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Explosion Engineering (MACE61054) Discussion Blog

Henry Tan's picture

You are always invited to join our course discussions!

Topics for MACE 61054 Explosion Engineering

Topic: Physics of Explosions
Physics of Explosions – part I
Physics of Explosions – part II
Spalling and Fragmentation –I
Spalling and Fragmentation –II

Topic: High Energy Rate Processes
Energy Related Materials
Explosive Welding

Topic: Underwater Explosion 
Underwater Explosion -part I
Underwater Explosion -part II

Course summary

Tutorial questions
Tutorial solutions
 

Suggested topics for Explosion Engineering Projects

Directions for students registered for course unit: MACE 61054 Explosion Engineering
(1) Go to the website node/2979, and read the discussion topics and previous posts.
(2) Register (only once) at user/register
(3) Post you questions, comments.

Comments

Henry Tan's picture

 sp
SEM image showing fracture surface of a solid propellant.
Reference: Ide KM, Ho SY, Williams DRG (1999) Fracture behaviour of accelerated aged solid rocket propellants. J Mater Sci 34:4209-4218.

A solid propellant consists of ammonium perchlorate (AP) particles with two size ranges (coarse and fine), embedded in HTPB binder.

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What is a plastic bonded explosive?

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Why plastic bonded explosive?

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a b c d e
From Prof. Ko van der Weele

A steel ball dropped onto loose, very fine sand creates an impressive jet: Upon impact, sand is blown away in all directions, forming a crown. The ball dives deep into the soft sand, creating a void (like a mine shaft) that immediately collapses again: the "hydrostatic" pressure focuses upon the axis of impact and pushes the sand straight up into the air. (from van der Weele's research website)

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Something relate to a Leaping Shampoo phenomenon?
http://imechanica.org/node/1265

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How may this relate to the void collapse in energetic materials, such as solid propellants and explosives, which is one of the major mechanism for the formation of hot spots.

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What are hot spots in explosives?

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pbx-crack
From Rae PJ, Goldrein HT, Palmer SJP, Field JE, Lewis AL (2002) Quasi-static studies of the deformation and failure of beta-HMX based polymer bonded explosives. Proc R Soc Lond A458:743–762.

Optical micrograph of the post failure route in a high explosive suggests that macroscopic crack propagation is mainly along interfaces.

Henry Tan's picture

While high speed explosion are typical for the behaviour of explosives, why study quasi-static processes?

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A solid rocket or a solid-fuel rocket is a rocket with a motor that uses solid propellants (fuel/oxidizer).

solid rocket

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why not use liquid rocket as a lunching vehicle?

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A simple solid rocket motor consists of a casing, nozzle, grain (propellant charge), and igniter.

solid rocket motor

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combustion surface

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A metal foam is a cellular structure consisting of a solid metal - frequently aluminum - containing a large volume fraction of gas-filled pores.

 

closed-cell
A large-cell closed-cell aluminium foam produced from molten aluminium by the Shinko Wire Company (sold under the trade name Alporas).


open-cell
An open-cell aluminium foam produced by ERG Aerospace

Firas's picture

 

Explosion Engineering, Manchester university

 

 

Firas Al-matook

Henry Tan's picture

Thanks. I will put more things as supplments to the classroom lecturing.

Henry Tan's picture

I put a lot of links to the internet figures, and the images show automatically. I do not want the pictures be treated as if they are generated by me. But, am I breaking any intellectual property laws by providing these links?

I think the main feature of exlplosive welding is the less time required for the process .If we have a large workpiece,i think using this  we can weld it faster  than any other welding technology.

Henry Tan's picture

Other welding technologies can be found here.

I think its worth mentioning the difference b/w cold welding and hot welding.

Henry Tan's picture

can you explain to us cold and hot welding?

 

I am sure that everyone is familiar with hot welding, which
is infact the ordinary welding where two metal forms a weld pool and on cooling
they will attach together. But in cold welding the melting of the two metals won’t
happen this has got lot of advantages because we can join materials which are
not weldable for eg, Powder metallurgy and ofcourse Explosive welding.

 

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why some metals are not weldable, some are?

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Detonation velocity of commonly used explosives can be found from here

Henry Tan's picture

Dear Sibson, good point.

Henry.

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can you give some references to justify your point?

With regards to a question on the surface finish of explosion welding in the last lecture  - it seems that some slight deformation must occur as the two layers are generally flattened after they have been explosively welded together. See www.dynamicmaterials.com/divisions/clad%20Metal%20Group/Explosion%20Weld...

The page also has a video of the explosion welding (although you cant see much)

Henry Tan's picture

I watched the video, it is very interesting. John, thank you for providing the link.

Is Stand-Off Distance a pure function of the Jeting Angle??ie , While choosing the stand-of distance do we have to consider any other things other than jetting angle?

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Does it also depend on the yield of the
explosive?

Can u make it clear? Wat is yield of the explosive and how it deprnds on the stand-off Distance

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Stephen Reid, who used to be a Professor in this school (UMIST), did a lot of original work on explosive welding in 1970s. Maybe you can read some of his papers, and get deeper understanding of the subject.

Firas's picture

Firas Al-matook

how can we classified the type of underwater explosion if d/W1/3 is more than 1 and less than 16 because if it less than one is shallow and if it more than 16 classified as deep underwater explsosion.

  

Henry Tan's picture

<1 (shallow) and > 16 (deep) are two extreme cases for underwater explosion. For those two cases, mathematically the controlling equations can be simplified, and physically they each share common behaviours.

For the cases in between, the behaviours are complicated. Taking an example for bubble dynamics:
(1)    for deep underwater explosion, the interactions between the bubble and the water surface can be ignored;
(2)    for shallow underwater explosion, bubble burst into the air quickly.
(3)    for >1 and < 16 underwater explosion, the interactions between bubble and the water surface need to be accounted for.

Firas's picture

Firas Al-matook

am hazitated to do flying impact analysis ( shock wave and Rankine-Hugoniot equations) on my dissertation topic despite of it is about Aluminium aircraft impacting a concrete rigid barrier with impact velocity. the reason why am hazitated that am assumed the density after impact remains the same as before during my experimenta analysis, i.e. no pentration or structure deformation though Hugoniot considers two densities.

plz Dr, if you can give me an advice to solve this issue, I would like to do it becous in real life the impact of aircraft with a rigid structure as what happened in WTC sustains obviously two different densities.

 many regards

FIRAS Al-MATOOK

MED

Manchester University

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