MecMovies 4.0 : M3.2: The Stress-strain Diagram

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The graph plots stress in p s i versus strain in inch per inch. The horizontal axis ranges from 0 to 0.1 and the vertical axis ranges from 0 to 80,000. The graph starts at the bottom left of the viewing window at the origin, goes up and to the right with constant steepness till the point (0.050, 50,000). The graph then goes up and to the right with a reduced positive slope till (0.1, 60,000). A straight line is drawn passing through (0, 0) and (0.0040, 43,700) and it overlaps the linear portion of the curve. The triangular region below the line joining the points (0, 0) and (0.0040, 43,700) is shaded. The shaded triangular region has a run length of delta epsilon which equals 0.0041 inch per inch and a rise length of delta sigma which equals 43,700 p s i.

Using the proportional limit and the origin, the elastic modulus $E$ would be computed as:

$E = \frac{∆ σ}{∆ ε} = \frac{43, 700 psi}{0.0041 in . / in .} = 10, 660, 000 psi$