Using Piezoelectric Sensors to Detect Damage Inside Concrete
By Yue Huang
Similar to a human getting sick, building materials like concrete can have health issues after years of use. Civil engineers, working as “doctors,” use techniques to help detect potential health issues for the materials, attempting to solve them in time.
WSU Ph.D. student, Ayumi Manawadu, is one of the civil engineers who seeks techniques to help detect inner damage in concrete. Ayumi uses piezoelectric sensors, which are “an efficient, inexpensive, and in-situ alternative to existing techniques.”
Describing her research, Ayumi won the Three-Minute Thesis (3MT) competition held by the Western Association of Graduate Schools. She was also the second-place winner of the 2019 WSU 3MT competition.
Get Interested in Civil Engineering
Ayumi was born in Kyoto, Japan, and raised in Colombo, Sri Lanka. After receiving her B.S. in civil engineering from the University of Peradeniya, Sri Lanka, Ayumi joined the civil engineering doctoral program at WSU in 2016, under the mentorship of Dr. Pizhong Qiao. While working toward her doctoral degree, Ayumi also earned a master’s degree in civil engineering.
Ayumi’s interest in civil engineering was motivated by an accident that took place when she was a middle-school student.
In 2004, a tsunami, which resulted from the Indian Ocean earthquake, swept across Sri Lanka, leading to about 30,000 deaths in the country. Ayumi’s father was a survivor of the disaster, thanks to the Galle Fort located on the southern coast of Sri Lanka. The strong walls of the Galle Fort blocked the huge waves and kept many people, including Ayumi’s father, out of harm’s way.
“This was a life-changing moment for me,” recalls Ayumi. “I cannot imagine how different my life would have been if it wasn’t for the strong walls of Galle Fort.”
That was also the moment when Ayumi realized the importance of resilient structures, which inspired her to pursue a career in civil engineering “to help maintain structural integrity.”
Research on Damage Detection
At WSU, Ayumi focuses her research on structural health monitoring of concrete structures, with the aim to help solve the structural integrity issues caused by material degradation and structural damage. Specifically, Ayumi uses surface-bonded piezoelectric sensors to detect damages in concrete structures.
The idea of using piezoelectric sensors for damage detection comes from awareness of the drawbacks of traditional detection techniques.
“Traditional techniques, such as visual inspection and laboratory tests of core samples, usually fail to provide a complete picture of the damage, because the results obtained are highly localized and confined to a specific area of the structure,” Ayumi says. “Although some other techniques can solve the problem by showing the complete situation, they are too expensive and require a lot of equipment to do the test, which is very inconvenient.”
The piezoelectric sensors overcome these drawbacks. To detect damage, the sensor system emits ultrasonic waves that travel across the concrete structures, and then, return signal data to Ayumi for further analyses. “This will give me an overview of the structure,” says Ayumi.
Moreover, compared with techniques that embed sensors into the structure, the approach developed by Ayumi is non-destructive because it simply needs to bond the sensors to the external surface of the structure.
Currently, Ayumi has applied the sensor to collect signal data from sample concrete slabs and is at the stage of learning, understanding, and specifying the signal data. So far, she has used the technique to identify material property changes and to detect collisions.
“The biggest challenge for me is to analyze and process signals that have a lot of noise due to the inherent complexities in concrete,” says Ayumi. “It requires a large amount of coding, reading, and learning different processing techniques.”
Share Research with the General Public
Ayumi is willing to share her research with the general public.
She participated in 2019 WSU 3MT and was the second-place winner. In March 2020, with financial support from the WSU Graduate School, she took her research to the 3MT held by the Western Association of Graduate Schools and won First Place.
“3MT is a good opportunity for me to share my research with audiences outside my primary research area,” says Ayumi. “This is interesting but challenging, because these audiences usually do not have background knowledge in civil engineering, I must explain my research in a way that they can understand.”
To meet this goal, Ayumi compares civil engineers to doctors and concrete structures to patients. The process of detecting damage in concrete structures with the use of piezoelectric sensors is likened to the techniques that doctors use to identify patients’ health issues.
“The comparison works well. Almost everyone knows how doctors work, so they can easily grasp the main idea of my research,” says Ayumi. “Creating a connection between your research and your audiences is important for a successful presentation. Making appropriate comparisons will help create the connection.”
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