Hi,
I am working on a nonlinear contact problem with Abaqus. One of the parts
involved in the complete model is very small and as its behaviour needs to
be studied when it interacts with other parts it is modelled with pretty
smaller elements as compared to other parts in the model. When I do a Dynamic explicit
analysis then the time increment which Abaqus calculates from an Element by
element estimate is of the order 1e-8 due to that very small part. I did
mass scaling such that the increment becomes 1. e-7 (by DT= 1. E-7) and
used selective subcycling to complete my simulation. The percentage change
of mass in this process is 2.6 % which I think is pretty acceptable. But
there is one problem now. When I observe the transient response of my
simulation then I see that the part which is very small and of material
rubber is kind of jittering a lot.
However, on the positive note this jittering is almost dying out as the simulation progresses further. I think that as the time increment size is very
less i.e. 1e-7 it could be high frequency vibrations that I see at the start
of the simulation. I tried increasing the default Bulk Viscosity parameter
to (0.25, 4.0) and I do observe that the high frequency jittering has
reduced at the start of the simulation itself. But I want to completely get
rid of with such high frequency vibrations (if I am right that they are the
same)...Is increasing the Bulk Viscosity parameter more further until I get
rid of them is the solution? Also there are limits to this value as
increasing the Bulk Viscosity parameter reduces the stable time increment
and affects accuracy also.
Thanks for your help.