By storing material properties in an unified data structure, one aims to ease data retrieval that can be carried out in different contexts:
To manage material properties, it is proposed to create a specific data model that will be instanced when a new material is created whithin FreeCAD.
It will be possible to create a material either by defining by hand its properties through a material workbench, or by reading material properties from a file. The formats of such files is to be defined (some already exist, like MatML, STEP AP235 & IGR45...).
Also, it will be possible to save the material properties in a collection of files in a format still to be chosen as well. The collection of files that can be stored in a common directory will form the FreeCAD material database.
Through this data model, material can be defined in FreeCAD without the need to define a component.
A new pointer will be created in the component data model, to link to a material that has been defined through the material data model.
Through this material data model, it is proposed to offer a tool to manage easily material data within FreeCAD.
Different kinds of data need to be managed to describe a material. A material data model is proposed below. Some examples of the data that can be stored within this structure are given as well.
In addition to classical "string" attributes like a name, and a family, 3 different specific kinds of information need to be managed to describe a material in FreeCAD.
All of these kind of information do not need necessarily to be defined for the material to exist. Finally, below is the list of attributes retained to describe a material in FreeCAD.
A string indicating the name of the material. It is its designation.
A string indicating the family of the material, such as for instance:
Additionnally, it is proposed to create a map between the families (for instance stored in a XML file) so as to be able to browse the FreeCAD material database.
Such a map could for instance contain a tree presenting relationships between families, like:
A string indicating the manufacturer of the material.
A string indicating the web page presenting the material.
The material data model includes a collection of properties. The size of such a collection is not fixed and may be extended with new user-defined properties.
A property contains the following attributes.
Material properties will be identified thanks to their name in order to process them, i.e. for instance writing the Yield strength in a finite element model. In order to ease material data creation within FreeCAD, a standardized list of property names along with their standard units will be proposed to the user. Nonetheless, the user is free to create new properties, with new names, new units, and so on...
Below is proposed the dictionary of standard properties. Feel free to add new ones.
<?xml version="1.0" encoding="UTF-8"?>
<MatPropDictionary LastUpdate="2011-10-24T09:00:00">
<Property Name="Yield Stress" Symbol="YS" UnitSignature="-1 1 -2 0 0 0 0" />
<Property Name="Ultimate tensile strength" Symbol="UTS" UnitSignature="-1 1 -2 0 0 0 0" />
<Property Name="Mean Lankford coefficient" Symbol="r_{mean}" UnitSignature="0 0 0 0 0 0 0" />
<Property Name="Hardening coefficient" Symbol="n" UnitSignature="0 0 0 0 0 0 0" />
<Property Name="Strain hardening" UnitSignature="-1 1 -2 0 0 0 0" />
<Property Name="Elastic modulus" Symbol="E" UnitSignature="-1 1 -2 0 0 0 0" />
<Property Name="Density" Symbol="\rho" UnitSignature="-3 1 0 0 0 0 0" />
<Property Name="Poisson coefficient" Symbol="\nu" UnitSignature="0 0 0 0 0 0 0" />
<Property Name="Uniform elongation" Symbol="UE" UnitSignature="0 0 0 0 0 0 0" />
<Property Name="Total elongation" Symbol="TE" UnitSignature="0 0 0 0 0 0 0" />
</MatPropDictionary>
Notes: "Mean Lankford coefficient is representative of the anisotropy of a thin metal sheet." "The Hardening coefficient is representative of the hardening capacity of a metal. It appears in Hollomon formula that can relates cumulated plastic strain to stress."
A first example is given below to show how a Cost per tonne property can be stored.
A second example is given below to show how the Yield strength property can be stored.
A third example is given below to show how the Strain hardening property can be stored. This is a more complex example because Strain hardening is represented by a serie of curves. The curves represent the stress evolution with respect to plastic strain. 3 curves have been obtained at different strain rates. All curves have been obtained at room temperature.
[Yet to be filled up]
[Yet to be filled up]
A string where the user can add its own comments about the material.
Brick masonry
?string?
?string?
?string?
Notes about maintainance, special cares to be taken, etc...
CSI/MasterFormat code (as there are several systems used in the industry which give to all material a special code, I propose to enter it in the notes, because it doesn't appear to me relevant create a specific properties that we won't be able to name exactly).