DYNAMIC AXIAL CRUSHING OF ALUMINIUM ALLOY 6063 -T6 CIRCULAR TUBES

Abstract

AN EXPERIMENTAL INVESTIGATION WAS CARRIED OUT TO STUDY THE BEHAVIOUR OF CIRCULAR THINWALLED ALUMINIUM ALLOY 6063T6 EXTRUSIONS SUBJECTED TO LARGE AXIAL IMPACT LOADINGS. THE SPECIMENS, HAVING AN EXTERNAL DIAMETER OF 51 MM, WERE 1.5 MM THICK, GIVING A 2R/H RATIO OF 33, APPROXIMATELY. EIGHTEEN QUASI-STATIC AND THIRTY-SEVEN DYNAMIC TESTS WERE PERFORMED AND THE PRIMARY VARIABLES WERE THE SPECIMEN LENGTH (250 MINORTHAN L MINORTHAN 1200 MM), THE IMPACT MASS (72 MINORTHAN G MINORTHAN 248 KG) AND THE INITIAL VELOCITY (3,33E-5 MINORTHAN VI MINORTHAN 8,33 M/S) OF THE IMPACT MASS. THE TWO LATTER VARIABLES WERE COMBINED TO GIVE A CONSTANT INPUT ENERGY OF 2.5 KJ IN ORDER TO INVESTIGATE THE EFFECT OF INERTIA ON THE AXIAL CRUSHING OF THE ALUMINIUM ALLOY TUBES WITHOUT THE CONTRIBUTORY EFFECT OF MATERIAL STRAIN RATE SENSITIVITY. THE TENSILE STRESS-STRAIN RELATIONS FOR THE ALUMINIUM ALLOY 6063T6 OF THICKNESS 1.50 MM HAVE BEEN EXPERIMENTALLY DETERMINED AT ROOM TEMPERATURE (APPROXIMATELY 20ºC) OVER A RANGE OF OVERALL STRAIN RATES FROM 5E-4S^-1 TO 118S^-1, APPROXIMATELY. THE YIELD AND THE ULTIMATE TENSILE STRESSES OF THE MATERIAL SHOW A NEGLIGIBLE DEPENDENCY ON STRAIN RATES, WHILE THE OVERALL ELONGATION EXHIBITS A SLIGHT MINIMUM AT 0.03S^-1, APPROXIMATELY. THE CORRESPONDING LARGE VALUES OF THE COWPER-SYMONDS COE±CIENTS OBTAINED USING A LEAST MEAN SQUARE FIT, CONFIRMED THE STRAIN RATE INSENSITIVITY OF THE MATERIAL.