add new material parameter

A forum to discuss the implementation of a good Materials system in FreeCAD
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bernd
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Re: add new material parameter

Postby bernd » Wed Jul 04, 2018 4:33 am

BTW: I have no glue what "Elasticity" as property means? See https://github.com/FreeCAD/FreeCAD/blob ... al.py#L124 Do you have an idea?
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HarryvL
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Re: add new material parameter

Postby HarryvL » Wed Jul 04, 2018 4:50 am

bernd wrote:
Wed Jul 04, 2018 4:32 am
Would be cool if you could extend this if you have a minute ... https://www.freecadweb.org/wiki/Materia ... properties
Under mechanical? Can do. I will add Concrete Compressive strength, Concrete friction angle and Steel yield strength (with mention that this is also the value used in reinforcement calculations).

I still have major issues with changing the material properties in the editor. (Again here: https://forum.freecadweb.org/viewtopic. ... 30#p242567). Am I the only one?
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HarryvL
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Re: add new material parameter

Postby HarryvL » Wed Jul 04, 2018 4:54 am

bernd wrote:
Wed Jul 04, 2018 4:33 am
BTW: I have no glue what "Elasticity" as property means? See https://github.com/FreeCAD/FreeCAD/blob ... al.py#L124 Do you have an idea?
Nope. No such thing as "Elasticity". Maybe Young's Modulus is meant, but that is already in the list.
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HarryvL
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Re: add new material parameter

Postby HarryvL » Wed Jul 04, 2018 7:47 am

bernd wrote:
Wed Jul 04, 2018 4:32 am
Would be cool if you could extend this if you have a minute ... https://www.freecadweb.org/wiki/Materia ... properties
Doing this at the moment, but getting confused on where certain material properties are entered by the user. For example, "Yield Strength of Steel" does not get entered anywhere in the material dialogues. Only when a non-linear material object is created the user can enter "Yield Points", which are (Yield Stress, Equivalent Plastic Strain) Tuples ... but this is not said anywhere. Entering such yield points only makes sense for steel (or similar ductile materials satisfying a von Mises yield criterion with strain hardening), but no mention is made of this in the non-linear material object, nor is the above meaning of Yield Point defined.

The Wiki defines tensile strength, but I don't see that back in the standard materials available and it is not clear if (brittle) tensile strength, like in glass or concrete, or (ductile) tensile strength, like in steel or similar at ultimate rupture (maximum equivalent plastic strain), is meant.

So I am afraid I will add to the confusion if I add "Yield Strength" without a clear point to enter it. Also, using a non-linear material object to enter the value for concrete reinforcement may create the illusion that the reinforcement ratio and Mohr Coulomb analysis are non-linear analyses ... which they are not. They are just a post-processing step of a linear elastic analysis to visualize where the material strength is exceeded and reinforcement needs to be applied.

Hence my earlier suggestion to add "Reinforcement Yield Strength" as a parameter in the concrete card. When put to zero the user can specify unreinforced concrete.

"Compressive Strength" and "Concrete Friction Angle" are less of an issue and I will describe them as mechanical parameters.
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HarryvL
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Re: add new material parameter

Postby HarryvL » Wed Jul 04, 2018 8:44 am

bernd wrote:
Wed Jul 04, 2018 4:32 am
Would be cool if you could extend this if you have a minute ... https://www.freecadweb.org/wiki/Materia ... properties
Have a look: https://www.freecadweb.org/wiki/Materia ... properties
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HarryvL
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Re: add new material parameter

Postby HarryvL » Wed Jul 04, 2018 9:39 am

HarryvL wrote:
Wed Jul 04, 2018 4:50 am
I still have major issues with changing the material properties in the editor. (Again here: https://forum.freecadweb.org/viewtopic. ... 30#p242567). Am I the only one?
here is what I mean:

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bernd
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Re: add new material parameter

Postby bernd » Thu Jul 12, 2018 4:34 pm

HarryvL wrote:
Wed Jul 04, 2018 4:54 am
bernd wrote:
Wed Jul 04, 2018 4:33 am
BTW: I have no glue what "Elasticity" as property means? See https://github.com/FreeCAD/FreeCAD/blob ... al.py#L124 Do you have an idea?
Nope. No such thing as "Elasticity". Maybe Young's Modulus is meant, but that is already in the list.
git commit 35b92641