A Si-containing K273 superalloy was made using intermediate frequency induction furnace in the study. In the testing of oxidation resistance, the oxidation process of the alloy specimens during the testing at 900℃ fo...A Si-containing K273 superalloy was made using intermediate frequency induction furnace in the study. In the testing of oxidation resistance, the oxidation process of the alloy specimens during the testing at 900℃ for 500 h was examined by oxidation weight gain method. The morphology and composition of the oxide scales were determined using scanning electron microscope （SEM） and X-ray diffraction （XRD）, respectively. The effects of the transferring of ions and electrons on the oxidation resistance were further analyzed microscopically by semiconductor oxide models. The results show that the composite oxide scales consist of Cr203, SiO2 and spinel- type oxide MCr204, with flat and compact structure, and fine grains in uniform distribution. All of these endow the superalloy K273 with strong oxidation resistance. The reason for the powerful oxidation resistance of the composite scale is that the formation process of P＋N type semiconductor oxide enables to consume most of the surplus negative and positive ions in the oxide scales, which makes the number of the mobile ions and electrons dropped enormously, and the transfer rate of them falls heavily. So the oxidation rate of the metal phase in the alloy matrix is reduced significantly.展开更多
A new fault diagnosis technique for rolling element bearing using multi-scale Lempel-Ziv complexity(LZC) and Mahalanobis distance(MD) criterion is proposed in this study. A multi-scale coarse-graining process is used ...A new fault diagnosis technique for rolling element bearing using multi-scale Lempel-Ziv complexity(LZC) and Mahalanobis distance(MD) criterion is proposed in this study. A multi-scale coarse-graining process is used to extract fault features for various bearing fault conditions to overcome the limitation of the single stage coarse-graining process in the LZC algorithm. This is followed by the application of MD criterion to calculate the accuracy rate of LZC at different scales, and the best scale corresponding to the maximum accuracy rate is identified for fault pattern recognition. A comparison analysis with Euclidean distance(ED) criterion is also presented to verify the superiority of the proposed method. The result confirms that the fault diagnosis technique using a multi-scale LZC and MD criterion is more effective in distinguishing various fault conditions of rolling element bearings.展开更多
文摘A Si-containing K273 superalloy was made using intermediate frequency induction furnace in the study. In the testing of oxidation resistance, the oxidation process of the alloy specimens during the testing at 900℃ for 500 h was examined by oxidation weight gain method. The morphology and composition of the oxide scales were determined using scanning electron microscope （SEM） and X-ray diffraction （XRD）, respectively. The effects of the transferring of ions and electrons on the oxidation resistance were further analyzed microscopically by semiconductor oxide models. The results show that the composite oxide scales consist of Cr203, SiO2 and spinel- type oxide MCr204, with flat and compact structure, and fine grains in uniform distribution. All of these endow the superalloy K273 with strong oxidation resistance. The reason for the powerful oxidation resistance of the composite scale is that the formation process of P＋N type semiconductor oxide enables to consume most of the surplus negative and positive ions in the oxide scales, which makes the number of the mobile ions and electrons dropped enormously, and the transfer rate of them falls heavily. So the oxidation rate of the metal phase in the alloy matrix is reduced significantly.
基金the National Natural Science Foundation of China(No.51075220)the Special Research Fund for the Higher Education Doctoral Program(No.20123721110001)+1 种基金the Basic Research Project of Qingdao Science and Technology Plan(No.12-1-4-4-(3)-JCH)the Privileged Shandong Provincial Government’s "Taishan Scholar" Program
文摘A new fault diagnosis technique for rolling element bearing using multi-scale Lempel-Ziv complexity(LZC) and Mahalanobis distance(MD) criterion is proposed in this study. A multi-scale coarse-graining process is used to extract fault features for various bearing fault conditions to overcome the limitation of the single stage coarse-graining process in the LZC algorithm. This is followed by the application of MD criterion to calculate the accuracy rate of LZC at different scales, and the best scale corresponding to the maximum accuracy rate is identified for fault pattern recognition. A comparison analysis with Euclidean distance(ED) criterion is also presented to verify the superiority of the proposed method. The result confirms that the fault diagnosis technique using a multi-scale LZC and MD criterion is more effective in distinguishing various fault conditions of rolling element bearings.
