I wanted to get some insight in the transient stress intensity factor (SIF).

In the time history, we notice there is an overshoot (~27%)  from the
steady state SIF for a fixed (not propagating crack). I found the
overshoot occurs at the time when the reflected wave from the opposite
crack-tip comes back to the first crack tip. I wanted to know why this
overshoot occurs, what is the physical explanation?

Sandip Haldar