SOLIDWORKS Simulation Premium has 11 material model types that will influence the results of a Linear or Nonlinear Analysis. These models types are located in the Properties tab in the material properties (See Figure 1) and will be defined individually in this article. These definitions are not comprehensive. They are only intended to give SOLIDWORKS Simulation Premium users a general understanding of how each material model works in the solver.
Figure 1: List of the Material Model Types in SOLIDWORKS Simulation Premium
The top three material models listed (See Figure 1) are elastic material models. This means that they are only accurate in the elastic zone of the stress-strain curve (see figure 3) of the material that is being applied to the model in the study. As long as the material being put under load has a max stress that is still in the elastic region it will return to the pre-load state once the load has been released.
Hyper-Elastic material models have the capacity to take large amounts of strain while exhibiting relatively minor stress. These types of materials can deform significantly under small loads. Rubber is a really good example of this type of material model. Materials that fit this model can exhibit highly complex behaviors that can be simulated in the program to a high degree of accuracy if the proper elastic constants are input into the material CommandManager. The user can input 2, 5, or 6 constants. With each correct elastic constant being placed into the program, a higher level of accuracy can be noticed in the solution.
These elastic constants are found through experimentation and are generally provided by the manufacturer. If they are not provided, the user has the option to input up to three stress-stretch curves into the Tables & Curves tab. These curves can be accessed by clicking on the Type drop-down menu (See Figure 2) and are entered exactly like a stress-strain curve. Once these curves have been provided the program will automatically calculate the proper elastic constants for the material from the curves. Only one of the three curves is required but the more curves that are provided by the user the better the elastic constants can be calculated, and the greater the accuracy of the material model.
Figure 2: Three stress-stretch curves available in hyper-elastic material models.
Elasto-Plastic models become necessary after the material being simulated reaches the yield point and enters the plastic range of the materials stress-strain curve (See Figure 3). Once in the plastic region, the object being deformed will not return to its original configuration after the load on the object has been removed.
The deformation at this point will be permanent. If the load is then placed back on the object it will not follow the original loading path but the previous unloading path back up into the plastic region. The yield point will have also moved to a higher stress location than it was originally, this is what is known as material hardening. As the object is loaded and unloaded into the plastic region the load path changes so that the same stress results give different strain results.
Figure 3: Typical Stress-Strain Curve
Super-Elastic models can undergo extremely large strains (as much as 20%) without reaching their yield point. After the first yield point has been reached, if loading continues, the material softens and becomes more elasto-plastic in its behavior. If loading continues to increase, the material will eventually reach a final yield point where it will harden significantly under increased loading. The shape of unloading superelastic materials is much the same as loading them. When the load is back to zero there is no permanent deformation if the yield strength was not exceeded.
Viscoelastic is the only material model type that is time-sensitive. All of the other material models used in SOLIDWORKS Simulation Premium will show the exact same loading stress-strain path no matter how quickly or slowly the load is applied. Viscoelastic materials are different they are strain-rate dependent meaning a load of equal magnitude applied to this material model at a different rate will produce a different stress-strain curve even if the max magnitude remains the same.
About Taran Packer
Taran is a SOLIDWORKS Simulation Technical Support Specialist at GoEngineer. He has a Bachelor’s degree in Biomedical Engineering from the University of Utah. Taran enjoys learning about different tools in SOLIDWORKS Simulation, Flow Simulation, and Plastics.
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