Shock and Vibration

The magnitude of pretension force serves as an important indicator of the effectiveness of anchor bolt active support and is one of the significant factors influencing the stability of tunnel surrounding rock. Therefore, in practical engineering, it is crucial to establish the relationship between pretension torque and pretension force. However, current research in this field has some limitations. With a specific mine in western China as the engineering background, this paper first analyzed the influence factors of surrounding rock deformation and failure, established a mechanical model for pretension structure of anchor bolt support, and derived the quantitative relationship between pretension torque and pretension force based on hypothetical conditions. Finally, it proposed the loss effect of anchor bolt support and modified the pretightening loss coefficient for engineering application. The research results show that the actual pretightening force of anchor support is lower due to the influence of deep soft coal seam, which leads to failure of coal pillar under mining stress. The loss effect of surrounding rock on pretightening force was represented by a coefficient k, and the modified value of the coefficient was calculated as 0.19∼0.43. By applying the modified relationship between pretightening torque and pretightening force, it was found that the actual pretightening torque of 300 Nm applied to 11307 return air roadway effectively controlled surrounding rock deformation and failure, with coal pillar displacement less than 120 mm.

This article investigates the movement of concrete subjected to vibration employing mass-spring model. For this purpose, two different prefabricated concrete-formworks, on which experimental work was done before, were analysed analytically. The theoretical modeling of precast formworks employed in experiments has been made by the three-dimensional finite element method employing the SAP2000 program. Modeling of mortar is performed to resolve the interaction between the fresh concrete and formwork using the mass-spring model. Considering the dynamic behavior of the fluid, it is possible to define multiple oscillation (convective) masses with different frequency values in addition to the impulse mass. Thus, one impulse mass and two convective masses were used in the mass-spring model. This study is essentially theoretical, and its accuracy has been strengthened by experimental work. The time-dependent results of concrete movement obtained from the dynamic mass-spring model were compared with the measured ones. The matches indicate that the findings are consistent.

A novel split-type air conditioning system is introduced to balance usability and portability. Unlike conventional split-type systems, where the compressor is typically placed outside, this system situates the compressor within the indoor unit, which may expose users to compressor noise. There are prominent peaks in the compressor noise spectrum, particularly at the compressor operating frequency and its harmonics, notably the second and third harmonics. The research presents a multilayered acoustic enclosure specifically designed for air conditioning compressors to address this issue without modifying the compressor or indoor unit casing. In order to get better sound insulation performance, a response surface methodology (RSM) is applied to optimize the thickness ratio, open area ratio, and open area height of the acoustic enclosure with predefined thickness. In addition, topological optimization is employed to strengthen weak areas of the acoustic enclosure. Then, experimental trials using the proposed acoustic enclosure are conducted in a semianechoic chamber. Results demonstrate significant reductions in noise levels, including 7.99 dB(A), 5.69 dB(A), and 5.19 dB(A) reductions in the fundamental frequency, second harmonic, and third harmonic noise of the compressor’s operating frequency, respectively.

This article proposes a formula for calculating the nonlinear displacement of the electrothermal V-shaped actuator aims to determine more accurately its displacement. The nonlinear displacement model is established based on the axial deformation of V-beams with two fixed ends. Hence, the theoretical displacements of a particular V-shaped actuator (i.e. dimension as beam length of 750 μm; beam width of 6 μm; beam thickness of 30 μm; inclined angle of 2°) are compared with the simulation and experimental results. The evaluation shows that our calculation error compared with the simulation and experiment is less than 5% and 12.4%, respectively. This confirmed the advantages of the proposed formula according to the nonlinear displacement model. This work provides a theoretical model for predicting more precisely the displacement of a V-shaped actuator. The advantage of this model is that it will significantly reduce the time in the design and trial manufacturing process.

In this study, the vibration characteristics of a bullet-loaded recorder’s vibration damping system under various preload conditions are investigated through theoretical analysis, numerical simulations, and experimental verification. The findings indicate that the inclusion of a polyurethane elastomer vibration damping buffer layer between the cartridge and the recorder, along with the application of a specific preload, significantly reduces the amplitude of vibration acceleration transmitted to the recorder’s interior. This, in turn, enhances the overload resistance of the cartridge’s internal circuit. Numerical simulation results and theoretical analysis suggest that increasing the preload on the buffer material between the elastomer and the recorder reduces both the frequency ratio and damping ratio of the damping system. This reduction further decreases the amplitude of vibration transmitted to the recorder. However, excessively high preload generates substantial compressive stress within the recorder under static conditions, intensifying during the projectile’s accelerated movement. As a consequence, deformation and damage occur to the internal circuitry. Therefore, ensuring that the recorder possesses the structural strength necessary to withstand increased preload is crucial. This balancing act improves the recorder’s resistance to shock, vibration, and overload, while also preventing excessive stress-induced damage.

This paper introduces an innovative approach, Deep Multiscale Soft-Threshold Support Vector Data Description (DMS-SVDD), designed for the detection of anomalies and prediction of faults in heavy-duty gas turbine generator sets (GENSETs). The model combines a support vector data description (SVDD) with a deep autoencoder backbone network framework, integrating a multiscale convolutional neural network (M) and soft-threshold activation network (S) into the Deep-SVDD framework. In comparison with conventional methods, such as One-Class Support Vector Machine (OCSVM) and autoencoder (AE), DMS-SVDD demonstrates improvements in accuracy (by 22.94%), recall (by 32%), F1 score (by 12.02%), and smoothness (by 39.15%). The model excels particularly in feature extraction, denoising, and early fault detection, offering a proactive strategy for maintenance. Furthermore, the DMS-SVDD demonstrated enhanced training efficiency with a reduction in the convergence rounds by 66% and overall training times by 34.13%. The study concludes that DMS-SVDD presents a robust and efficient solution for gas turbine anomaly detection, with practical advantages for decision support in turbine maintenance. Future research could explore additional refinements and applications of the DMS-SVDD model across diverse industrial contexts.