The Mechanism Of Formation And Penetration Of Shaped Charge Particle Jets

Porous shaped charge liner has been widely used in the civilian sectors especially the field of petroleum perforation, as which is characterized by a simple process, flexible composition ratio, high production efficiency, good formability, avoiding the occurrence of the slug and other phenomena. Porous shaped charge liner is collapsed by the detonation wave. A continuous never-ending particle state is composed of numerous small particles on its axis, known as the shaped charge particle jet. Comparing with the dense material jet, shaped charge particle jet has many unique features, such as no necking fracture and expansion. Therefore, it is needed to study the mechanism of shaped charge particle jet.Based on the material properties of porous materials, the speed, formation conditions, temperature rise calculations and numerical simulation of the shaped charge jet, preparation and influencing factors of the porous shaped charge liner, the characteristics of penetrating different target are analytical research systematically by theoretical analysis, experimental investigation and numerical simulation method.Firstly, the existing porous material initial completely and partially shock compressed are evaluated and discussed. The shock adiabatic curve and the relationship of associated parameters of the porous materials are analyzed and discussed; some theoretical models of the incompletely compacted porous materials were introduced in accordance with the rate independent and rate-related; the shock adiabatic curve and the relationship of associated parameters of the ideal mixture are analyzed and discussed. Through comprehensive analysis, the relevant parameters of the dense material of tungsten-copper was determined by the superposition principle of the ideal mixture, and the shock compression state of porous tungsten-copper shaped charge liner was described by the shock adiabatic curve of initially porous material completely compacted.The calculation method of the collapse velocity of porous shaped charge liner and the velocity of shaped charge particle jet is given by considering the influence of the initial porosity on the collapse velocity of porous liner. The criterion of angle and sound velocity which judge porous liner to form cohesive shaped charge particles jet is present. The results show that:under the same pressure, as the increase of porosity, collapse velocity increase while the sound speed decrease; in the uniform porosity, collapse velocity increases with increasing pressure, while sound velocity is also reduced; the velocity shaped charge particle jet increases with the increase of porosity, and the collapse angle increase with the increase in the collapse velocity. The calculated results agree well with experimental results.The temperature rise of shaped charge particle jet is computed theoretically, which consisted of three parts:porous liner heating due to the shock wave transferred to the porous liner by the explosive detonation wave and due to plastic work performed during porous liner collapse and shaped charge particle jet elongation. The calculated results show that:for porous copper liner, porous liner heating by explosive wave make50%contribution to the temperature rise of the shaped charge particle tip jet, heating by plastic work performed during porous liner collapse and shaped charge particle jet elongation make70%contribution to the temperature rise of the shaped charge particle tip jet. For dense copper liner, it is45%and45%respectively. The temperature rise of shaped charge particle jet is higher than the temperature rise of dense shaped charge jet, because the heating by explosive detonation wave.The penetration model of the existing dense material jet and the porous materials shaped charge particles jet is introduced and analyzed. The penetration calculation model of shaped charge particles jet is proposed by considering the compressibility of the material and the characteristics of the porous shaped charge liner materials. Under different circumstances, this model can be transformed into the existing forms of penetration model. The model has broad application prospects.A W-Cu shaped charge liner with better performance was prepared by mixing powder with mechanical alloying method, pressing with spin-mode suppression method and sintering under the protection of methanol cracking gas. The penetration performance of W-Cu shaped charge particle jet will be improved by adding the lead powder on the basis of the original peculiarities of tungsten copper liner. However, an excess of lead powder can descend the penetration performance of W-Cu shaped charge particle jet. The relationship of penetration depth and stand-off shows that: W-Cu shaped charge particle jet is suitable for small stand-off and the best stand-off is2.1times the charge diameter. The experiment results of penetrating different targets show that:the relationship of penetration depth and time is the exponential function when W-Cu shaped charge particle jet penetration the45#steel, and is the exponential function when penetration A1and concrete targets. W-Cu shaped charge particle jet is well suited for penetration into low-density target. The parameters of Shock equation of state of W-Cu porous liner are determined by the ideal mixture equation of state. W-Cu shaped charge particle jet is numerical simulated using AUTODYN. The results show that:the meshing is greater influence on the velocity of shaped charge particle jet."Middle" meshing can basically meet the requirements of the calculation, and the calculation time can save40%, but shaped particle velocity descend11.1%compared with the experimental results. The flying speed of the shaped charge particles jet declines as the time increases, while the velocity decreases slowly after four times the charge diameter position. This main reason is that the tip is separated from the main body of shaped charge particles jet and the speed change slowly. When W-Cu shaped charge particle jet penetrating into Al target, the velocity decrease fastly in cavitation stage, and slowly in quasi-steady state. W-Cu shaped charge particle jet has a "maceration" phenomenon in this process. The fitting curve of the relationship penetration depth with time which obtained by numerical simulation and experimental result is similar. However, the penetration depth value lower than the experimental value at the same time. This is mainly because the velocity is lower than the experimental velocity. Numerical simulation and experimental results agree well with the Al target profile.This research work can provide some theoretical guidance for the structure design and engineering application of the porous liner shaped charge.