Suez Canal University
Faculty of Engineering
Production Engng & Mechanical Design Dept
Machine Elements Design
Port Said
Time 1 hour
2 nd Year
Mid Term, April 2008
Answer All the questions and assume any missing data
Question No. 1 25 Marks
Design a cotter joint to support a load varying from 30 kN in compression to 30 kN in tension. The material used is carbon steel for which the following allowable stresses may be used. The load is applied statically. Tensile stress = compressive stress = 50 MPa shear stress = 35 MPa and crushing stress = 90 MPa.
Present a neat sketch of the assembled joint indicating the important dimensions. The stresses developed in the various members have to be checked before finalizing the design . ( The Final neat Drawing of the joint has a direct effect on the evaluation of the total marks )
Question No. 2 5 Marks
(Solve either of the following 2 questions)
Question No. 2 - A
A central steel rod 18 mm diameter passes through a copper tube 24 mm inside and 40 mm outside diameter, as shown in the Fig. It is provided with nuts and washers at each end .The nuts are tightened until a stress of 10 MPa is set up in the steel. The whole assembly is then placed in a lathe and turned along half the length of the tube removing the copper to a depth of 1.5 mm. Calculate the stress now existing in the steel. Take Es= 2Ec.
OR :
Question No. 2 - B
A rectangular base plate is fixed at each of its four corners by a 20 mm diameter bolt and nut as shown in Fig 1. The plate rests on washers of 22 mm internal diameter and 50 mm external diameter. Copper washers which are placed between the nut and the plate are of 22 mm internal diameter and 44 mm external diameter.
If the base plate carries a load of 120 kN (including self- weight, which is equally distributed on the four corners), calculate the stress on the lower washers before the nuts are tightened.
What could be the stress in the upper and lower washers, when the nuts are tightened so as to produce a tension of 5 kN on each bolt ?
