Sciencemadness Discussion Board

What does brisance depend on besides detonation velocity?

DennyDevHE77 - 20-8-2023 at 02:28

What does brisance depend on besides detonation velocity?

Looking through various reference books on explosives, I noticed these things:

1. Why C4 (and especially its British analog PE-4) having detonation velocities of 8000-8150 m/s are so much inferior to ordinary molten ETN (with velocity of 8000 m/s)? On the forum someone even posted the results of detonation of plastic explosives and molded ETN on a sewer manhole, and if the plastic only bent it, the ETN penetrated through.

2. Why such explosive as dinitroguanidine with density and detonation rate similar to HMX is similar to RDX in brisance?

3. Or such an explosive as NTO (nitrotriazolone) has a density higher than that of HMX and detonation velocity like that of ETN, but is similar in power to TNT.

4. Or picric acid has a density of 1.813 (RDX has 1.816), but pressed to 1.8 it is not even superior to tetryl. Is this due to the low presence of nitro groups?

I was thinking what else influences, saw such a parameter as heat of explosion (MJ/kg), it was very different between aromatic explosives and nitramines and even more so nitroesters.

But then why EGDN (which has a heat of explosion of 6.8-7 MJ and a detonation velocity of 8200 m/s) is only 15% breezier than TNT. The same PETN is 45% more powerful, although its heat of explosion is lower.

Can you explain in a simple way what is the matter? And, if you can, can you throw the literature that will sort it all out?

[Edited on 20-8-2023 by DennyDevHE77]

Etanol - 20-8-2023 at 03:25

1. These data are correct for industrial plastic explosives with a high content HMX or RDX. Homemade plastic explosives is not equal to industrial. Its density and percentage are much lower.

2. The detonation pressure = density * VoD^2 / (k +1)
Politropic indicator "k" is individual for each substance and its density.

3. Politropic indicator "k" is individual for each substance and density. Brisance is not equal to power. Power (throwing ability) is determined by the heat of the explosion to a large extent.

4. Politropic indicator from bad composition of detonation products
Quote: Originally posted by DennyDevHE77  

Is this due to the low presence of nitro groups?

Yes

EGDN density is lower.
Look for books about the theory of detonation.

[Edited on 20-8-2023 by Etanol]

Microtek - 21-8-2023 at 03:32

Brisance itself is not super well defined. It is the ability of an explosive to shatter a hard target, but how exactly this should be measured is a bit ambiguous. It depends on how rapidly the explosive can transfer the largest amount of momentum to the target, or accelerate parts of the target. This is a function of at least explosion energy, density, VOD, detonation pressure, gas volume and gas composition.
Several methods of generating estimates from easily tabulated properties exist, but you are bound to find inconsistencies in any one of them.

PLSHY - 21-8-2023 at 09:11

In my book, the intensity is not equal to the detonation pressure, but the intensity is the comprehensive value of the detonation pressure, various charges and constraints, and the detonation velocity is approximately equal to the detonation pressure. What needs to be corrected is that if the actual detonation speed of c4 can reach the same as that of casting etn, then their violentness should also be the same. The same is true for egdn. Someone on youtube has tested the comparison between egdn, etn and petn. Because egdn is a liquid, it is easy to reach the maximum detonation velocity, while etn can be cast, and it is easier to achieve the maximum detonation velocity. Petn needs to be suppressed, and it is extremely difficult to achieve the maximum detonation velocity. The maximum detonation velocity of the three is almost the same, so the result is egdn>etn>>petn, which also proves from the side that under the same bottom area, mass, and detonation velocity, the density has almost no effect on the jerk, while the density measured in ordinary times has little effect on the explosion velocity. The impact of the jerk is because more explosives are packed in the same volume, so the specific impulse (jerk) is increased. Therefore, it is concluded that the jerk is affected by the detonation velocity and the charging method, and is affected by the density under certain conditions.:D

PLSHY - 21-8-2023 at 09:14

My translation software is very bad, I am considering whether to use Chinese dialogue directly in the future, and you can use better translation software for translation

PLSHY - 21-8-2023 at 09:23

猛度与做功能力有关系，但是不是强关系，最终还要看爆速才行
My evaluation of egdn is very high, because after I read the books about pyrotechnics, I found that the force is closely related to the workmanship ability, and the workmanship ability of egdn is the strongest, there is no one, although the density is relatively high Low, but due to the characteristics of the liquid, its maximum detonation velocity is extremely high, so the violence is very strong, especially in the shaped charge, and the strong constraints can further improve the acceleration efficiency of the metal jet! Resulting in perfect formation of the shaped jet. And its biggest advantage is that it is not sensitive, which is about 10 times more insensitive than NG!

OneEyedPyro - 21-8-2023 at 13:33

Quote: Originally posted by PLSHY  
In my book, the intensity is not equal to the detonation pressure, but the intensity is the comprehensive value of the detonation pressure, various charges and constraints, and the detonation velocity is approximately equal to the detonation pressure. What needs to be corrected is that if the actual detonation speed of c4 can reach the same as that of casting etn, then their violentness should also be the same. The same is true for egdn. Someone on youtube has tested the comparison between egdn, etn and petn. Because egdn is a liquid, it is easy to reach the maximum detonation velocity, while etn can be cast, and it is easier to achieve the maximum detonation velocity. Petn needs to be suppressed, and it is extremely difficult to achieve the maximum detonation velocity. The maximum detonation velocity of the three is almost the same, so the result is egdn>etn>>petn, which also proves from the side that under the same bottom area, mass, and detonation velocity, the density has almost no effect on the jerk, while the density measured in ordinary times has little effect on the explosion velocity. The impact of the jerk is because more explosives are packed in the same volume, so the specific impulse (jerk) is increased. Therefore, it is concluded that the jerk is affected by the detonation velocity and the charging method, and is affected by the density under certain conditions.:D


Brisance is essentially the peak pressure generated at the detonation wave front.
The pressure generated can be estimated by the VoD, the amount of gasses liberated per volume of explosive, the heat of those gasses and the ratio of different gasses based on the elemental composition of the molecule. Typically N2, H2O, CO2 and CO are the primary gasses we would be interested in.

EGDN is very powerful by mass and so is methyl nitrate for example but by volume they are not quite as impressive and their brisance suffers as a result. Regarding the sensitivity of EGDN, I believe it's similar to NG and borders on if not exhibits primary levels of sensitivity to impact. It's certainly not something to handle carelessly.

[Edited on 22-8-2023 by OneEyedPyro]

PLSHY - 22-8-2023 at 09:33

This is the source of egdn sensitivity data

[Edited on 22-8-2023 by PLSHY]

E0170196-0489-4D37-98EC-4585DB565596.jpeg - 261kB

PLSHY - 22-8-2023 at 09:36

I just reviewed the concept of jerk, and the following is my conclusion after simplifying the content in the book: jerk is actually related to three points, we need to talk about the definition of jerk first, jerk refers to the impulse per unit area , and the calculation method of impulse is I=FT, which is force multiplied by time, and the calculation of jerk is actually very simple. The jerk can be calculated by burst pressure (force per unit area)*charge length/detonation velocity, so because of the burst pressure *Square of detonation velocity*Density, so the formula can be simplified into violent force=density*Charge length*Detonation velocity, and because of density*Charge length*Detonation wave area (area of ​​the bottom of the charge column)=Charge mass, so the final formula It can be simplified as violent =detonation velocity multiplied by charge mass *detonation wave area. Note that the above conditions are valid for the detonation on the surface of a rigid body without external constraints. According to my detailed elaboration on the force in the paragraph above, I hope you have a better understanding of the force. What I said yesterday is correct. The force is determined by the detonation velocity, the quality of the charge and the method of charge. The same quality The downward force has nothing to do with the density! But under the same volume, the intensity is proportional to the density (the detonation velocity is equal)

Microtek - 23-8-2023 at 01:14

No, what you are describing here as "jerk" is, as far as I can tell, more akin to heaving power. Impulse per unit area would give pressure multiplied by time, which is an important metric for thermobaric devices, but not for evaluating brisance. Brisance requires a shock (which is what I assume you mean when you introduce the non-technical term "jerk") which means that there must be a large pressure rise in a very short amount of time. Thus it would be better to divide by the overpressure duration than to multiply by it.

PLSHY - 23-8-2023 at 10:21

Quote: Originally posted by Microtek  
No, what you are describing here as "jerk" is, as far as I can tell, more akin to heaving power. Impulse per unit area would give pressure multiplied by time, which is an important metric for thermobaric devices, but not for evaluating brisance. Brisance requires a shock (which is what I assume you mean when you introduce the non-technical term "jerk") which means that there must be a large pressure rise in a very short amount of time. Thus it would be better to divide by the overpressure duration than to multiply by it.
In fact, the shorter the time, the higher the intensity, because the calculation method of the time is the charge length divided by the detonation velocity, and the detonation pressure is equal to the density multiplied by the square of the detonation velocity, so when the charge length is fixed, the detonation velocity increases, and the intensity does not change. will decrease, but increase. This is an area that is easily misunderstood. It seems that this formula shows that the lower the detonation velocity, the higher the force, but in fact it is the opposite

OneEyedPyro - 23-8-2023 at 11:02

Quote: Originally posted by PLSHY  
Quote: Originally posted by Microtek  
No, what you are describing here as "jerk" is, as far as I can tell, more akin to heaving power. Impulse per unit area would give pressure multiplied by time, which is an important metric for thermobaric devices, but not for evaluating brisance. Brisance requires a shock (which is what I assume you mean when you introduce the non-technical term "jerk") which means that there must be a large pressure rise in a very short amount of time. Thus it would be better to divide by the overpressure duration than to multiply by it.
In fact, the shorter the time, the higher the intensity, because the calculation method of the time is the charge length divided by the detonation velocity, and the detonation pressure is equal to the density multiplied by the square of the detonation velocity, so when the charge length is fixed, the detonation velocity increases, and the intensity does not change. will decrease, but increase. This is an area that is easily misunderstood. It seems that this formula shows that the lower the detonation velocity, the higher the force, but in fact it is the opposite


The density and VoD of a given explosive cannot be used as constant values since brisance and useful heaving power don't scale up in a linear manner.
As density and VoD increases so does the reaction rates between the detonation products such as with hydrogen and oxygen for example.
ETN at 1.6 g/cc as a cast charge will not have 60% more brisance than a charge pressed to 1 g/cc.

It's a complex thing with no exact universal formula. There are different models that disagree with each other, but they tend to give a reasonably close approximation.

[Edited on 23-8-2023 by OneEyedPyro]

PLSHY - 23-8-2023 at 19:18

Quote: Originally posted by OneEyedPyro  
Quote: Originally posted by PLSHY  
Quote: Originally posted by Microtek  
No, what you are describing here as "jerk" is, as far as I can tell, more akin to heaving power. Impulse per unit area would give pressure multiplied by time, which is an important metric for thermobaric devices, but not for evaluating brisance. Brisance requires a shock (which is what I assume you mean when you introduce the non-technical term "jerk") which means that there must be a large pressure rise in a very short amount of time. Thus it would be better to divide by the overpressure duration than to multiply by it.
In fact, the shorter the time, the higher the intensity, because the calculation method of the time is the charge length divided by the detonation velocity, and the detonation pressure is equal to the density multiplied by the square of the detonation velocity, so when the charge length is fixed, the detonation velocity increases, and the intensity does not change. will decrease, but increase. This is an area that is easily misunderstood. It seems that this formula shows that the lower the detonation velocity, the higher the force, but in fact it is the opposite


The density and VoD of a given explosive cannot be used as constant values since brisance and useful heaving power don't scale up in a linear manner.
As density and VoD increases so does the reaction rates between the detonation products such as with hydrogen and oxygen for example.
ETN at 1.6 g/cc as a cast charge will not have 60% more brisance than a charge pressed to 1 g/cc.

It's a complex thing with no exact universal formula. There are different models that disagree with each other, but they tend to give a reasonably close approximation.

[Edited on 23-8-2023 by OneEyedPyro]
Yes, what I am discussing is the detonation wave formed by the detonation products flying to one dimension under ideal conditions. The actual detonation products are flying to the surroundings, so it is necessary to introduce a concept of effective charge quality. My formula is correct when the drug quality is low or in an ideal state, but if you need to discuss the actual state, you need to introduce calculus, which is very complicated, so I won’t elaborate

OneEyedPyro - 23-8-2023 at 20:27

PLSHY
As density changes so do the fundamental dynamics of the detonation.
At higher densities the atoms are closer to each other and moving at higher speeds as the molecules break apart upon detonation. This results in more nitrogen bonding and oxidization of fuels near the detonation wavefront meaning significantly higher peak detonation pressure than your idea of density and VoD working as fixed values would suggest.

At lower density more unbonded nitrogen and oxygen and fuel are left to react later behind the detonation wave. This effects brisance much more than heaving power generally speaking.

Microtek - 24-8-2023 at 00:08
Quote:

In fact, the shorter the time, the higher the intensity


This is true, but not what you are getting from multplying by time, which is what my critique was about.
Much of what you are saying is contradictory or doesn't make sense, possibly because of language barriers. I think you should go into the calculus if you can, that way the language will be less of a problem.

PLSHY - 24-8-2023 at 06:49

Quote: Originally posted by PLSHY  
Quote: Originally posted by Microtek  

Quote:

In fact, the shorter the time, the higher the intensity


This is true, but not what you are getting from multplying by time, which is what my critique was about.
Much of what you are saying is contradictory or doesn't make sense, possibly because of language barriers. I think you should go into the calculus if you can, that way the language will be less of a problem.
Very simple reason, due to the formula "detonation pressure is equal to density multiplied by the square of detonation velocity". Notice! square! Therefore, every time the time is doubled, the detonation speed will be doubled, and the detonation pressure will become 1/4 of the original!Twice the time, half the brisance！I still hope that you can read my previous speech and try my best to understand it before replying, because I have never objected to your point of view from beginning to end!


[Edited on 24-8-2023 by PLSHY]

[Edited on 24-8-2023 by PLSHY]

PLSHY - 24-8-2023 at 06:52

I think I know the problem, google translate keeps translating "double the time, half the force" to "double the time, double the force"

[Edited on 24-8-2023 by PLSHY]

03170F90-1B6B-42CA-9B06-55336EE24372.jpeg - 330kB

PLSHY - 24-8-2023 at 07:00

Quote: Originally posted by OneEyedPyro  
PLSHY
As density changes so do the fundamental dynamics of the detonation.
At higher densities the atoms are closer to each other and moving at higher speeds as the molecules break apart upon detonation. This results in more nitrogen bonding and oxidization of fuels near the detonation wavefront meaning significantly higher peak detonation pressure than your idea of density and VoD working as fixed values would suggest.

At lower density more unbonded nitrogen and oxygen and fuel are left to react later behind the detonation wave. This effects brisance much more than heaving power generally speaking.
You are right, but in the case of the same detonation velocity, the density is not important, but most charges with different densities have different detonation velocities, so I just want to explain the root cause, that is, the violentness ultimately depends on the detonation velocity Instead of density, if the density is low but the detonation velocity is high, then the brisance will be high (under the same mass). Also, I will try my best to check whether the translation is correct in the future, so as not to cause misunderstandings. I am very sorry for the misunderstandings just caused.

[Edited on 24-8-2023 by PLSHY]

PLSHY - 24-8-2023 at 07:10

Quote: Originally posted by Microtek  

Quote:

In fact, the shorter the time, the higher the intensity


This is true, but not what you are getting from multplying by time, which is what my critique was about.
Much of what you are saying is contradictory or doesn't make sense, possibly because of language barriers. I think you should go into the calculus if you can, that way the language will be less of a problem.
If you agree, I will delete a few replies with unclear meaning, but I will keep a few excellent and clear replies. Although the derivation of the formula makes people drowsy, it is very helpful for understanding the fundamental concept of brisance , again apologizing for the misunderstanding I caused and criticizing the hateful Google Translate

[Edited on 24-8-2023 by PLSHY]

PLSHY - 24-8-2023 at 07:26

I just found out that Google has translated "brisance" into strange words such as "VoD" and violence. It would be too difficult to correct them one by one. Sorry everyone, my foreign language level is very average, and I will try to reduce the use of professional words in the future

PLSHY - 24-8-2023 at 07:38

I will give the original version of my most painstaking reply, I hope you can use a better translator for translation, I spent about an hour reading and rewriting this text, he can really help you understand brisance which is a good teaching material in China:

我刚刚复习了一下关于猛度的概念，以下是我将书中内容简化后的结论：猛度其实关乎到三个点，我们需要先讲到 猛度的定义，猛度是指单位面积的冲量，而冲量的计算方式是I=FT，就是力乘以时间，而计算猛度实际非常简单， 压（单位面积的力）*装药长度/爆速即可计算出猛度，那么因为爆压=爆速的平方*密度，所以式子可以化简成猛度= 密度*装药长度*爆速，又因为密度*装药长度*爆轰波面积（药柱底面积）=装药质量，所以最终式子可以简化成猛度= 爆速乘以装药质量*爆轰波面积。注意，以上条件是在刚体表面爆轰，并且没有外在束缚的情况下成立。根据我上 这一段对猛度的详细阐述，希望你对猛度有更好的理解，我昨天说的并没错，猛度是由爆速，装药质量以及装药 式而决定的，同等质量下猛度与密度无关系！但是同等体积下，猛度与密度成正比例（爆速相等）

[Edited on 24-8-2023 by PLSHY]

Microtek - 24-8-2023 at 09:30

OK, when I plug your post into the best translation software I can find, I get this:

"jerk is actually related to three points. The calculation method is I=FT, which is force multiplied by time, and the calculation of the intensity is actually very simple, the intensity can be calculated by pressure (force per unit area)*charge length/detonation velocity, then because the explosion pressure = the explosion velocity Square*Density, so the formula can be simplified into Violence=Density*Charge Length*Detonation Velocity, and because Density*Charge Length*Detonation Wave Area (Collum Bottom Area)=Charge Mass, so the final formula can be simplified as Violence = detonation velocity multiplied by charge mass * detonation wave area."

I tried a few different translators, but apart from translating brisance as either "jerk" or "sharpness", there wasn't much difference.

There are still major problems however:

Is the "I" in your formula supposed to be impulse or intensity (you state both)? If you mean intensity, you are simply wrong in stating that it is calculated as force multiplied by time. If you mean impulse, you are using the correct formula, but using it here does not make sense. Impulse is not related to brisance!
Then you say that "intensity" is calculated as I=P*L/VOD, but that will give a quantity with units of newton times seconds over square meters. This is the units for viscosity, not intensity.
Also, the explosion pressure is not equal to the square of the VOD times density, though it can be approximately proportional to it.
Finally, IF brisance could be expressed as density*charge length*VOD, your formula would simplify to VOD*mass DIVIDED by the cross sectional area, not multiplied by it as you say.

PLSHY - 24-8-2023 at 20:33

Quote: Originally posted by Microtek  
OK, when I plug your post into the best translation software I can find, I get this:

"jerk is actually related to three points. The calculation method is I=FT, which is force multiplied by time, and the calculation of the intensity is actually very simple, the intensity can be calculated by pressure (force per unit area)*charge length/detonation velocity, then because the explosion pressure = the explosion velocity Square*Density, so the formula can be simplified into Violence=Density*Charge Length*Detonation Velocity, and because Density*Charge Length*Detonation Wave Area (Collum Bottom Area)=Charge Mass, so the final formula can be simplified as Violence = detonation velocity multiplied by charge mass * detonation wave area."

I tried a few different translators, but apart from translating brisance as either "jerk" or "sharpness", there wasn't much difference.

There are still major problems however:

Is the "I" in your formula supposed to be impulse or intensity (you state both)? If you mean intensity, you are simply wrong in stating that it is calculated as force multiplied by time. If you mean impulse, you are using the correct formula, but using it here does not make sense. Impulse is not related to brisance!
Then you say that "intensity" is calculated as I=P*L/VOD, but that will give a quantity with units of newton times seconds over square meters. This is the units for viscosity, not intensity.
Also, the explosion pressure is not equal to the square of the VOD times density, though it can be approximately proportional to it.
Finally, IF brisance could be expressed as density*charge length*VOD, your formula would simplify to VOD*mass DIVIDED by the cross sectional area, not multiplied by it as you say.

I'm glad our discussion is finally back on track, I'll explain: i refers to brisance, and L refers to length, so L/VoD=time, explosion pressure*time=i, which is a unit of impulse, It is not a viscosity unit, I=FT is an expression of impulse. Because explosion pressure=F/area, so i=I/area, which also fits the Chinese definition of brisance: brisance is the impulse per unit area. Then there is the problem of simplification, I think you and I simplify the same, and they are all simplified as: VoD*quality/cross-sectional area, I think I may have copied it wrong, because my initial version is by Special characters, so I copied it again before posting it on the website. The last is explosion pressure=VoD squared*density, I will give a picture of Uehara's formula below. And attach the derivation process of the original book.
D0D5BD5A-F8F4-43F4-B574-E2455570D7DA.jpeg - 411kB 8B4BB2A4-6365-4690-AFE6-B44F52285CD3.jpeg - 8kB

[Edited on 25-8-2023 by PLSHY]

DennyDevHE77 - 24-8-2023 at 20:36

In one thread here on the forum, I was advised to use DeepL to translate from Chinese.

Etanol - 24-8-2023 at 20:47

Quote: Originally posted by PLSHY  
The last is explosion pressure=VoD squared*density

8B4BB2A4-6365-4690-AFE6-B44F52285CD3.jpeg - 8kB
This is an approximate detonation pressure formula for k=3. It is valid only for similar CHNO-substances at a density of about 1.0 g/cm3.
In general
P=ro*D^2/(K+1)
K is not a constant.
Quote: Originally posted by Microtek  

Finally, IF brisance could be expressed as density*charge length*VOD

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


[Edited on 25-8-2023 by Etanol]

Microtek - 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.

MineMan - 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.

PLSHY - 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

PLSHY - 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.

OneEyedPyro - 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.

Etanol - 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]

PLSHY - 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

Etanol - 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.

PLSHY - 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！:)