Impact, Cavitation and Fracture of Polymers with Liquid-Filled Nucleation Sites

固体材料通常包含小空隙形式的损伤。如果填充有液体，则这些空隙可以用作水的成核位点，以在压力突然变化时将相从液态变为气态。如果固体结构受到突然的高脉冲动态冲击，则会产生应力波，并将通过固体和充满液体的空隙传播。当受到压力的突然变化时，充满液体的空隙内的小气泡有可能破裂或空化，并发出液体射流和冲击波，这可能会增加对周围固体的损害。当液体经历空化时，空化气泡和随后的喷射的复杂物理学将决定周围固体如何变形和破裂。本研究的目的是使用实验来量化所产生的变形在真实的时间与高速，非侵入性的可视化技术。如果成功的话，这个跨学科的项目，将流体力学理论与固体力学和断裂动力学相结合，将为理解在高动态短期测试中固体的破坏模式提供重要的一步，以评估结构的强度，并导致可行的选择，以尽量减少或避免损坏。该项目为有趣的应用开辟了新的领域，例如从波浪对沿海建筑物的冲击和地震对大坝建筑物的影响到肾结石的非侵入性治疗。该项目将资助南加州大学的一名博士生。重点是促进代表性不足的群体的参与，本科生和高中生将被邀请参加与这项研究有关的短期暑期项目。

Solid materials usually contain damage in the form of small voids. If filled with a liquid, these voids can serve as nucleation sites for water to change phase from liquid to gaseous state if sudden pressure changes occur. If the solid structure is subjected to a sudden high-impulse dynamic impact, stress waves are generated and will propagate through the solid and the liquid-filled voids. When subjected to sudden changes in pressure, small bubbles within the liquid-filled voids have the potential to rupture, or cavitate, and emit liquid jets and shockwaves that can increase the damage to the surrounding solid. As the liquid undergoes cavitation, the complex physics of the cavitation bubbles and subsequent jetting will determine how the surrounding solid deforms and breaks. The goal of this research is to use experiments to quantify the resulting deformation in real time with high-speed, non-invasive visualization techniques. The fractured specimens will be post-processed to further evaluate the difference between various scenarios.If successful, this cross-disciplinary project, integrating fluid mechanics theory with solid mechanics and fracture dynamics, will provide an important step towards understanding the failure modes of solids during highly dynamic short duration tests to assess the strength of structures and lead to viable options to minimize or avoid damage. This project opens new venues for interesting applications, with examples ranging from wave slamming on coastal structures and earthquake impact on dam buildings to non-invasive treatment of kidney stones. This project will support one PhD student at University of Southern California. With focus on promoting the participation of underrepresented groups, undergraduate and high-school students will be invited to work on short-term summer projects related to this research.