InstituteofLubricationTheoryandBearing;
Xi'anJiaotongUniversity;
Xi'an710049;
P.R.China;
The4thResearchInstituteoftheSecondArtillery;
Beijing100085;
P.R.China;
InstituteofLubricationTheoryandBearing;
Xi'anJiaotongUniversity;
Xi'an710049;
P.R.China;