# Bending moment graph

1. Jun 28, 2012

### aaalanc

how can i graph the equation of the bending moment?
The equation is: σ = MC / I and i want to graph in excel or matlab, , so i know that the graph is a straight line, and i have the values, but i don't know how draw the graph

2. Jun 29, 2012

3. Jul 8, 2012

### OffTheRecord

let's say you've got a set of x-coordinates, from x=0 to x=L. If you're using matlab, type the following:

x=linspace(0,L,L)

where L is the total length of the beam. That will give you an entire array of x-values.

I'm assuming M is dependent upon x. You should have some sort of equation already. C and I are constant the whole length of the beam, I hope. (If not, then they still depend on x, and you can simplify MC/I into one big function of x). So now, define M, C, and I in the program:
M= whatever
C= whatever
I = 1/12*whatever*whatever^3

Then, define Sigma in terms of M, C, and I (which are already defined in terms of x).

Sigma = M*C/I

Finally, you can plot the results by typing:

plot(x,Sigma)

4. Jul 8, 2012

### Studiot

Did you do as I suggested and revise what a bending moment is?

You say you want to plot a graph of bending moment but your formula is for something different.

What is sigma, M, C and I in your formula and how is a plot of sigma v x a plot of bending moment?