Research On Equivalent Analogy Test Method For Mechanical Overload Of Air Gun

The explosive detonators will be suffered milliseconds acceleration overloads,during the process of penetrating the concrete target.The air gun device could simulate the mechanical overload environment,but the acceleration pulse width is difficult to reach the millisecond level.In order to assess the reliability of the explosive detonators during the process of penetrating the concrete target,a laboratory simulation test method was established,which based on mitigation apparatus and air gun.In this research,the acceleration waveform shaping technology and the equivalent theory and technology based on the air gun were studied.The main contents are as follows:(1)Numerical simulation method was applied to the research of acceleration waveform shaping technology,which copper,polyurethane and open-cell foam aluminum were selected as the mitigation material.The results showed that polyurethane and open-cell foam aluminum have a significant effect on the acceleration of the pulse width broadening,which can increase the acceleration pulse width from 28 μs to about 1 ms,while the peak value will drop to about 10,000 g.(2)Based on the results of numerical simulation,the experiment of acceleration waveform shaping has been carried out.The influence of different kinds and sizes of mitigation materials on the acceleration of overload has been obtained,and the influence of bullet muzzle velocity(57.4m/s ～ 86.6m/s)on the characteristic value of acceleration waveform of overload has been studied.The results showed that the acceleration pulse width increases with the increase of the thickness of the mitigation material and decreases with the increase of the diameter of the mitigation material,and the peak value is the opposite.The acceleration pulse width have reached the order of milliseconds,by changing the size of the mitigation material.Acceleration pulse width was able to achieved 2ms,when open-cell foamed aluminum was used,while the peak value drops to about 3000 g.The pulse width of polyurethane and rubber was less affected by the bullet muzzle velocity,and the peak value increases linearly with the bullet muzzle velocity.When open-cell foam aluminum mitigation material was used,the acceleration pulse width and peak value were less affected by the bullet muzzle velocity.The open-cell foam aluminum has a significant effect on waveform broadening,due to the wide and high stress plateau in the stress-strain curve.(3)Based on strain equivalence principle,which used the method of combining numerical simulation with experiment,the equivalence relationship between air gun and cannon test was studied.The effects of acceleration waveform,pulse width and peak value on the damage of specimen were obtained.Reliability of numerical simulation results has verified by experiments.The equivalent relation between the short pulse width mechanical overload environment of air cannon and the long pulse width mechanical overload environment of cannon test was established.