Methodology for Assessing Ammunition Reliability According to the Nut Test Plan

Abstract

In the article an ammunition dependability evaluating methodology is created. It is based on test results according to the NUT plan, according to which an initial number N of weapons and military equipment is tested during planned time T, failed products are not restored or replaced, the tests are stopped after the end of the testing time T. Standard evaluating ammunition dependability methods are absent now, so an ammunition dependability evaluating method by results of tests according to the NUT plan for the reliability function during time T P(T)=(0.9; 0.95; 0.98; 0.99; 0.997; 0.999; 0.9994) and confidence probability q=(0.8; 0.9; 0.95; 0.99) is proposed. It is proposed to consider ammunition reliability as its dependability, because ammunition is non-repairable and non-renewable objects. A theoretical method to calculate the instantaneous failure rate λ for the exponential distribution law, which is the most appropriate for random ammunition failures, has been developed. Instantaneous failure rates from P(T)=0.9 and q=0.8 to P(T)=0.9994 and q=0.99 have been calculated. It is calculated also the minimum amount of ammunition required to start testing according to the NUT plan for P(T)=(0.9; 0.95; 0.98; 0.99; 0.995; 0.997; 0.999; 0.9994) and q=(0.8; 0.9; 0.95; 0.99). Application of the exponential distribution law of the probability of failure- free operation of ammunition as complex objects that can suddenly fail made it possible to calculate the smallest initial quantities of ammunition Nstart, which are necessary to start the tests: from Nstart=79 for P(Т)=0.9 and q= 0.8 to Nstart=30058 for P(Т)=0.9994 and q=0.99. The calculation results for other P(T) and q are shown in Table 7. We can estimate the ammunition reliability, that is, P(T) and q, based on the results of counting number of failures from available amount of ammunitions using data in Table 2, Table 3. In addition, an ammunition reliability coefficients t1 calculation method, i.e. the conditional time of failure-free operation of one ammunition depending on P(T) and q, is proposed, and their values are calculated for P(T)=(0.9; 0.95; 0.98 ; 0.99; 0.999; 0.999) and q=(0.9; 0.99). In addition, it is proved mathematically that NATO and Ukraine standards requirements regarding of weapons and military equipment dependability and, in particular, ammunition reliability, are the same.