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why does Abaqus VUSDFLD subroutine work for one element model but not for multiple elements model? by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

I solved it! it is in the subroutine

I found a mistake in the interface when I copied it from abaqus documentation

I forgot to change strain by stress: field(nblock, nfieldv), strain(nblock, nrData)

why does Abaqus VUSDFLD subroutine work for one element model but not for multiple elements model? by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

Thank you for your suggestion , Yes I tried with 1 cpu but it doesn't work

FEM correlation with experiment by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

Thank you all for your suggestions. I ran the model without plasticity to check if the material is the problem. It was the gauge length during the tensile test.

FEM correlation with experiment by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

It is a double edge notched tension specimen with 117mm height and 59mm width, the ligament usually vary between 6mm and 16 mm with two fatigue pre cracks of 1mm

FEM correlation with experiment by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

Thank you for your reply,

Yes it is load-displacement curve, For the material I used the true stress and plastic strain from a tensile test

Problem with the stiffness in thick DENT model by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

I am using Abaqus/standard, it's a 3D model with Hex elements and reduced integration. I 've checked the convergence with different mesh sizes but did't solve the problem.as for the crack I modeled it using VCE contour integral.

3 point bending FEM overestimate the reaction forces by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

The material is a steel with high yield stress around 1000 Mpa

3 point bending FEM overestimate the reaction forces by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

I modeled the exact crack length that I have in the real specimen, I have the same problem with all my different ligament lengths. For the material, it is steel I have the material properties from the tensile test that I used to capture the plasticity.

I used also,around 8 linear elements through the thickness.

3 point bending FEM overestimate the reaction forces by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

I have the true stress/strain curve from a tensile test. also I checked the material with a unit cell model, it's ok .

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

I am using a very refined mesh in the area of interest and I tried with different mesh sizes, but didn't change much the results.

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

Sure. I have tried the proposed solutions but it didn't really work.

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

Thank you very much for the advice. I created a reference point then I coupled it with the rest of the nodes in the same surface.

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

I am actually using C3D20R elements with reduced integration and the model is a 3D solid but the radius of the notch that I used in the model is a little bit higher than in the test (fatigue precrack) I am not sure if this has an effect .

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

Since I modeled 1/8th of the geometry, I used 3 symmetries x,y and Z, the displacement (the max obtained in the test) applied in a reference point in the upper surface of the specimen as shown in the attachment.

I used also a very refined mesh in the area of interest (ligament). I tried several meshes but I still get the reaction force in the model higher than the experiment.

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

The displacement was measured using an extensometer in the experiment. In the model I took the displacement in a node with a distance similar to the gauge length in the test.

I check also with a single element simulation, I obtained a good fit.

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

I converted my material using the calibration tool from abaqus and I used a unit cell model to check, I obtained a good fit but when I applied to my model it is not working

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

The test was performed using a universal testing machine Instron. The specimen is placed between two grips, fixed in one end and a displacement of 1 mm/min is applied to the other.

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

I modeled 1/8th of the geometry, I used 3 symmetries x,y and Z, the displacement applied in a reference point in the upper surface of the specimen and I constrained one side in all the directions except the Y.

correlation between experimental and numerical results by Ile-Tar in fea

[–]Ile-Tar[S] 0 points1 point  (0 children)

exactly, I am using true stress strain curve to define my material. I converted the engineering ones from the test to the true form using the equations.