Question

Problem #1 (35 pts.) A solid 5 cm by 5 cm square aluminum rod, with a 70 GPa modulus of elasticity, is stretched by an unknown axial load. The initial rod length is 1 m, and its final length (after applying the axial load) is 1.0005 m. Assume that a strain gauge (with a gauge factor of 2.2) is firmly affixed to the rod, its active axis aligned with the length of the rod. You may assume the strain gauge is part of the bridge circuit shown below, in the Z1 position. Consider the bridge circuit to be balanced before the rod is stretched, and let the bridge supply voltage be 10 V Answer the following questions: a) After the axial load is applied, what is the axial strain? b) After the axial load is applied, what is the axial stress (in MPa)? c) What is the applied axial load (in kN)? d) What is the output voltage before the rod is stretched? e) What is the output voltage after the rod is stretched? f) Keeping everything else the same, you apply a different axial load to the rod. With this new load applied, you measure a voltage of 1 mV at the bridge output. What is the new strain, stress, and applied load? g) What is the relationship between the bridge output voltage and the applied load? Is this relationship linear, or non-linear?

Answer 1

Solution (す) To () Axia skas e)(r005 I 11000S 00oS e ss 235 Mpa (t) Applied load 87,5 kN

CD 1.1 x1. 12

Xia Cr) 3.18 MPa 79S kN