I know it’s been ages since our last chat, but fear not – it is my responsibility to sprinkle CAE wisdom your way at least once a month, no matter how busy my schedule gets!
Welcome to the 18th edition of the CAE Compass newsletter!
In today's edition, I'll take you through a crucial topic: Nonlinear Material Models.
When we talk about materials and how they react to forces, we often think about simple stretching or bending. But some materials behave in more complex ways.
So, let’s explore these nonlinear materials and how they work.
- Nonlinear Elastic Material:
This type of material nonlinearity applies specifically to isotropic materials. A nonlinear elastic material won’t permanently change its shape, no matter how much force is applied.
Even after removing the force, it always goes back to its original shape without any lasting deformations. Additionally, it stays consistent without showing any increased resistance to deformation, even after being loaded and unloaded multiple times.
Example: A rubber ball. When you squeeze or stretch it, it deforms temporarily but returns to its original shape once the force is removed. It doesn't permanently change its shape.
2. Bilinear Elastoplastic Material:
This type of material is commonly used for steel. It’s not the most advanced option, but it’s simple to set up. Unlike the first type, this material can change its properties after being stretched or compressed multiple times.
To use this material in a simulation, you first decide how it will behave when it starts to deform. There are several criteria to choose from, but for steel, the von Mises criterion is usually used.
Example: A paperclip. You can bend it back and forth several times (plastic deformation), but eventually, it becomes harder to bend (strain hardening) and may break if bent too much.
3. Multilinear Plastic Material:
This is a more advanced option than the bilinear material. You still need to choose a yield criterion and an initial yield point, but instead of a simple hardening rule, you define a curve that shows how the material stretches and stresses at multiple points.
Example: Modeling clay. As you shape and mold it, it changes resistance and shape (plastic deformation) at different stages of molding. Each stage shows different levels of stiffness.
4. Rigid Plastic Material:
This material type is less common. It assumes that the material doesn’t deform at all when under small stresses but behaves plastically (permanently deforms) when a certain stress level is reached.
This type is simpler because you only need to define the plastic part of the stress-strain relationship.
Example: A plastic ruler. It stays straight and rigid under normal use (no deformation under small stresses), but if you apply enough force, it may permanently bend or break (plastic deformation).
And that's it on the nonlinear materials.
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🔧 Tool of the day - Materials Resource Registry​
Offers links to various material databases, standards and tools provided by the National Institute of Standards and Technology.
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I hope you learned something new today. CAE is such a field where learning never ends.
See you in the next edition.
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