Characterization of Dynamic Tensile Testing Using Aluminum Alloy 6061-T6 at Intermediate Strain Rates

Dynamic tensile tests are conducted on aluminum alloy (AA) 6061-T6 using a high-speed servohydraulic machine at intermediate strain rates to validate the testing technique and to investigate the strain-rate effect on the material's stress-strain behavior and failure mode. We present the experimental procedures and results discussing the constitutive response of the alloy at strain rates up to approximately 200 s^-1. The predominant frequencies of the high-speed testing machine were characterized by modal analysis, and we analyzed the effect from vibration of the system and loading rate on flow stress by using a single degree-of-freedom (SDOF) spring-mass-damper model. We tested two different specimen sizes at a wide range of actuator velocities to achieve the desired strain rates. Results show that the yield strength, ultimate strength, and failure strain were dependent on strain rate. We fitted the data to the Johnson-Cook (JC) constitutive model, and the resulting parameters are comparable to published results in the literature. The fracture surface of specimens tested at different strain rates obtained by scanning electron microscopy (SEM) showed that the ductile failure mode was dominant for the alloy, and strain rates within the range examined affected the fracture morphology.