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Springback result far from experiment

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Hello guys, 

 

I am trying to validate a springback model to be used in a more complex forming simulation. For now I am performing some 90º bend experiment on a lab and trying to compare the results with my model. Unfortunately I am getting more than 25% error, while I see on literature that the result for simple cases like that should be much better. What am I doing wrong? I already tried a bunch of tips and different parameters. Please, find the results and the model attached. Could someone please take a look and give me some hints?

 

Is there a way to "turn off" or "reduce" dynamic/impact effects? I could notice the sheet body bouncing and waving. I am not sure if it also happens in reality but our eyes can't capture.

Thank you in advance.

image.thumb.png.3d344cf1e6193278b0ffbba560c80472.png

 

 

Springback_standard3_0000.rad

Springback_standard3_0001.rad

Springback_standard3_0002.rad

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Hi,

 

sorry for the late reply- I was hoping someone with spring-back expertise would respond. Anyway, here are my suggestions:

 

1. In Example 24 – Spring-back it is noted in table 1 that dynamic relaxation using explicit also during spring-back improves correlation with experimental results.

 

2. Looking at the comparison it can be observed that the experimental specimen is not as flat (or is slightly rotated upwards) in the left portion (where the sheet is constrained). Modeling appropriate boundary condition in this region would improve the correlation (there should be some examples in literature)

 

To reduce dynamic effects three approaches are available in RADIOSS: Dynamic Relaxation (/DYREL), Energy Discrete Relaxation (/KEREL) and Rayleigh Damping (/DAMP). Refer to Example Guide for application examples. I suggest using Rayleigh Damping in this case.

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Hello @Ivan, thank you very much for the reply. It is really helpful, even after reading the guides and Radioss book, it is still difficult to evaluate how accurate a model is or is there are mistakes.

 

About the Dynamic relaxation with explicit method from the Example 24, I just missed it because actually this 90º test was a validation model for a much more complex springback study case (after single point incremental forming). So we wanted to use the same simulation method now and later. But of course I will give a try to it.

 

Regarding the boundary conditions, I will take another look, but this image was only made to explain how the measures were taken. 

In any case, have you take a look at the model? Did you see any significant mistake on it?

 

I will play around with these cards related to the dynamic effects. 

 

Thank you very much indeed Ivan. 

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I have looked into your model and found no obvious errors when compared to Example 24.

Only the contacts were modified and Advanced Mass Scaling is used. Newly defined contacts gave higher plastic strains which would probably result in even less correlation after spring-back. The explicit spring-back simulation failed to run, because of the problems with released BC after the forming step.

 

The contact definition influences the residual plastic strain so perhaps it can be tuned to match the experiments.

 

springback_edit.hm

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