A test method has been published for measuring forces from bird cadavers and artificial birds to demonstrate equivalency to support the use of artificial birds in aircraft certification testing. The test method involves a large diameter Hopkinson bar as the technique for measuring and comparing forces. The method involves the assumption that a force on one end of the bar results in a one-dimensional plane wave that travels down the bar. To avoid reflected waves from the end of the bar overlapping the input pulse, and due to practical limitations on the length of the bar, strain transducers are located relatively close to the impacted face of the bar, raising questions about the validity of the assumption of one-dimensional wave propagation. In addition, the large diameter of the bar can introduce dispersion effects in the propagated pulse. These must be assessed to determine the impact on the accuracy of impact force measurements and, if significant, dispersion correction techniques must be used. In this study analytical, experimental, and computational methods are used to analyze the wave propagation characteristics for impact forces expected from realistic bird impacts. While wave dispersion and effects of non-concentric impacts are present, the resulting errors are small relative to typical test-to-test variation observed in bird impact testing. For the response we expect to see in bird impacts up to velocities of approximately 300 m/s the large diameter Hopkinson bar test appears to be an acceptable method for measuring the impact forces and comparing the response of real and proposed artificial birds.

中文翻译：

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霍普金森杆冲击力测量在人造鸟开发中的应用

已经发布了一种用于测量鸟类尸体和人造鸟类的力的测试方法，以证明支持在飞机认证测试中使用人造鸟类的等效性。该测试方法涉及大直径霍普金森杆作为测量和比较力的技术。该方法假设杆一端的力会产生沿杆传播的一维平面波。为了避免来自棒材末端的反射波与输入脉冲重叠，并且由于棒材长度的实际限制，应变传感器位于相对靠近棒材受影响面的位置，这引发了关于以下假设的有效性的问题：一维波传播。此外，棒的大直径会在传播的脉冲中引入色散效应。必须对这些进行评估，以确定对冲击力测量精度的影响，如果影响很大，则必须使用色散校正技术。在本研究中，使用分析、实验和计算方法来分析实际鸟类撞击所预期的冲击力的波传播特性。虽然存在波分散和非同心撞击的影响，但相对于鸟类撞击测试中观察到的典型测试间变化而言，产生的误差很小。对于我们预计在速度高达约 300 m/s 的鸟类撞击中看到的响应，大直径霍普金森杆测试似乎是测量撞击力并比较真实和拟定的人造鸟类的响应的可接受的方法。