Stress at c'sink holes of enclosed box with internal pressure

AI Thread Summary
The discussion centers on assessing the structural integrity of a battery pack chassis under internal pressure from gas venting. The chassis is a sealed 5052 aluminum enclosure, and the user seeks to calculate the pressure exerted on the walls when additional gas is introduced. The ideal gas law is suggested as a method for determining the pressure, requiring knowledge of the gas mass. Additionally, stress concentration around countersunk holes should be analyzed, with references to Roark's book recommended for guidance. The overall goal is to demonstrate that the chassis will not deform or burst under these conditions.
patrickv
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I have an issue I'm not quite sure how to approach. A customer is requesting that we prove that our battery pack chassis will not burst or deform if additional gases are introduced inside the enclosed box (the batteries could vent).

The chassis is assumed to be a sealed .05" thick 5052 AL enclosure with dims shown (attached). There are four countersunk screws attached to standoffs securing a PC board inside. The volume of air in the box is approximately 205.8 mL. If 2400 mL is introduced, how would I find the pressure exerted on the inside walls of the box and, more importantly how do I illustrate that the thinnest portion of the wall (at the countersinks) won't give. Pressure inside and outside the box during installation is 11.777 psi. Thank you.
 

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Couldn't you use the ideal gas law to calculate the pressure? You will need to know the total mass of gas inside your container. As far as the stress concentration around your countersunk holes, I would look through Roark's book to see if anything is listed. As a rough first approximation, you could treat them as circular holes under plane stress. Keep in mind that there will be additional stresses due to the screw/standoff and weight of the board.
 

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