Shape Memory Alloy (SMA) Simulation in Ansys Mechanical: Part 2
Hi, this is MingYao from Ozen Engineering, Inc. In this video, I'll demonstrate how to set up a shape memory alloy (SMA) simulation using ANSYS Workbench. Today, we're focusing on the shape memory model.
Introduction
Previously, I created a simulation video using the superelastic model, which is excellent for modeling very stretchy metal structures in 3D. However, it only accounts for superelasticity. The shape memory model combines the effects of temperature changes, allowing us to model both temperature changes and shape memory effects in shape memory alloys. It also includes features like plasticity and other phenomena.
Model Setup
There are two separate shape memory effect models. In this session, I'll create a Nitinol model and input the shape memory material properties. Similar to the superelastic model, we need to specify:
- Young's Modulus: 60,000 (in millimeters and kilograms)
- Poisson's Ratio: 0.36
The shape memory option allows us to specify additional parameters:
- Martensite Modulus
- Hardening Parameter (H): 933 MPa
- Reference Temperature: Room temperature
- Elastic Limit (E): 122 MPa
- Temperature Scaling Parameter (Beta): 20
- Maximum Transformation Strain: 0.086
- Load Dependency Parameter: Set to zero
Simulation Process
One of the significant benefits of the shape memory effect model, in addition to superelasticity, is its ability to simulate beam elements. This allows us to treat Nitinol as a wire with a defined cross-section, reducing the computational cost significantly.
Here's how the simulation is set up:
- Assign a fixed support and insert a fixed rotation to prevent rotational degrees of freedom.
- Use four steps with auto time stepping enabled, setting each step to 20.
- Set one side as a fixed support and the other side for displacement, adjusting x and z to zero.
- Simulate tension and compression by pulling out to 2, compressing to -2, and setting to zero.
Results and Analysis
The simulation shows the deformation under exaggerated conditions, highlighting the pulling and compressing actions. The force reaction on displacement is plotted, showing a transformation that is symmetric.
By adjusting the temperature, we can observe phase changes. For example, heating to 40 degrees shifts the phase changes, and at 100 degrees, further variations are evident. Cycling the temperature between 20 and 50 degrees demonstrates different effects on the results.
Advanced Features
The shape memory model in ANSYS includes:
- Superelastic Model
- Shape Memory Model
- Plasticity Model
These models allow for advanced simulations, including plasticity, thermal strain, transformation strain, and plastic yielding. The advanced shape memory alloy model includes additional material properties and features like tension-compression asymmetry response and smoothing behavior for hardening functions.
Conclusion
This demonstration highlights the capabilities of the shape memory alloy model in ANSYS, considering temperature changes and transformations while modeling beam elements. For more information, refer to the ANSYS Learning Hub, which offers comprehensive documentation and training materials.
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Thank you, and have a great day!
Hi, this is MingYao from OZ Engineering and in this video I'll be looking at how to set up a shape memory alloy (SMA) simulation using ANSYS Workbench. Today we're going to use the shape memory model.
So I've done a previous simulation video with super elasticity, and the idea here is that the super elastic model allows for modeling of very stretchy metal structures in 3D, with super elasticity only.
The shape memory model, on the other hand, combines the effect of temperature change, allowing for the modeling of temperature change and shape memory effects of the SMA. It also has the ability to include things like plasticity and a variety of other phenomena.
There are actually two separate shape memory effect models, so I'm going to create a model and put in the shape memory material properties.
Similar to super elasticity, we need Young's modulus, which I'm going to switch to millimeters and kilograms here and set to 60,000, and the Poisson's ratio of 0. 36. The shape memory option allows for the specification of martensite modulus, so for now, I'm going to specify the same one.
And then there are a number of other parameters, such as a hardening parameter, reference temperature, elastic limit, temperature scaling parameter, maximum transformation strain, and low dependency parameter.
We can convert some of our test data into this by looking into the ANSYS Learning Hub, which has a handy little chart that allows for the specification of hardening parameters.
So we can see that we have the hardening parameter, R, beta, elastic limit, and maximum transformation strain, which defines the difference between compression and tension. So, the first value is H, which is our hardening parameter.
I've done the calculation, and this works out to something like 933 megapascals. For the tempered reference temperature, I'm going to set this to room temperature. We're not going to actually model the temperature effect, although we certainly could.
Instead, we're going to just run this as a super elastic type of material, just to compare. The elastic limit is 122 megapascals.
Temperature scaling parameter is 20. Maximum transformation strain is 0. 086. One of the big benefits of the shape memory effect model, in addition to super elasticity, is that it allows for the simulation of beam elements.
So we can treat our nitinol as a nitinol wire with some defined cross section, instead of modeling it in full 3D. This can obviously dramatically reduce the computational cost of our simulation.
I'm going to assign a fixed support here and I'm actually also going to insert a fixed rotation, so the rotational degrees of freedom don't move. I'm going to have four steps, with auto time stepping on. I'm going to have 20 steps for each one.
We're going to leave a large succession off, otherwise we get nonlinear buckling effects when we try to do the compression. One side is a fixed support, the other side is going to be a displacement, and we're going to set x and z to zero.
And this, we're going to pull out to 2, to take it back to 0. Pull it out to compress the minus two and set this to zero. So, it's going to be tension and compression, and we're going to try to generate the same kind of curve.
In the next part of the video, we'll go over the results of the simulation. Thank you for watching. If you have any questions, please visit the OZ Engineering website or contact us at [info@ozengineering.com](mailto:info@ozengineering.com).
