How can I define an PML in model solids mechanics ?

I need a help !

I'm using a model of a small rectangle onto a large rectangle 2D axisymmetric
to denote of wave propagation
I have to put the PML absorbed wave to not be reflects
But when i put it and i do the compute
I don't see a difference => PML like does not work !
can you help me please ? what do I do?


note:
-> Model Wizard -> 2D axisymmetric -> structural mechanics -> solid mechanics -> temporel
-> Definitions -> PML

I have searched through the documents COMSOL a model that contains a sample of the PML but I have not found.