Vibration signal analysis has been widely used in the fault detection and condition monitoring of rotation machinery. But the practical signals are easily polluted by noises in their transmission process. The raw signals should be processed to reduce noise and improve the quality before further analyzing. In this paper an improved wavelet threshold denosing method for vibration signal processing is proposed. Firstly, a new threshold is developed based on the VisuShrink threshold. The effect of noise standard deviation and wavelet coefficient is retained, and the correlation of wavelet decomposition scale is considered. Then, a new threshold function is defined. The new algorithm is able to overcome the discontinuity in hard threshold denoising method and reduce the distortion caused by permanent bias of wavelet coefficient in soft threshold denoising method. At last five kinds of threshold principles and three kinds of threshold functions are compared in processing the same signal, which is simulated as the mechanical vibration signal added white noises. The results show that the improved threshold is superior to the traditional threshold principles and the new threshold function is more effective than soft and hard threshold function in improving SNR and decreasing RMSE.

Hot bending and die quenching for U-shaped parts with ultra-high strength boron steel were experimented and simulated to study its quenching effect and accuracy. The results indicate that through the hot contact bending and die quenching, bending parts with higher strength and forming precision than that of cold stamping can be achieved. And the hot contact bending improves the quenching effect at the bottom of the bending part. The springback of hot contact bending decreases gradually when the blank holder force (BHF) increases, which is mainly negative for the impact of the thermal shrinkage moments. The numerical simulation results are consistent with the experiments’. Therefore, it verifies the reliability of finite element model and lays the foundation for the numerical simulation of the hot stamping process applied in complicated shape parts’ production.

Most of the lubricants are made of mineral oil which has bad biodegradability, and, hence, seriously contaminate the environment. To minimise the lubricants’ impact on the environment, this research developed a new type of lubricant, titanium complex grease. Its base oil is the admixture of vegetable oil and mineral oil. Its production method and experimental results are presented in this paper. The friction, wear and physical-chemical properties of the grease were investigated. The morphology of wear scar of steel ball was observed using the sweep electron microscope. The results obtained contribute to the further development of environmentally friendly lubricants.

In this article, a new type of visualizer for point contact flow field has been developed. The principle, constitution and application are introduced in details. The flow field of point contact area are captured and analyzed.

Mechanical seal plays a very important role in rotating machinery for space exploration, but it is very difficult to estimate its friction performance by simulative experiment. In this paper, a experimental system for measuring friction properties of mechanical seal materials used in spacecraft is developed. It is able to provide some adjustable parameters in the experiment, such as environment temperature -60°C~60°C, load 100N~300N, rotational speed of 30r/min~110r/min and atmospheric pressure and high vacuum. Friction coefficients of babbitt graphite M120B and hard alloy YG6 are obtained by the test rig and the experimental results testify that the device can conduct simulative experiment effectively.