Dynamic Stress—Strain Properties of a Steel and a Brass at Strain Rates up to 104 Per Second

Abstract

Results of compression tests on 70:30 brass and a mild steel at strain rates from 10-3to 104per second are reported. The tests were carried out on a reactionless gas forging rig, using a high-frequency response piezo-electric load cell. The brass is shown to be relatively insensitive to strain rate over the range of the tests. The mild steel in the ‘as-received’ condition showed a marked increase in initial flow stress at high strain rates; pre-straining removed the phenomenon and ageing re-established it so that the rise in yield stress can be attributed to a ‘yield-point phenomenon’. The strain associated with the drop in stress following yielding is noted to be large and it is demonstrated that this results from the finite time for yielding to propagate along the specimen.