Study of High Strain Rate Behaviour Of Aluminum Alloy Under Dynamic Loading Using Split Hopkinsons Pressure Bar(SHPB) and Computational Techniques

Abstract

The intent of the present study is to study the stress-strain characteristics of aluminum alloy(LM- 13) at high strain rates and different combinations of length and diameter of the specimen using Split Hopkinsons Pressure Bar (SHPB). This apparatus comprises of a short cylinder-like specimen sandwich between two long slender bars. A compressive stress wave is generated by hitting the end of a bar and the wave immediately begins to traverse towards the specimen. The mechanism involved in the apparatus is well explained in the thesis. By tracking the strains in the two bars using different instruments, stress-strain properties of the specimen can be determined. A 3D finite element model was generated in ANSYS and was simulated at very high strain rates as in the experiments to explore the dynamic behavior of the aluminum specimen. Three different materials were compared for better validation. Experimental results used for present study are having diameter less than the diameter of the incident/transmitting bars of the SHPB machine. A conventional SHPB setup can only test on the specimen with length and diameter less than 20mm. Four combinations of length and diameter were tested at high strain rate while keeping the length constant at 20mm in one set and 24 mm in the other set with increasing the diameter from 20 to 32 mm in ANSYS at very high strain rate to establish a study for the impacts greater than 20 mm in diameter. The model was validated with the help of literature and experiments conducted on SHPB setup. A particular case of metal matrix composite (MMC) specimen was also taken from the literature and modelled in ANSYS and results were compared with the experiment. Based on the comparison study, cogency, applicability and accuracy of simulation was ensured for samples with large diameter.