Good day,
I'm trying to numerically simulate the compression of a polyurethane foam shock absorber for car.
I use ABACUS/Explicit
The constants for the equation of state were obtained from experimental data for compression, at a "characteristic" (small) compression rate using the MCalibration program.
While resolving, an error message was received:
The ratio of deformation speed to wave speed exceeds 1.0000 in at least one element.
One of the possible causes of the error is the incorrect calculation of the constants for the polyurethane foam equation of state.
*** using the "standard" equation of foam, which is in ABAQUS
I am ready to send the model and experimental data to anyone who has the desire and opportunity to devote time to this task.
Previously, I tried to simulate this task with ABAQUS/Standart and with ANSYS Workbench
Hi Valery Anpilov,
I suggest starting with the basics. Check your material data. I mean, check with another data sheet, an article, or real experimental data.
Next, check the units of your input data. Of course, you know this stuff, but I have seen many engineers make these simple mistakes, so I think it’s worth looking at.
Check your mesh. You need the fine and proper mesh for this analysis.
And the most important part is to check the speed of the impact load. For example, you cannot implement an impact with the 10000 tones of force in a millisecond. It’s against the law of physics, and that’s why you get this error “The ratio of deformation speed to wave speed exceeds 1.0000 in at least one element.” The deformation speed cannot physically exceed the wave speed that propagates in the material.
I recommend referring to the link below. You might find it helpful.
https://caeassistant.com/product/impact-analysis-in-abaqus/
I hope I could have helped you.
Best luck.
Hi Martin,
thanks for the advices
All of these questions have been checked over and over again.
The loading is very slow - 50 mm in 5 seconds - this is the customer's condition.
Dear Valery Anpilov, if you haven't figured it out yet. I recommend visiting this website and explaining your problem to them. maybe they can help you out.
https://caeassistant.com/consultancy-application-from/
Best regards.
Good evening,
I was able to solve these problems with the help of LS-DYNA program.
I calculate and calibrate the constants for the used equations of state using the MСalibration program.
Unfortunately, the Abaqus/Standard could not simulate such large deformations and multiple contacts.
Abaqus/Explicit could not simulate the tasks taking into account the viscosity of materials under the condition of "long" exposure.
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