Yttria-reinforced copper matrix composites were prepared by dry ball milling （DBM） and wet ball milling （WBM）, respectively, followed by spark plasma sintering （SPS）. It is to determine which milling process is ...Yttria-reinforced copper matrix composites were prepared by dry ball milling （DBM） and wet ball milling （WBM）, respectively, followed by spark plasma sintering （SPS）. It is to determine which milling process is better for fabricating Cu-Y2O3 composites. It is found that Cu-Y2O3 composites synthesized by DBM exhibit better densification, mechanical and electrical properties than those by WBM. Less agglomeration of reinforcements in the bulk composites by DBM is responsible for the better perfor- mances. To further understand the reason of less agglomeration of Y2O3 in the bulks by DBM, morphologies of prepared powders were investigated and analyzed. Higher ball＇s impact energy and the formation of copper oxide on the matrix surface during DBM process contribute to small matrix particles, which is beneficial for less agglomeration.展开更多
Sliding and spinning behaviors significantly affect the performance of rolling bearings,especially for dry-lubricated bearings,micro and macro sliding may lead to increased wear of the solid lubricating film.A unified...Sliding and spinning behaviors significantly affect the performance of rolling bearings,especially for dry-lubricated bearings,micro and macro sliding may lead to increased wear of the solid lubricating film.A unified rolling contact tribology analytical model is proposed for dry-lubricated angular contact ball bearings(ACBBs)considering the extreme conditions including high combined loads and rolling contact effects.A comprehensive solution framework is proposed to ensure the robustness of the model under different loading conditions.Equilibrium equations are solved to study the effects of friction coefficients,rotating speeds,and combined loads on the skidding and spinning characteristics of the ACBB.The results show that the rolling contact effects and combined loads significantly affect the skidding and spinning performance of the ACBB.Further analysis reveals that the skidding mechanism is related to the interaction between ball kinematical motion and traction forces.The developed analytical model is proved to more accurately predict the bearing kinematical and tribological behavior as it discards the raceway control hypothesis and considers the macro/micro-slipping,creepage,and self-spinning motions of the ball,which is validated using both the existing pure axial loading dry-lubricated ACBB model and the classical Jones–Harris model.The study would provide some guidance for the structure and lubrication design of dry-lubricated ACBBs.展开更多
基金financially supported by the National Key Research and Development Program of China (No. 2016YFB0301400)the Organization Department of Jiangxi Province(No. 2012215)+1 种基金the Education Department of Jiangxi Province (No. KJLD13041)the Outstanding Doctoral Dissertation Project Fund of JXUST (No. YB2017011)
文摘Yttria-reinforced copper matrix composites were prepared by dry ball milling （DBM） and wet ball milling （WBM）, respectively, followed by spark plasma sintering （SPS）. It is to determine which milling process is better for fabricating Cu-Y2O3 composites. It is found that Cu-Y2O3 composites synthesized by DBM exhibit better densification, mechanical and electrical properties than those by WBM. Less agglomeration of reinforcements in the bulk composites by DBM is responsible for the better perfor- mances. To further understand the reason of less agglomeration of Y2O3 in the bulks by DBM, morphologies of prepared powders were investigated and analyzed. Higher ball＇s impact energy and the formation of copper oxide on the matrix surface during DBM process contribute to small matrix particles, which is beneficial for less agglomeration.
基金This work was funded by the National Natural Science Foundation of China(Nos.52175119 and 61633001).The authors are also grateful for the support of Xi’an Aerospace Propulsion Institution(China Aerospace Science and Technology Corporation).
文摘Sliding and spinning behaviors significantly affect the performance of rolling bearings,especially for dry-lubricated bearings,micro and macro sliding may lead to increased wear of the solid lubricating film.A unified rolling contact tribology analytical model is proposed for dry-lubricated angular contact ball bearings(ACBBs)considering the extreme conditions including high combined loads and rolling contact effects.A comprehensive solution framework is proposed to ensure the robustness of the model under different loading conditions.Equilibrium equations are solved to study the effects of friction coefficients,rotating speeds,and combined loads on the skidding and spinning characteristics of the ACBB.The results show that the rolling contact effects and combined loads significantly affect the skidding and spinning performance of the ACBB.Further analysis reveals that the skidding mechanism is related to the interaction between ball kinematical motion and traction forces.The developed analytical model is proved to more accurately predict the bearing kinematical and tribological behavior as it discards the raceway control hypothesis and considers the macro/micro-slipping,creepage,and self-spinning motions of the ball,which is validated using both the existing pure axial loading dry-lubricated ACBB model and the classical Jones–Harris model.The study would provide some guidance for the structure and lubrication design of dry-lubricated ACBBs.
