Abstract
The dynamic behaviors of super duralumin (24S) have been studied through experiments in which the material in the form of bars was shot from a gun of compressed nitrogen gas at a steel anvil bar. The impact speeds was varied from tens of meters per sec to 190 meters per sec by which the test was made in the range of about 20% strain. The test of the specimens was performed just after the quenching and after the age-hardening for 80min at 100°C. The main results obtained are as follows;
(1) By comparison of the dynamic stress-strain curve of which the strain rate is estimated at about 104 1/sec and the static stress-strain curve of which the strain rate is (1∼4)×10-4 1/sec, the sensitivity to the strain rate is hardly recognized in the age-hardened specimen, but is obviously recognized in the specimen fresh following the quenching.
(2) It is assumed that even after the age-hardening of the material there will be variation in the internal structure of the specimen due to the nature of the deformation, whether it is static or dynamic. The effect of the variation on flow stress is not obvious till the strain is increased up to about 10%.
(3) All the stress-strain curves obtained statically and dynamically of the specimen after age-hardening and those immediately following the quenching are approximately represented by the following equation,
σa=σe+C2(εa-σa/E)1/2,
where σe: yield stress, E: Young's modulus and C2: constant. It can be recognized in these curves that the stress value extrapolated from these curves at strain 100% is approximate to the characteristically constant value of the material.
(4) The relation between the impact speed V1 and the strain ε1,
V1=∫ε10(1/ρdσ/dε)1/2 dε,
is applicable to the range of strain up to about 18% or to the range of impact speed up to about 180 meters per sec of both the specimen fresh following the quenching and of the age-hardened specimen.
