Hall Petch Equation: Is My Math Right?

[richard9678]

What is the Hall Petch equation. When I Google (images) I get::

σ_y = σ_o + k_y / √d

or

σ_y = σ_o + k_y d^1/2

In the first k_y is divided by √d and in the second multiplied by √d.

The second equation is in a study book I have.

Am I making a math error? Thanks.

 

[Ssnow]

I saw from different references that is $\sigma_{y}= \sigma_{0}+k_{y}d^{-\frac{1}{2}}$

 

[richard9678]

I saw from different references that is $\sigma_{y}= \sigma_{0}+k_{y}d^{-\frac{1}{2}}$

Yes, the minus sign should be there. :-)