In this picture, we can change the rate-start-time to control when the traction changes, and I want to know how to control the ending time.
For example, in a total of 30 days, I just want the traction of the first 20 days to change at a constant rate.
Thank you.

The rate of change is for a constant rate with an initial starting time. If you want a more complicated time history use the th_change See equation 6.1 in section 6.2.

Hi Brad.
The 6.2 th_change just have one factor of every time, does it means the perturbation just enlarge like the stress in db_change by a same ratio every step? Can we change the perturbation both in time and space？

I assume you are referring to equation 6.1 in the PyLith v2.2.2 manual.

f(x)=f0(x)+fdot0(x)(t−t0(x))+f1(x)a(t−t1(x))

db_initial corresponds to f0(x)

db_rate corresponds to fdot0(x) and t0(x)

db_change corresponds to f1(x) and t1(x)

th_change corresponds to a(t)

f0(x), fdot0(x), t0(x), f1(x) and t1(x) can all be spatially variable and are given as values in the spatial databases.

a(t) is a single time history, so the shape (but not amplitude or starting time) must be the same everywhere. We plan to support more generate spatial and temporal variations in PyLith v3.