Lifetime-study on signal cartridges; critical components and kinetic analysis

Nowadays an increase of the storage time of ammunition can be noticed for many countries, partly as a result of decreasing defence budgets. This implies that the safety aspects of stored ammunition but also the effect of longer storage times on the actual performance and functioning of the ammunition becomes increasingly important.
In this paper first of all a general approach of lifetime prediction is presented. This approach is applied to pyrotechnic ammunition, signal cartridges charges, in order to predict the most critical component of this ammunition article.
The lifetime of an ammunition article ends if the article does not function properly anymore. In order to function properly, all of it’s ‘subfunctions’ have to meet their requirements. TNO-PML has developed a tool, for setting up a function-failure-analysis (FFA) in order to evaluate the critical ‘sub-functions’.
In the FFA, first of all it is necessary to define the different ‘subfunctions’ of the article. The ‘subfunctions’ can degrade due to high temperature, low temperature, temperature shock, sunshine, high relative humidity, vibrations, low-pressure etc. These expected conditions during the lifetime of the article are identified after which their influence on the ageing behaviour of all of these ‘sub-functions’ is estimated.
As a result of this study, the life time determining ‘sub-function(s)’ are identified. The compositions investigated, contain of a combination of nitrates to give the different colour effects together with metal additives for the burning properties.
Generally, the energetic composition is the main cause of degradation of an ammunition article. Chemical analyses and thermal analyses could be performed to elucidate the ageing mechanism.