In order to detect the incipient fault of rolling bearings and to effectively identify fault characteristics, based on amplitude-aware permutation entropy (AAPE), an enhanced method named hierarchical amplitude-aware permutation entropy (HAAPE) is proposed in this paper to solve complex time series in a new dynamic change analysis. Firstly, hierarchical analysis and AAPE are combined to excavate multilevel fault information, both low-frequency and high-frequency components of the abnormal bearing vibration signal. Secondly, from the experimental analysis, it is found that HAAPE is sensitive to the early failure of rolling bearings, which makes it suitable to evaluate the performance degradation of a bearing in its run-to-failure life cycle. Finally, a fault feature selection strategy based on HAAPE is put forward to select the bearing fault characteristics after the application of the least common multiple in singular value decomposition (LCM-SVD) method to the fault vibration signal. Moreover, several other entropy-based methods are also introduced for a comparative analysis of the experimental data, and the results demonstrate that HAAPE can extract fault features more effectively and with a higher accuracy.

This paper explores the characteristics of processing carbon fiber-reinforced plastic (CFRP) materials with ultra-short pulsed lasers. By combining experimental and numerical simulation methods, the processing characteristics when ultra-short pulsed lasers interact with CFRP are analyzed, including processing depth, processing width, the formation of heat-affected zone (HAZ), and the microstructure of the processed surface. The experimental part involves using picosecond and femtosecond lasers to machine holes or slots in CFRP under different process parameters and comparing their morphologies. Numerical simulation constructs a three-dimensional model to predict the temperature field distribution and material removal dynamics during the laser processing process. The results of experiments and simulations indicate that picosecond laser processing produced a visible HAZ and thermal damage; as the power of the picosecond laser increases, the ablation holes and HAZ gradually expand. In contrast, no HAZ is observed in femtosecond laser processing. Femtosecond pulsed lasers can effectively reduce the thermal damage during the CFRP processing. The anisotropic properties of CFRP materials have a significant impact on the laser processing effects. The research findings provide a theoretical basis and technical support for the precise processing of CFRP materials, which is of great significance for the application of CFRP materials in fields such as aerospace and automotive manufacturing.