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Thread: Material Properties - Real World vs. DMM

  1. #1

    Material Properties - Real World vs. DMM

    Hi,

    What is the relationship between real world material properties and those in the DMM material library? For example, in the real world the Young’s moduli of steel and aluminium are approximately 200 GPa and 70 GPa respectively. But in DMM, the “sheetmetal” material has a Young’s modulus of only 8 MPa. Similarly for iron; the real Young’s modulus of iron might be 100 – 200 GPa , DMM “cast iron” density = 11 MPa. So there is a 4-5 order of magnitude difference.

    Is there any way to convert / calibrate between the two? Or are the DMM properties rather arbitrary values that simply produce the right-looking material responses?

  2. #2

    Re: Material Properties - Real World vs. DMM

    The thing about material properties is that there is what people perceive how they want materials to react and how they react in the real world. Then there is the added issue of how DMM reacts based on the mesh density. A mesh with only 10 tets is going to behave differently than a mesh with 1000 tets. While you can certainly type in values from a material textbook and get results similar to those in real-life, it ends up being simpler to tune the material properties to achieve a certain visual effect. The materials that are included with the plugin are pretty stable and close to the giving the kind of effect one might expect of their named counterparts, but they are really a starting point for you to adjust them to suit your own needs.

    Case in point, the other day we were simulating a spaceship being pummeled by asteroids and noticed that the skin of the ship buckled in a place that was not visually connected to where the asteroid hit it. The reason this happened was that the DMM simulation was accurately modeling the stress of the ship's superstructure and skin and the crack appeared where physics dictated where the stress in the structure was the most.

    Now we could have weakened the ship in the place where we wanted the crack to appear, or we could change the material properties to see how that affects it, but those are both things that are related to the visual result we are trying to achieve and not so much to be accurate to the physical properties of the materials that make up the ship or the asteroids.

    Hopefully that answers your question.

  3. #3

    Re: Material Properties - Real World vs. DMM

    Thanks dmmjedi, that's perfectly clear.

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