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Your thinking is muddled. Pressure is pressure and the only pressure that matters is PEAK.

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Bolt Thrust

Bolt thrust is easy to calculate. Only two inputs are required. They are peak chamber pressure in PSI and as mentioned, the inside area of the case head that the gas pressure can work on. The formula then is:



THRUST=AREA*CPSI Where:



AREA=3.1416*(HS/2)^2



HS=the diameter of the inside of the case head.

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How much is the bolt thrust, 4 or 5 tons. What if a force of 5 tons was applied to the bolt for 12 months...I think that would be considered a greater load on the bolt than firing 10 shots.

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It simply doesn't work that way. From the bolt's perspective if you apply 5 tons of force for 10 milliseconds or 10 months, it is the SAME 5 tons of force. Of course if, in your example, the bolt was heated to 300 deg F or higher you might see some creep (I would guess on the magnitude of 0.0005" or less). Creep is a funtion of contact pressure, temperature, and the material under load. Steels are relatively creep resistant (compared to aluminum, steel hardly creeps at all). The endurance limit is another area you may find of immense interest. You will also want to work on obtaining a working understanding of the concept of strain energy, and the von Mises theory of strain energy / distortion (effects of combined stresses acting upon a system).



In my last post I stated the facts as tersely as possible. If you NEED a more detailed explanation I suggest you buy some Mechanical Engineering books (Strength of Materials, Machine Design, would be two excellent reference books), or you could go to www.SAE.org and look for fatigue analysis books in their book store. You may also want to review SAE's list of Technical Papers.



I apologize, but it is too blinking hard to try and explain this stuff on a forum chat board. Don't feel bad though, they don't teach fatigue in college very well either, so we get to teach the children about it after they start out in the real world.



Anyway, if you get the textbook or technical papers and have any specific questions I will try and answer them for you, to the best of my meager ability.



Here is a question for you (you may find the answer interesting)



Are any of the following steels significantly stronger / weaker in tensile strength that any of the others?( singificantly would mean a difference of greater than 5% ):



SAE 1040 @ Rockwell C 55

SAE 4140 @ Rockwell C 55

SAE 8640 @ Rockwell C 55

SAE 4340 @ Rockwell C 55



ASS_CLOWN