Laboratory of Adaptive and Regenerative Biology, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, United States.
Laboratory of Adaptive and Regenerative Biology, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, United States; Department of Diagnostic and Interventional Radiology, Translational Lung Research Center, Univeristy of Heidelberg, Heidelberg, Germany.
Carbohydr Polym. 2020 Jan 1;227:115282. doi: 10.1016/j.carbpol.2019.115282. Epub 2019 Sep 5.
Acoustic emissions are stress or elastic waves produced by a material under external load. Since acoustic emissions are generated from within and transmitted through the substance, the acoustic signature provides insights into the physical and mechanical properties of the material. In this report, we used a constant velocity probe with force and acoustic emission monitoring to investigate the properties of glass phase and gel phase pectin films. In the gel phase films, a constant velocity uniaxial load produced periodic premonitory acoustic emissions with coincident force variations (saw-tooth pattern). SEM images of the gel phase microarchitecture indicated the presence of slip planes. In contrast, the glass phase films demonstrated early acoustic emissions, but effectively no force or acoustic evidence of periodic or premonitory emissions. Microstructural imaging of the glass phase films indicated the presence of early microcracks as well as dense polymerization of the pectin (without evidence of slip planes). We conclude that the water content in the pectin films contributes to not only the physical properties of the films, but also the stick-slip motion observed with constant uniaxial load. Further, acoustic emissions provide a sensitive and practical measure of this mechanical behavior.
声发射是材料在外力作用下产生的应力或弹性波。由于声发射是从材料内部产生并通过物质传播的，因此声发射信号提供了对材料物理和机械性能的深入了解。在本报告中，我们使用带有力和声发射监测的恒速探头来研究玻璃相和凝胶相果胶膜的性能。在凝胶相膜中，恒速单轴载荷会产生周期性的先兆声发射，同时伴有力的变化（锯齿形图案）。凝胶相微观结构的 SEM 图像表明存在滑移面。相比之下，玻璃相膜表现出早期的声发射，但实际上没有力或声发射的周期性或先兆性证据。玻璃相膜的微观结构成像表明存在早期微裂纹以及果胶的高密度聚合（没有滑移面的证据）。我们得出的结论是，果胶膜中的含水量不仅影响膜的物理性质，还影响在恒单轴载荷下观察到的粘滑运动。此外，声发射提供了对这种机械行为的敏感且实用的测量方法。
