I am trying to do a simple compression test, where the top plate is fixed and the bottom plate is moved up. The loading has 2 steps (Step 1 = 1 mm upwards displacement, Step 2 = 0.1 mm ADDITIONAL upwards displacement).

When I made the model in Abaqus explicit, everything was running correctly and the bottom plate was moving up for both the steps. My BCs for the two steps were X2=1 and X2=0.1 respectively, all others (X1, R3) being equal to zero.

However, when I copied the model and replaced the steps with Dynamic Implicit instead, the first step moved the bottom plate up but the second step moved it down. It is almost like it is treating the displacement as relative in Explicit, while absolute in Dynamic Implicit. Why might this be happening?

N.B. I have NOT defined a new coordinate system in either case.