Interface Elements

[Prof. R.L. Taylor]

Thank you for your wishes.

You should be able to mix standard feap elements with user elements provided the degrees-of-freedom are in the identical locations.   It is unusual to mix a frame and interface element though.  Maybe you should describe how you are using the the elements in a problem.

The file you posted is not useful as a pdf?

[Nish]

Dear prof. Taylor

Thank you for your reply.
I will send you the txt format now.
my layer is Timoshenko beam element with 3 dof and interface with 2 dof per node. will you please tell me why do you call it unusuall?

Regards

[Prof. S. Govindjee]

What type of element does the interface element connect to?

Timoshenko + Interface + ??

[Prof. R.L. Taylor]

You need to read the programmer manual carefully to see how the  element stiffness matrix is defined for each node.

Your element sets the locations explicitly and will only work for problems with 2 degrees-of-freedom at a node.  the frame element has 3 so your element now will not work.

Look at an element in feap, say sld2d1.f in ./elements/solid2d to see how the stiffness matrix is organized so that it can work no matter how big ndf is, as long as it is 2 or more.

[Nish]

Dear prof. Govindjee

FRAME (SHEAR ON) is connected to interface elements (which are implemented in my subroutine elmt01). nothing more.

Regards

[Prof. S. Govindjee]

What is your 'Interface' element supposed to do?

[Nish]

Dear prof. Govindjee,

It is supposed to soften as soon as its deflection comes to a threshold and breaks after experiencing a critical value of deflection.
in fact,each integration point, follow a bilinear cohesive zone model. we expect to simulate the crack propagation in the frame elements by using the interface elements.

Regards

[Prof. S. Govindjee]

sounds like you want to be using all three dofs.  u,v,theta tied and then at some stage they start to develop a 'discontinuity' in all three dofs.

[Prof. R.L. Taylor]

It would help if you can send a picture showing how the interface element is to be used with the frame element.

[Nish]

Dear prof. Taylor,

I did based on you told and now it is working properly!
Many thanks

Regards

[Nish]

Dear Prof. Taylor, Prof. Govindjee,

In a nonlinear problem, if the residuals are as order of E0 or E1, but the results are very close to the analytical solution, what could be the error source?
I mean, in my nonlinear solution I have the warning for nonconvegency with the residual in order of 1 or 10, but my results agree with the analytic solution so much.

Regards

[Nish]

The schematics of the problem is also attached.

[Prof. S. Govindjee]

The residual is show as large but the solution is converged there could be a scaling problem between the dof if they are reflecting different units/physics.  Or there can be an error in the residual computation.

[Nish]

Dear FEAP community,

I am solving a nonlinear problem with FEAP without changing the default tolerances for convergency.
As I read in the user manual, the default residual value is 1e-6,
but I have this message in my output file:

*WARNING* NO CONVERGENCE: Time =  9.01100E-02: Residual =  9.12040E-08

why does it assume e-8, as nonconvergency?

Regards