proof stress vs yield stress

[H Cameron]

Good morning guys,

I see “proof stress 0.2% & 0.1%” in a MTR. What’s the relation between them and yield stress? Can I compare them with min Y stress in the Section II and pass the material?

Thanks.

 

[metengr]

The proof stress by definition is a reported tensile yield strength. So, 0.2% offset would be equal to 0.2% tensile YS.

 

[H Cameron]

Metengr

Actually, I didn’t get your point, we have a column in section II for Tensile Strength and another for Yeild Strength. In this case MTR gave me the Tensile Strength and two proof Stress Rp=0.2% & 1%. But it doesn’t have anything about YS.

Is it required?

 

[metengr]

My point is proof stress is used as yield stress, as I stated above. The 0.2% proof stress would be the equivalent to 0.2% YS. So this is the reported YS value and satisfies Table 2.

 

[H Cameron]

thanks metengr.

you are one of the best metengr i have ever seen

 

[mrfailure]

As already noted proof stress in the manner you have specified is yield stress. I think of proof stress as the stress (or corresponding proof load) that are a specified applied stress/load where no deformation occurs. For example, I commonly test fasteners first at specified proof load, then continue with increasing load until fracture for the tensile strength as specified in ASTM F606. Offset proof stress really means yield stress in non-US standards.