Liu Yue, Wang Yongshuai, Deng Qiong
Joint International Research Laboratory of Impact Dynamics and Its Engineering Applications, School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China.
Shaanxi Key Laboratory of Impact Dynamics and Its Engineering Application, School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China.
Materials (Basel). 2024 Aug 1;17(15):3793. doi: 10.3390/ma17153793.
The split-Hopkinson pressure bar technique is widely used to determine the dynamic mechanical behavior of materials. However, spike-like stress features appear in the initial stress behavior of ultra-soft materials tested with a split-Hopkinson bar. These features are not intrinsic characteristics of the materials. Potential causes were investigated through experiments and numerical simulations. It was found that the spike feature represents derived stress resulting from the radial inertia effect during dynamic loading. In this work, we propose and experimentally verify effective methods to reduce this effect. The influences of density, strain acceleration, ratio between inner and outer diameter, and Poisson's ratio on the radial inertia effect were investigated. The spike stress was found to change linearly with density and strain acceleration but decrease significantly when the inner/outer diameter ratio was below 0.3, after which it remained nearly constant. A parabolic stress distribution was observed along the radial direction due to the Poisson effect, especially when the ratio exceeded 0.3, leading to higher spike stress. Finally, suggestions were proposed as experimental guidance when testing ultra-soft materials.
分离式霍普金森压杆技术被广泛用于测定材料的动态力学行为。然而，在用分离式霍普金森杆测试超软材料时，其初始应力行为中会出现尖峰状应力特征。这些特征并非材料的固有特性。通过实验和数值模拟对潜在原因进行了研究。发现尖峰特征代表动态加载过程中径向惯性效应产生的衍生应力。在这项工作中，我们提出并通过实验验证了减少这种效应的有效方法。研究了密度、应变加速度、内外径比和泊松比对径向惯性效应的影响。发现尖峰应力随密度和应变加速度呈线性变化，但当内外径比低于0.3时显著降低，此后几乎保持不变。由于泊松效应，沿径向观察到抛物线形应力分布，特别是当该比值超过0.3时，会导致更高的尖峰应力。最后，针对超软材料测试提出了作为实验指导的建议。
