8/17/2015 Basic Engineering Knowledge

[FastTrack Guru]

Question:

The piston of a hydraulic actuator is 1.5 inches in diameter and is subject to a hydraulic line pressure of 1500 psi.  Calculate what the cross sectional area should be (in2) if the design stress for the piston is 20,000 psi:

(A) .132 in2
(B) .232 in2
(C) .332 in2
(D) .432 in2

[FastTrack Guru]

The Answer is (A).

A basic principle is:

Pressure = Force / Area

Therefore:

1500 psi = Force / [π (1.5)2/4]   (the area of a circle = πd2/4)

1500 psi (1.76 in2) = Force

Force = 2640 lb (This force is acting on the piston)

Therefore:

Pressure = Force / Area
20,000 psi = 2640 lb / Area
Area = 2640 lb / 20,000 psi

Area = .132 in2