[1] Northwestern Univ, Dept Mech Engn, Evanston, IL 60208 USA
[2] Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA
[3] Northwestern Univ, Theoret & Appl Mech, Evanston, IL 60208 USA
[4] Northwestern Univ, Dept Ind Engn & Management Sci, Evanston, IL 60208 USA