Estimate of Storage Life for M392/M728 Projectiles Based on Finite Element Thermal Stress Analysis
M392 projectiles have exhibited a high percentage of erratic exterior ballistic flight trajectories, especially in firing series which had been conditioned for elevated temperature testing. This erratic flight behavior has resulted in unacceptably large dispersion patterns on target. The sources of the erratic rounds tested were stockpile lots after extended storage and lots shipped to and tested in hot, dry climatic areas. The poor performance has been observed to occur with greater frequency in gun tubes with high secondary wear characteristics. Examination of the vulcanized fiber rotating bands indicated a shrinkage of the material from the dimensions specified in the technical data package. Failure of the bands in shear was also reported. Significantly different results have been obtained with rotating bands manufactured from vulcanized fiber produced by different suppliers. Preliminary tests of the M728 projectile indicated that there was a high probability of the same problem existing, particularly after extended storage.
KeywordsReduction Ratio Critical Ratio Storage Life Extended Storage General Cross Section
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