Compressive Yield vs. Compressive Strength for Iron

yield is yield, ultimate is ultimate (also called tensile strength), when discussing metal strengths, whether compressive or tensile. General rule but funny exception is gray iron, class 20-60 ...

Tell me specific grade/class of iron you look for compressive strength?

Then 8,68-16,53GPa is yield and >110GPa is ultimate strength. Before ultimate strength is reached material is plasticaly deformed and after it is crushed or raptured. Yield is point where plastic deformation starts. Corect me if I didn't get it right.

Careful, Iron is a brittle metal, there's very minimal plastic deformation and/or elasticity, but there is some, and yes, that's accurate about yield point. The key is to nail down the exact alloy of iron you have. Hopefully these images will help of pertinent tables:

"Before ultimate strength is reached material is plasticaly deformed and after it is crushed or raptured."

Which definition of rapture were you thinking of?

Main Entry: ¹rap·ture
Pronunciation: 'rap-ch&r
Function: noun
Etymology: Latin raptus
1 : an expression or manifestation of ecstasy or passion
2 a : a state or experience of being carried away by overwhelming emotion b : a mystical experience in which the spirit is exalted to a knowledge of divine things
3 often capitalized : the final assumption of Christians into heaven during the end-time according to Christian theology

But sites 1 and 2 refer to diamond, not iron. I thought the figures looked unfamiliar!

Site 3 is for single iron crystals, presumably chemically pure? I doubt whether this data is much practical use (for engineering) as crystals behave different from bulk metal, and iron is always used in form of alloys.

If it's any use, data I have on ductile (SG) iron is tensile strength 420 MPa, elastic modulus 170 GPa. For low-carbon steel tensile strength is about 490 MPa, for (eg) high-tensile bolts it's ~ 1400 MPa. Elastic modulus ~ 200 GPa for most grades of steel (which is why higher-grade steel is no advantage in a structure if it's limited by deflection rather than stress, as is often the case)

I haven't worked much with plain iron as I'm in aerospace and everything is steel, titanium or aluminum.

I've always used the milspec documents that contain material information on just about everything imaginable. The values of strength (compressive, tensile, shear for example) are vary depending on the specifics of how the metal was formed. Cold worked or heat treated metals will be more rigid than a simple cast part. The values also change depending on the grain direction in the metal.

In a nutshell there's just a whole lot of data attained from testing and no two sources completely agree with one another.

For simplified specs, I would recommend www.matweb.com

Sweet