In this paper, the influence of different machining methods (including rough turning, finish turning, and longitudinal polishing after finish turning) on rotating bending fatigue properties of TC21 which belonged to a new ultra high strength titanium alloy was studied. The influence of machining methods on surface integrity of TC21 titanium alloy was measured by using surface profile measurement, scanning electron microscopy, metallography microscope, micro-hardness instrument and X-ray diffraction residual stress analyzer. And fatigue fractography of specimens was further investigated. Then the mechanism of fatigue resistance which was affected by machining surface integrity was discussed. The results indicated that the fatigue life of finish turning and longitudinal polishing after finish turning was increased 3.96 times and 17.34 times compared with rough turning, respectively. The machining surface integrity had important influence on fatigue property of TC21 titanium alloy, which caused by the differences of surface roughness and texture as the dominant factors, and then the variation in surface micro-hardness, metallographic microstructure and the surface residual stress were not the main factors on three above-mentioned machining methods. By using longitudinal polishing after finish turning processing method for preparation of TC21 titanium alloy parts could ensure good surface integrity and excellent fatigue performance.

W-Mo and W-Mo-N surface-modified layers on Ti6Al4V alloy were obtained using a double glow plasma surface alloying technique. The morphology, microstructure, and chemical composition distribution of the modified layers were analyzed by scanning electron microscope, Xray diffraction, and glow discharge optical emission spectrometry. The hardness and toughness of the modified layers were measured using a micro-hardness tester, and dynamic repeating press equipment. The wear resistance in ambient air and the corrosive wear resistance in NaCl solution were evaluated using a ball-on-disk wear tester. The results show that W-Mo and W-Mo-N surface modified layers are composed of the alloying layers which vary in composition and phase form along the depth. A microhardness gradient was observed in the modified-surface layers. The surface hardness of the W-Mo-N and W-Mo modified layers was 25.3 and 14.2 GPa, which is seven-fold and 3.9-fold harder than the Ti6Al4V substrate, respectively. W-Mo and W-Mo-N surface-modified layers significantly improved the wear and corrosion resistance of Ti6Al4V. It seems that the wear resistance of W-Mo and W-Mo-N surface-modified layers in NaCl solution is better than that in ambient air owing to the strong lubricating effect of NaCl solution and the excellent corrosion resistance of the modified layers.

TiN/CrN multilayer coating was deposited on AZ91D magnesium alloy by pulsed bias cathodic arc PVD process. Effects of the coating on wear and corrosion behaviours of magnesium alloy were investigated. The stick-tearing for adhesion evaluation, nanoindentation for hardness measurement, ball-on-disc testing for wear tests, and potentiodynamic polarization for corrosion tests were used. The results show that the friction coefficient is decreased and the wear resistance is improved remarkably by TiN/CrN multilayer coating on AZ91D magnesium alloy. The corrosion resistance of the alloy is increased at a certain degree.

Based on the present problems existed in electric load characteristic statistical indexes, a correlation analysis method for load characteristic statistical indexes is proposed in this paper. Low-level correlation indexes are extracted by using correlation analysis, then the linkage analysis theory in econometrics is applied and the load characteristic indexes are analyzed by using vector auto-regression model. The Synchronous movement trend and causal leading relationship among electric load characteristic indexes are confirmed by co-integration test and granger-casualty analysis. The purpose of this paper is to help power decision makers grasp the alteration situation of load characteristic indexes comprehensively and analyze correlation indexes accurately, so it can enhance the monitoring, forecasting and early-warning function of electric system.

The stress and strain condition of the corroded line pipe with single hemisphere bottom defect under deferent inner pressure were analyzed by the Finite Element Methods (FEM) in this paper; At the same time, the residual strength models for the corroded pipe were established based on both the Von Mises equivalent stress and the Von Mises equivalent strain of the finite unit on the defect local zone respectively, the residual strength was decreased with the defect size (d/t) linearly. This way, the residual strength for the corroded pipe with a given defect size (d/t) could be conducted by using the model properly, which could help the owner make a decision when happened to the same defect in the operation. The analysis results shown that the residual strength calculation should choose based on stress when the defect depth (d/t) was less than 0.5, or else choose based on the strain when defect depth (d/t) was exceeds 0.5.