Question

A steel bar has cross-sectional area A=10^-3 m², Young modulus E= 2 x 10¹¹ Pa and Poisson’s ratio of 0.4. The steel bar has a rectangular cross sectional area.

a.         If the bar is subject to a compressive force of 10⁵ N, find the corresponding longitudinal and transverse strains.                                                    [3 marks]

b.         Two strain gauges, each with unstrained resistance of 120 Ω and a gauge factor of 2.0 are bonded on to the top surface of the steel bar.

            Determine the corresponding gauge resistance for the longitudinal and transverse strains.                                                                                     [4 marks]

c.         Draw a diagram that show how the strain gauges are placed on the bar and to which resistor location of the Wheatstone bridge is each of them connected.

            Assuming that you have another two additional strain gauges with the same specifications, how would you place these additional strain gauges and draw the set-up of the 4 strain gauges together with the Wheatstone bridge.                                                                                                                                [3 marks]

Answer 1