# Stress / strain

1. Feb 5, 2010

### williamx11373

After making a chart in Excel and obtaining the equation " Y= 3E+07x+2445.3 "

Now i need to calculate the modulus of elasticity. I know that the slope of the equation gives the modulus of elasticity.

but I have no clue how to even begin solving the equation Y= 3E+07x+2445.3

I do know E=stress/strain.... any hint or advice would help.

(do i just find the slope of elastic portion)? is that the answer?

2. Feb 6, 2010

### magwas

I am also struggling with a mech problem and it seems there are relatively few mechanical engineers are here. So let's try to help each other. Sorry if I can give you only general advice.
It always helps to write the units with the equations. I could pretend understanding physics a lot of times because I could deduce the rules from the units. Serious scientists also cheat the same way: http://en.wikipedia.org/wiki/Dimensional_analysis
It also helps to state the meaning of the letters used.
For now I will pretend that y is stress, x is strain, and E is not Young modulus, but 3E+07 wants to mean 3*10^7
So we have
y = ax+b
where a=30 MPa
and b=2445.3 (dimensionless)
the stress/strain function is
f(x) = ax + b
it's slope is simply its derivative
f'(x) = a
So the elastic modulus is 30 Mpa