SOLIDWORKS Simulation: Material Model Types Defined

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1 SOLIDWORKS Simulation: Material Model Types Defined In SOLIDWORKS Simulation Premium there are 11 material model types which 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 indivdually in this document. These definitions are not comprehensive. They are only intended to give SOLIDWORKS Simulation users a general understanding on how each material model works in the solver. (Figure 1: List of the Material Model Types in SOLIDWORKS Simulation Premium)

2 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. Linear Elastic Isotropic This material model solver should be applied to materials that are materially the same in the X, Y, and Z direction, and is defined by two material constants (Elastic s modulus and Poisson s ratio). This means that if the user where to apply a force in the X, Y, or Z direction, individually all three axies would show the same results equally Linear Elastic Orthotropic Exhibits different matieral properties and behaviors in all three Cartisian Coordinants axies, and has nine different material constants. Nonlinear Elastic While because this material is elastic it does exhibit the property of returning to it s preloaded state postload. It does not have a linear reagion. It exhibits nonlinearity from the very beginning of load being applied to the object. Hyper-Elastic Material Models have a capacity to take large amounts of strain while exhibiting relativly 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 inputed into the material command manager. The user can imput 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 expiramentation 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.

3 (Figure 2: Three stress-stretch curves available in hyper-elastic material models) Hyper-Elastic Blatz Ko Is used to simulate compressible hyper-elastic materials such as foam. It only requires one elastic constant, and the elastic modulus of the material to calculate an accurate result. The Poisson s ratio is assumed to be 0.25 by defalt for this material model. Hyper-Elastic Mooney - Rivlin This is one of the most popular hyper-elastic material models because of the high amount of experimentation that has been done to these types of materials. This material model has a greater number of available constants overall provided by the manufacuterer of the material. This matieral has the option of inputting all 6 possible elastic constants but all 6 are not required, just suggested for greater accuracy. Hyper-Elastic Ogden This model uses an elastic strain energy density function that is considered to be the most accurate at simulating very large deformation in rubber-like materials.

4 Elasto-Plastic Models become necessary after the material being simulated reaches the yeild point and enters the plastic range of the materials stress-strain curve (See Figure 3). Once in the pastic region, the object being deformed will not return to it s 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 pastic region. The yeild point will have also moved to a higher stress location then it was origonally, 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. Plasticity von Mises In this material model the material starts to yeild when the Von Mises stress at a single point reaches a specific expiramentally known constant scalar value called the yield strength of the material. This material model is widly used and is especially accurate when being used with a ductile material like metal. Plasticity Tresca In this material model the material starts to yeild when the maximum shear stress material equals the specific expiramentally known maximum shear stress at a single point in the model for that material. The Tresca model is generally more conserative then the von Mises model and Tresca does not support large strain plasticity formulation. Plasticity Drucker-Prager Is good at simulating the behavior of granular soil materials like sand or gravel. Only two parameters are absolutly necessary. The angle of internal friction, and the material cohesion strength. Like the Tresca model this material model also does not support large strain plasticity formulation. (Figure 3: Typical Stress-Strain Curve)

5 Super Elastic Models These materials can undergo extreamly large strains (as much as 20%) without reaching it s yeild point. After the first yeild point has been reached if loading contiunes the material softens and becomes more elasto-pastic in it s behavior. If loading contiues to increase the material will eventually reach a final yeild point where it will harden significantly under increased loading. The shape of unloading super elastic materials is much the same as loading them. When the load is back to zero there is no permanent deformation if the yeild strength was not exceeded. Nitinol This is the only Super Elastic Material Model in SOLIDWORKS. If the end user is trying to find the Super Elastic category in the material model types they will not find it. This category is under the word Nitinol in SOLIDWORKS Nonlinear Simulation. Viscoelastic This is the only material model type that is time sensitive. All of the other material models used in SOLIDWORKS Simulation 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 stressstrain curve even if the max magnitude remains the same.