Yang (https://doi.org/10.1557/jmr.2010.0267) developed a formula that relates yield stress and hardness of materials under indentation interaction. This is valid for isotropic solids with elastic and plastic regimes defined by stress-strain power laws.

I think that formula could help you. Good luck!

thanks Mr. Simon Roa for your kind answer.

I read the article you sent. But it looks like that it needs some structural data (like size of the core and the plastic region of the material etc) for calculation of yield stress that can only be found from testing the material directly...

I have the half included angle of the conical indenter, Poisson's ratio and elastic modulus but they don't look enough for the calculation.

Sincerely

Hi Arman Darbandi.

In the paper I mentioned, there is an analytical formula (Eq. (36)) to estimate the material Yield stress (Y) from indentation Hardness (H), strain hardening exponent (n), Young´s modulus (E), and indenter half-angle (α). The formula is:

H = (2Y/3) [ (1/n)(Ecot(α)/3Y)n + 1 - 1/n ]

If you have some idea about the magnitude of n, H, E and α (= 70.32° for Vickers indenter), you could easily estimate the magnitude of Y. In this case, H has units of N/m2, i.e., it is measured following the S.I. units. To convert Vickers hardness (in HV) to H in S.I. units, you can use the following formula:

(g x10-3 )Hvickers [HV] = H [GPa] ; with g: gravity acceleration ≈ 9.8 [m/s2]

To practical effects, it has been observed that the following relation is satisfied for most metals and alloys:

Y ≈ H/c ; with c varying between 2 and 4, depending on materials elastic-plastic behavior.

It is generally well-accepted to use the relation Y ≈ H/3 for a wide variety of metals and alloys of engineering interest. More details about this approach can be found in the following references:

Article Scaling approach to conical indentation in elastic-plastic s...

Article General relationship between strength and hardness

I hope this information can be useful.

Kind regards.

The answer given by Simon Roa is pretty good, only I inform that this kind of conversion is discussed by me, using different references on this article:

An Overview of the Hardness Differential Required for Abrasion | Request PDF (researchgate.net)

Best regards, Giuseppe

Article Correlation of Yield Strength and Tensile Strength with Hard...

Thanks Mr. Tadeu Borba for the article recommendation.

It also gave me good idea of how to calculate the yield stress from hardness. But i should have mentioned that the region of stress that i am looking for is almost above 1800MPa and the formulation of this article works for below 1700MPa and doesn't have good correlation for above that tension.

best regards

I use flat tip indenter to estimate the yield strength for different materials please have a look at the manuscript and let me know if you have any questions

Article Novel techniques for estimating yield strength from loads me...

Regards,

Thank you Mr. Abdelbaset R. H. Midawi for the answer

I have read your article and it was a very interesting work. Unfortunately i don't have access to data like forces that you have mentioned in the article nor the indenter for testing the material. But i have reached an approximate answer from the articles that are mentioned in previous messages.

I had a lack of data and that's why i was looking for a direct method to approximately calculate the yield stress from hardness, like those that you have mentioned in first references in your article.

Best regards.