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Abstract:Low-field nuclear magnetic resonance (LF-NMR) technology has the advantages of fast, nondestructive, continuous and accurate, which has attracted attention in the fields of cross-linking density, curing process monitoring and aging property evaluation of explosives and propellants. The basic principle of LF-NMR was introduced. The application of LF-NMR in the curing monitoring of composite solid propellants, cross-linking aging assessment of composite solid propellants and polymer bonded explosive(PBX), and aging property evaluation of new type fuel air explosives (new-type FAE) was summarized. It was proposed that the application of LF-NMR in the aging performance monitoring of explosives and propellants should be further studied, the problems of classification monitoring of different ¹H relaxation characteristics and establishment of correlation equations between relaxation characteristic parameters and key parameters of mechanical properties should be solved, and the application of key parameters——transverse relaxation time (T₂) of LF-NMR in the aging performance evaluation of explosives and propellants should be strengthened.

Abstract:Life-extension of missile is a systematic project with both military and economic benefits. As the domestic test on storage and life-extension is not scientific and systematic, it affects the effectiveness and efficiency of missile life-extension. This paper expounded the fundamental connotation of missile storage and life-extension test, summarized the main difficulties in storage and life-extension test, and proposed the basic flow of missile storage and life-extension test. The storage and life-extension test was divided into four parts: natural storage test, life extension test, accelerated storage test and validation test. The main research contents and research progress of each part were analyzed, and the key technologies such as storage life prediction based on natural storage test data, failure mechanism analysis and residual life prediction, overall planning for life-extension technical scheme, and accelerated storage test design based on actual service environment were summarized. Finally, the development trend and key research directions of storage and life-extension test technology were discussed. It has certain academic value and engineering guiding significance for promoting the technology development of missile storage and life-extension test.

Abstract:Aiming at the criterion of evaluating the shelf life of explosives by Bourdon method, the decomposition depths of 0.05% and 0.1% were used as the end points of life. The comparison results of storage life of 32 kinds of explosives at 25-50 ℃ were obtained by linear regression based on Berthelot equation. Two cases were found: 1) For most explosives, the estimated storage life at the same temperature that obtained by taking 0.05% decomposition depth as the end point was less than the estimated shelf life that obtained by taking 0.1% decomposition depth as the end point, but sometimes the estimated shelf life by the former would be extremely short; 2) For very few explosives, the estimated shelf life with 0.05% decomposition depth as the end point was greater than the estimated shelf life estimated at 0.1% decomposition depth at room temperature. However, as the temperature increased, the shelf life estimated by the 0.05% decomposition depth was again less than the estimated shelf life of 0.1% decomposition depth. Whether the selected experimental data points at each temperature are in the isokinetic decomposition period of the explosive is the reason for the difference. Results show that it is more scientific to use the decomposition depth of explosives in the isokinetic decomposition period as the end point criterion for evaluating the shelf life by Bourdon method.

Abstract:The influence of diphenylamine (DPA) on the thermal stability of nitrocellulose (NC) was investigated by isothermal decomposition kinetics. Pressure versus time curves of the gas generated by the thermal decomposition of NC/DPA (3%) mixed sample at 378.15-398.15 K were obtained by using the isothermal decomposition gas metering device. There is a visible inflection point in this curve. The thermal decomposition kinetic parameters of NC/DPA (3%) composite were calculated by Arrhenius equation and model-fitting method. The storage life of NC and NC/DPA composite was estimated using Berthelot equation. The results show that the activation energy of NC/DPA (3%) before the inflection point is 164.6 kJ·mol^-1, and the activation energy of NC/DPA (3%) mixed sample after the inflection point is 150.4 kJ·mol^-1. Compared with the NC raw material, the activation energy of NC/DPA (3%) before the inflection point is increased by 17.7 kJ·mol^-1. With a decomposition extent of 0.1% as the criterion, the storage life of NC/DPA (3%) at room temperature is 18.3 years, indicating that the storage life of NC can be extended by 7.7 years after the addition of 3%DPA.

Abstract:Conventional methods for evaluating aging effects of solid propellants stored at natural temperature need long-term (at least 10 years) and detailed (at least daily) environment temperature data. It is very difficult or expensive to access those data in storage places. Even if the data has been obtained, it would be a very heavy workload to process them. A novel method has been established to substitute the conventional methods limited by data acquisition and processing. The method is based on monthly average temperature data. According to seasonal and diurnal variation models of natural temperature, the parameters of these models have been calculated from monthly average temperature data and local climate characteristics. Therefore, the aging equivalent temperature could be evaluated, and the natural temperature aging effects could be predicated. This method is simpler than conventional method in data processing. And the required temperature data of the method can be easily obtained through public ways. Aging equivalent temperatures of three typical solid propellants （(hydroxyl-terminated polybutadiene(HTPB）, nitrate ester plasticized polyether (NEPE）, composite modified double-base（CMDB)） stored in four typical regions was calculated by the novel method. Results show that the aging equivalent temperature is much higher than the annual average temperature. The difference between the aging equivalent temperature and the annual average temperature increases with the increase of the annual temperature range. As the aging activation energy of solid propellant increases, the aging equivalent temperature approaches the maximum monthly average temperature, and the difference between the equivalent temperature and the annual average temperature becomes larger.

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