PROBLEMS IN THE ANALYSIS OF A SHOCK SEQUENCE WITH APPLICATION TO GUNFIRE ANALYSIS AND SIMULATION

摘要

In the planning of a laboratory simulation based on a transient sequence, non-conventionalrntechniques must be applied to the analysis of the sequence, due to the non-stationary character of thernsignals. The present paper deals with the specific analysis problems of a transient sequence. ThernRMS and spectral content analysis of a single transient elucidates the distortion in therncharacterization of the sequence, when stationary time-series analysis methods are implemented. Thernway this distortion affects the simulation of the sequence is presented next. From this presentation, itrncan be concluded that the best method for the laboratory simulation of a transient sequence, is thernapplication of a measured time-history, while preserving the statistical features of the sequence. Thisrnconclusion has been implemented in the planning of the laboratory simulation of a gunfire-generatedrnsequence of transients, produced by a gun installed on a helicopter. Statistics of the maximum valuesrnof each transient were calculated, for the sequences measured under changing firing conditions.rnBased on these statistics and on the knowledge of the total number of rounds, the number ofrntransients of different maxima during the entire life cycle could be evaluated. Also a life-cyclernrepresentative sequence that could be simulated by a shaker was generated. A second method for therngun firing sequence simulation was also tested. In this case, the shot with maximal peak value wasrnused and the number of equivalent shocks representing the entire lifecycle calculated, using a fatiguernaccumulation model. The weakness of the method is in the fatigue model.