Yang Lianfa

Vibration signals denoising using minimum description length principle for detecting impulsive signatures

Vibration signals are usually affected by noise, which is in turn related to the measurement and data processing procedures. This paper presents a new subband adaptive denoising method for detective impulsive signatures based on minimum description length principle with improved normalized maximum likelihood density model. The threshold of the proposed denoising method is determined automatically without the need to estimate the noise variance. The effectiveness of the proposed denoising method over VisuaShrink, BayesShrink and minimum description length denoising methods are given through simulation and practical applications.

Determination of Material Parameters of Welded Tube via Digital Image Correlation and Reverse Engineering Technology

Material characteristics play an important role in tube hydroforming (THF). A method, based on digital image correlation (DIC) and reverse engineering (RE) technology, is proposed to determine the material parameters of a welded tube in hydroforming with a single tubular blank. The material parameters of the weld and parent metal are determined by applying membrane theory and the force equilibrium equations, as well as the deformation data which are obtained by DIC and RE technology in the THF process. Finite element simulations of welded THF are performed with these material parameters and the maximum bulge radii and axial profiles of the weld and parent the metal obtained from the simulations are compared with those obtained from the hydroforming experiments to verify the reliability of the proposed method. The results show that the material parameters of the weld are lower than those of the parent metal. With the material parameters adopted in FE simulation there is a good agreement between the simulation and the experiment as for the maximum bulge radii and axial profiles of the weld and parent metal. This verifies that the proposed method is acceptable for determining material parameters of a welded tube.

Prediction of wrinkle types in tube hydroforming under pulsating hydraulic pressure with axial feeding

Wrinkling frequently occurs in tube hydroforming, resulting in an undesirable loss of quality and precision of the formed workpiece, and is generally regarded as a defect. However, wrinkling can also be utilised to improve the formability of tubular materials if it can be gradually reduced or even flattened in the follow-up tube hydroforming. For this reason, wrinkling is classified into two types—harmful wrinkle and useful wrinkle. In this paper, two prediction methods, geometry-based prediction method and mechanics-based prediction method, are proposed to predict the wrinkle type occurring in tube hydroforming under pulsating hydraulic pressure with axial feeding. Then, the corresponding tube hydroforming experiments are presented, which were carried out to validate the two proposed prediction methods by comparing the deformation and wrinkling behaviours. Finally, the characteristics of the two approaches are compared and discussed. The results indicate that the wrinkle type occurring in the present tube hydroforming experiments under pulsating hydraulic pressure with axial feeding could be predicted by both prediction methods, with the geometry-based prediction method providing more accuracy than the mechanics-based prediction method.

The Analysis of Thermal Field and Thermal Deformation of a Water-Cooling Radiator by Finite Element Simulation

A water-cooling radiator is the effective heat dissipation device to ensure the high-power electrical equipment work properly and the heat transfer process and thermal deformation of the water-cooling radiator become hot research areas currently. Based on a water-cooling radiator of a company, the simulation model for its single water-cooling flow channel is established and the influence of the flow velocity of the inlet fluid and thermal convection of air on the outlet temperature of fluid is analyzed by the commercial software ANSYS. In addition, the thermal deformation of the water-cooling flow channel is discussed. The simulation results show that the outlet temperature declines progressively as the inlet velocity increases, the outlet temperature goes downlinearly with the increase of coefficient of air convection. And the thermal deformation of the brass water-cooling radiator is obviously non-uniform and becomes warp inevitably.