King Salman International University
Field of Engineering (Mechatronics Program)
MEC 314: Mechanical System Design
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Sheet (1): Introduction to Design Concepts
1. A mild steel rod of 12 mm diameter was tested for tensile strength with the gauge
length of 60 mm. Following observations were recorded: Final length = 80 mm;
Final diameter = 7 mm; Yield load = 3.4 KN and Ultimate load = 6.1 KN.
Calculate: yield stress, Ultimate tensile stress, Percentage reduction in area, and
Percentage elongation.
2. A cast iron link, as shown in the following figure is required to transmit a steady
tensile load of 45 KN. Find the tensile stress induced in the link material at sections
A-A and B-B
3. A coil chain of a crane required to carry a maximum load of 50 KN, is shown in the
following figure. Find the diameter of the link stock, if the permissible tensile stress
in the link material is not to exceed 75 MPa.
4. A steel shaft 35 mm in diameter and 1.2 m long held rigidly at one end has a hand
wheel 500 mm in diameter keyed to the other end. The modulus of rigidity of steel
is 80 GPa. Find
a. What load applied to the tangent to the wheel's rim produces a torsional shear
of 60 MPa?
b. How many degrees will the wheel turn when this load is applied?
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Dr. Ahmed Hegazy
King Salman International University
Field of Engineering (Mechatronics Program)
MEC 314: Mechanical System Design
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5. A spindle as shown in the following figure is a part of an industrial brake and is
loaded as shown. Each load P is equal to 4 KN and is applied at the mid-point of its
bearing. Find the diameter of the spindle, if the maximum bending stress is 120
MPa.
6. A 20-mm-diameter steel bar (G=79.3 GPa) is to be used as a torsion spring. If the
torsional stress in the bar is not to exceed 110 MPa when one end is twisted through
an angle of 15°, what must be the length of the bar?
7. Two circular rods of 50 mm diameter are connected by a knuckle joint, as shown in
the following figure by a pin of 40 mm in diameter. If a pull of 120 KN acts at each
end, find the tensile stress in the rod and shear stress in the pin.
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Dr. Ahmed Hegazy