Introduction
Mechanical stress analysis is a critical aspect of electric motor design, ensuring the structural integrity of the system. Even if an electric motor delivers excellent electromagnetic and thermal performance, it must also maintain these characteristics consistently over time without exceeding the safe stress limits of its materials.
For radial flux electric motors, which have a cylindrical shape and a uniform active length along the stack, analyzing one or two representative laminations can provide highly accurate stress predictions for the entire motor.
Ansys offers multiple simulation workflows for this task. In this blog, we will explore two methods:
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Ansys Mechanical – a general-purpose structural FEA tool offering detailed modeling and customization.
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Motor-CAD Mechanical Module – a dedicated electric motor design tool with a streamlined mechanical analysis workflow.
You can download the files used in this project here: ElectricMotorStressFiles.zip
1. Ansys Mechanical Workflow
1.1 Importing Geometry
In this example, we import the geometry directly from Ansys Maxwell (created using the Motor-CAD e10 IPM template).
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Open an Ansys Workbench project.
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Import the Maxwell 2D model into the workspace.
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Drag a Static Structural block next to the Maxwell block and couple the geometry.
(Alternatively, you can right-click Geometry → Import Geometry to load a model directly.)
Ensure the Analysis Type is set to 2D for a 2D model, or 3D if running a full 3D simulation.
1.2 Parts & Materials
Open Mechanical (Model):
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Suppress non-rotating parts (stator, coils, etc.). Keep only the rotor, magnets, and shaft.
Assign materials (editable in Engineering Data; temperature dependence can be added):
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Rotor laminations: Laminated steel (NO18)
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Magnets: N42
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Shaft: Cast iron
1.3 Contacts (Magnets ↔ Rotor/Shaft)
By default, contact detection can connect parts across small gaps. To prevent this:
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Set the Contact Detection Slider to 100% so only touching bodies are connected.
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Right-click Contacts → Create Automatic Connections to regenerate the contacts.
What we’re modeling here: the magnet outer edge is attached to the rotor OD, while the other side has a 0.2 mm gap to reflect manufacturability (a “hanging” fit). Alternatively, you can fill with epoxy/adhesive and set those interfaces to bonded.
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For magnet–rotor interfaces, set Frictional contact and use these typical coefficients (Carvill, Mechanical Engineer’s Data Handbook, 1994):
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Epoxy-bonded Magnet–Rotor: 0.1–0.3
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Steel–Cast Iron (dry): 0.4–0.5
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1.4 Meshing
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Insert a Mesh Connection Group to resolve magnet–rotor interfaces; set its tolerance slider as tight as possible to avoid unintended connections. Then Detect Connections.
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Enable Capture Curvature and reduce Curvature Normal Angle to refine corners.
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Adjust element size as needed and visually inspect the mesh quality.
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Note: If you see mesh-connection errors, reduce element size around the interfaces.
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1.5 Loads, BCs & Requests
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Right-click Static Structural and insert:
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Rotational Velocity: 15,000 rpm about the Z-axis (applied to all rotor bodies)
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Frictionless Support: apply on appropriate edges to constrain motion
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Thermal Condition (optional) if you’re doing temperature-dependent stress
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Under Solution, request:
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Equivalent (von Mises) Stress
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Total Deformation (optional)
1.6 Solve & Results
Run the analysis (typically 1–10 minutes, depending on complexity).
Results:
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Max von Mises stress: 413.91 MPa, concentrated near magnet slot corners
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Max deformation: 0.03757 mm at the outer side of the rotor
2) Motor-CAD Mechanical
Motor-CAD provides a direct, motor-specific workflow.
2.1 Setup
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Open the e10 PMSM example (8 poles, 48 slots; 200 kW, 15,000 rpm max).
e10 200kW PMSM model,8 pole 48slots design. 15000 maximum rpm.
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Go to Mechanical Model.
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Under Input Data → Settings, set Maximum Mesh Length = 0.1 mm for higher mesh density.
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In Calculation:
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Set Shaft Speed = 15,000 rpm
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Include magnets with Adhesion Factor = 1
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(25R2 update) Include shaft
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Set Radial Interference = 0.02 mm to simulate press fit between rotor and shaft
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Run the model.
2.2 Results
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Stress: Maximum at magnet slot edges (same location as Mechanical).
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Peak stress = 368.42 MPa (lower than Mechanical’s 413.91 MPa).
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Deformation: Maximum at outer center of rotor = 0.039 mm (very close to Mechanical’s 0.03757 mm).
Safety Factor (Yield / Max Stress):
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Motor-CAD: 1.208
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Mechanical: 1.075
Both indicate the rotor lamination remains below yield at 15,000 rpm, so the design is structurally sound.
Conclusion
Both Ansys Mechanical and Motor-CAD Mechanical provide reliable insights into rotor stress and deformation, with closely matching results. Motor-CAD offers a fast, motor-focused workflow, while Ansys Mechanical allows detailed customization for complex contact and meshing scenarios. Using both approaches together can give designers confidence in the mechanical integrity of high-speed electric motors, ensuring safe operation under maximum load conditions.
Ozen Engineering Expertise
Ozen Engineering Inc. leverages its extensive consulting expertise in CFD, FEA, optics, photonics, and electromagnetic simulations to achieve exceptional results across various engineering projects, addressing complex challenges such as antenna design, signal integrity, electromagnetic interference (EMI), and electric motor analysis using Ansys software.
We offer support, mentoring, and consulting services to enhance the performance and reliability of your electronics systems. Trust our proven track record to accelerate projects, optimize performance, and deliver high-quality, cost-effective results. For more information, please visit https://ozeninc.com.
If you want to learn more about our consulting services, please visit: https://www.ozeninc.com/consulting/
CFD: https://www.ozeninc.com/consulting/cfd-consulting/
FEA: https://www.ozeninc.com/consulting/fea-consulting/
Optics: https://www.ozeninc.com/consulting/optics-photonics/
Photonics: https://www.ozeninc.com/consulting/optics-photonics/
Electromagnetic Simulations: https://www.ozeninc.com/consulting/electromagnetic-consulting/
Thermal Analysis & Electronics Cooling: https://www.ozeninc.com/consulting/thermal-engineering-electronics-cooling/
