Study on the relation between the input strain, strain stored in the bar and input strain to the specimen using the torsional Hopkinson bar.
Date of Issue2009
School of Mechanical and Aerospace Engineering
This Final Year Project (FYP) deals with the various relationships of the strains at different sections of the Torsional Hopkinson Bar (TSHB) apparatus between different stages of the experiments. The following objectives to find the relationship between the input strain and the strain stored in the bar as well as the relationship between the input shearing strain and the strain transmitted to the bar have been set out at the start of the experiment. In the course of the experiment, a fixture to determine the angle of twist was designed on the TSHB apparatus and used to calculate the theoretical strain stored in the bar. The theoretical strain obtained is used to compare with the different values of input shearing strain derived from the measurement on the strain indicator at the respective angles of twist. These two strains were compared to establish a direct relationship between the input strain obtained from the equipment and the strain stored in the bar which is calculated through the torsion theory. The results showed that the input strain is equal to the strain stored in the bar which verifies that the torsion theory is correct. Several experiments at different input strains were conducted on the TSHB apparatus. This allows the collection of data for the incident strain at the corresponding input strain. The incident strain due to its position is a good measure of the amount of strain that is being transmitted to the specimen from the input loading torque. These values of the incident strain are compared to the input strains at which they were obtained. A relationship between the input strain and the strain transmitted to the specimen was established in this way. The results showed that the input strain is approximately half of the strain that was being transmitted to the specimen in the TSHB apparatus. In conclusion, the torsion theory and the experiments conducted were used to verify the relationship between the input strain and the strain stored in the bar and it was found to be equal. Secondly, the relationship of the strain transmitted to the specimen is found experimentally to be half of the input strain. The inability of the apparatus to transmit all the incident strain to the specimen could be attributed by the partial reflection of the incident strain back to the input torque device during the release of the input loading torque.
DRNTU::Engineering::Mechanical engineering::Mechanics and dynamics
Final Year Project (FYP)
Nanyang Technological University