Design of machine elements question bank

This post covers the important university questions which were already asked in previous Anna university semester examinations April/may 2015, for the subject ME6503 Design of machine elements. Make preparation well with use this as reference.

B.E/ B.Tech Degree Examinations April/May 2015

Anna University, Chennai

Department of Mechanical Engineering

Design of Machine Elements

Regulation 2008/2010

Part B (16 marks)

1.     Design a muff coupling to connect two steel shafts transmitting 25 kW power at 360 rpm. The shafts and keys are made of plain carbon steel 30C8 (S_yt=S_yr=400 N/mm²). The sleeve is made of grey cast iron FG 200 (S_xt = 200 N/mm²). The factor of safety for the shafts and key is 4. For the sleeve, the factor of safety is 6 based on ultimate strength. (AU April/May 2015)

2.         It is required to design a square key for fixing a gear on a shaft of 30mm diameter. The shaft is transmitting 20 kW power at 600 rpm to the gear. The key is made of steel 50C4 (S_yt=460 N/mm²) and the factor of safety is 4. For key material, the yield strength in compression can be assumed to be equal to the yield strength in tension. Determine the dimensions of the key.    (AU April/May 2015)

3.         A rigid coupling is used to transmit 60 kW power at 350 rpm. There are six bolts. The outer diameter of the flanges is 250 mm, while the recess diameter is 175mm. The coefficient of friction between the flanges is 0.15. The bolts are made of steel 45C8 (S_yt=380 N/mm²) and the factor of safety is 3. Determine the diameter of the bolts. Assume that the bolts are fitted in large clearance holes. (AU April/May 2015)

4.         Load on hydrodynamic full journal bearing is 30 kN. The diameter and speed of the shaft are 150 mm and 1200 mm respectively. Diametral clearance 0.2 mm. Sommerfield number is 0.631.L/D ratio 1:1. Calculate temperature rise of oil, quantity of the oil, heat generated and type of oil required. (AU April/May 2015)

5.         Enumerate the detail steps involved in the selection of bearings from the manufacturer’s catalogue. (AU April/May 2015)

6.         A butt welded joint with ground and flush surface is subjected to tensile load which varies from 50 kN to 100 kN. Plates are 10mm thick. Determine the length of weld required for over 2,500,000 cycles. (AU April/May 2015)

7.         Design a helical compression spring to sustain an axial load of 4 kN. The deflection is 80 mm. spring index is 6. The shear stress is not to exceed 350 Mpa. Rigidity modulus for spring material is 81 Gpa. (AU April/May 2015)

8.   Design a leaf spring for the following specifications for a    truck. Assume factor of safety is 2.

            Maximum load on springs = 100 kN

            No of springs   = 4

         Material of spring= Cr Va steel (σ_a = 138 Mpa and 

            E=206 * 10³ Mpa)

            Span of spring = 1000 mm

            Width of central band  = 150 mm

            Permissible deflection = 100 mm

Assume 2 full length leaves and 6 graduated leaves. (AU April/May 2015)