Pratyush thanks for asking questions.Pratyush wrote:Looking at the images of the shattered gun barrels.
As someone with a non engeneering background. I have a question regarding the testing of the metallurgy and strength of different materials.
In oil and natural gas industry or even for municipal applications it is required that the pipes be fit to handle certain amount of flow and pressure on a daily basis for a certain period of time. Before it reaches a point of failure and needs to be replaced.
1) How is this quality assured for customers?
2) Is it possible for non invasive means such as x-rays or ultrasound be used to check for flaws in materials?
3) Can such techniques be used to assure the quality of the arty gun barrels as well?
As Niran also wrote the shattered barrels show it's a failure due to premature bore explosions. In other words, it's not due to defective gun barrels. See the tank barrel splitting like leaves shows how good the metal is. Its ductile fracture.
The other barrel failures are mid-way and not at the end. This means the shell travelled some distance and exploded. Now every shell has a fuze that has safety features to ensure it gets armed after a set distance. Here the shells burst before the shell leaves the barrel. So Fuze is not the problem.
So having ruled out the barrel and fuze it's the shell that is a problem.
Now, the shell can explode if the base is compromised like a loose rotating band, weak materials of the shell casing etc. These are observable defects. Shells are forged and machined from certified steel ingots. And the forces of the forging process are as severe as those in an explosion. So if the shell survives the forging process intact to the machining stage, we can be assured it's not a metallurgy defect.
As to every gun barrel, it is proofed and test-fired for acceptance just like the oil and gas pipelines.
There is a process to replace gun barrels after a certain number of firings.
All these are for the quality assurance of guns.
We need a proper COI that creates a root cause diagram and goes into shell manufacture, explosive filling, and packing and storing, the batch number of the shells that blew up. In other words, a pedigree analysis to find out what caused the flaw to be hidden and emerge to cause the accident.
What is happening is an inherent latent flaw in the process that emerges occasionally but is catastrophic when it happens. If it was more common we would have more frequent flaws.
Looks like all COIs done so far is to deduce the shell as the root cause.
They have not gone one step below to find out why the shell blows up even without a fuze.
During the late 60s the USN found that they were having premature bore explosions due to the shells being filled with Composition B which is TNT based.
From open sources, we know OFB uses TNT for filling the ERFB shells.
We know TNT exudation in anti-tank mines led to the Pulagoan Depot fire.
So COI should go to the OFB factory and bird dog the shell filling process to see what introduces latent flaws.
* The USN found that the TNT melting process introduces small bubbles in the filling. And with time and temperature gases fill the voids. When the shell is fired the base sees compression force and when it travels in the barrel the shell springs back. This happens in milliseconds and is almost an adiabatic expansion of the trapped gases that auto detonates leading to the shell explosion. So no need for Fuze.
The way they solved the problem is to use Insensitive explosive filling.
That could be the long term solution.
However, COI should look at how they are storing the shells and transporting them.