In this paper, we have developed and demonstrated a novel high-velocity impact experiment to study dynamic fragmentation of additively-manufactured metals. The experiment consists of a light-gas gun that fires a conical nosed cylindrical projectile, that impacts axially on a thin-walled cylindrical tube fabricated by $3\text{D}$ printing. The diameter of the cylindrical part of the projectile is approximately twice greater than the inner diameter of the cylindrical target, which is expanded as the projectile moves forward, and eventually breaks into fragments. The experiments have been performed for impact velocities ranging from $\approx 180\text{m}/\text{s}$ to $\approx 390\text{m}/\text{s}$, leading to strain rates in the cylindrical target that vary between $\approx 9000$s^-1 and $\approx 23500{\text{s}}^{-1}$. The cylindrical samples tested are printed by Selective Laser Melting out of aluminum alloy AlSi10Mg, using two printing qualities, with two different outer diameters, $12$ mm and $14$ mm, and two different wall thicknesses, $1$ mm and $2$ mm. A salient feature of this work is that we have characterized by X-ray tomography the porous microstructure of selected specimens before testing. Three-dimensional analysis of the tomograms has shown that the initial void volume fraction of the printed cylinders varies between 1.9% and 6.1%, and the maximum equivalent diameter of the 10 largest pores ranges from $143\mathrm{\mu }\text{m}$ to $216\mathrm{\mu }\text{m}$, for the two different printing conditions. Two high-speed cameras have been used to film the experiments and thus to obtain time-resolved information on the mechanics of formation and propagation of fractures. Moreover, fragments ejected from the samples have been recovered, sized, weighted and analyzed using X-ray tomography, so that we have obtained indications on the effect of porous microstructure, specimen dimensions and loading velocity on the number and distribution of fragment sizes. To the authors’ knowledge, this is the first paper (i) providing a systematic experimental study (34 impact tests) on the fragmentation behavior of printed specimens, and (ii) including $3\text{D}$ reconstructions of dynamic cracks in porous additively-manufactured materials.

在本文中，我们开发并展示了一种新型高速冲击实验，用于研究增材制造金属的动态碎裂。该实验由一个轻气枪组成，该枪发射锥形鼻柱形弹丸，轴向撞击由制造的薄壁圆柱形管$\mathrm{3个}\text{丁}$印刷。弹丸圆柱部分的直径大约是圆柱靶内径的两倍，随着弹丸向前移动而膨胀，最终破碎成碎片。已经针对从以下范围的冲击速度进行了实验$\approx 180\text{米}/\text{秒}$到$\approx 390\text{米}/\text{秒}$，导致圆柱形目标中的应变率在$\approx 9000$小号^-1和$\approx 23500{\text{秒}}^{-\mathrm{1个}}$. 测试的圆柱形样品是通过选择性激光熔化铝合金 AlSi10Mg 打印的，使用两种打印质量，具有两种不同的外径，$12$毫米和$14$mm，以及两种不同的壁厚，$\mathrm{1个}$毫米和$\mathrm{2个}$毫米。这项工作的一个显着特点是，我们在测试前通过 X 射线断层扫描对选定样品的多孔微观结构进行了表征。断层图的三维分析表明，印刷圆柱体的初始空隙体积分数在 1.9% 和 6.1% 之间变化，10 个最大孔隙的最大等效直径范围为$143\mathrm{\mu }\text{米}$到$216\mathrm{\mu }\text{米}$, 对于两种不同的打印条件。已使用两台高速摄像机拍摄实验，从而获得有关裂缝形成和传播力学的时间分辨信息。此外，从样品中喷射出的碎片已使用 X 射线断层扫描进行回收、确定尺寸、称重和分析，因此我们获得了关于多孔微结构、试样尺寸和加载速度对碎片尺寸数量和分布的影响的指示。据作者所知，这是第一篇 (i) 对打印样本的破碎行为提供系统实验研究（34 次冲击测试）的论文，以及 (ii) 包括$\mathrm{3个}\text{丁}$多孔增材制造材料中动态裂纹的重建。