Working alongside the University of Washington’s Applied Physics Laboratory and Woods Hole Oceanographic Institute, researchers with the U.S. Army Engineer Research and Development Center’s Cold Regions Research and Engineering Laboratory are currently collaborating to conduct ice stress tests on an Arctic Energy and Communication Pod, which is a support buoy prototype. Once tested and developed, the APOD will be a high-capacity energy storage container and communications device for operation in the Arctic.
The goal of this testing is to decrease and understand the risk sources for system failure due to the extreme conditions expected during its planned one-year deployment in the Arctic.
By utilizing CRREL’s onsite Geophysical Research Facility, researchers were able to prepare the simulated Arctic environment by growing an ice sheet, then dividing the basin into separate sections incorporating the control and the test section. The APOD was frozen into the basin’s ice layer. Hydraulic rams were then incorporated with a push plate system capable of applying up to 300 tons of in-plane crushing force on the ice.
“With the force of the rams on the ice sheet, the stress rates of an Arctic ice sheet against the APOD will be mimicked,” said Leonard Zabilansky, a CRREL rehired annuitant and engineer working on this project.
The UW’s APL researchers were at the ready preparing the APOD sensor pack to measure the ice stress exerted.
“We have prepared a sensor pack for data collection that uses a Stress Photonics Inc. system as well as strain gauges,” said Dave Dyer, a researcher with UW’s APL. “This system allows us to measure a broad area strain field along with discrete point measurements. We are scanning the strains of the entire APOD surface, but can also see discrete point strains. Through the APOD’s inertial measurement unit, any movement of the buoy can trigger data collection. We have also incorporated acoustic monitoring that will allow us to monitor cracks and pops of a stressed ice sheet, also triggering data collection. All the data will be transmitted to the university by Iridium satellite.”Dr. Arnold Song, a CRREL research mechanical engineer and project lead took measurements using LiDAR, a surveying method that measures the distance to a target by illuminating the target with pulsed laser light; thereby, measuring the reflected pulses.
This method measures the ice’s strain during the crushing process.
“Our interest in this test is to validate our numerical ice mechanics model and to exercise our Bayesian inversion framework that will allow us to infer the ice loads on the buoy,” said Song. “The long-term vision is to be able to use these buoys that will be distributed throughout the Arctic basin as stress sensors, which will hopefully lead to major improvements in basin scale sea ice dynamics modeling and forecasting.”
“Learning about the data system is huge,” said Dyer. “So, in our search for a testing facility we needed the capabilities of scale testing in a controlled environment, an understanding of measuring acoustic emissions and experts with a working knowledge of ice. We knew of CRREL because we are collaborating with Arnold through an Office of Naval Research-funded effort to deploy these developed systems in the Arctic. In this phase of testing, we hope to establish an understanding of how to use the stress photonics system, the acoustic and IMU sensors, and gain an understanding of energy consumption of the APOD data collection system.”
This effort was funded by Dr. Scott Harper, lead for the Office for Naval Research’s Arctic and Global Prediction program.