60	= 0.8
   		20 × 10-3				1.25

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3. Ball bearings are rated by a manufacturer for a life of 106 revolutions. The catalogue rating of a particular bearing is 16 kN. If the design load is 2 kN, the life of the bearing will be P x 10⁶ revolutions, where P is equal to _________

1. 1. 2/5

   
   
   

   2. 5/2

   
   
   

   3. 4/3

   
   
   

   4. 3/4

   
   
   

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1. View Hint View Answer Discuss in Forum

   L10 =		C		³
   		W

   
   where L₁₀ = Basic life rating in millions of revolutions C = Basic dynamic load rating
   P = Equivalent dynamic radial load
   

   ∴ L10 =		16		³	=	5
   		2				2

   Correct Option: B

   L10 =		C		³
   		W

   
   where L₁₀ = Basic life rating in millions of revolutions C = Basic dynamic load rating
   P = Equivalent dynamic radial load
   

   ∴ L10 =		16		³	=	5
   		2				2

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4. Two identical ball bearings Pand Q are operating at loads 30 kN and 45 kN respectively. The ratio of the life of bearing P to the life of bearing Q is

1. 1. 81/16

   
   
   

   2. 27/8

   
   
   

   3. 9/4

   
   
   

   4. 3/2

   
   
   

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1. View Hint View Answer Discuss in Forum

   For ball bearing
   P.(L)^1/₃ = C
   Given: P_P = 30 kN
   P₂ = 45 kN
   

   LP	=		P2		³
   L2			PP

   
   

   	45		³	=		3		³	=	27
   	30					2				8

   Correct Option: B

   For ball bearing
   P.(L)^1/₃ = C
   Given: P_P = 30 kN
   P₂ = 45 kN
   

   LP	=		P2		³
   L2			PP

   
   

   	45		³	=		3		³	=	27
   	30					2				8

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5. A bracket (shown in figure) is rigidly mounted on wall using four rivets. Each rivet is 6 mm in diameter and has an effective length of 12 mm.
   
   Direct shear stress (in MPa) in the most heavily loaded rivet is

1. 1. 4.4

   
   
   

   2. 8.8

   
   
   

   3. 17.6

   
   
   

   4. 35.2

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given: Number of rivets = 4,
   Diameter of each rivet, d = 6 × 10^–3m
   Direct load on the bracket = 1000 N
   since there is no eccentricity
   

   ∴ Load on each rivet =	1000	= 250N
   	4

   
   

   ∴ Shear stress =	P	=	250	= 8.8 MPa
   	A		π/4 (6)²

   Correct Option: B

   Given: Number of rivets = 4,
   Diameter of each rivet, d = 6 × 10^–3m
   Direct load on the bracket = 1000 N
   since there is no eccentricity
   

   ∴ Load on each rivet =	1000	= 250N
   	4

   
   

   ∴ Shear stress =	P	=	250	= 8.8 MPa
   	A		π/4 (6)²

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