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To study the effect of different surface structures on the aggregation level and interfacial adhesion, nano-Sb2O3 particles were treated with cetyltrimethylammonium bromide (CTAB), silane coupling agent KH550 and their compounds (CTAB + KH550). The surface properties and morphologies of the nano-Sb2O3 particles were characterized by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The aggregation level and interfacial adhesion of nano-Sb2O3 particles within PBT matrix were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), and quantitatively evaluated by some semi-empirical parameters including aggregates size (Dagg), real filling degree (Vre), interfacial adhesion ( B ) and aggregated interfacial adhesion (Bagg) from the tensile strength and the Young's modulus measurements. The results showed that the highest interfacial adhesion and lowest aggregation level were obtained for the CTAB + KH550 modified nano-Sb2O3/PBT composites followed by the KH550 modified, CTAB modified and bare nano-Sb2O3/PBT composites, respectively. [ABSTRACT FROM AUTHOR]

Rolling bearings play a crucial role as components in rotating machinery across various industrial fields. Bearing faults can potentially lead to severe accidents in operating machines. Therefore, condition monitoring and fault diagnosis of rolling bearings are essential for preventing equipment failures. Multiple faults are a common occurrence resulting from the prolonged operation of rolling bearings, and numerous research efforts have been made to study multiple faults in different components of the bearing. However, diagnosing multiple faults in a single component of the rolling bearing still remains a highly challenging task. In this paper, a multiple faults separation and identification method based on time-frequency (TF) spectrogram (TFS) is proposed for vibration signals of rolling bearings. Firstly, the fast path optimization method is improved to match the TFS of original vibration signals in bearing faults generated by short-time Fourier transform. Then multiple TF curves are extracted from the TFS by the proposed multiple transient component curves extraction method based on the improved fast path optimization method. With the fault characteristic period, a classification criterion is introduced to separate TF curves. Secondly, a TF masking method is constructed to retain the TF information closely related to fault components of vibration signals. Finally, the novel TF representation can be obtained to develop signal reconstruction, and multiple faults can be detected based on envelope analysis separately. The experiments from rolling bearings with multiple faults on raceways are used to verify the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Dynamic modelling of rolling element bearing (REB) is a significant method to explore the vibration mechanism generated by fault, and it is the theoretical basis of fault diagnosis of REBs. Aiming at the complexity of defect-rolling-element interaction under radial load, the whole contact process of rolling element (RE) passing over defective area of outer or inner ring is analysed in detail. The impact force excitation function is derived by rotation and revolution velocity of RE. A four degree-of-freedom (DOF) dynamic model of REB with compound fault of both inner and outer raceway surface is developed by considering the time-varying displacement, impact force excitative and elastohydrodynamic lubrication (EHL) condition, and the novelty of the model is that the improved impact force excitation function is used. The experimental validation is carried out on test tig of Machinery Fault Simulator. The change of impact force with shaft speed and defect size is analysed. It is shown that the simulation results of the proposed model are closer to experimental results. A mapping method from defect-rolling-element-defect (DRED) behaviour to time is proposed to study the vibration characteristics of DRED behaviour, the results show that the amplitude of vibration will decrease when the same RE collides with inner and outer raceway defects simultaneously. When the same RE collides with inner and outer raceway defect successively, the amplitude of vibration will reach the maximum during the inner raceway defect rolling over each RE once. The proposed model can be used in practical application to study the influence of compound defects on vibration response of REB. [ABSTRACT FROM AUTHOR]

Nano-sized Sb2O3 particles were prepared and modified by high-energy ball milling (HEBM) using cetyltrimethylammonium bromide (CTAB), and the modification and dispersion mechanism were discussed. The surface properties, morphologies, and dispersion stability of nano-Sb2O3 particles were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), UV absorbance, contact angle (CA), zeta potential measurement, and water adsorption measurement, respectively. The results showed that the nano-Sb2O3 particles prepared by HEBM arrived to an average particle size of 22.1 nm and exhibited a good dispersion stability in water system when the CTAB's concentration arrived to 15 wt.%. After being modified by CTAB, the long alkyl chains of CTAB were successfully grafted onto the surface of nano-Sb2O3 particles and the surface characteristics of modified nano-Sb2O3 particles exhibited more hydrophobic than those of unmodified nano-Sb2O3 particles. [ABSTRACT FROM AUTHOR]

The surface modification of nano-Sb2O3 particles with silane coupling agent KH-570 was carried out by chemical modification method (CM) and ball milling modification method (BMM). The modification mechanism was also analyzed and discussed. The surface characteristics of modified nano-Sb2O3 particles were characterized by FTIR, TEM, BET and UV absorbance. The results showed that silane coupling agent could chemically anchor onto the surface of nano-Sb2O3 particles though the effect of covalent bond (Sb-O-Si), and the modified nano-Sb2O3 particles exhibited a good dispersive capacity in organic solvent. Comparative modification effect showed that the dispersion of nano-Sb2O3 particles modified by BMM was better than that of CM, due to the secondary aggregations of nano-Sb2O3 particles could be crushed in the ball milling modification process, which provided more reaction chance with silane coupling agent. [ABSTRACT FROM AUTHOR]