Dr. Morgan L. Funderburk Profile

Dr. Morgan L. Funderburk

at Univ of California San Diego

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Publications (2)

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Proceedings Article | 31 March 2021 Presentation + Paper

Active scour monitoring using ultrasonic time-domain reflectometry to detect a soil interface

Morgan Funderburk, Michael Todd, Anton Netchaev, Kenneth Loh

Proceedings Volume 11591, 1159113 (2021) https://doi.org/10.1117/12.2582457

KEYWORDS: Ultrasonics, Reflectometry, Wave propagation, Sensors, Microsoft Foundation Class Library, Interfaces, Aluminum, Soil science, Safety, Composites

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Local scour is arguably the most pressing issue regarding the safety and longevity of overwater civil infrastructure. Many modern scour detection techniques do not provide continuous scour depth measurements, nor can they function under extreme flow conditions, which is when scour monitoring becomes most critical. Thus, the objective of this study was to develop scour depth monitoring sensors using ultrasonic time domain reflectometry (UTDR). The scour sensor was based on an aluminum strip with two piezoelectric macro fiber composites (MFCs) bonded at one end. The aluminum strip or rod-like sensor is intended to be driven and buried at the location where scour depth measurements are desired. The two MFCs were used to either generate or sense ultrasonic Lamb wave pulses propagating in the aluminum strip. During scour, as sediment is eroded from around the base of the strip, the distance (i.e., scour depth) between the MFCs and the soil interface would increase. The hypothesis was that increasing scour depth would change the mechanical impedance of the system to cause measurable and unique signatures in the residual Lamb wave signals. To test this hypothesis, different interfaces (i.e., metal-metal, polymer-metal, and soil-metal) were applied at different locations along the aluminum strip and MFC system. The MFC sensor-actuator pair was actuated to propagate and measure the corresponding Lamb waves during each test. The results showed clear changes in the residual signal, which were well-correlated to the changing locations of the artificial interface. In particular, the time-of-flight of the response pulse within the residual signature could be used to accurately determine the location of the soil interface or scour depth. Overall, this study demonstrated feasibility of an UTDR sensor for scour monitoring.

Proceedings Article | 27 March 2018 Paper

Actuation of soft materials through ultrasonic atomization

Han-Joo Lee, Morgan Funderburk, Kenneth Loh

Proceedings Volume 10593, 105930Z (2018) https://doi.org/10.1117/12.2296627

KEYWORDS: Ultrasonics, Transducers, Liquids, Robotics, Wave propagation, Capillaries, Temperature metrology, Actuators

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Soft robotics have the potential to improve traditional robotics since soft materials are safer and more compliant to unpredictable surroundings. To date, various methods have been investigated to actuate such soft materials. The main objective of this research is to introduce a new method of soft robotic actuation through ultrasonic atomization. The mechanism of actuation is based on purposefully embedding pockets of liquid in a soft polymer matrix. It is known that, when a layer of liquid is subjected to ultrasonic waves, a capillary wave forms on the surface. When the amplitude of the ultrasonic wave exceeds a critical point, small droplets are ejected from crests of the capillary wave. The small droplets allow the liquid to evaporate at faster rates even when the temperature is below the boiling point, thereby building up vapor pressure and expanding the soft polymer matrix. Here, a soft structure was fabricated that enclosed a small amount of ethanol. Ultrasonic waves generated by a piezoelectric transducer atomized and evaporated ethanol in the expandable structure. During the expansion, temperature, displacement, and stress was measured to characterize the resulting actuation behavior of the system. Separate sets of tests were conducted on a hot plate to compare the effect of atomization versus evaporation. In addition, the voltage of the piezoelectric transducer was controlled to analyze the relationship between voltage and actuation rate. Finally, the durability of the expandable structure was also shown through cyclic actuation and cooling. The results showed the potential of ultrasonic atomization as a new mechanism for soft robotic actuation, where actuation could be produced and controlled in a noncontact manner (i.e., without requiring a tethered connection to deliver air or fluid).

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