1. State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou 730000 China
2. Department of Mechanical Engineering Tufts University Medford Massachusetts 02155
3. Department of Mechanics Huazhong University of Science and Technology Wuhan 430744 China
4. Institut fuer Struktur‐ und Funktionskeramik Montanuniversitaet Leoben Leoben A‐8700 Austria
5. Department of Mechanical Engineering Northwestern University Evanston Illinois 60208