I'd like to thank the Preacher for that link he provided for the complete story about the Boxall and Edmiston FEA Stress Analysis. It confirms what I said earlier; i.e. that the picture Kip posted was very incomplete information.
However, I'm not sure how or where the Preacher came up with these statements:
100,000,000 newtons/sq. meter = 14,504 psi yield (not ultimate) strength.
Boxall & Edmiston stated in 2011 that the frame was EN series chrome moly steel
Shotshell pressure is distributed in every direction; most, likely down the (unobstructed) barrel, some contained by the chamber walls, and some directed toward the standing breech.
Recoil is directed back against the standing breech, up (depending on the axis of the bore), and (in a SxS) laterally and (maybe) down initially.
The stress analysis pic clearly shows a color chart or table on the right of the frame. And at the very bottom of the scale it notes that a red color indicates the yield strength for the steel in this frame. As I noted earlier, that
yield strength is 220,594,000 newtons/ sq. meter. If this action really had a yield strength of only 100,000,000 newtons/sq. meter, or 14,505 psi, it is likely a standard SAAMI 19,800 psi average proof load would cause permanent plastic deflection, or worse. Uh... no! The action depicted in this FEA simulation is far stronger than that.
The Boxall and Edmiston link informs us this:
Please note - for this stress analysis we put far more force onto the action than would be exerted with a normal cartridge, to highlight potential weak points.So even with their simulated proof load, the junction of the action bar and standing breech shows a green color, which is far below the actual stated yield strength.
It was also incorrect for the Preacher to state that "Shotshell pressure is distributed in every direction; most, likely down the (unobstructed) barrel, some contained by the chamber walls, and some directed toward the standing breech." Actually, at any given point in time, the pressure recorded by a transducer or crusher would be roughly equal on all points inside the barrel, the chamber, and behind the wad and shot. We've all seen pressure curves that show a very rapid rise to peak pressure, and a rapid drop as the wad and shot moves down the barrel. So the pressure and resulting force exerted upon the base of the wad would be roughly equal to an equivalent area at the breech. And this is why a shell with a larger base, as in a 12 ga. vs. a 20 ga., will exert a greater force on the standing breech if the pressures in both are equal. This is called breech thrust, and is based upon the formula; FORCE = PRESSURE x AREA
My experience with FEA Stress analysis is admittedly limited. But from having a lot of experience with other analytical tools such as FDA, ibaPDA, and ibaAnalyzer, I can confidently say any of these tools are only as useful as the ability of the user to understand and interpret the data they are looking at.
