Technologies for loading and diagnosis of expanding cylinder experiments with linearly-initiated explosives
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摘要: 基于电爆炸丝引爆炸药、继而驱动尼龙对金属柱壳进行碰撞加载的方式,在金属柱壳中部、半柱高范围内实现了一维柱面膨胀加载。同时,基于沿轴向的加载(或径向速度)一致性和沿环向的加载(或径向速度)轴对称性,提出了一维柱面加载的有效性判据。相比于滑移爆轰加载,一维柱面加载方式具有应力状态相对简单、易简化为二维轴对称问题分析的优点。在柱壳断裂诊断方面,建立了分布式表面速度诊断方法来监测柱壳圆周范围内的初始断裂。其原理为:均匀承载壳体断裂引起的局部承载失效将导致均匀速度曲线簇出现分叉(或演化趋势变化)。与高速分幅照相诊断方法相比,分布式表面速度诊断方法可准确获取柱壳圆周范围内的初始断裂信息(含断裂时刻和断裂位置)。利用建立的线起爆膨胀柱壳实验加载和诊断技术,获得了304钢和45钢柱壳的一维柱面动态拉伸初始断裂性能数据(含断裂应变、平均应变率),其中,45钢柱壳的断裂应变(或延展性)低于304钢柱壳的。Abstract: One-dimensional cylindrical load was imposed on the middle part and half height of the metal cylinders which have the initial height of 160 mm, the wall thickness of 4 mm and the external diameter of 48 mm, by the way of an electric exploding wire initiating explosives, and then drove the nylon lining to expand the metal cylinder. At the same time, a validity criterion of the one-dimensional cylindrical load was proposed based on the load or radial velocity monitoring on the outside surface of the cylinder along its axis and circumference. Compared with the load of sliding detonation, the one-dimensional cylindrical load has the advantages of simple stress state and easy analysis as a problem on a simplified two-dimensional axial symmetrical structure, and can provide an explicit analysis on the stress components related to the fracture of the cylinder. Based on the radial velocities of the test points distributed at the outside surface of the cylinder, a method was proposed to diagnose the initial fracture over the periphery of the cylinder. The principle of the proposed diagnosis method is that the fracture of the cylinder under homogeneous load can result in the bifurcation (or change of the evolution trend) in the uniform velocity-curve cluster. And the initial fracture time and position will be the same as the bifurcating time of the velocity curves and the position of bifurcated velocity curve, respectively, when the bifurcation angle of the velocity curves exceeds the normal scope corresponding to structure strength of the tested cylinder. Compared with the high-speed framing photography which can obtain the exact fracture information over part of the periphery of the cylinder, the distributed velocity monitoring can obtain the exact initial fracture information over the whole periphery of the cylinder. The initial fracture parameters of the 304 steel and 45 steel cylinders under one-dimensional dynamic expanding load were obtained by using the established loading and diagnosis technologies for expanding cylinder experiment with linear initiation explosives. These parameters include the fracture strain and the average strain rate. The fracture strain or ductility of the 45 steel cylinder is lower than that of the 304 steel cylinder.
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Key words:
- expansion fracture /
- metal cylinder /
- linear initiation /
- diagnosis technology
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表 1 304钢和45钢柱壳外壁各测点的速度曲线起跳时刻
Table 1. Jump-up times in velocity curves of the outside surfaces of the 304 steel and 45 steel cylinders
柱壳材料 t11/μs t12/μs t13/μs t21/μs t22/μs t23/μs t24/μs 304钢 10.27 10.17 10.09 10.27 10.27 10.14 10.25 45钢 12.13 11.97 11.87 12.13 12.11 12.06 表 2 钢柱壳的初始断裂参数
Table 2. Initial fracture parameters of steel cylinders
材料 断裂时刻/μs 断裂应变/% 平均应变率/s−1 304钢 51 37 0.9×104 45钢 37 24 1.0×104 -
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