# Mechanics

posted by on .

A tension test was performed on a steel specimen having an original diameter of 12.5 mm and gauge length
of 50 mm. Using the data listed in the table, plot the stressâ€“strain diagram, and determine approximately the
modulus of toughness. Use a scale of 20 mm-50 MPa and 20 mm = 0.05 mm/mm.

0
11.1
31.9
37.8
40.9
43.6
53.4
62.3
64.5
62.3
58.8

Elongation (mm)
0
0.0175
0.0600
0.1020
0.1650
0.2490
1.0160
3.0480
6.3500
8.8900
11.9380

I know that I have to use the equations sigma=(P/A) and epsilon=(dL/L) to get the points for stress and strain... but how do I get the values for the equations? I tried to get the stress with the second values of the table:

sigma=(11.1e3 Pa)/(pi*(0.0175e3m)^2)
I get 11.54 and it is supposed to be 90.45 MPa. How do I do these?

• Mechanics - ,

sigma is in fact Pressure, which is force/area. you are given force, compute area from the diameter.

epsilon is change of length divided by length. You are given deltaL (elongation). L was given as 50mm.
Surely you can calculate delta L /L

For each data point given, calculate those two quantities (sigma, deltaL/L), and plot the graph