Simulation Experimental Research On Equivalence Of Mechanical High-g Overload Environment For Explosive Initiator

Explosive initiator suffered milliseconds overload during ammunition penetrating target and multiple consective overloads during multi-layer target penetration process. The Hopkinson pressure bar and airgun experimental methods, to some extent, could simulate such impact overload environment with low cost, while the impact duration under both environments was about 100μs, much shorter than the duration under cannon test environment, and both the methods could not supply continuous impact environment. To compensate for the lack of Hopkinson pressure bar and airgun experimental methods, equivalent experimental theory and method should be built to solve the relationship between high long and low short impact pulses and the relationship between single and multiple impact pulses. Damage equivalence model and experimental method corresponding to amplitude and duration of the overload pulse and damage equivalence model and experimental method corresponding to the loading times were built in the thesis and supplied a better way to solve these scientific and engineering application problems.Based on the one-dimensional wave theory, by considering the wave propagation in the specimen, equivalence relationship between the acceleration pulse on the specimen and the acceleration pulse on the incident bar were obtained by wave iteration approach. The model calculation results showed that the acceleration on the bar represented the average acceleration on the specimen. The basic physical and mechanical properties of the specimen had an effect on its loading acceleration, and the specimen with bigger size, lower mass and larger stiffness was subjected to higher acceleration. Of the rising time, amplitude and lasting time of the input strain pulse, the rising time led to greater effect on the acceleration of the specimen.The damage rules of the specimen under the loading of acceleration with different peaks and durations were obtained in order to solve the equivalence relationship between long and short acceleration pulse. Results showed that length change ratio of specimen linearly increased with the increasing of the peak acceleration, while first increased, and then decreased with the increasing of the acceleration duration. Subquently, according to strain equivalence principle, equivalence relationships between long and short acceleration pulse were acquired based on the free Hopkinson pressure bar high-g overload environment, and then the equivalence analysis mathematical model was built. Model calculation results indicated that rectanglar velocity pulse whose peak vc and duration trise satisfied the formula Vc=y0+A0exp(R0trise), and the sinusoidal velocity pulse whose peak acceleration vb and duration vt satisfied the formula vb=vt{yo+A1exp[v,/(2t1)]+A2exp[v1/(2t2)]}/(20π) showed equivalent relationship on the damage of specimen. The acceleration pulses differentiating from the corresponding rectanglar velocity pulse and the sinusoidal velocity were equivalent.The cumulative damage rules of the specimen under discontinuous multi-pulse loading were obtained based on the free Hopkinson pressure bar high-g overload environment. Followingly, the equivalence relationship approach between single and multiple acceleration pulse were analyzed, and then the equivalence analysis mathematical model was built. Conclusions were that the relative length change ratio of the specimen increased exponentially with the increasing of loading times. According to strain equivalence principle, equivalence relationships between single and multiple acceleration pulse were acquired based on free Hopkinson pressure bar high-g overload environment, and then equivalence analysis mathematical model was built. The equivalence relationship between single velocity pulse vo(t) and multiple velocity pules v1(t)、v2(t)……、vn(t) was-ui(τ)]dτ. The acceleration pulses derivated from the above velocity pulses were equivalent.Based on strain equivalence principle, both the velocity and acceleration equivalence relationship bwteen the free Hopkinson pressure bar, the split Hopkinson pressure bar, the airgun and the realistic cannon test experiment on the damage of the specimen were obtained. Results showed that acceleration equivalence relationship between the split Hopkinson pressure bar and the airgun experiment was asHPB=0.7392aairgun+0.2446. The acceleration equivalence relationship between the free Hopkinson pressure bar and the airgun experiment was aairgun=0.143aFHPB+0.2656.150000g peak acceleration environment in realistic connon test experiment was equivalent to 80000g acceleration environment in airgun experiment. Lastly, the differences of the above high-g overload experimental techniques between loading environment, loading boundary condition, damage mechanism and the overload evaluation norm were analyzed, leading to the conclusion that the airgun was a more effective technique than the split and free Hopkinson pressure bar for characterizing the anti-overload ability of explosive initiator under the realistic connon test environment.