An Analysis of V50 Ballistic Limit Results Adjusting 1st Shot Velocity, Step-Up Step-Down Increments, Truth Characteristics and Velocity Control Distributions
Abstract
Perforation performance of body armor is typically evaluated by V50 ballistic limit testing. Shot velocities are sequentially controlled by a up/down method to populate a sample containing results on both sides of the true value of the V50 velocity. The V50 velocity is the velocity at which the probability of perforation is 50 percent. Test protocols control starting velocities and the up/down method, but acquisition of the desired shot velocity is limited by the velocity control of the firing system. Since allowable sample sizes can be relatively small, it is questionable in such cases whether perforation and non-perforation results are sufficiently balanced about the true V50 response of the test item to yield accurate results. Bias in the result likely exists depending on how far away from and on which side of the true V50 the first shot takes place. Further, insufficient data may exist to yield an accurate V50 result if the zone of mixed results for the test item is relatively large. The analysis reveals how the V50 estimate is influenced by varying the discussed parameters relative to a realistic soft armor binary response relationship defined by a logistic regression function. The nominal parameter settings and function are used as the true underlying response curve for the simulations conducted. Different methods of calculating V50 are also examined which include simple averaging of six round and ten round samples as well as a logistic regression solution. Larger samples are examined as well as the influence of step size on the V50 result. The truth set is varied from a step response to a characteristic logistic distribution in order to analyze the effects of the zone of mixed results. Trends are presented relative to the V50 truth set and are used to take a broad look at the test methodology as a whole. Recommendations are made to improve the consistency and accuracy of the V50 test methodology.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2012
- Accession Number
- ADA624217
Entities
People
- C. Andres
- W. Boughers