How can I vary hardness for material?

[LosAngeles]

Hi people,

How can I assign hardness to material in Pro Mechanica?
What can i set are young's modulus are poisson's ratio.
Are those enough?

Thanks

 

[LosAngeles]

What is the relation between hardness and young's modulus?


Can i use young's modulus for part that works under pressing?

 

[MichailS]

You are asking a bit too wide. A bit like "How do I write in french?"

The relationship between stiffness and hardness is complex and it doesn't help that nobody ever really made a good definition of what "hardness" really is. They're all a bunch of made-up scales of how deep some object will go into another given some certain force.

Hardness is really dependant on stiffness, strength AND ductility, so it is no mean feat to find a good representation.

What is it that you are trying to compute?


Edited by: MichailS

 

[LosAngeles]

I am trying simulate human's foot. I fix heel and apply force to toe.


I need to minimize localized stresses by varying hardness of components.

 

[MichailS]

If it is bone vs. flesh you are modeling, then it is the stiffness (Young's modulus) you need to change rather than hardness (Rockwell, Vickers, etc).

Poissons ratio should be about 0.3 for crystalline materials, but I have no idea what it should be for a bag of water like flesh. 1.0 sounds right but I don't know really.

Flesh is viscoelastic, so you ought to compare it to some sort of soft rubber. Incidentally, rubber also has a "hardness" index named Shore.

You can find a lot of material data on www.efunda.com and www.matweb.com .

 

[Israr]

You can change or assign hardness properties by editing material inside Mechanica in Wildfire 3.0


Israr

 

[paoloz]

1- Poisson ratio cannot be greater than 0.5 (rubber is about 0.49);


2- Hardness has a rude relation with Ultimate tensile strength for steel. I don't know for bones;

 

[LosAngeles]

I am trying to model foot as beam which made of some kind of plastic (nylon, polyurethane).
I tried to set hardness in ProMech 3.0 but it is likely to has no influence to my model.
So, i will vary young's modulus.

Thanks to all!