EG$-207$

Class exercise $-$ Strain Gauge $/$ Stress Calculation

A local force is applied to a A$36$ steel plate. A single strain gauge is used to measure the maximum stress on the plate. The strain gauge GI is placed in a Wheatstone bridge shown below. G$1.$ R$2,$ R$3,$ and R$4$ all have a nominal resistance of $3500$ hms $.$ The supply voltage into the circuit is $5$ volts. When a load is applied the resistance of G$1$ changes by positive $0\mathrm{.}07$ ohms.

Calculate the output voltage of the Wheatstone bridge, the measured strain. and local stress value. Does the plate yield or fail?

A$36$ Steel Properties

Young's modulus E $\backslash (=30\backslash$mathrm$\{$Mpsi$\}\backslash )$

Yield strength $\backslash (36,000\backslash$mathrm$\{$psi$\}\backslash )$

Ultimate tensile strength $\backslash (=58\mathrm{.}000\backslash$mathrm$\{$psi$\}\backslash )$