1. Department of Mathematics, Linköping University581 83 Linköping, Sweden
2. Department of Mechanical Engineering, Linköping University581 83 Linköping, Sweden
3. Department of Mechanical Engineering, University of MichiganAnn Arbor, MI 48109-2125, USA
4. CEMEC-PoliBA—Centre of Excellence in Computational MechanicsV.le Japigia 182, Politecnico di Bari, 70125 Bari, Italy