# Material units

• posted

To begin our conversation, I am using SolidWorks 2005 SP3.

I'm writing a software tool to manage SolidWorks materials a little more easily that the included tools and I'm flummoxed. The material data is kept in data files ending in .sldmat. These are basically XML files which makes them fairly easy to parse and manipulate.

What I don't understand is the units. Lets take the ultimate and yield strengths as an example.

In the solidworks materials.sldmat file, lets look at AISI 304.

Just for grins, set your units to IPS.

Pull up AISI 304 in the edit material gizmo

The Tensile Strength is 74,987.0 lb/in^2 The Yield Strength is 29994.8 lb/in^2

Now open up solidworks materials.sldmat in a text editor.

Find AISI 304 and if you look further, it contains the two lines:

Okay, doing some simple proportioning (to get an idea of what the conversion factor might be)

4.20507E+8/74987 =5607.7...

and

3.51571E+8/29994.8 = 11721.1...

WTF?

Now, assuming that the units in the solidworks materials.sldmat file for stress would be kilopascals (for a well behaved metric unit), to convert from psi to kilopascals to psi you would multiply by 6.894, so that's not it.

Okay, assuming the units are in N/mm^2, converting from psi to N/mm^2 you multiply by 6894.757

Does anyone have a clue what in the world is going on?

Thanks =========================================================================== Chris

• posted

Oh sorry thats length..

• posted

Create a material with nice round numbers for stress values and see what results.

• posted

It AISI values you are working with are incorrect

Machinery Handbook Pascal x 0.0001450377 = PSI PSI x 6.894.757 = Pascal

Material Property Values for AISI 304 from SolidWorks 2004/SP4 file:

Tensile Strength: 5.17017E=08 / 74,987 = 6.894755E+03 ~ 0.00014503 (matches handbook)

Kman

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