Meeting & Exceeding Standards: Pyroshock, Gunfire and Ballistics

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Previously, we reviewed resistance testing guidelines for general shock and vibration. However, shock can come from many sources. Military standard MIL-STD-810G outlines testing for a device’s ability to withstand shock from pyrotechnics, gunfire and ballistics.

Pyroshock

Near-Field Actual Configuration: Testing in a near-field environment using the actual pyrotechnic shock device
Test equipment is subjected to at least three shocks. 80% of the shock response spectra (SRS) must be within –3 dB and +6 dB with a frequency bandwidth between 100 Hz and 20 kHz. 20% of the SRS must be within –6 dB and +9 dB.

Near-Field Simulated Configuration: Testing in a near-field environment with the pyrotechnic shock device isolated from the test equipment (to minimize damage)
Testing is conducted as with Near-Field Actual Configuration.

Mid-Field Mechanical Test: Testing in a mid-field environment using a mechanical device to simulate high frequency pyroshock
Test equipment is subjected to a number of shocks as required to test each axis in both directions. 90% of the SRS must be within –3 dB and +6 dB with a frequency bandwidth between 100 Hz and 3 kHz. 10% must be within –6 dB and +9 dB.

Far-Field Mechanical Test: Testing in a far-field environment using a mechanical device to simulate high frequency pyroshock
Testing is conducted as with Mid-Field Mechanical Test with the exception of a far-field environment.

Far-Field Electrodynamic Shaker: Testing in a far-field environment using an electrodynamic shaker to simulate low frequency pyroshock
Test equipment is subjected to a number of shocks as required to test each axis in both directions. 90% of the SRS must be within –1.5 dB and +3 dB with a frequency bandwidth between 10 Hz and 3 kHz. 10% must be within –3 dB and +6 dB.

Gunfire Shock

Direct Reproduction: Time waveform replication is used to simulate gunfire shock according to the expected environment
Equipment is placed on a vibration table and tested along all axes. Vibration is run for a length of time and a number of times on each axis dependent on the nature of equipment and expected environmental condition.

Stochastically Generated: Stochastic generation is used to simulate gunfire shock that is equivalent to time waveform replication
Testing is performed as with Direct Reproduction.

Stochastically Predicted: Where time waveform replication for the specific testing environment isn’t available
Time waveform replication from other testing environments is used to design a prediction model for the specific environment. This test method is considered lacking and only recommended as a last resort if the other two methods cannot be conducted. Testing is performed as with Direct Reproduction.

Ballistic Shock

Ballistic Hull and Turret: For all equipment types
Equipment is mounted inside a ballistic hull and turret and live fired upon. This test method simulates the unpredictable shock environment of the real world but requires the expense of an actual vehicle and munitions. The following less expensive methods are often used instead.

Large Scale Ballistic Shock: For equipment weighing less than 500 kg (1100 lbs) and sensitive to all frequencies between 10 Hz and 1000 kHz
Equipment is mounted in a large scale ballistic shock simulator and oriented along the axis of greatest shock sensitivity. An explosive charge is set off three times.

Light Weight Shock: For equipment weighing less than 113.6 kg (250 lb) and sensitive to all frequencies between 10 Hz and 3 kHz
Equipment is mounted on a shock table in its weakest orientation and struck consecutively with a one-foot hammer drop, a three-foot hammer drop and three five-foot hammer drops.

Mechanical Shock: For very lightweight equipment weighing no less than 0.5 to 1.8 kg (1 to 4 lb) and sensitive to shock up to 10 kHz
Equipment is mounted on a shock table in its weakest orientation and struck three times with a gas-driven projectile.

Medium Weight Shock: For equipment weighing less than 2273 kg (5000 lb) and sensitive to frequencies between 10 Hz and 1 kHz
Equipment is mounted on a shock table in its weakest orientation and struck with a hammer drop between 0.75 and 3.25 feet (dependent on equipment weight) and three more hammer drops between 1.75 and 5.5 feet.

Drop Table: For equipment weighing less than 18 kg (40 lbs) and sensitive to shock up to 500 Hz
Equipment is mounted on a drop table and dropped three times (from a height dependent on expected environment) in each direction on all three axes for a total of 18 drops.

Sealevel MIL-STD-810G Testing

Sealevel has experience designing and testing equipment to withstand shock according to MIL-STD-810G standards.