Material law similar to Law2 but with ability to reduce stress?

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

I am trying to get a material model law for simulating a concrete block.

The concrete stress strain curves are shown in the attached image, of which my need is for the 55MPa curve.

 

Now, I am not choosing LAW36 because it deletes the element or brings the stress to zero after the element strain goes beyond the last point.

So I am choosing LAW2 which allows me to keep straining the element and fixing the stress to the max value.

 

But I want a law that allows me to let the stress reduce below the max value and keep constant thereafter so that the element keeps absorbing energy by continuing to strain.

Please suggest a better law or how to modify law2 to achieve this?

<?xml version="1.0" encoding="UTF-8"?>fig17.gif

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2016

    Hi Bongirs,

    Can you try with material law 24 (/MAT/LAW24 (CONC)), which is designed to model brittle elastic-plastic behavior of reinforced concrete. This law is compatible only with solid elements. And also please review the example in our Help menu, Example 47 - Concrete Validation where concrete failure modeling under compression and tension is shown.

     

     

     

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2016

    Hi George!

     

    Thank you for your answer!

    I checked the law24 reference manual and there are so many parameters!

    Hardly any information about these parameters is given in the document.

    Can you please tell me how to model this law from the stress strain curve that I have?

    I also do not have access to the example you mentioned.

    Please just tell me which parameters I need to use for curve fitting and the meaning of these parameters....

    My mesh is in 3D tetra, and the concrete is for drop testing an object on the concrete.

    Thanks again!

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited November 2020

    Hi Bongirs,

    This material model is a plasticity-based, damage model for concrete. It assumes that the main two failure mechanisms are tensile cracking and compressive crushing of the concrete material. The material law will enable to formulate the brittle elastic – plastic behavior of the reinforced concrete. With the basic material parameters like density, Young's modulus, Poisson's ratio and compressive strength of concrete this material card can be used.With the experimental results only user can determine the material parameters like tensile strength ratio, biaxial strength ration..etc.

    Please see this recorded webinar http://www.altairhyperworks.com/html/en-us/rl/Explosives_and_Concrete/index.html which gives more explanation on this material.

    The above mentioned example file and an example model file is attached along for your reference .

    Meanwhile I'll search for similar kind of material law you mentioned and will update.

     

    Unable to find an attachment - read this blog

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2016

    Thanks George for the fantastic answer!

    Its really surprising to see that RADIOSS parameters in general are anti-user friendly.

    In case you have the ability to report to your UX team then please tell them in which era they are living?

    Just look at ANSYS or LS-Dyna, the documentation and user experience are superb.

    If I have a stress strain curve, I should be able to model that in any FEA software.

    I will check the recording and will let you know.

    I am really thankful to you for providing your useful insight and support from time to time., great job!

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