This research aims to develop a status imaging system for a Li-Ion battery by utilizing guided ultrasonic waves with an embedded sensor network. Li-Ion Battery (LIB) has emerged as an essential powering element in the future mobility industry including electric vehicles, unmanned aerial vehicles, and urban air mobility. Conventional safety monitoring of LIB mostly depends on the electric signals of each LIB unit, yet the electric signal-based monitoring has shown its technical limitations in detecting local mechanical/chemical status in LIBs. Therefore, this study investigated a status imaging system to detect local changes in an LIB using an active sensing system. The research scope of this study is to detect and localize the simulated mechanical degradation within a LiFePo4 (LFP) battery having a relatively large dimension (300×210×12 mm3 ). Nine piezoelectric wafers were embedded on the LIB surface. The excitation frequency was determined by observing the signal-to-noise ratio in the frequency range from 60 to 280kHz. As for the status imaging algorithm, we employed a probabilistic reconstruction algorithm, where the index was developed based on the Continuous Wavelet Transform (CWT). The local mechanical change in the LIB was realized by placing a heavy (~ 0.5 kg) weight on a certain spot. The experiment results showed that the proposed imaging method (i.e., CWT-based imaging) could detect the localized mechanical degradation of the LFP battery in a more significant imaging contrast (⪆+20%) compared to other existing methods. This research will provide a new methodology to monitor the localized state-of-health of a large LIB.
This study aims to detect micro defects in Multilayer Ceramic Capacitors (MLCC) using a new signal processing method for Electromechanical (EM) responses. Microscopic defects within MLCC structures, not screened during the manufacturing production stage, can cause damage to electronic products and further lead to overall system failure. Therefore, it is very important to secure reliable defect detection technology. However, conventional methods, such as x-ray and ultrasound tests, are destructive, cost-ineffective, and inaccurate. In this study, we applied a new signal processing method based on the Hilbert-Huang transform (HHT) of the EM response for the nondestructive screening of MLCCs with hidden defects. We first observed that infinitesimal, irregular oscillation in the instantaneous frequency in the transient response when the MLCC had defects. Therefore, we introduced a new signal processing method that takes the Fourier Transform (FT) of the Weighted-Instantaneous Frequency (WIF) concerning the frequency-oscillatory rate, to capture the infinitesimal change in the HHT signal. Specifically, we confirmed that subharmonic terms, possibly caused by the nonlinear effect, arose in the WIF when the target MLCC had a micro defect. The method was first validated through signals obtained from transient finite element analysis, followed by a comparison with the test data from actual MLCCs. The increased subharmonic terms in the WIF could be an effective indication of the defect in the MLCC. This study will provide a new methodology for detecting microdefects in MLCC.
There is a growing need for non-invasive structural health monitoring in extreme environments. For nuclear power plants, pressure and temperature sensing under hazardous environment plays an important role for coolant system safety and stability management. Current sensing methods are intrusive, and suffer from degradation in the plant environment, limited life cycle, and complicated repair and replacement procedures. In this paper, we present an advanced Bi-In-Sn liquid metal (LM) transducer with the addition of candle-soot nanoparticles (CSNP) for improved photoacoustic efficiency and a metallic stencil for control of the liquid metal layer thickness. The sensitivity of the liquid metal candle-soot nanoparticle (LM-CSNP) ultrasound transmitter was characterized under 2 mJ/cm2 at 65 °C, and 6 mJ/cm2 at 100 °C —300 °C. Compared with existing LM transmitter, the newly presented transmitter showed a sensitivity 6.6 times stronger than previously reported LM only transmitter.
Shape morphing is one of the most appealing applications of adaptive structures. Among the various means of achieving shape morphing, origami-inspired folding is particularly advantageous, because folding is a powerful approach to induce three-dimensional and sophisticated shape changes. However, attaining large-amplitude folding is still a challenge in origami engineering. While promising, the use of active materials as a folding activation strategy is limited due to the constant voltage supply that is required to maintain the desired configuration of the structure. One possible solution is to embed bi-stability into the structure. Bi-stability can play two significant roles here: first, it can significantly reduce the actuation requirement to induce shape morphing, and second, it can maintain the shape change without demanding sustained energy supply. In a previous study by the authors, a unique shape morphing (or self-folding) method using harmonic excitation has been proposed for a bi-stable water-bomb base. However, this approach has some drawbacks because the nonlinear dynamic behaviors of origami are quite sensitive to different design parameters, such as initial conditions, excitation parameters, and inaccuracies in manufacturing. In this study, via numerical simulations, we show that by harnessing the intra-well resonance of the water-bomb structure and incorporating a relatively simple feedback control strategy, one can achieve a rapid and robust morphing using relatively low actuation magnitude. The results of this study can lay the foundation of a new category of morphing origami mechanisms with efficient and reliable embedded actuation.
The aim of this research study is to develop a flexible ultrasound transducer capable of determining the blood volume flow. Currently, there are a few different methods of measuring fluid flow inside a vessel using ultrasound. In Doppler shift and time transit flowmeters, a wedge has been used to mount a piezoelectric transducer in order to create a known angle between the direction of fluid flow and the direction of generated wave propagation. In general, the flat nature of piezoelectric transducers has restricted the application of this method to mounting surfaces with known geometry. However, in a recent study, a flexible piezo-composite ultrasonic transducer was developed using PZT-5H and a passive polymer matrix (PDMS). Due to the flexibility of this unique transducer, it can be mounted on surfaces of unknown and varying geometry. In the context of measuring the blood flow rate in a human vessel, the transducer can be integrated into a wearable device capable of determining the orientation and position of the vessel’s path using wave time of flight. In this article, we measured a flow speed using the flexible transducer embedded on a curved surface of a tissue-mimicking material, in which water flows through an artificial flow vessel aligned in a known angular direction. Then, the velocity of the flowing medium in the vessel is estimated by using the Doppler shift method. The experimental results will provide the fundamental background for application of the flexible transducer to the wearable device capable of measuring the blood flow and the pressure.
This article aims to develop a pressure sensing method by utilizing both a contacting active sensor and a non-contacting laser ultrasound transmitter. An overloaded stress in an industrial pressure tank such as a nuclear reactor may cause a catastrophic explosion; thus, it is essential to monitor the mechanical stress in a reliable manner for the structural safety. Among many different types of stress sensing methods, ultrasound sensing has been attractive due to its non-invasive measurement feature. For the recent decades, subsurface longitudinal (SSL) ultrasonic wave has been widely used since it is not only less dependent on the internal medium and the surface condition, but also has the fastest wave speed without wave distortion. In our work, laser source and Aluminum nitride (AlN) wafer are used to generate and to receive SSL ultrasonic waves, respectively. In order to increase the photoacoustic efficacy, a composite of carbon-soot nanoparticles (CSNP) and polydimethylsiloxane (PDMS) was attached onto the intermediate wedge at the transmitter side. The photoacoustic experiment results demonstrate a reasonable linear relationship between the stress level and the time-of-flight variation of the propagated wave signal.
A matching pursuit (MP) algorithm is effective tool to decompose the overlapped wave packets in a signal so that each wave mode can be identified. For the successful separations of the wave packets, an atom function should be properly designed, that can well resemble the physical features of the signal of interest. In this paper, a novel atom function for the MP algorithm is proposed based on the wave propagating model due to an excitation of a Hann-windowed toneburst signal, which performs very accurately compared to the MP algorithm with the existing Gaussian-type atom functions. The decomposed wave packets, including the directly scattered wave from damage as well as the reverberant waves from the free edges of the plate, via the MP method are employed in the damage imaging algorithm, highlighting the damaged location with higher intensity than the conventional algorithm utilizing only a direct reflected wave. The proposed approach is verified from the experiment where four piezoelectric wafers can accurately identify the damage location in a plate.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.