Help with Converting Physical Characteristics for Simulation...

[techshopjim]

I have a spec sheet for King StarBoard ST here (https://www.kingplastic.com/products/king-starboard-st/).  The product is an HDPE, but is stiffer than normal HDPE.

For a current project, I need to do a load flex test (two ends of a plank supported by blocks, with a known weight in the center to to determine the amount of deflection).

The problem is that the spec sheet for the King StarBoard ST does not list the characteristics that Fusion 360's Material Properties panel is asking for, specifically:

  "Young's Modulus"

  "Poisson's Ratio"

  "Yield Strength"

  "Ultimate Tensile Strength"

On the spec sheet, they do provide the following characteristics values:

  "Density"

  "Tensile Strength @ Yield" (I'm assuming this is the same as "Ultimate Tensile Strength")

  "Tensile Modulus"

  "Elongation @ Break" (probably not needed for a load flex test?)

  "Elongation @ Yield"

  "Flexural Modulus"

  "Flexural Stress @ 5% Strain"

  "Compressive Properties 10% Strain"

  "Durometer"

  ...and others that I don't think are applicable to my test needs.

I have asked the manufacturer for the characteristics that Fusion 360 wants, but they are saying that all they have is what is in the spec sheet.

How can I convert the manufacturer's values into what Fusion 360 is asking for?

Thank you!

--

Jim

[jhackney1972]

For Standard Materials you can get most of your required information from MatWeb.  If you test with these values you can at least get a close approximation how your special HDPE will perform.

[techshopjim]

Hi John...

Good idea!  I checked MatWeb, but I could not find any material that was stiffened HDPE.

All the materials on MatWeb seem to also be missing the parameters that Fusion 360 asks for (such as Young's Modulus, etc.).  Why does Fusion 360's Material Properties panel not just use the standard characteristics that are used by the industry?

Thank you!

--

Jim

[John_Holtz · Accepted solution]

Why can't manufacturers provide the most basic information needed for a calculation? That is a question for manufacturers.

• The Young's modulus is the same as the tensile modulus, so you have that input. (Young's modulus is also the same as the modulus of elasticity. I'm confident that MatWeb gives this for most materials.)
• The data sheet does not provide the Poisson's ratio. Either find a similar material that provides the Poisson's ratio, or perform 5 different analyses with Poisson's ratio between 0.8*similar material to 1.2*similar material and see how it effects the results.
• You do not need to enter any other material properties in order to perform the analysis. Of course, you will want to know what the allowable limit is for your design, whether that is an allowable displacement (more a design constraint than a material property) or an allowable stress (a material property). The "Tensile strength @ yield" sounds like the yield strength to me. It probably should read "Yield strength in tension" to differentiate it from the yield strength in bending or any other form of loading.
• I do not see the ultimate tensile strength in the data sheet. If you are not planning on exceeding the yield strength, then you do not need to know the ultimate tensile strength.

P.S. The screw and nail removal load is being added to the next release of Fusion, so you will be able to enter that property. (Just joking. 😁)

[TrippyLighting]

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@John_Holtz wrote:

P.S. The screw and nail removal load is being added to the next release of Fusion, so you will be able to enter that property. (Just joking. 😁)

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Ha ha ha. Good one!

[techshopjim]

Hi John...

This is great information.  Thank you for clarifying the variables!

--

Jim

[MichaelT_123]

Hi Mr. TechShopJim,

The significant portion of the material properties as supplied by the producer are result of readings from particular testing rigs and they are more or less applicable to their respective setups only. So, in the sense they don't constitute physical properties of material, which is in your case is less than perfect candidate to utilize the standard engineering/mechanical models.
Assuming that you accept Young's Modulus value supplied by the producer, you might estimate Poisson’s Ratio (and others) by building your own simplified rig (let's say, single or double supported beam) and estimate it (them) from experiments reflecting your probable real life loads. You might find that resulting values are non-linear functions of a load. If so, F360 non-linear FEA gives another tool to verify the acquired/estimated in the previous step values.

Regards
MichaelT

[techshopjim]

Hi Michael...

That's essentially what I ended up doing.  I used a vertical mill with a DRO on Z and a digital scale to set up a load on the Z axis and used the DRO's Z as the deflection meter.  This gave me a rough relationship between MDF and HDPE, and I was able to extrapolate this information in Fusion 360.

Thank you everyone!