Expansion Of Metallic Tubes Driven By Grazing Detonation Products Behind Two Head-on Colliding Detonation Waves

Since the pressure gradient abruptly increase in the detonation products undergoing a head-on collision of two detonation waves propagating in the cylindrical charge embedded in a metallic tube, the movement of tube wall driven by which would be of particular pattern. A series of issues are involved in the considered problem, not only high strain rate deformation and fracture behaviors of the inert media under detonation, but also properties and related flow field of shock compressed detonation products as well as interactions of detonation waves. The problem has been comprehensively studied in this dissertation, including related theory, experiments and numencal simulation. After the research status in the problem and the basic concepts of detonation products EQS and numerical simulation on detonation driving are reviewed, a simplified theory of the problem has been proposed here, which includes the pressure decay histories in the head-on collision detonation products affected by longitudinal and transversal rarefactions, and the expansion process of the tube wall driven by the products. Especially, the wall velocities at the fracture moment of tubes undergoing the head-on collision detonation waves and an normal grazing detonation wave are compared by means of the Taylor criteria on damage of expanding tubes. The data of expansion, deformation and fracture of the tube were obtained in the experiments with diagnostics of flash X-ray cine radio graphy and high speed framing photography. A new type of light source of pulsed Xe lamps has been employed to replace the explosive lights in merits in front and rear illuminations, low operation cost and results in high quality pictures in high-speed photography. As a valuable application, the explosive sealing experiments on red copper tubes were also conducted here, which will be used to seal the petrol tube in microseconds. It is difficult to numerically simulate the considered problem properly, since the parameters of shock compressed detonation products are still unknown and vary anomaly. Meanwhile the collision resulting products flow is complicated, where two shock waves propagating oppositely emerge after the collision in addition to the rarefaction waves. A 2-D elastic-plastic-hydro dynamic Lagrangian code T~D2C has been compiled during this dissertation work and succeeded in simulating the head-on collision of two detonation waves and the resulting products flow, also the expansion process of metallic tubes driven by it. The calculated and measured results agree well with each other, and the approximate theoretical analysis is shown to be valid. Therefore the effective applications of the code T1扗2C in design and performance prediction of explosive devices have been demonstrated. In the other hand, the numerical simulation of the explosive sealing of copper tubes were carried out with the 3-D finite element code LS-DYNA and it is predicted that there exists rebounding phenomena during the tube converging inwards.