Thank you very much.

Regards,

Melly

]]>for a learning purpose i am trying to replicate this analysis described in the Abaqus Example Problems Guide, in the Tire analyses paragraph (my final goal is to perform a Steady-state rolling analysis of a tire ). In the Abaqus documentation are given the .inp files needed to perform this type of analysis but i don't know how to use them, because i' ve always used abaqus CAE but this time i have to use abaqus command because there are some keywords not supported by CAE.

Is there anyone who already made this example and could help me, explaining me the steps to be made?

Thanks for your attention.

]]>I always get similar results to the following example.

101If I'm wrong, please tell me the efficient methods to optimize hysteresis loops. Should I input the loading and the unloading separately?

Regards,

Mate

]]>In my team, we implemented the Bergstrom Boyce model in a in-house 3D FE code to simulate the mechanical behavior of TPE and adhesives. Even though we implemented an implicit formulation with no restiction on the time step for the evolution law ( network) integration, we are looking for a "natural" time scale for the model to set up our simulations

My guess would be that it would depend on the constitutive parameters, but it might also be related to the strain rate dynamics of the problem at stake.

I am struggling to find any literature on such a topic, so if anyone has a clue on the topic, it would be appreciated

Thanks, by advance,

Quentin

]]>I have a Question regarding a reinforced v-belt model...

Is it possible to calibrate to a certain tension modulus (Et) and a certain bending modulus (Eb)? (Et = 10 * Eb)

What material model would offer enough freedom?

Would this be implemented in MCalibration? (For use in Ansys)

Thanks and BR

Anton Höller

]]>

Regards,

Mate

]]>I'm running ABAQUS Explicit with a VUMAT subroutine to determine the ultimate strength of a polymer matrix UD composites under tension. I'm not interested in the post-failure behaviour so ideally I would halt the simulation as soon as a drop in load is detected (this load corresponding to the reaction force of a node set where the displacement is applied). The only way I found of doing this (from the documentation) is to set an extreme maximum value for the reaction force, halting the simulation when this value is reached. This, however, is not very helpful, because the maximum reaction force is precisely what I'm trying to find by running the analysis.

Some ideas so far (although a bit convoluted) would be to:

-Output the nodal reaction force as a history output to an external file; read this file during runtime and kill the job once the load drop is detected.

-Pass the reaction force to a user subroutine and call xit command once the drop is detected.

I'm not sure if these are even possible so any help would be greatly appreciated.

Thanks

]]>Regards

Mario]]>

This topic is not strictly related to polymers but I hope I'll receive some help.

I intend to write a UMAT subroutine in order to perform a heat treatment simulation using CalculiX (the residual sytresses generated during quenching are my major subject of interest).

I will most probably use the CalculiX native UMAT subroiutine rather than writing an Abaqus UMAT code and using it later with CalculiX.

My plan is to write a UMAT code for a thermo-elasto-plastic model first (combined isotropic and kinematic hardening). After verifying that everything works fine I will extend the code by adding the phase evolution kinetics and proper dependence of the elastic and plastic constants (on the percantage of anayzed phases).

There are some issues that remain unclear for me. I will list them below.

1) If I used Abaqus, it would be possible for me to perform a coupled thermo-mechanical analysis. In that case my Abaqus UMAT code should contain the definitions of the tangent operator (DDSDDE matrix) and a matrix defining stress dependence on temperature (DDSDDT).

However, I am using CalculiX (not Abaqus) and to my best knowledge the official release of CalculiX does not support the coupled thermo-mechanical analysis while using UMAT. Thus, I will have to utilize the uncoupled thermo-mechanical analysis (the step is called "uncoupled temperature-displacement"). I understand that in this case all I need to define in my UMAT subroutine is the mechanical tangent operator (the stiff matrix in CalculiX UMAT or DDSDDE in Abaqus UMAT). Of course, I will include in my tangent operator the terms which yield from the thermal expansion and the phase/temperature dependence of the elastic and plastic constants. But that is basically it. No need to define DDSDDT since I perform an uncoupled thermo-mechanical analysis and all I need to define is the mechanical tangent operator (DDSDDE or stiff matrix) and update the stress vector (STRESS or stre).

Please correct me if I'm wrong in this reasoning.

2) In order to obtain a realistic simulation of the quenching process I want to take into account the existance of latent heat. I understand that a proper user subroutine to achieve this is DEFLUX where I can define the heat generated per unit volume during each increment.

In order to calculate the latent heat generated during a given time increment, I need to know the volume fraction of the transformed phase. Suppose that I used the UMAT subroutine to define the kinetics of phase evolution. The volume fractions (of each analysed phase) are defined as separate state variables (STATEV) within UMAT. Here is a question: will I be able to use the state variables (STATEVs) defined in UMAT subroutine for further calculations of latent heat preformed in DEFLUX subroutine?

3) The documentation of the CalculiX UMAT native interface says that the "emec" vector contains the components of the Lagrange mechanical strain. I understand that if I do not utilize the nonlinear geometry (NLGEOM option) "emec" will simply contain the components of the small strain tensor. Is that correct?

Furthermore, the documentation states that at each increment the thermal strains are automatically subtracted from the total strain to obtain the strain components collected in the "emec" vector. Does this also apply if I define the thermal strains all by mhyself in UMAT?

Any help much appreciated,

Best regards,

Cyprian Suchocki

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