Because of technical limitations, most experimental studies on the energy-absorbing properties of ballistic fabrics are limited to discrete evaluations based on impact and residual velocities. Consequently, the continuous interaction between a projectile and a target material is still commonly assessed with analytical models or numerical simulations, the validation of which is based on the aforementioned discrete values. The present document aims at describing and validating a new experimental method to make it possible to evaluate the continuous evolution of the projectile velocity during penetration into a fabric material. The method is based on the Doppler effect and a specific and complex nonstationary signal treatment. A high-frequency continuous-wave Doppler radar was adapted to assess the continuous evolution of the velocity of a projectile penetrating a fabric material. Based on two ballistic-grade fabric configurations, a perforating and a nonperforating case were described and evaluated. The instantaneous Doppler frequency was extracted based on the Hilbert-Huang transform. A validation of the proposed method was performed based on high-speed camera images, giving the displacement of the apex of the deformation pyramid of the fabric with time. Additionally, a Weibel® Doppler radar was used to measure the impact velocity. Based on instantaneous frequencies deduced from the high-frequency radar signal analysis, Doppler theory and high-speed camera images, velocity–time and displacement–time plots were obtained. Additionally, the evolution of the fabric deformation (pyramid morphology) was recorded from the high-speed camera images. Comparisons between the data assessed with the high-frequency Doppler radar and those deduced from the high-speed camera indicated that good agreement exists between the two methods. The new Doppler radar method seems to be a promising complementary tool for measuring the continuous interaction between a projectile and a fabric target material.

中文翻译：

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用高频多普勒雷达实时测量弹道织物中的弹丸速度

由于技术限制，大多数关于防弹织物吸能性能的实验研究仅限于基于冲击和残余速度的离散评估。因此，弹丸和目标材料之间的连续相互作用仍然通常通过分析模型或数值模拟进行评估，其验证基于上述离散值。本文件旨在描述和验证一种新的实验方法，以评估在穿透织物材料期间弹丸速度的连续演变。该方法基于多普勒效应和特定复杂的非平稳信号处理。高频连续波多普勒雷达适用于评估穿透织物材料的射弹速度的连续演变。基于两种弹道级织物配置，描述和评估了穿孔和非穿孔案例。基于希尔伯特-黄变换提取瞬时多普勒频率。基于高速相机图像对所提出的方法进行了验证，给出了织物变形金字塔顶点随时间的位移。此外，还使用 ​​Weibel® 多普勒雷达来测量撞击速度。基于从高频雷达信号分析推导出的瞬时频率、多普勒理论和高速摄像机图像，获得了速度-时间和位移-时间图。此外，从高速相机图像记录织物变形（金字塔形貌）的演变。用高频多普勒雷达评估的数据与从高速摄像机推导出的数据之间的比较表明两种方法之间存在良好的一致性。新的多普勒雷达方法似乎是一种很有前途的补充工具，用于测量弹丸和织物目标材料之间的连续相互作用。