To model the hardening process in Ansys Workbench, you need to define a material model that captures the plastic deformation and strain hardening behavior of the material. There are several plasticity models available in Ansys, such as multilinear hardening, isotropic hardening, kinematic hardening, etc. You can choose the model that best fits your experimental data and application.
One of the most commonly used plasticity models is the multilinear hardening model, which allows you to specify the true stress-strain curve of the material beyond the yield point. You can obtain this curve from a tensile test or from literature sources. You can also use Ansys to calculate the slope of the curve up to the yield point, which is the elastic modulus of the material.
To define a multilinear hardening model in Ansys Workbench, you need to follow these steps:
- In the Engineering Data section of Ansys Workbench, add a new material or edit an existing one.
- In the Material Models tab, expand the Structural branch and select Plasticity.
- In the Plasticity branch, select Multilinear Hardening.
- In the Multilinear Hardening table, enter the true stress and true plastic strain values for each point on the curve. You can also import these values from a file or copy and paste them from another source.
- In the Isotropic Elasticity branch, enter the Young’s modulus and Poisson’s ratio of the material. You can also use Ansys to calculate these values from the true stress-strain curve.
- Apply the material to your geometry in the Model section of Ansys Workbench.
- Set up your boundary conditions, loads, and analysis settings in the Setup section of Ansys Workbench.
- Solve your analysis and view the results in the Solution section of Ansys Workbench.
For more details and examples on how to define a multilinear hardening plasticity model in Ansys Workbench, you can watch this video1 or read this article2. You can also download the accompanying geometry and simulation files from these links34.
What is the difference between multilinear and isotropic hardening?
The difference between multilinear and isotropic hardening is that multilinear hardening allows you to specify the true stress-strain curve of the material beyond the yield point, while isotropic hardening assumes that the yield stress increases uniformly with plastic strain1.
Multilinear hardening is defined by a series of plastic strain/yield stress points, which can be obtained from a tensile test or from literature sources2. Isotropic hardening is defined by a single parameter, which can be calculated from the slope of the true stress-strain curve at the yield point3.
Multilinear hardening is more accurate and flexible than isotropic hardening, as it can capture the nonlinear and anisotropic behavior of some materials4. However, isotropic hardening is simpler and easier to implement, as it requires less input data and computational effort5.
I hope this answers your question. If you want to learn more about plasticity models and how to use them in Ansys Workbench, you can watch this video1 or read this article4.
What is the difference between true stress and engineering stress?
The difference between true stress and engineering stress is that true stress takes into account the changing cross-sectional area of the material as it undergoes deformation, while engineering stress assumes that the area remains constant12.
Engineering stress is calculated by dividing the applied force by the original cross-sectional area of the specimen, while true stress is calculated by dividing the applied force by the instantaneous cross-sectional area at each point in the deformation process12.
Engineering stress is simpler and easier to use in material analysis and design calculations, but it may not accurately represent the actual stress experienced by the material in situations where significant elongation or compression occurs12. True stress is more accurate and precise in capturing the material behavior in scenarios involving extensive deformations or non-uniform stress distributions12.
I hope this explains the difference between true stress and engineering stress. If you want to learn more about these concepts and how to convert between them, you can watch this video1 or read these articles234.
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