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Creep modelling, can't replicate input data — Ansys Learning Forum

Creep modelling, can't replicate input data

Martin_nMartin_n Member Posts: 2

Dear all

I have the creep curve from a tensile test. The data is used in the APDL-module to extract the constants for Modified Time Hardening using the curve fit functionality.

When I use the constants with the modified time hardening creep model the fit to the experimental data is quite good.

I then use the creep constants to define a modified time hardening material in Ansys where I run a simulation on a cube with friction less support on 3 sides and the same pressure used for the test data. This setup ensures uniaxial loading. The outcome should be the same as the input. It is not. I have tried to perform this simple test numerous times in different versions of Ansys but with the same result.

The entire setup made in Workbench 2019 R2 is attached.

If anyone has similar issues or even an explanation I will be grateful.

Martin

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Comments

  • 1shan1shan Ansys Employee Posts: 262

    Hello @Martin_n,

    It looks like the trend is being captured accurately but there exists an initial offset between the two at t=0. When you apply the pressure there should be an immediate deformation at t=0 (this is not seen in your simulation) and then the creep strain should develop over time. Please check this. Also, ANSYS employees are not allowed to download attachments.

    Regards,

    Ishan.

  • ramgopisettiramgopisetti Member Posts: 102

    Hi @Martin_n , whats your temperature of tensile test.

  • Martin_nMartin_n Member Posts: 2

    Thank you for your comments. There is an immediate deformation but it is elastic and therefore not shown on the curve. The simulation is done in two steps. First a load step without creep followed by a step with creep and constant load. Shown here is the total strain for the species where you can see the initial elastic strain.

    The creep input data I have used for 1000000 Pa are:

    The constants obtained for Modified Time Hardening are

    The temperature does not play a role in this. C4 is set to 0.

    This should be enough information to replicate my results without downloading anything.

    Regards, Martin

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