Quantifying explosions - how to determine force/pressure/etc?

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    Explosions
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SUMMARY

The discussion centers on quantifying the forces generated by explosions, specifically using PETN (Pentaerythritol tetranitrate) as the primary explosive. A key formula presented is R = (E t² / ρ)^(1/5), where R represents the explosion radius at time t, E is the energy released, and ρ is the ambient air density. This formula, historically applied to the Trinity test, provides a method to estimate energy output with a 10% accuracy margin. The conversation highlights the challenge of correlating the rate of detonation with the total energy expended as explosive material increases.

PREREQUISITES
  • Understanding of explosive materials, specifically PETN.
  • Basic knowledge of physics, particularly in energy and force calculations.
  • Familiarity with the concept of detonation rates.
  • Knowledge of ambient density and its impact on explosion dynamics.
NEXT STEPS
  • Research the application of the formula R = (E t² / ρ)^(1/5) in various explosive contexts.
  • Explore the characteristics and applications of PETN in explosive engineering.
  • Study the principles of detonation and how they relate to energy output in explosives.
  • Investigate methods for measuring ambient air density and its effects on explosion force calculations.
USEFUL FOR

This discussion is beneficial for explosive engineers, physicists, and safety technicians involved in the handling and analysis of explosive materials, particularly those working with PETN and similar compounds.

denver75
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We're doing another demonstration about explosives, discussing the forces created.

Our primary explosive is PETN (detcord) - handled by a licensed technician of course.

I need to prepare some facts about the physical forces at play with the explosions. How can I quantify the energy expended? I've been digging around and the only statistic that is readily available is the rate of detonation. However, as more explosive material is used, the rate of detonation doesn't increase, but the explosion does.

Any info/facts/stats/formulas that might get me on the right path?
Thanks!
-D75
 
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I don't have any expertise in this area, but I do recall that the equation:

R = (\frac{E t^2}{\rho}})^{\frac{1}{5}}

where R is the radius of the explosion at time t, E is the released in the explosion, and \rho is the ambient density of air in the vicinity, was correctly used by a physicist who wasn't working on the Manhattan project to determine the energy released in the trinity test based on measurements of R vs t, although the value for the total energy was classified for decades, this method yields the answer within 10%. By the way, the formula should also apply for light explosives too.

I will wait for others to say more, since I don't know much about explosives.
 

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