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Question 1 An accident causes a descending elevator to stop suddenly half way between the 3rd and 4th floor of a 10 story building.
Question 1
An accident causes a descending elevator to stop suddenly half way between the 3rd and 4th floor of a 10 story building. At the time of the accident, the single cable that supports the elevator has a nominal length of 21 meter. The diameter of this stranded steel cable is 4.5 cm and has an elastic modulus of 83 GPa. The elevator including the passengers has a mass of 5000kg and is descending at a velocity of 2 m/s.
a) Determine the maximum elongation of the 21 m long cable due to the sudden stop.
b) What is the maximum tensile stress developed in the cable.
Question 2.
The drive shaft of an industrial fan is machined from a cold drawn steel with a hardness 160 BHN. The shaft has a diameter of 30 mm, is 0.3 m long and has a 6 mm diameter transverse hole. Estimate the safety factor with respect to static yielding and infinite fatigue life for:
a) a torque fluctuation between 0 and 80 Nm,
b) a completely reversed torque of 40 Nm,
c) a mean torque of 47 Nm plus a superimposed alternating torque of 34 Nm.
