how to update the stiffness of a spring element during a step

[alero]

Hi, I am using a SPRING2 element in Abq/Standard. I need to update the value of the spring stiffness during a step, at each increment.

In particular, the stiffness value to be used in an increment (i) depends on some output variables of the increment (i-1).

Is there a way to do so, for example by means of a user subroutine in which I can recall output variables of the previous increment?

Any suggetion would be very much appreciated!

 

[FEA way]

Abaqus supports nonlinear springs (their behavior is defined by specifying force-displacement pairs) but I assume that it’s not what you need. In such a case you could code a UEL subroutine to create your own finite element. Another option would be to add field variable dependency to spring stiffness definition.

 

[alero]

I thought I could define the stiffness spring as a tabular function of a field variable and I could update the field variable value during the step by means of
an user defined amplitude (UAMP).

Since Kspring= alfa/h with h field variable to be updated, I was wondering what does Abaqus to when h does not match exactly one of the values listed in the definition of the table?
Does Abaqus interpolate between the extremes of the interval in witch h lies?

 

[FEA way]

That’s yet another way to do it and there are more but the ones listed here seem to be the simplest.

Abaqus interpolates linearly between the provided values and keeps them constant outside of the specified range.

 

[alero]

Thank you very much for your help!