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    This website is an independent forum for discussing finite element simulations of all types of polymers. To perform an accurate FE simulation requires 3 types of inputs:
    • Geometries
    • Material models
    • Applied loads and boundary conditions

    The specification of the material models is typically the most challenging, and is therefore the focus of this site. I have been working in this field for close to 20 years, and this site now has more than 11,000 posts and 17,000 members. My goal of running this website is to provide expert advice on how to perform proper computer simulations of polymers, and to discuss some of the tools that I have developed (PolyUMod and MCalibration). Researchers and users are encouraged to submit results and to request information.

    I am excited to announce that my book "Mechanics of Solid Polymers - Theory and Computational Modeling" is now available. The book is very comprehensive and covers both detailed theory and hands-on practical advice on how to perform accurate FE simulations of any polymer. These topics are not discussed in any other book that is currently available. See PolymerMechanics.com for more information about the book.

    This Oct 7-8, 2015, course is an extension of the original Part 1 class, and covers in more depth the theory of different material models, and hands-on exercises designed to teach how to use the different models to solve real problems. The training class is targeted to people with an interest in performing non-linear finite element simulations of parts made from plastics, rubbers, thermosets, or other types of polymers.

    By the end of the class you will:
    • Know the strengths and weaknesses of both simple material models (hyperelasticity, linear viscoelasticity, and metal plasticity) and advanced material models (e.g. Bergstrom-Boyce, Three Network Model, Parallel Network Model).
    • Know what experimental tests are necessary and sufficient for calibrating any material model.
    • Be able to quickly calibrate any material model using the MCalibration software.
    • Be able to use any of the standard built-in material models, or any of the material models in the PolyUMod library, to simulate the response of polymer products.

    Contact us soon if you want to register!

    Most FE software has the capability to calibrate simple material models, such as hyperelasticity and linear viscoelasticity. But the calibration functions do not give you much flexibility about what experimental data to use and how the calibrations should be performed. MCalibration is an application that is much more powerful and faster. It contains functions for cleaning up experimental data, it contains a library of already calibrated material models, and it can calibrate all material models Abaqus, ANSYS, and the PolyUMod library. Many of the commonly used viscoplastic material models in Abaqus and ANSYS are directly built into MCalibration. That means you can calibrate those models very fast without even using a FE solver. MCalibration is awesomely great. Contact me if you would like a trial license.

    The schedule for my 2016 training classes is now available. The classes cover the following topics: polymer mechanics, experimental testing, material model selection, and advanced finite element modeling techniques.

    Both online (web-based) and in-person (classroom-style) training classes are available. The training classes are targeted to people with an interest in learning the state of the art in testing and analyzing the mechanical performance of parts made from plastics, rubbers, thermosets, or other types of polymers.

    I also give custom training classes directly to different companies. Contact me if you want more information.

    Experimental testing can be performed for different reasons. Sometimes the purpose is simple to make sure that a material satisfies a given set of requires property values. Other times the purpose is to obtain sufficient experimental data to calibrate a suitable material model. When the goal of the testing is to calibrate a material model then the testing can be performed using "smart experiments" in order to obtain as much information as possible using as few tests. The required number of tests will depend on the material behavior and the material model that will be used. If a material is isotropic then it is frequently sufficient to perform only uniaxial tests with multiple load-relax-unload cycles.

    When possible, I also typically recommend that validation tests be performed. Validation tests are specific tests that are typically multiaxial and are specifically designed to probe the material in a way that is similar to the intended application. The calibrated material model will then be used in Finite Element (FE) simulations of the validation experiments. If the calibrated material model match the validation results then the material model likely provides a reasonable representation of the true material response. Validation experiments are often performed using Small Punch testing, V-notch shear testing, or Indentation testing.

    Contact me if you are interested in obtaining a quotation for experimental characterization of validation testing.

    I created a short movie that demonstrates the MCalibration software. If you ever need to calibrate a material model for use with Abaqus, ANSYS, or LS-DYNA, then you should check out MCalibration. This software can calibrate all user-material models in the PolyUMod library, and also all built-in material models in Abaqus.

    A new version of MCalibration and PolyUMod was just released (4.0.1). The new version contains a large number of interesting and useful new features, for example:
    • Now supports Abaqus 2016, ANSYS 17, and COMSOL 5.2.
    • The default file format has been switched to XML. It is still possible to save the mcal file in the old txt-format using the menu item "Save MCal-file in Version 3 format".
    • The next XML file format stores the experimental data inside the file. The experimental data is compressed if a global options flag is set.
    • The initial material parameters for most PolyUMod models are now set based on the experimental data available in the load cases.
    • Can now calibrate and store multiple material models in the same mcal-file.

    Check out the following page for more info, you can also read the detailed change log here.
    Article Preview

    I wrote this article (Annals of Biomedical Engineering, DOI: 10.1007/s10439-015-1455-8, 2015) to provide an overview of the connection between the microstructural state and the mechanical response of various bioresorbable polylactide (PLA) devices for medical applications. PLLA is currently the most commonly used material for bioresorbable stents and sutures, and its use is increasing in many other medical applications. The non-linear mechanical response of PLLA, due in part to its low glass transition temperature (Tg = 60C), is highly sensitive to the molecular weight and molecular orientation field, the degree of crystallinity, and the physical aging time.

    We have created a new website specifically for the PolyUMod library of material model. The new website, PolyUMod.com, contains lots of information about how to accurately perform Test-Calibrate-Simulate workflows using the PolyUMod library of advanced user-material models for Abaqus, ANSYS and other non-linear FE solvers.

    We encourage everyone who is interested in accurate FE simulations of polymers and rubbers to checkout PolyUMod.com!
    Article Preview

    ANSYS version 17 was recently released and it seems like it contains a large number of nice improvements. I am also happy to announce that the current version of the PolyUMod library works great also with this new version of ANSYS.

    The latest version of the MCalibration software can now calibrate any of the built-in material models in ANSYS Mechanical.

    Here is a tutorial on how to use MCalibration to simultaneously calibrate a material model to both traditional stress-strain data, and dynamic storage modulus (E') and loss modulus data (E''). The attached pdf-file and MCalibration files contain all the details.
    One of the most useful features of MCalibration is the ability to calibrate a material model simultaneously using many different types of experimental data.

    I gave a presentation on advanced FE modeling of PLLA intereference screws at the ANSYS User's conference in Boston on Sep 14, 2011. In my presentation I discussed how the design of degradable screws can be optimized for use in Anterior cruciate ligament (ACL) reconstruction surgery. PLLA is a non-linear viscoplastic material that can be accurately modeled using the PolyUMod library.

    If you are looking for free, high quality experimental data for various polymers, then you might be interested in learning that you can download and use the experimental data from the following links:

    Also note that I provide experimental testing services for all kinds of polymers through Veryst Engineering. Send me a private message if you are interested in having your material tested and a suitable material model calibrated.

  • Recent Forum Posts


    Link Abaqus and Fortran compiler

    Hello everybody,

    I am using Abaqus version 2016 and need to use the subroutine UMAT. To do that, I need a Fortran compiler.
    Simulia suggests using Intel Fortran Composer XE 2011, but we don't...

    dacthuongngo Yesterday, 07:24 Go to last post

    As I mentioned in my previous post: If your...

    As I mentioned in my previous post: If your experiments are measuring the eng strain and eng stress, then you import them as such. And similar for true stress and true strain.

    There is a feature...

    Jorgen 2016-05-28, 04:31 Go to last post

    What kind of code are you using? if you use...

    What kind of code are you using?
    if you use Abaqus, toggle Nlgeom on means you account for large deformations.

    dacthuongngo 2016-05-27, 09:04 Go to last post

    Linking Abaqus and subroutines

    I'm having the same problem.
    I am using the 2016 version of Abaqus but still don't have a Fortran compiler. So the use of "Abaqus make" utility may help me.
    To my understanding after...

    dacthuongngo 2016-05-27, 08:56 Go to last post
    Andreas Gierse


    Dear Simulaters

    Thank you very much for the answers.
    I tried to use the informations; here is what i got:

    Answer Bergström:
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    Andreas Gierse 2016-05-26, 06:04 Go to last post