Impact force refers to a transient phenomenon with a very short-acting time, but a large impulse. Therefore, the detection of impact vibration is critical for the reliability, stability, and overall life of mechanical parts. Accordingly, this paper proposes a method to indirectly characterize the impact force by using an impact stress wave. The LS-DYNA software is utilized to establish the model of a ball impacting the steel plate, and the impact force of the ball and the impact response of the detection point are obtained through explicit dynamic finite element analysis. In addition, on this basis, a correspondence between the impact force and the impact response is established, and finally, an experimental platform for impact force detection is built for experimental testing. The results obtained by the finite element method are in good agreement with the experimental measurement results, and it can be inferred that the detected piezoelectric signal can be used to characterize the impact force. The method proposed herein can guide the impact resistance design and safety assessment of structures in actual engineering applications.

Anchored steel bars have been widely used in retrofitting of existing concrete structures. The bonding strength between the anchored steel bar and the concrete is critical to the integrity of the strengthened concrete structure. This paper presents a method to monitor epoxy-grouted bonding strength development by using a piezoceramic-enabled active sensing technique. One concrete beam with an anchored steel bar was involved in the monitoring test, and two concrete beams with six anchored steel bars were used in the pull-out test. To enable the active sensing, a Lead Zirconate Titanate (PZT) patch was bonded to the surface of the exposed end, and piezoceramic smart aggregates were embedded in each concrete specimen. During the monitoring experiment, signals from PZT sensors and smart aggregates were acquired at intervals of 0, 20, 40, 60, 80, and 100 min. In addition, a pull-out test was performed on each of the remaining six anchored steel bars in the two concrete beams, while the signal was recorded in the test. Furthermore, a wavelet packet analysis was applied to analyze the received signal energies to investigate the bonding strength development between the concrete and the anchored steel bar during the epoxy solidification process. The test results demonstrate the effectiveness of the proposed method in monitoring the bonding strength development between the anchored steel bar and the concrete, using the PZT-enabled active sensing.

Existing acoustic logging instruments do not fulfill the requirements for forward-looking advanced detection. Therefore, research has been undertaken on forward-looking acoustic logging technology utilizing a multi-pole acoustic source. The finite difference algorithm was used to simulate the acoustic logging responses of monopole and dipole sources in the presence of a formation interface ahead of the drill bit while drilling. The simulation results indicate that, due to the influence of bottomhole scattering, the wave field of forward-looking acoustic logging is more complex than that of conventional reflected acoustic logging. In contrast to the monopole acoustic radiator, the dipole sound wave exhibits a more robust emission of sound wave energy toward the formation in front of the drill bit. The amplitude of the reflected wave generated at the formation interface is dozens of times greater than that of the monopole reflected wave. Therefore, the dipole sound source proves to be more advantageous for forward detection. Moreover, the comparison of the signal-to-noise ratio for the reflected wave generated by the dipole sound source across different frequencies is further examined. The findings reveal a direct correlation between the primary frequency of the dipole sound source and the signal-to-noise ratio of the reflected wave—specifically, a lower main frequency corresponds to a higher signal-to-noise ratio. Additionally, it is observed that the signal-to-noise ratio undergoes periodic changes in magnitude.. The research results validate the feasibility of using dipole acoustic logging technology for detecting geological anomalies before drilling. Furthermore, they offer a theoretical base for the subsequent development of industrial prototypes.

Butt welding is extensively applied in long-distance oil and gas pipelines, and it is of great significance to conduct non-destructive ultrasonic testing of girth welds in order to avoid leakage and safety accidents during pipeline production and operation. In view of the limitations of large transducer size, single fixed beam angle, low detection resolution and high cost of conventional ultrasonic inspection technologies, a 16-channel piezoelectric micro ultrasonic transducer (PMUT) array probe was developed through theoretical analysis and structural optimization design. After the probe impedance characterization, the experimental results show that the theoretical model can effectively guide the design of the ultrasonic transducer array, offering the maximum operating frequency deviation of less than 5%. The ultrasonic echo performance tests indicate that the average −6 dB bandwidth of the PMUT array probe can be up to 77.9%. In addition, the fabricated PMUT array probe has been used to successfully detect five common internal defects in pipeline girth welds. Due to the multiple micro array elements, flexible handling of each element, large bandwidth and high resolution of defect detection, the designed PMUT array probe can provide a good application potential in structural health monitoring and medical ultrasound imaging fields.

Single-well imaging plays an increasingly important role in the exploration and production of hydrocarbon in horizontal wells. Depending on the scattering strength, reflections from lateral sections below heterogeneous regions around the borehole suffer signal distortion and amplitude loss, which complicates the imaging of deeper structures. Thus, the understanding of scattering phenomena and their impact on single-well imaging is of significant interest for hydrocarbon exploration. This paper establishes a complex horizontal well numerical model with which the effects of heterogeneous overburden on deep reflection imaging are studied using dipole acoustic logging. Synthetic data were analyzed with respect to the observed reflectivity in the heterogeneous layer and along the deep reflection. The results show that strong velocity fluctuations increase the severity of the scattering effect when correlation distances are in the order of the dominant wavelength. The reflection images migrate and reveal additional structural details of the medium. Low frequency band imaging enables the extraction of undistorted real reflectors by using the Reflection Image Spectroscopy method. The results explain the influence of the heterogeneous overburden on single-well imaging results and provide theoretical guidance for logging interpretation.

Incoherent scattered waves are generated when seismic waves propagate through heterogeneous media. These scattered waves contain statistical information, such as random heterogeneity. In order to study the influence of random heterogeneity on seismic waveforms, four series of simulation experiments were performed in the presents study, as follows: (1) Waves were excited by the same source and propagated through four models with different parameters; (2) Waves were excited by different frequencies, but spread in the same model (0.25, 0.50, 1.00, 2 MHz); (3) Waves were excited by the same source and propagated through three different velocity fluctuation models (5%, 10% and 15%); (4) Waves were excited by the same source and propagated through three different propagation distances (30, 60, and 90 mm). In the present study, the correlation between coherent waveforms and observed waveforms, the energy distribution with respect to the elapsed time, and the statistical distribution of the waveform correlation coefficient were calculated. Next, the variation of the waveform parameters with the normalized scale parameter ka was investigated. Stronger scattered waves and more complicated waveforms were observed when the ka value increased, indicating the transition from an equivalent homogeneous medium to a heterogeneous medium.