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

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SUMMARY

The discussion focuses on calculating the internal pressure exerted on a sealed 5052 aluminum battery pack chassis when additional gas is introduced. The chassis dimensions and the volume of air (205.8 mL) are specified, along with the introduction of 2400 mL of gas. The internal and external pressure during installation is noted as 11.777 psi. To assess the stress concentration at the countersunk holes, it is recommended to reference Roark's formulas for stress and consider the ideal gas law for pressure calculations.

PREREQUISITES
  • Understanding of ideal gas law and its application in pressure calculations
  • Familiarity with stress concentration factors, particularly around countersunk holes
  • Knowledge of material properties of 5052 aluminum
  • Basic principles of mechanics of materials, including plane stress analysis
NEXT STEPS
  • Research Roark's Formulas for Stress and Strain for stress concentration calculations
  • Study the application of the ideal gas law in confined spaces
  • Explore finite element analysis (FEA) tools for simulating stress in mechanical components
  • Investigate methods for testing the structural integrity of enclosures under internal pressure
USEFUL FOR

Mechanical engineers, product designers, and quality assurance professionals involved in the design and testing of battery enclosures and pressure vessels.

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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