Veronica Eliasson - US grants

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.

PI: Eliasson, Veronica
Proposal Number: 1437412


The goal of the proposed experimental study is to investigate the interaction of shock waves with liquids and to discover ways to mitigate shock wave effects. This proposal is aimed at the investigation of how shock wave attenuation can be obtained by adding liquid sheets in specific geometric shapes in the path of a propagating shock wave. The fundamental work proposed here can have applications on designing cheap and reliable methods to protect buildings, vehicles, and humans from threats of shock and blast wave impact. For example, it can have an impact in the construction and mining industries where blast technology, explosives and detonation are important. Accidents in both surface and underground mines can lead to shock wave propagation with devastating effects, therefore, shock wave attenuation should be promoted to reduce damage and injury.

The primary research objectives are (a) to understand the dynamics between the incident shock wave and the free surface, and (b) to explore and quantify how the degree of attenuation depends on the role of Newtonian and non-Newtonian fluids and their mass, as well as thermal and inertial properties. Direct measurements of shock wave amplitude, peak pressure, total impulse in addition to quantitative and qualitative high-speed shock wave imaging will be obtained for all cases. Gaining such fundamental understanding can lead to methodologies to reduce shock impact using available and environmentally friendly liquids. Experiments will be performed in a shock tube, and numerical simulations will be performed using a finite volume approach. In terms of outreach and education, the proposal includes a well-articulated plan to involve graduate and undergraduate students in research. The Pi will work with the WiSE Program (Women in Science and Engineering) at the U of South California, whose purpose is to support and promote the participation of women and minorities, both students and faculty, in the academic life at USC. The PI will also involve high school students from the Los Angeles area in her research throughout this project.

This Major Research Instrumentation (MRI) award supports the acquisition of a versatile, high-performance data acquisition system (DAQ) for fundamental research at the NSF Large High-Performance Outdoor Shake Table (LHPOST) at UC San Diego. To advance fundamental knowledge, it is vital to collect and disseminate highly accurate earthquake engineering experimental datasets that are well documented. Such data on system-level behavior of civil infrastructure during earthquakes--from the initiation of damage to the onset of collapse--are scarce. The MRI- enabled LHPOST facility will allow researchers to conduct in-depth seismic response studies of complex large-scale civil infrastructure systems?pushing the boundaries of knowledge on resilient communities and contributing to enhanced design codes and standards to promote public safety. Research activities will broadly impact science, technology and engineering practice and the data collected from the new DAQ system will be integrated into course work that will bring the laboratory experience into the classroom, reaching a large number of students, particularly underrepresented students.

The LHPOST is currently being upgraded from its current single-degree-of-freedom (SDOF) configuration to a full six-degree-of-freedom (6-DOF) capability-- to reproduce all six components of ground motion experienced during earthquakes. The DAQ system will complement this upgrade--providing higher resolution (24-bit, 768 channels, max sampling rate of 25.6 kS/sec per channel), superior aliasing rejection with user-configurable digital anti-aliasing filters, and zero skew time between different channels, thus enabling accurate recordings from very small (ambient vibrations) to very large (seismic testing) motions. This will facilitate the generation of critical landmark datasets to support the development, calibration, and validation of high-fidelity 3D computational models of civil infrastructure systems that will progressively shift the current reliance on physical testing to simulation-based assessment and design. The instrumentation will help to enable potentially transformative research on soil-structure interaction, hybrid testing and measurement of structural response during dynamic loading. The high-quality data enabled by this instrumentation will be made available through the Natural Hazards Engineering Research Infrastructure (NHERI) repository?serving a global community of researchers and catalyzing collaborative research.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.