Hot impact direct extrusions have been carried out to test the workability of steel with high strain rate and large deformation using the high energy rate metal-working machine, Dynapak.The strain rate was up to 3.6X 103 sec-1, and the extrusion ratios were from 4 to 25.The extrusion pressure and the relative displacement of punch and die were recorded by synchroscope.
Results obtained are summarized as follows:
(1) Impact energy E and extrusion length x0 are approximately proportional, i. e., E=S qxo, whers S is the cross-sectional area of container and q is the mean extrusion pressure.
(2) Mean extrusion pressure is approximately proportional to the natural logarithm of extrusion ratio γ i. e., q =B ln γ.
(3) Extrusion pressure q is proportional to the n-th power of extrusion velocity x, i. e., q=qo xn.
(4) When the extrusion velocity becomes higher, there appear inertia forces of the form of 1/2 Spγx2 2 and S pγxx, where p is the density of materials.
These behaviors are discussed in comparison with those in tension-compression test and hydraulic extrusion.
