# Math Help - Partial diff

1. ## Partial diff

HI everybody

so I'm sorry about my poor English.

Tank u very much

2. ## Re: Partial diff

These equations are a little confusing. Equations (1), (2) and (4) all define $f$ and are set equal to 0. Need more info before I can say how (8) is arrived at. What is $f$ actually?

3. ## Re: Partial diff

But we can ignore equations (1),(2) and just use of another equations. Please just use of equations (3),(4),(5),(6),(7) and (8). and sigma is a constant. and f is a yield function in plasticity. In fact, f represents a surface in the space of (sigma1,sigma2). I have uploaded piece of this paper for u, maybe that help.
Thank u again

4. ## Re: Partial diff

It's not a matter of ignoring equations; I'm saying they make no sense. I've looked at the paper and your equation (8) is not there. Are you talking about their equation (10)? That equation does make sense.

5. ## Re: Partial diff

sorry
yes. equation (10)

6. ## Re: Partial diff

I'll need the rest of the paper to see how $\varepsilon_{i j}$ are defined.