Design of Machine Elements (ME306002)

Class Test

1. Answer all questions. All questions carry equal marks2. Make suitable assumptions wherever necessary3. Put √ on your chosen answer.

1. Adaptive design is based on(a) Existing design adapted for new application (b) New inventions for new application (c) Conceptual design for new application (d) New Technology for new application

2. The composition of 20Cr18Ni2 is:(a) 20% Cr, 18%Ni, 2%Carbon (b) 0.2% carbon, 18% chromium and 2% nickel.(c) 2% Cr, 0.18%Ni, 0.2%Carbon (d) 2% carbon, 0.18% chromium and 0.2% nickel.

3. Resilience is the property of a material:(a) that enables it to resist indentation (b) that enables it to resist wear (c) that enables it to resist shock and impact(d) that enables it to resist scratching

4. Tolerance is the difference between:(a) Maximum and minimum dimensions of a component(b) Maximum dimension of the shaft and maximum dimensions of the hole(c) Minimum and minimum dimensions of a component(d) Minimum dimension of the shaft and the maximum dimension of the hole

5. A 3m long cantilever beam of solid rectangular cross-section of 100mm width and 150mm depth is subjected to an end loading P as shown. If the allowable shear stress in the beam is 150 MPa, the safe value of P based on shear alone is

(a) 1 MN (b) 1.5 MN (C) 2.3 MN (d) 3.5 MN

6. A vertical load Py = 20 KN is applied at the free end of a cylindrical bar ofradius 50 mm as shown in figure. The principal stress at the point A is

(a) 56Mpa, 7.4Mpa (b) 84Mpa, −8.9Mpa (c) 105Mpa, 9.3MPa (d) 112.5Mpa, −14.72Mpa

7. A heat treated steel shaft of tensile yield strength of 350 MPa has a diameter of 50mm. The shaft rotates at 1000 rpm and transmits 100 kW through a gear. An appropriate keyDimension is:

(a) Width = 16 mm, Length = 45 mm, Depth = 10 mm. (b) Width = 10 mm, Length = 35 mm, Depth = 8 mm.(c) Width = 18 mm, Length = 55 mm, thickness = 11 mm. (d) Width = 20 mm, Length = 65 mm, thickness = 12 mm.

Data Provided

8. In a steam engine the steam pressure is 2 MPa and the cylinder diameter is 250 mm.The contact surfaces of the head and cylinder are ground and no packing is required. Assuming that the number of bolts to be used is 12 a suitable bolt for the joint to be leakproof would be :

(a) M20x1.5 (b) M16x1.5 (c) M5x0.8 (d) M10x1.25

Data Provided

9. In the plate shown below it is required that the stress concentration at hole does not exceed that at the fillet. The hole diameter is

(a) 21.5 mm (b) 35 mm (c) 41.9 mm (d) 53mm

Data Provided

10. In a typical clamp coupling the clamping pressure between the shaft and the sleeve is given by

(a) nπdc2 σt/(d L) (b) 0.5nπdc

3/2 σt/(d L1/2) (c) 0.75nπdc4

σt/(d L)2 (d) 0.25nπdc2 σ t/(d L)

Where dc is the core diameter of the bolts, d is the clamp diameter, L the clamp length and σt is the tensile yield stress.

11. A single square thread power screw is to raise a load of 50 KN. A screw thread of major diameter of 34 mm and a pitch of 6 mm is used. The coefficient of friction at the thread and collar are 0.15 and 0.1 respectively. If the collar frictional diameter is 100 mm and the screw turns at a speed of 1 rev per second. The power input to the screw is

(a) 1549 watts (b) 2300 watts (c) 2614 watts (d) 3167 watts

12. A helical spring of wire diameter 6mm and spring index 6 is acted by an initial load of 800N. After compressing it further by 10mm the stress in the wire is 500MPa. Taking G = 84000MPa the number of active coils is

(a) 13 turn (b) 21 turns (c) 27 turns (d) 32 turns

13. For a simple cantilever type leaf spring with uniform strength the leaf thickness can be given by(a) σmax L3/2/(E δmax

1/2) (b) σmax L3/(E δmax2)

(c) σ max L 2 /(E δ max) (d) σmax L4/(E δmax3)

Where δmax is the spring deflection, L is the characteristic length, σmax is the design stress or maximum stress and E is the Modulus of elasticity

14. A solid shaft of length 1m carrying a load of 5 kN at the center is simply supported. If the maximum shaft deflection is 1mm and E=200GPa the diameter of the shaft based on deflection is

(a) 23mm (b) 31mm (c) 44mm (d) 58mm

15. Two plates of 7 mm thickness are connected by a double riveted lap joint of zigzag pattern. If the rivet diameter is 19mm and σt = 90MPa, σc = 120MPa, τ= 60 MPa the rivet pitch is

(a) 29mm (b) 53mm (c) 73mm (d) 102mm

16. If the yield strength of the weld material is 150Mpa the safe value of F is

(a) 108 KN (b) 213 KN (c) 269 KN 313 KN

17. If in the band brake shown below drum dia=400mm, lining width=75mm, rotational speed is 200rpm,a=250mm, m=75mm,α =2700,μ =0.2 and the maximum lining pressure is 0.5Mpa the torque is

(a) 632 Nm (b) 915 Nm (c) 1150 Nm (d) 3160 Nm

18. A plate clutch has a single friction surface with 250 mm OD and 100 mm ID, μ= 0.2 and p max= 0.7 MPa. If the uniform wear theory is valid the required axial force is:

(a) 67N (b) 109N (c) 197N (d) 288N

19. An axially loaded brass (Ebr=90GPa) strut hinged at both ends is 1m long and is of a square cross-section of sides 20mm. The dimension of steel (Esteel=200 GPa) strut of the same length and subjected to the same axial loads is:

(a) 5.92mm (b) 9.73mm (c) 16.38mm (d) 32 mm

20. Hydrodymic Lubrication occurs at:

(a) Very low Sommerfeld Number (b) Low Sommerfeld Number (c) Medium Sommerfeld Number (d) High Sommerfeld Number