JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year DESIGN OF MACHINE MEMBERS - I Previous Question Paper (November/December - 2017 - R13)

A mild steel shaft of 50 mm diameter is subjected to a bending moment of 2000 Nm and a torque T. If the yield point of the steel in tension is 200 MPa, find the maximum value of this torque without causing yielding of the shaft according to:

a) The maximum principal stress

b) The maximum shear stress and

c) The maximum distortion strain energy theory of yielding.

A cantilever beam made of cold drawn carbon steel of circular cross-section is subjected to a load which varies from – F to 3 F. Determine the maximum load that this member can withstand for an infinite life using a factor of safety as 2. The theoretical stress concentration factor is 1.42 and the notch sensitivity is 0.9. Assume the following values: Ultimate stress = 550 MPa, Yield stress = 470 MPa, Endurance limit = 275 MPa.

Two lengths of mild steel tie rod having width 200 mm and thickness 12.5 mm are to be connected by means of a butt joint with double cover plates. Design the joint if the permissible stresses are 80 MPa in tension, 65 MPa in shear and 160 MPa in crushing. Make a sketch of the joint.

Determine the size of the bolts and the thickness of the arm for the bracket, if it carries a load of 40 kN at an angle of 60 degrees to the vertical. The material of the bracket and the bolts is same for which the safe stresses can be assumed as 70, 50 and 105 MPa in tension, shear and compression respectively.

Design and draw a sleeve and cotter joint to resist a tensile load of 60 kN. All parts of the joint are made of the same material with the following allowable stresses: σt = 60 MPa ; τ = 70 MPa ; and σc = 125 MPa.

Design and draw a knuckle joint to connect two mild steel bars under a tensile load of 25 kN. The allowable stresses are 65 MPa in tension, 50 MPa in shear and 83 MPa in crushing.

A horizontal nickel steel shaft rests on two bearings A and B and carries two gears C and D. Power transmitted is 20 kW at 120 RPM. Power is delivered to C and taken out at D. FtC and FtD act vertically downwards. Find the diameter of the shaft, if the working stress is 100 MPa in tension and 56 MPa in shear. Assume given shock/fatigue factors 1.5 for bending and 1.2 for torsion.

Design and draw a cast iron flange coupling for a mild steel shaft transmitting 90 kW at 250 rpm. The allowable shear stress in the shaft is 40 MPa and the angle of twist is not to exceed 1 degree in a length of 20 diameters. The allowable shear stress in the coupling bolts is 30 MPa.

Design a close coiled helical compression spring for a service load ranging from 2250 N to 2750 N. The axial deflection of the spring for the load range is 6 mm. Assume a spring index of 5. The permissible shear intensity is 420 MPa and modulus of rigidity G = 84 kN/mm^2. Neglect the effect of stress concentration. Draw a fully dimensioned sketch.

Design and draw a valve spring of a petrol engine for the following operating conditions: Spring load when open = 400 N, closed = 250 N. Maximum inside diameter of spring = 25 mm. Length when open = 40 mm, closed = 50 mm. Maximum permissible shear stress = 400 MPa.