Search Results (7)

This study investigated the changes in the acoustic emission (AE) activity emitted in fiber-reinforced concrete (FRC) under flexure at two temperatures (25 °C and −20 °C). Seven concrete mixtures were developed with different water-binder ratios (w/b) (0.4 and 0.55), different fiber materials (steel fiber (SF) and synthetic polypropylene fiber (Syn-PF)), different fiber lengths (19 mm and 38 mm), and various Syn-PF contents (0%, 0.2%, and 1%). Prisms with dimensions of 100 × 100 × 400 mm from each mixture underwent a four-point monotonic flexure load while collecting the emitted acoustic waves via attached AE sensors. AE parameter-based analyses, including b-value, improved b-value (Ib-value), intensity, and rise time/average signal amplitude (RA) analyses, were performed using the raw AE data to highlight the change in the AE activity associated with different stages of damage (micro- and macro-cracking). The results showed that the number of hits, average frequency, cumulative signal strength (CSS), and energy were higher for the waves released at −20 °C compared to those obtained at 25 °C. The onset of the first visible micro- and macro-cracks was noticed to be associated with a significant spike in CSS, historic index (H (t)), severity (S_r) curves, a noticeable dip in the b-value curve, and a compression in bellows/fluctuations of the Ib-value curve for both testing temperatures. In addition, time and load thresholds of micro- and macro-cracks increased when samples were cooled down and tested at −20 °C, especially in the mixtures with higher w/b, longer fibers, and lower fiber content. This improvement in mechanical performance and cracking threshold limits was associated with higher AE activity in terms of an overall increase in CSS, S_r, and H (t) values and an overall reduction in b-values. In addition, varying the concrete mixture design parameters, including the w/b ratio as well as fiber type, content, and length, showed a significant impact on the flexural behavior and the AE activity of the tested mixtures at both temperatures (25 °C and −20 °C). Intensity and RA analysis parameters allowed the development of two charts to characterize the detected AE events, whether associated with micro- and macro-cracks considering the temperature effect. Full article

Objectives: This study aims to evaluate the effectiveness of current conventional and advanced irrigation techniques after minimally invasive instrumentation in necrotic oval root canals by histological analysis. Methods: Seventy extracted necrotic lower premolars with single oval canals classified utilizing bidirectional radiographs (mesiodistal diameter 2.5 times larger than buccolingual) were prepared up to 20.04 v. The samples were assigned to five experimental groups (n = 14) using the complementary irrigation technique: needle (control), passive ultrasonic, and shockwave-enhanced emission photo-acoustic streaming activation using Er:YAG laser (SWEEPS), Er,Cr:YSGG laser (Waterlase iPlus), and multisonic ultracleaning technology (GentleWave). After irrigation protocols, the roots were demineralized and the apical 5 mm was multi-sliced and processed for histologic examination. The residual necrotic tissue and debris percentage was calculated via image analysis software. One-way ANOVA and Tukey’s test were used to verify the variables influencing debridement (p < 0.05). Results: The mean value of the GentleWave group was the record low at 1.54 ± 1.46, and the utmost was needle irrigation with 15.64 ± 7.23. The main effect of techniques on the debridement was statistically significant (p < 0.001). The course of debridement effectiveness, according to the levels of significance between the groups, was as follows: Multisonic ultracleaning > Er:YAG > Er,Cr:YSGG > Passive ultrasonic irrigation > Needle irrigation (p <0.05). Conclusions: In necrotic oval-shaped canals after minimally invasive instrumentation, multisonic ultracleaning with updated software was considerably more effective in removing remnants in the apical level. Er:YAG and Er,Cr:YSGG lasers were highly promising, with results close to multisonic ultracleaning. It should be considered that needle irrigation and passive ultrasonic activation may not be able to provide competent debridement in treating such types of root canals. Full article

This study focuses on the possibility of generating divergent surface acoustic waves (SAWs) with interdigital transducers (IDTs) deposited on Y128° Lithium Niobate for non-destructive testing applications, particularly in the context of manufacturing layer-on-substrate systems for microelectronic components. The selected approach is to diffuse the SAWs over a large surface area and in various directions in order to analyze the structure and detect any defects when using the well-known passive imaging by correlating the diffuse acoustic field. The introduction of SAWs is achieved using offset interdigital transducers that make acoustic contact with the sample under analysis without causing damage. The considered IDTs are characterized based on criteria for maximizing the divergence angle, maximizing SAW emission amplitude, and minimizing the acoustic contact area. Three IDT configurations were tested to compare their performance: (i) a transducer with circular electrodes emitting from its wide convex end; (ii) a circular IDT emitting from its narrow concave end; and (ii) a narrow transducer with an aperture close to two wavelengths. It was shown that the second configuration provides the highest SAW amplitude, which is important while measuring the diffuse acoustic field. Nevertheless, the third one was particularly efficient in terms of reducing the contact area. Full article

The rapid adoption of electric vehicles (EVs) has increased the demand for efficient methods to assess the state of health (SoH) of lithium-ion batteries (LIBs). Accurate and prompt evaluations are essential for safety, battery life extension, and performance optimization. While traditional techniques such as electrochemical impedance spectroscopy (EIS) are commonly used to monitor battery degradation, acoustic emission (AE) analysis is emerging as a promising complementary method. AE’s sensitivity to mechanical changes within the battery structure offers significant advantages, including speed and non-destructive assessment, enabling evaluations without disassembly. This capability is particularly beneficial for diagnosing second-life batteries and streamlining decision-making regarding the management of used batteries. Moreover, AE enhances diagnostics by facilitating early detection of potential issues, optimizing maintenance, and improving the reliability and longevity of battery systems. Importantly, AE is a non-destructive technique and belongs to the passive method category, as it does not introduce any external energy into the system but instead detects naturally occurring acoustic signals during the battery’s operation. Integrating AE with other analytical techniques can create a comprehensive tool for continuous battery condition monitoring and predictive maintenance, which is crucial in applications where battery reliability is vital, such as in EVs and energy storage systems. This review not only examines the potential of AE techniques in battery health monitoring but also underscores the need for further research and adoption of these techniques, encouraging the academic community and industry professionals to explore and implement these methods. Full article

The acoustic emission (AE) technique is one of the most widely used in the field of structural monitoring. Its popularity mainly stems from the fact that it belongs to the category of non-destructive techniques (NDT) and allows the passive monitoring of structures. The technique employs piezoelectric sensors to measure the elastic ultrasonic wave that propagates in the material as a result of the crack formation’s abrupt release of energy. The recorded signal can be investigated to obtain information about the source crack, its position, and its typology (Mode I, Mode II). Over the years, many techniques have been developed for the localization, characterization, and quantification of damage from the study of acoustic emission. The onset time of the signal is an essential information item to be derived from waveform analysis. This information combined with the use of the triangulation technique allows for the identification of the crack location. In the literature, it is possible to find many methods to identify, with increasing accuracy, the onset time of the P-wave. Indeed, the precision of the onset time detection affects the accuracy of identifying the location of the crack. In this paper, two techniques for the definition of the onset time of acoustic emission signals are presented. The first method is based on the Akaike Information Criterion (AIC) while the second one relies on the use of artificial intelligence (AI). A recurrent convolutional neural network (R-CNN) designed for sound event detection (SED) is trained on three different datasets composed of seismic signals and acoustic emission signals to be tested on a real-world acoustic emission dataset. The new method allows taking advantage of the similarities between acoustic emissions, seismic signals, and sound signals, enhancing the accuracy in determining the onset time. Full article

The acoustic emission (AE) method is a popular and well-developed method for passive structural health monitoring of metallic and composite structures. The current study focuses on the analysis of one of its processes, sound source or signal propagation. This paper discusses the principle of plate wave signal sensing using piezoelectric transducers, and derives an analytical expression for the response of piezoelectric transducers under the action of stress waves, to obtain an overall mathematical model of the acoustic emission signal from generation to reception. The acoustic emission caused by fatigue crack extension is simulated by a finite element method, and the actual acoustic emission signal is simulated by a pencil lead break experiment. The results predicted by the mathematical model are compared with the experimental results and the simulation results, respectively, and show good agreement. In addition, the presence of obvious S0 mode Lamb waves is observed in the simulation results and experimental results, which further verifies the correctness of the analytical model prediction. Full article

Injuries and disorders affecting the knee joint are very common in athletes and older individuals. Passive and active vibration methods, such as acoustic emissions and modal analysis, are extensively used in both industry and the medical field to diagnose structural faults and disorders. To maximize the diagnostic potential of such vibration methods for knee injuries and disorders, a better understanding of the vibroacoustic characteristics of the knee must be developed. In this study, the linearity and vibration transmissibility of the human knee were investigated based on measurements collected on healthy subjects. Different subjects exhibit a substantially different transmissibility behavior due to variances in subject-specific knee structures. Moreover, the vibration behaviors of various subjects’ knees at different leg positions were compared. Variation in sagittal-plane knee angle alters the transmissibility of the joint, while the overall shape of the transmissibility diagrams remains similar. The results demonstrate that an adjusted stimulation signal at frequencies higher than 3 kHz has the potential to be employed in diagnostic applications that are related to knee joint health. This work can pave the way for future studies aimed at employing acoustic emission and modal analysis approaches for knee health monitoring outside of clinical settings, such as for field-deployable diagnostics. Full article