This paper investigated the effect of nano-SiC particle on microstructure and properties of brush electroplated nano-Al2O3/Ni composite coating. Three kinds of coatings, such as pure nickel coating, nano-Al2O3/Ni composite coating and nano-SiC-Al2O3/Ni composite coating, were fabricated on 1045 steel substrate. Before deposited, Zeta potential of nano-particles in the solution was examined. The results show Zeta potential of the nanoparticles in the nano-Al2O3/Ni electrolyte is negative, but that of the nanoparticles in nano-SiC-Al2O3/Ni electrolyte is positive when the pH value of electrolyte is about 7.5. Energy dispersive spectroscopy (EDS) results show Al element content in the nano-Al2O3/Ni coating is 5.65%, while the content of Al and Si elements in nano-SiC-Al2O3/Ni coating is 5.63% and 4.86% respectively. It confirms that nano-SiC particle co-deposited in the composite coating while nano-Al2O3 particle content keeps constant. The microhardness of nano-SiC-Al2O3/Ni coating exhibits the highest, while the pure nickel coating is the lowest. And surface morphology of nano-SiC-Al2O3/Ni coating is the most smooth and compact among the three coatings. The wear test results reveal that wear resistance of nano-SiC-Al2O3/Ni coating is 1.7 times of that of nano-Al2O3/Ni coating, and 2.3 times of that of pure nickel coating. The above results show the nano-SiC particle services a strengthening effect on the combination performance of nano-SiC-Al2O3/Ni coating.

In order to enhance the performances of laser remanufacturing part, we combined laser cladding with active screen plasma nitriding duplex treatment to repair metal part. The microstructure, phase structure and micro-hardness of duplex treated coating were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and micro-hardness tester. Wear tests were carried out on reciprocating wear tester under dry sliding condition. The results show that the white layer and the nitrogen diffusion layer were formed after nitriding treatment. The duplex treated coating consists mainly of γ-Fe, CrN, Fe4N and Fe3N. The duplex treated coating improved not only surface hardness but also wear resistance.

The use of ultrasonic nondestructive testing of material internal defect，ultrasonic signal acquired at actual working spot usually includes large amount of noise.Extraction of the defect characteristic information will be influeced greatly if the ultrasonic signal is not effectively denoised. A new method based on best wavelet packet base is present to denoise and detect the ultrasonic signal. The superiority of new method is verified by simulation examples. Experiment of processing ultrasonic signal which comes from the 45 Steel specimen with flaws has been implemented. The accurate information that characterizes of defect size,location can be extracted from the processing result, the results show that the new method based on best wavelet packet base is in favor of enhancing the degree of accuracy for quantitatively analyzing the defect inside the material.

A novel high-precision subdivision system for high-speed encoders is designed in this work. The system is designed with an arc second of Sin-Cos Encoder (SCE) based on zero phase bandpass filter. The system collects the analog output signals of an encoder with a high-speed data acquisition system (DAS); the noise of a digital signal can be effectively eliminated by zero phase bandpass filter with appropriate prior parameters. Finally, the actual rotation angle of the encoder is calculated by the software subdivision technique in the system. The software subdivision technique includes two methods, which are the Analog Pulse Counter (APC) and the Arc Tangent Subdivision (ATS). The APC method calculates the encoder angle by counting the analog pulses acquired by the arc tangent signal. The ATS method calculates the encoder angle by computing the arc tangent results of each point. The accuracy and stability of the system are first verified with a simulated signal; second, the real signals of an SCE are acquired by a high speed DAS on a test bench of a precision reducer, which is employed in industrial robots. The results of the proposed system are compared. The experimental results show that the system can significantly improve the accuracy of the encoder angle calculation, with controllable costs.

Eddy current testing and metal magnetic memory testing, cooperated with special testing devices, were applied to detect the superficial defects of old cylinder barrel. It was indicated that there were three types of the signals, which were non-defect signals, discontinuous peak signals and continuous peak signals. Non-defect signals indicated that there was no defect in cylinder barrel, and the discontinuous peak signals denoted that there was circumferential cracking, and the continuous peak signals showed that there was longitudinal cracking in the surface of cylinder barrel. The amplitude of eddy current testing signals characterizes the depth of cracking, and the gradient of magnetic signals descript the degree of stress concentration. The method mentioned above detects the cracking and stress concentration in the superficial coat of old cylinder barrel, which effectively guarantee the quality of automobile cylinder.