strength - different brittle material law in failure model

Hello Colleagues !

I read:

HELP > RADIOSS > Reference guide > Starter Input > Materials > Failure models / Elasto-Plastic Material / Concrete and rock materials
RADIOSS THEORY MANUAL 14.0 ver. - July 2005 LD FEA PART 2

RADIOSS > Tutorial and Example > Examples47

I'm looking for the material law and failure model that would meet my needs:

1) my object - solid
2) my material - brittle elasto-plastic (without yield stress)

3) my material - strength-different (failure tensile stress = 40 MPa, failure compressive stress = 400 MPa)

4) my load - transverse bending

eg cast iron, silicified graphite, i.e material corresponding to the diagram in my picture.

In my opinion, the most suitable - LAW24 (concrete). It may be better to use another law ? What do you advise me?

But I do not fully understand LAW24 card.

p₀ (density) - ok, i have

E_c - ok, i have

f_c - failure compressive stress ? - if yes, ok, i have

f_t - failure tensile stress ? - if yes, ok, i have

f_b - biaxial compressive/tensile or bending stress ? I have failure bending stress = 100 MPa

f₂ - what is it ?

S₀ - what is it ?

H_t = -E_c - ok

D_sup - what is it ? (not use in Example47, value 0) - Do I need this?

eps_max - what is it ? (not use in Example47, value 0) - Do I need this?

H_v0 - what will this value give me? I don't have it. (not use in Example47, value 0)

And E , sigma_y , E_t , alpha1 , alpha2 , alpha3 - for steel in concrete, don't need me.

Help me find the right law, please.

And help me understand and find all the parameters.

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Altair Forum User

Hi Andrey,

f2 and S0 are concrete confined strength ratio and concrete confined stress ratio respectively. For a confined concrete behavior the strength and stress may vary from the traditional values and those we are specifying here. Dsup and Epsmax are damage/failure parameters. The material will fail when these parameters are reached.

Similarly other parameters mentioned are described in Help menu.

If you are looking only for a brittle material law, please go through /MAT/LAW27 in Help Menu, which is an elasto-plastic Johnson-Cook material model with an brittle failure model.

Altair Forum User

Hello @George P Johnson !

please go through /MAT/LAW27 in Help Menu

I already read a help about LAW27, but it's ONLY for Shells & Sandwich Shells and damage occur ONLY in tension.

My model - Solid.

My model should have two possible of failure: tensile & compressive, because I have bending load.

P.S. Сarbon steel (сast iron) also has a different tensile-compressive strength.
In the case of longitudinal bending, it is not known in advance what will occur before: compression failure or failure at stretching.

Altair Forum User

Hi Andrey,

Please go through the Example 47 - Concrete Validation in Help Menu. The purpose of this example is to compare the simulation results to experimental data. RADIOSS includes the material model CONC to model concrete failure modeling under compression and tension.

Altair Forum User

Yes @George P Johnson , I read this section, I indicated this in the first message.

RADIOSS > Tutorial and Example > Examples47

My question is: is this the only material law (LAW24) that is suitable for my task? This material law for iron-concrete.

1. Maybe there is a separate model of brittle fracture of tension-compression.
2. Or there are two models of brittle fracture: one for compression, another for stretching, and they can be used simultaneously.
And these models can be used in conjunction with the Johnson-Cook material law.

Really, to solve the problem of destroying any brittle material (cast iron, high-carbon steel, graphite, ceramics, glass etc.) with complex loading, there is only one way - to use a model of iron-concrete (LAW24) ??! =(

Altair Forum User

Hi Andrey,

We only have this material law for brittle materials which has these two failure mechanisms.