Original Date: 07/13/1992
Revision Date: 01/18/2007
Best Practice : Breech Fatigue Simulation Testing
The Experimental Mechanics Laboratory of the Benet Laboratories is responsible for determining the safe firing lives of breeches for field use. Although the main responsibility is data acquisition for statistical processing, the laboratory also studies prototype designs, correlation of FEM analysis for both new and existing breeches, and fatigue areas due to stress risers on existing inventory. This allows the laboratory to understand and document the fatigue life characteristics of a particular design before it is entered into the fleet.
The simulation of actual loads that the breech mechanism incurs during the firing of a round is generated by hydraulic pressure pulses. The breeches are attached to a short gun tube fixture and placed into the test fixture. The fixture is then subjected to the simulated firing of its designed round by the hydraulic pulse. The system -- called a Dynamic Breech Tester -- creates the pulses from the action of an air driven hammer that strikes the hydraulic piston within the gun tube. This system allows a round per second to be simulated, thus dramatically reducing test time and costs. Energy from the existing hammers ranges from 18,000 ft-lbs to 240,000 ft-lbs, encompassing the projectile next-generation requirements in the current inventory.
The proof firing test simulation program for breech mechanisms allows rapid, cost effective testing of hardware before it enters service and establishes the fatigue life characteristics for service safety.
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