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Hey everyone, I am back. First of all, I would like to thank you all for helping me with this project, your tips were truly remarkable. My project is long completed now, but the research hasn't stopped. Many of you were correct in pointing out that the data was not collected properly, we did...

Sorry then. Not gonna happen again

To everyone. Thanks a lot for your help, I really do, you have given me some great advice! Unfortunately, I couldn't come to a conclusion on the problem with the model/analysis. The experiments were accurate and there is no doubt about that. I could share the code with anyone that's...

Yes, indeed shear buckles. Ansys mechanical APDL What do you mean by flat sheet?

No all of the elements appear to be approximately in the middle of the height(where the red areas are) and I want to simulate the shear deformation of the core.

Is this good ?

Hello everyone, I am modeling a structure with shell elements in mechanical APDL. My problem is that the solution stops due to excessive element distortion in very low displacements thus giving unwanted results. Elements on the edges show this problem but not on the inside. I cannot find a way...

I am not sure I understand why to do these calculations. Your point is that the number of walls changes the stiffness of the core and thus the results don't match?

Here is the test setup. The displacement is measured by the movement of the bottom crosshead. To scale the shear stress I took the force data measured from the experiment and divided it by ( L*W) length and width of the specimen. The FEM results give the force calculated at each sub-step of...

Some calculations are involved to convert the force into equivalent shear stress, deciding the force with the area of the specimen and the unit cell respectively. A model close to the experiments is possible and it's been made but I was trying to reduce the time by modeling a unit cell or a...

All the experimental data was taken the same way and was evaluated so I don't think that they are way off. I converted the force into relative stress for both the experimental data and the unit cell in order for them to be comparable. I used the unit cell because the whole model takes a lot of...

Why be the displacement data wrong? The Instron machines are equipped with an lvdt at the crosshead. Subtracting the initial position of the crosshead from all the data should give the relative displacement which is the one I use. SWComposites is correct in saying that's how most models of a...

Okay okay, I get it now. I will try to find how to implement that in my model and see the results. Thanks a lot!

yes, the applied bc simulates a rigid connection. Rigid body motion is satisfied. I am not quite sure how I could implement the idea you suggest. Adding a real constraint to simulate some kinda of stiffness?

I haven't applied spring constants (not very familiar with how they are applied), in my model I used boundary conditions (BC) to simulate the loading plates. The applied BC used to output a perfect shear loading without rigid body motion and deformed shape matched well with the experimental...

I did a study to see how imperfections affect the structure. I took the results from an Eigen Buckling analysis and updated the geometry with the first buckling mode, after that, changed the values of the scale factor to see how they will affect the curve. the results show a significant drop in...

Greglocock, So, if I understand correctly you think the magnitude of the load is the problem? I will take a better look and see if I can make changes at how the load is applied and BC.

Yes, it is for the hex core model. The displacement is measured from the crosshead of the machine. I haven't done any hand calculations about the stiffness. Should I make the BC less rigid? FEA way you can find in a previous post of mine.

Hello everyone, I am running a nonlinear analysis with imperfections included by an eigenvalue buckling analysis with a factor of 0.1-0.5 ( the max dmx from buckling analysis is 1 , units are N/mm ) but the stiffness is much higher than the experimental results. How can I reduce the stiffness...

How I would be able to calculate the equivalent shear stress for the cell? Can anyone help me with that?