Computational Mechanics Forum

As per Maxwell reciprocal theorem, it is valid only for elastic materials and structures indergoing small displacements.That is k12 = k21, kij = kji hence stiffness matrix is symmetric.

Howbver, I just have been going through MY OWN written programs for geometric non linear problems and I observe that stiffness matrix (assembled stiffness matrix) is well symmetric.

How can stiffness matrix be symmmetric for non linear behaviour of structures?

Hi All,

While using LS-DYNA to simulate the impact damage of composites, I have a question about modeling.

I plan to create the model by solid element. Each ply has one element in the thickness direction. The contact between plies is *contact_automatic_surface_to_surface_tiebreak. My question is how to create separate ply models while using this contact. It is clear that common nodes are not allowed. So there might be two possibilities.

Hallo,

 I am a Computational Mechanics Student. I always come across during class of Finite Element Methods. I want to know what does actual mean by "Weak Form"? IAnd What are we take Test Function while using in Galerkin Method?

Hi all,

I'm trying to model kelvin-Voigt type material (response of it during time)

The equation is very basic : sigma*epsilon+d/dt epsilon*viscosity coefficient(eta)

i'm wondering how to impliment the viscous term eta in Pa.s (experimental results gave me the value) in my model.

The theory is very simple but i can't figure out how to do such thing in Abaqus.

I tried Pony type but i don't now how to calculate the coefficients..

Can you help me?

I'm a little bit lost with this. I have two questions.

1) I want to write variational (weak) formulation for a single deformable body, that can undergo large discplacements (rotation), but small strains. I searched lots of places. Finally, I managed to find this:

div(S) + rho*F = rho*a,

Hi all,

I am stuck with a problem while starting to learn programming UEL in FEAP.

As a starting point, I programmed Isotropic Linear Elastic element (3D 8 node linear interpolation/shape functions), with one-point integration.

Before running this UEL, I wrote a simple 8 element input file and used FEAP standard Solid element (ELAStic, ISOtropic), the results for this input file were nice.

However when I ran the analysis for this input file with my UEL (USER 04), the displacements were unbelievable (x10^16).

Hi all,

Anyone knows if the concrete smeared cracking model in ABAQUS can model the strain softening behaviour of concrete i.e the descending bramch of the stress-strain curve in the post ultimate stress.

Thanks

Hussam 

Hello,

Is it possible to predict value of lateral torsional buckling moment using three dimensional beam elements in Abaqus? A lot of analysis is performed using shell elements. I want something easier for now and later I'm going to do my research on shell elements too.

What things should I focus on modelling an I-beams using beam elements in Abaqus?

The problem is that my actual results from abaqus using beam elements are lower about 20% then I expected.

Hi all!

I try to simulate crack propagation using subroutine UMAT and XFEM, but I can't fix the error

***ERROR: THE PENALTY STIFFNESS HAS TO BE PROVIDED BY USING *SURFACE 

           BEHAVIOR,PRESSURE-OVERCLOSURE=LINEAR OR *SURFACE BEHAVIOR,AUGMENTED 

           LAGRANGE WHEN USER MATERIAL IS USED FOR A CRACK PROPAGATION ANALYSIS 

           WITH XFEM

 although I define *Surface behavior in .inp file:

Hey all

 i have tried to simulate a contact problem which is descibed thoroughly by the PDF attached.

I have followed all the steps needed (like in the PDF), but the results show stresses which are 2 times greater. although the general behavior of the model is like in the PDF.

still, i have no idea why i dont receive the same stresses.

thx a lot

Iftah