Accurate knowledge of snow mechanical properties, including Young's modulus, shear modulus, Poisson's ratio, and density, is critical to many areas of snow science and to snow-related engineering problems. To facilitate the assessment of these properties, an innovative non-contacting laser ultrasound system (LUS) has been developed. This system acquires ultrasound waveform data at frequencies ranging from tens to hundreds of kHz in a controlled cold-lab environment. Two different LUS devices were compared in this study to determine which recorded more robust ultrasound in granular ice mix samples. We validated the ultrasound observations with poro-elastic traveltime modeling based on physical and empirical constitutive relationships, comparison to and replication of previous studies, and the use of other accredited snow property measurement systems, i.e., the SnowMicroPen. For ice mixes, we determined that the PSV-400 Scanning Vibrometer (Polytec GmbH) produces higher quality ultrasonic wavefield observations (i.e. has a better signal-to-noise ratio) than the VibroFlex Fiber Vibrometer (Polytec GmbH) in the lab conditions tested here. Using the PSV-400, we then demonstrated the utility of this new LUS to study the relationship between snow compression-wave speed and density during snow compaction experiments.

中文翻译：

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用于非侵入性测量颗粒冰混合物中的压缩波的激光超声系统

准确了解雪的力学特性，包括杨氏模量、剪切模量、泊松比和密度，对于雪科学的许多领域和与雪相关的工程问题至关重要。为了便于评估这些特性，我们开发了一种创新的非接触式激光超声系统 (LUS)。该系统在受控的冷实验室环境中采集频率范围为数十至数百kHz的超声波波形数据。本研究对两种不同的 LUS 设备进行了比较，以确定哪种设备在颗粒冰混合样品中记录了更稳健的超声波。我们基于物理和经验本构关系、与先前研究的比较和复制以及使用其他认可的雪特性测量系统（即 SnowMicroPen），通过孔隙弹性走时模型验证了超声观测结果。对于混合冰，我们确定在此处测试的实验室条件下，PSV-400 扫描测振仪 (Polytec GmbH) 比 VibroFlex 光纤测振仪 (Polytec GmbH) 产生更高质量的超声波场观测（即具有更好的信噪比） 。然后，我们使用 PSV-400 演示了这种新 LUS 在研究雪压实实验期间雪压缩波速度与密度之间的关系方面的实用性。