Due to the fact that measured vibration signals from a bearing are complex and non-stationary in nature, and that impulse characteristics are always immersed in stochastic noise, it is usually difficult to diagnose fault symptoms manually. A novel hybrid fault diagnosis approach is developed for the denoising signals and fault classification in this work, which combines successfully the variational mode decomposition (VMD) and one dimensional convolutional neural network (1-D CNN). VMD is utilized to remove stochastic noise in the raw signal and to enhance the corresponding characteristics. Since the modal number and penalty parameter are very important in VMD, a particle swarm mutation optimization (PSMO) as a novel optimization method and the weighted signal difference average (WSDA) as a new fitness function are proposed to optimize the parameters of VMD. The reconstructed signals of mode components decomposed by optimized VMD are used as the input of the 1-D CNN to obtain fault diagnosis models. The performance of the proposed hybrid approach has been evaluated using the sets of experimental data of rolling bearings. The experimental results demonstrate that the VMD can eliminate signal noise and strengthen status characteristics, and the proposed hybrid approach has a superior capability for fault diagnosis from vibration signals of bearings.
The deposition of synthesized zinc oxide nanoparticles on the surface of cotton fiber under ultrasonic irradiation was reported in this study. The presence of the hexagonal phase of the crystalline metal oxide was confirmed by the XRD results. We also studied the electrochemical features of ZnO employed as an anode material for lithium-ion batteries. ZnO showed favorable lithium storage properties.
After the workpiece is processed, the barrel mill is widely used as a burr removal device. Therefore, in order to improve the efficiency of burr removal and enhance the polishing effect on the surface of the workpiece, the conventional roller grinder is improved in design, and the continuous batch grinding method is used instead of the conventional batch grinding method, and the automatic workpiece transfer device is added after the end of the grinding. , thereby increasing the grinding efficiency. Using SolidWorks software, three-dimensional solid modeling and virtual prototype assembly were carried out on the feeding device, grinding device and conveying device. The static analysis of the roller bracket was carried out by ANSYS Workbench software, and the rationality of the design was verified. The results show that the burr removal rate is increased by 10%~20% compared with the traditional grinding machine, and the surface roughness is improved by 1~2, which improves the production efficiency to a certain extent.
In order to design a kind of mechanical vibration part with stable motion in ultrasonic composite vibration polishing equipment. firstly, the main working principle of ultrasonic composite vibration polishing equipment is briefly introduced. Secondly, the mechanical vibration structure of the design is analyzed theoretically, again, using ADAMS software to simulate the crankshaft connecting rod piston mechanism. When the crankshaft speed is 750r/min, the stroke of the piston is 90mm, which is similar to the theoretical analysis value. Finally, using ANSYS Workbench software to analyze the crankshaft statics. The analysis shows that the design of the mechanical vibration structure is reasonable, which provides a theoretical basis for the study of the mechanical vibration structure of ultrasonic composite vibration polishing equipment.
In order to develop a workpiece surface polishing equipment with high performance and high precision, the overall structural design and parameter selection of ultrasonic composite abrasive vibration polishing equipment were mainly completed. Secondly, static analysis of the crankshaft connecting rod piston mechanism is performed by ANSYS Workbench software. We can know that the crankshaft connecting rod piston mechanism has the most concentrated stress at the contact between the small end of the connecting rod and the connecting rod shaft. And the stress value is 121.04MPa but less than the allowable stress value of the connecting rod. Therefore, the strength of the crankshaft connecting rod piston mechanism meets the design requirements, and the modal analysis of the crankshaft is carried out, and the crankshaft right crank displacement deformation amount is the most. It provides a theoretical basis for the optimization design of the crankshaft later and provides a reference for the research of ultrasonic composite abrasive vibration polishing equipment.
In order to improve the anti‐penetration performance of gradient armor, the constitutive models of B4C/Al composites with different compositions were determined according to the bending curves. The anti‐bullet simulation of B4C/Al gradient armor was carried out by ANSYS‐DYNA finite element software, and the stress state of B4C/Al gradient material under 7.62‐mm bullet penetration was analyzed. Meanwhile, the propagation law of stress wave in armor was studied by Hopkinson bar simulation and the improved internal stress wave model, which further revealed the ballistic mechanism of B4C/Al gradient armor. The simulation results showed that, compared with the traditional laminated armor, the toughness of B4C/Al gradient armor material increased with the change of layer thickness, resulting in the fact that the whole armor could withstand greater stress without breaking, and the anti‐penetration time was prolonged. In addition, the performance difference between the layers of the gradient armor was slight, and the spallation phenomenon of the relative double‐layer armor decreases, which enhanced the multiple hit performance of the armor and the absorption capacity of the stress wave. The performance of B4C/Al gradient armor specimens and double‐layer specimens were tested by drop hammer impact test. The test results were consistent with the simulation results.
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