Scaling BH curves for non-fully-dense powdered metals 1

[DAlbertson]

I'm designing several small parts in 410 or 416 stainless, to be manufactured in powdered metal. It is common to specify the density of a part to be 80% to 85% of theoretical (solid) density. Higher densities, essentially to 100%, are achievable, but all these are much higher cost: initial mold, mold maintenance, and a much larger press. Keeping the density down is a good thing.

Interestingly, the drop in yield strength is proportional to the drop in density. What I'd like to know is this: if I want to specify a part to be 85% dense, can I reasonably multiply the BH curve by 0.85 and use it in an FEA?

Thanks very much!
Dave

 

[MagMike]

Given that you are only dealing with 85% density, it is a reasonable approximation. However, I would recommend only scaling the B values of the curve, not the H. Since B represents the response of the material to an applied magnetic field (H), it is the one that'll be decreasing.

 

[DAlbertson]

MagMike,

Thank you very much! I will use 0.85 as an approximation, multiplying only the magnetic flux density values, not the magnetic field strength values. (Sorry for the clumsy wording in my original post.)

This is great! It's wonderful when something that seems like it ought to be true turns out to be true!

Thank you again,
Dave