Final Year Exam May 2009 2nd Year

Suez Canal University Production Engng & Mechanical Design Dept

Faculty of Engineering Port Said

Machine Elements Design ( Code : PRD 214 ) : 2nd Year Prod.

Allowed Time : 3 Hours

Final Year Exam May 2009

§ Answer All the questions and assume any missing data you find it necessary to complete your answer

§ The quality of the needed drawing has a direct influence in the evaluation of the question mark

Question No. 1 25 Marks

screw jack is to lift a load of 80 kN through a height of 400 mm. The elastic strength of screw material in tension and compression is 200 MPa and in shear 120 MPa. The material for nut is phosphor-bronze for which the elastic limit may be taken as 100 MPa in tension, 90 MPa in compression and 80 MPa in shear. The bearing pressure between the nut and the screw is not to exceed 18 N/mm².

Design and draw the screw jack. The design should include the design of

1.screw, 2. nut, 3. handle and cup, and 4. body.

Question No 2 20 Marks

Design and draw a neat sketch of a knuckle joint to transmit 150 kN. The design stresses may be taken as 75 MPa in tension, 60 MPa in shear and 150 MPa in compression.

Question No. 3 10 Marks

A bar 3 m long is made of two bars, one of copper having E = 105 GN/m² and the other of steel having E = 210 GN/m². Each bar is 25 mm broad and 12.5 mm thick. This compound bar is stretched by a load of 50 kN. Find the increase in length of the compound bar and the stress produced in the steel and copper. The length of copper as well as of steel bar is 3 m each.

Question No. 4 10 Marks

A shaft made of mild steel is required to transmit 100 kW at 300 r.p.m. The supported length of the shaft is 3 meters. It carries two pulleys each weighing 1500 N supported at a distance of 1 meter from the ends respectively. Assuming the safe value of stress, determine the diameter of the shaft.

Question No. 5 20 Marks

The Fig. below shows a shaft carrying a pulley A and a gear B and supported in two bearings C and D. The shaft transmits 20 kW at 150 r.p.m. The tangential force Ft on the gear B acts vertically upwards as shown. The pulley delivers the power through a belt to another pulley of equal diameter vertically below the pulley A. The ratio of tensions T1 / T2 is equal to 2.5. The gear and the pulley weigh 900 N and 2700 N respectively. The permissible shear stress for the material of the shaft may be taken as 63 MPa. Assuming the weight of the shaft to be negligible in comparison with the other loads, determine its diameter. Take shock and fatigue factors for bending and torsion as 2 and 1.5 respectively.

Question No. 6 15 Marks

A bracket is riveted to a column by 6 rivets of equal size as shown in the Fig. It carries a load of 60 kN at a distance of 200 mm from the centre of the column. If the maximum shear stress in the rivet is limited to 150 MPa, determine the diameter of the rivet.