1. Division of Experimental Mechanics, Luleå Univ. of Technology, Luleå 971 87, Sweden (corresponding author).
2. Division of Experimental Mechanics, Luleå Univ. of Technology, Luleå 971 87, Sweden.
3. Division of Experimental Mechanics, Luleå Univ. of Technology, Luleå 971 87, Sweden. .