ON THE USE OF THE COMPRESSION SPLIT HOPKINSON PRESSURE BAR TO HIGH-STRAIN RATE

The compressive response of copper, steel, and tungsten alloys was gen erated with a Split Hopkinson pressure bar technique at strain rates v arying from 3 x 10(3) to 7 x 10(3) s(-1). Constant strain rate assumpt ions were examined using specimen surface strain records. During the e arly stage of the plastic deformation specimen strain rates near the l oading interface were found to exceed the conventionally measured stra in rate. This discontinuity was confirmed from the simulation of a tes t conducted at a strain rate of 7160 s(-1) using a hydrocode. Numerica l results also indicate a stress state discontinuity implying that the material response is not a uniaxial state of stress for strain less t han 0.1.