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Author: Subject: What does brisance depend on besides detonation velocity?
Microtek
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[*] posted on 24-8-2023 at 23:15



Quote:

There is an active charge length "La". At L>La pulse does not grow.



Precisely. In general, using the charge length divided by the VOD to calculate an explosion duration is irrelevant to the matter of brisance. The book PLSHY is quoting seems to be using some very outdated methods. Could you give us a proper literary reference, so we can look at the source?


Quote:

explosion pressure*time=i, which is a unit of impulse, It is not a viscosity unit, I=FT is an expression of impulse


No, your maths are wrong - you use both upper and lower case letter "i" to denote impulse, and the two expressions are not equal. Indeed, they are not even in the same units. Pressure*time is not impulse, it is viscosity.

Regardless, I think this is not a fruitful discussion, so I won't be commenting further on your idea of brisance.
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MineMan
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[*] posted on 25-8-2023 at 04:23


Agreed. Don’t see the point of this discussion. Anyways. It will of course always be VOD, density, volume of gases and heat of detonation. Tho that changes with the addition of nano metals.
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PLSHY
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[*] posted on 26-8-2023 at 01:19


Well, I will attach my book, my book was written in the 2000s, if you are interested, you can translate it yourself

09DA80BF-FCE9-4B3D-A023-1B8C72F686E4.png - 1.1MBCD255440-F28C-4E52-9765-726463FD6DD7.png - 1.4MB
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PLSHY
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[*] posted on 26-8-2023 at 01:24


I always think that my point of view is correct, but it may be my poor expression ability plus translation that caused this failed discussion. I hope that the books I gave can provide some help for DennyDevHE77. Finally, I want to say, distinguish between uppercase and lowercase Impulse and specific impulse are common mathematical methods, which are also used in the book.
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OneEyedPyro
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[*] posted on 26-8-2023 at 12:30


Quote: Originally posted by PLSHY  
I always think that my point of view is correct, but it may be my poor expression ability plus translation that caused this failed discussion. I hope that the books I gave can provide some help for DennyDevHE77. Finally, I want to say, distinguish between uppercase and lowercase Impulse and specific impulse are common mathematical methods, which are also used in the book.


The language barrier is an issue but don't worry about it, your English is likely better than nearly all of the forum members Chinese.
The issue is that you're using unfamiliar and undefined terms like 'jerk' and violence. Beyond that, when we respond with established facts you seem to argue either due to the language barrier or because you don't fully understand the topic but believe you do.
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Etanol
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[*] posted on 26-8-2023 at 23:07


Quote: Originally posted by PLSHY  
Well, I will attach my book, my book was written in the 2000s, if you are interested, you can translate it yourself


The language of mathematics is universal. Thanks for the scans.
I found these calculations in my language and was able to match them.

Pc-j - is short for Chapman–Jouguet Pressure. This is the detonation pressure.
But your article uses its approximate value of 1/4 ro D^2. It is only true for CHNO-compounds at 1.0 g/cc and the authors of your paper explicitly state that they are using 1.0 g/cc.

I - is really the impulse when a detonation wave (a charge of length L) is reflected from a rigid wall.

i=I/S

But this is purely a mathematical problem. This is detonation in a perfectly rigid non-deformable tube.
In a real explosion, the lateral expansion of detonation products takes place. L cannot be infinite. There is an L/R parameter of a cylindrical charge that limits this model. In my book (L/R)max=4.5.
You cannot use formulas 2-70...2-72 to calculate real impulse.

Formula 2-73 is the active mass of a real cylindrical charge at L>=4.5R.
Formula 2-74 is the active mass of the shorter charge.

You must insert the active mass, not the total mass!, into formulas 2-71 and 2-72 to get the shock wave reflection impuls.
But it will not be accurate, because you used an inaccurate detonation pressure formula and the real wall is elastic.

Oooh, I understand your problem.
Quote: Originally posted by PLSHY  
brisance is the impulse per unit area.

No, no, no.
Because this definition does not take into account the scale effect.
The same substance, by your definition, will have different brisance depending on the diameter of the charge.
Impulse per unit area for a charge of fixed length and area.
Or the impulse per unit area and divide by the length of the charge.
Or the impulse per unit area and divide by the radius of the charge.

[Edited on 27-8-2023 by Etanol]

[Edited on 27-8-2023 by Etanol]
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PLSHY
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[*] posted on 27-8-2023 at 03:38


Quote: Originally posted by Etanol  
Quote: Originally posted by PLSHY  
Well, I will attach my book, my book was written in the 2000s, if you are interested, you can translate it yourself


The language of mathematics is universal. Thanks for the scans.
I found these calculations in my language and was able to match them.

Pc-j - is short for Chapman–Jouguet Pressure. This is the detonation pressure.
But your article uses its approximate value of 1/4 ro D^2. It is only true for CHNO-compounds at 1.0 g/cc and the authors of your paper explicitly state that they are using 1.0 g/cc.

I - is really the impulse when a detonation wave (a charge of length L) is reflected from a rigid wall.

i=I/S

But this is purely a mathematical problem. This is detonation in a perfectly rigid non-deformable tube.
In a real explosion, the lateral expansion of detonation products takes place. L cannot be infinite. There is an L/R parameter of a cylindrical charge that limits this model. In my book (L/R)max=4.5.
You cannot use formulas 2-70...2-72 to calculate real impulse.

Formula 2-73 is the active mass of a real cylindrical charge at L>=4.5R.
Formula 2-74 is the active mass of the shorter charge.

You must insert the active mass, not the total mass!, into formulas 2-71 and 2-72 to get the shock wave reflection impuls.
But it will not be accurate, because you used an inaccurate detonation pressure formula and the real wall is elastic.

Oooh, I understand your problem.
Quote: Originally posted by PLSHY  
brisance is the impulse per unit area.

No, no, no.
Because this definition does not take into account the scale effect.
The same substance, by your definition, will have different brisance depending on the diameter of the charge.
Impulse per unit area for a charge of fixed length and area.
Or the impulse per unit area and divide by the length of the charge.
Or the impulse per unit area and divide by the radius of the charge.

[Edited on 27-8-2023 by Etanol]

[Edited on 27-8-2023 by Etanol]
Finally someone understands, yes, what I said has always been the ideal detonation in theory. I said a few days ago that if you need to convert it into an actual detonation, you need to bring in calculus, so what I said has always been It is ideal. In addition, charge efficiency * theoretical brisance = actual brisance, and the calculation of charge efficiency requires calculus
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Etanol
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[*] posted on 27-8-2023 at 06:40


Quote: Originally posted by PLSHY  

to convert it into an actual detonation,...
charge efficiency * theoretical brisance = actual brisance, and the calculation of charge efficiency requires calculus


In different languages, there are two concepts of brisance:
1. Brisance as the action of an explosion on solid objects
2. Brisance as a quantitative measure to compare different substances

Of course, the effect of an explosion depends on the shape, size, shell, critical detonation diameter, and the quality of the initial shock. It's all charge efficiency.
But I meant something else.

If we consider that "brisance" is a measure of comparing substances, then definition
Quote: Originally posted by PLSHY  
brisance is the impulse per unit area.

is mathematically incorrect.
This is some formula or raw result of the experiment. But not Brisance.
It will be correct if:

Quote: Originally posted by PLSHY  

Impulse per unit area for a charge of fixed length and area.
Or the impulse per unit area and divide by the length of the charge.
Or the impulse per unit area and divide by the radius of the charge.

Detonation pressure characterizes brisance quite well. However, it is very difficult to measure it experimentally. Therefore, deformation, impulse, and speed are experimentally measured.
At the same time, they try to choose the conditions of the experiment so that the influence of the shape, shell, size, critical diameter and detonator does not affect the result of the comparison.
The scale factor should not be so manifest in the brisance formula, whatever it may be.
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[*] posted on 27-8-2023 at 09:54


Quote: Originally posted by Etanol  
Quote: Originally posted by PLSHY  

to convert it into an actual detonation,...
charge efficiency * theoretical brisance = actual brisance, and the calculation of charge efficiency requires calculus


In different languages, there are two concepts of brisance:
1. Brisance as the action of an explosion on solid objects
2. Brisance as a quantitative measure to compare different substances

Of course, the effect of an explosion depends on the shape, size, shell, critical detonation diameter, and the quality of the initial shock. It's all charge efficiency.
But I meant something else.

If we consider that "brisance" is a measure of comparing substances, then definition
Quote: Originally posted by PLSHY  
brisance is the impulse per unit area.

is mathematically incorrect.
This is some formula or raw result of the experiment. But not Brisance.
It will be correct if:

Quote: Originally posted by PLSHY  

Impulse per unit area for a charge of fixed length and area.
Or the impulse per unit area and divide by the length of the charge.
Or the impulse per unit area and divide by the radius of the charge.

Detonation pressure characterizes brisance quite well. However, it is very difficult to measure it experimentally. Therefore, deformation, impulse, and speed are experimentally measured.
At the same time, they try to choose the conditions of the experiment so that the influence of the shape, shell, size, critical diameter and detonator does not affect the result of the comparison.
The scale factor should not be so manifest in the brisance formula, whatever it may be.
Yes, I think I finally understand what you mean. What you want to say is that the brisance is a fixed value for a type of explosive. I think I can understand this. This is also related to your reply. The difference is Appears on the definition! We are used to defining brisance as the action on an object, and the disagreement with the mainstream definition led to this discussion. Thanks for pointing out exactly what the problem is, I think I understand!:)
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