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This work is focused on performance computation of high speed rotor bearing system with partial composite texture. Since its viscosity at varying speeds affects working performance in different partial composite texture, therefore at design and development stage, it is necessary to know the composite texture and thermal effect acting on rotor‐bearing system that causes variation of performance. The effects of partial composite texture size and position on the performance of the bearing are studied. After the optimal structural parameters are determined, the effects of the partial composite texture and fluid thermos structure coupling on the bearing capacity, stiffness, and friction coefficient of the oil film are analysed. The results show that after considering the influence of thermal effect, the performance enhancement of composite texture bearing is better than that of smooth bearing. Considering the temperature effect, the bearing capacity of the composite textured bearing is increased by 51.4% compared with that of the smooth bearing, and the friction coefficient is reduced to 22.4%, which is better than the value without considering the temperature effect, the accuracy of the results is verified by experiments. This study provides a theoretical basis for the design of hydrostatic bearing and improving its performance. [ABSTRACT FROM AUTHOR]

The lubricating medium of the aerostatic spindle is gas, with relatively low rigidity, which is easy to cause rotor offset and additional vibration under the action of external load, thus affecting the processing accuracy of the spindle. To solve the problem of unbalanced vibration of the spindle, a new type of controllable radial aerostatic bearing is designed by combining piezoelectric ceramics, which use the inverse piezoelectric effect of piezoelectric ceramics to squeeze the air film to produce corresponding control force, and the radial unbalanced vibration of the spindle is suppressed. A bearing–rotor–piezoelectric ceramic coupling model was established, and the control method of feedforward combined with feedback was used to reduce the hysteresis characteristics of piezoelectric ceramics. On this basis, the sliding mode controller of the entire system, and through research, it is found that the sliding mode controller based on the extended observer has the best vibration suppression effect compared with other sliding mode controllers in the article; this research results can improve the rotation accuracy of the spindle system and the machining accuracy of ultra-precision machine tools. [ABSTRACT FROM AUTHOR]

Single crystal 3C-SiC as a typical hard and brittle material. Due to its extremely high hardness and brittleness, diamond tools can have drastic wear problems in a short period of time when performing nano-machining processes. Single-crystal 3C-SiC has good anisotropy. In order to gain insight into the effect of crystal orientation on the tool wear behavior during nano-cutting, this paper investigated the tool wear for six cutting crystals downward using molecular dynamics simulation. The tool wear process was analyzed in terms of tool wear, cutting stress, cutting temperature, cutting force and subsurface damage. The results showed that the tool is subjected to large hydrostatic stress concentrations, radial forces and tool temperature concentrations during machining. Under these effects, abrasive wear, graphitic wear and amorphous phase change were produced. In addition, the clearance face of the tool is more severely worn than the rake face. By reasonably selecting the cutting crystal orientation, well control and improvement of tool wear and machined surface quality can be achieved. [ABSTRACT FROM AUTHOR]

An acoustic signal acquisition experiment platform was constructed to gather the acoustic signals throughout the formation of 35 single-tracks of a 120 mm length copper-tin alloy in order to monitor and precisely manage the selective laser melting (SLM) forming process and enhance overall quality. The monitoring of the SLM forming process includes the analysis of the time and frequency domains, the extraction of the SLM process features using linear prediction techniques, and the development of support vector machine (SVM) model, back-propagation (BP) neural network models, and convolutional neural network models. The results show that the over-melted state can be identified by extracting time and frequency-domain features over a given range, but the normal and unmelted states are difficult to distinguish. The convolutional neural network model had a recognition rate of 99%, the BP neural network had an effective recognition rate of 90%, and the SVM model had a combined classification rate of 83.14% for the three states after optimization. In contrast, the convolutional neural network model performs best in monitoring and offers a framework and point of reference for acoustic signal analysis and online SLM quality monitoring. [ABSTRACT FROM AUTHOR]

The objective of this work is to study the characteristics of the hydrostatic bearing with nanolubricant. To investigate the effect of nanoparticle additives on the performance of hydrostatic bearings, a coupled heat transfer finite-element model of the hydrostatic bearing is developed, and the results of the static and dynamic performance of the hydrostatic bearing with lubricant and nanolubricant are evaluated based on computational fluid dynamics methods at different eccentricity ratios. The results show that the rotation error of the bearing–rotor system is reduced by using nanolubricant at a high eccentricity ratio. [ABSTRACT FROM AUTHOR]

To ensure the forming quality of SLM and to improve the forming efficiency of SLM, this paper investigates the forming effect of Ti6Al4V specimens formed by SLM based on an interlayer strategy. The conditions for improving the relative density of the specimens are high laser power, small point distance, long exposure time and long hatch spacing. High laser power provides sufficient laser energy density in the formation of thicker powder layers, reduced point distance ensures wetting behavior of the melt pool, longer exposure time provides the time required to fully melt the powder and increased hatch distance facilitates dispersion of the laser energy density. Process parameters have a strong influence on the relative density of SLM formed specimens, and by adjusting the process the highest density of 99.99% can be achieved. The microstructure of the specimens consisted mainly of acicular martensite α′ and columnar β grains due to the effects of repeated thermal cycling. Due to the presence of martensite α′, the tensile and yield strengths of the specimens are increased, but the elongation of the specimens is reduced.