TRAINING PROJECT SEMINAR
STUDY OF INTERNAL PRESSURE MEASUREMENTS INSIDE A GUN CHAMBER
PROOF AND EXPERIMENTAL ESTABLISHMENT(PXE),
DEFENSE RESEARCH AND DEVELOPMENT ORGANISATION(DRDO),
MECHANICAL ENGG DEPT.,
Scientist D,Weapon Wing
ROLE OF PXE
• Evaluation of Weapon Systems
Evaluation of ammunition and weapon platform performance through dynamic
firing and evaluation.
Provide a fully instrumented and calibrated firing range for test & evaluation of
all arms & ammunitions of Indian /Imported origin.
• Dynamic Proof
• Proof & evaluation of ammunition production batches from Ordnance
• Conduct design and developmental trials of armament stores, i.e., weapons,
ammunition and their components.
• Technical evaluation of imported weapons and ammunition. Conduct
developmental trials for different armour materials.
• Carry out out-turn proof of weapons, ammunition and their components,
as also armour produced by Ordnance Factories, PSUs and trade firms.
• Depot check proof.
• Investigation firing and failure analysis.
• Analysis of ballistic data and design parameters.
• Undertake projects for design and development of range
instrumentation, as also projects for improvement and modernization of
range techniques and facilities.
integrate all fire
Multiple rocket launchers - Mobile rocket
Howitzers - capable of high angle fire
Gun howitzers- capable of high or low angle fire with a
Field guns - capable of long range fire
Mortars - lightweight weapons that fire projectiles at an
angle of over 45 degrees to the horizontal
Mountain guns - lightweight weapons that can be
moved through difficult terrain
Infantry support guns - directly support infantry units
Internal ballistics, a subfield of ballistics, is the study of a projectile's
motion from the time its propellant's igniter is initiated until it exits
the gun barrel.
•Energy is imparted to the bullet in a firearm by the pressure of the gases
produced by the burning gunpowder.
•Chamber pressures in the range of 60,000 PSI are produced.
•PHYSICS OF FIREARMS:Delivering maximum destructive energy to the target
with minimum delivery of energy on the shooter. The momentum delivered to
the target however cannot be any more than that (due to recoil) on the gun-
pressure curve of a typical cartridge (in this case from the M193 5.56mm cartridge using 846 ball
TYPES OF PRESSURE MEASURING SYSTEMS
COPPER CRUSHER GAUGE
• The gas pressure is applied via a piston to a calibrated copper crusher.
• The amount of deformation of the crusher is used as a measure of the maximum
• Used for continuous pressure-time recording.
• Piezoelectric technology is insensitive to electromagnetic fields and radiation,
enabling measurements under harsh conditions
• A strain gauge takes advantage of the physical property of electrical conductance
and its dependence on the conductor's geometry.
• Typical input voltages are 5 V or 12 V and typical output readings are in mill volts.
• Discrete values of the projectile’s in-bore velocity can be obtained by mechanical or
• Most of these techniques imply the drilling of holes in the barrel. Non-destructive
and continuous in-bore measurement techniques for determining the projectile’s
velocity are generally based upon the Doppler effect.
WHY IS PRESSURE MEASUREMENT IMPORTANT?
1. For testing the barrel strength to withstand bends and
cracks on impact of known intensity and duration.
P1- 15% more than the working pressure
P2-20% more than the working pressure
2. For testing propellant charge.
3. For testing of internal bore and driving band accuracy.
4. For estimating range and time of flight.
5. To check for leakage and other technical glitches.
1.COPPER CRUSHER GAUGE
1. Calibrated by a special crusher gun and plotted on a tarage table.
2. Crusher balls material:
Oxygen-free high conductivity copper.
>99.95% Cu, <0.05% Oxygen, <0.003% Silver.
3. Impact of piston weight in gauge falls on the crusher balls.
4. Un-impacted by
duration of pressure
2. ELECTRONIC SENSOR GAUGE
1. Inbuilt battery triggered by force of inertia.
2. Piezoelectric crystals-PZT(Lead zirconate titanate, tourmaline, rochelle
3. Gives a dynamic P-T curve for all time instants.
4. Adopted low power technology and miniaturization with storage testing
technology upto 4KB.
3. STRAIN GAUGE
1. Comprises of insulate flexible backing
supporting a metal foil pattern.
2. Deformation causes electrical resistance
to change which is measured across the
Electrical conductance is dependent on
• Zero Offset - If the impedance of the four gauge arms are not
exactly the same after bonding the gauge to the force collector.
• Temperature coefficient of Gauge Factor (TCGF) - The change
of sensitivity of the device to strain with change in temperature.
• Zero Shift with temperature – Caused by anomalies in the force
• Linearity - This is an error whereby the sensitivity changes
across the pressure range.
• Hysteresis - This is an error of return to zero after pressure
• Repeatability - This error is sometimes tied-in with hysteresis
but is across the pressure range.
“One could spend a lifetime studying pressure measurement and still be
surprised on a regular basis by unexplained exceptions to the generally
• If you measure 100 rounds of exactly the same load, in
exactly the same gun, with exactly the same test
equipment the measurements will typically vary plus or
minus 5-10% or more from round to round.
•No method of measuring chamber pressure is 100%
•For reasons not yet understood there are numerous
exceptions for individual cartridges.
•This is not yet a perfected science and research on this
field is still going on.