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Yu J.,Shanghai University | Yu J.,Xian Jiaotong University | Liu M.,Shanghai University | Wu H.,Shandong Special Equipment Inspection Institute
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2011

The sensitivity of various features that are characteristics of machine health may vary significantly under different working conditions. Thus, it is critical to devise a systematic feature selection (FS) approach that provides a useful and automatic guidance on choosing the most effective features for machine health assessment. This article proposes a locality preserving projections (LPP)-based FS approach. Different from principal component analysis (PCA) that aims to discover the global structure of the Euclidean space, LPP can find a good linear embedding that preserves local structure information. This may enable LPP to find more meaningful low-dimensional information hidden in the high-dimensional observations compared with PCA. The LPP-based FS approach is based on unsupervised learning technique, which does not need too much prior knowledge to improve its utility in real-world applications. The effectiveness of the proposed approach was evaluated experimentally on bearing test-beds. A novel machine health assessment indication, Gaussian mixture model-based Mahalanobis distance is proposed to provide a comprehensible indication for quantifying machine health state. The proposed approach has shown to provide the better performance with reduced feature inputs than using all original candidate features. The experimental results indicate its potential applications as an effective tool for machine health assessment.

Zou B.,Shandong University | Zhou H.,Shandong University | Xu K.,Shandong University | Huang C.,Shandong University | And 2 more authors.
Journal of Alloys and Compounds | Year: 2014

Various ratios of superfine WC and TaC particles were added into Ti(C 7N3) matrices, and Ti(C7N3)-based composite cermets tool materials were prepared using a hot-pressed sintering technology by various processes. The effects of the superfine WC and TaC particles and sintering processes on the mechanical properties and microstructure were thoroughly investigated. The addition of superfine WC depressed the mechanical properties, but the addition of superfine WC and TaC together refined the microstructure, which optimised the mechanical properties of materials. Both a longer holding time and a higher sintering temperature facilitated the growth of (Ti,W,Ta,Mo)(C,N) grains that caused a reduction in the flexural strength and fracture toughness. A Ti(C7N 3)-based cermets tool material with a 9 wt% WC and a 6 wt% TaC, which is sintered at 1400 °C with 30 min at 30 MPa, exhibits the best mechanical properties. This cermet material was then manufactured into cutting tools which maintained good wear resistance after 85 min of high-speed cutting stainless steel. © 2014 Elsevier B.V. All rights reserved.

Wang H.-L.,Nanjing University of Science and Technology | Liu H.-O.,Beijing Institute of Technology | Wang J.,Shandong Special Equipment Inspection Institute
Journal of Beijing Institute of Technology (English Edition) | Year: 2013

In order to move vehicles with automated mechanical transmission (AMT) a little bit of distance, such as reversing into or moving in a garage, a control strategy for crawling vehicles was proposed. Based on the dynamic analysis of vehicle starting process and requirements of crawl driving for the vehicle, a control strategy of the clutch was designed. The strategy increased the slipping friction torque first and then decreased it, in order to realize the crawl driving. The speed increased by the engagement of the clutch, and then the clutch turned to disengage to the half disengage point, when the speed met the requirements. Based on the control strategy, a control software was designed. In the end, the software was tested on a vehicle with AMT. The lowest steady vehicle speed was reduced to 40% of the original value, which was set in the control strategy. © right.

Zou B.,Shandong University | Ji W.,Shandong University | Huang C.,Shandong University | Wang J.,Shandong University | And 2 more authors.
Journal of Alloys and Compounds | Year: 2014

A study to increase the mechanical properties of TiB2- TiC+Al2O3 composite ceramic cutting tool material by using superfine refractory carbide additives is presented. Four superfine refractory carbides are considered to investigate their effects on the phase composition, element distribution, grain size, fracture surface, crack propagation of the metal ceramic. The physicochemical properties of superfine carbides, such as chemical activities and atom radius, were found to have the significant effects on the microstructure and mechanical properties of the metal ceramic. Hafnium carbide (HfC) and Tantalum carbide (TaC) reduced the mechanical properties of the metal ceramic because of their poor solubility with the Ni binder phase and the formation of oxides. The mechanical properties of the metal ceramic were increased by the addition of superfine niobium carbide (NbC) and vanadium carbide (VC), and their optimum values were a flexural strength of 1100 ± 62 MPa, fracture toughness of 8.5 ± 0.8 MPa.m1/2 and hardness of 21.53 ± 0.36 GPa, respectively, when 3.2 wt% superfine VC was used. © 2013 Elsevier B.V. All rights reserved.

Zou B.,Shandong University | Ji W.,Shandong University | Huang C.,Shandong University | Li S.,Shandong Special Equipment Inspection Institute | Wang J.,Shandong University
International Journal of Refractory Metals and Hard Materials | Year: 2014

TiB2-TiC laminated Ti(C5N5) composite ceramic cutting tool materials are prepared at the argon and vacuum sintering atmospheres respectively. The microstructure and mechanical properties of the composite are investigated. It is found that the composite includes the bulk and surface layer before sintering, while the new diffusion and transitional layers are formed after sintering. The Ni binder phase is rich in the diffusion layer, and the diffusion layer of the composite sintered at the vacuum atmosphere is narrower. The formation of layers is driven by the outward diffusion of the N element which results in the depletion of carbo-nitrides and the flowing of the melting Ni phase during the sintering. The composite exhibits the higher flexural strength and surface hardness than the monolithic Ti(C 5N5) material. The Ni-rich diffusion layer acts as a tough subsurface in the composite, which can strengthen the effect of grain pulling-out as well as absorb the crack propagating energy. The flexural strength of the composite sintered at the vacuum atmosphere is slightly higher than at the argon atmosphere, while there are no obvious differences in the hardness and fracture toughness between these two composites. © 2013 Elsevier Ltd.

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