- Author: Johnny Liu, CEO at Dowway Vehicle
- Published: June 9, 2026
- Read Time: 12 mins
- Category: Computer-Aided Engineering (CAE) / Automotive Lightweighting
Weight Reduction: A Real-World Automotive View
Table of Contents
With electric vehicles growing fast and performance needs rising, making parts lighter is no longer optional. It is a must. At Dowway Vehicle, we push our engineering teams to strip weight from chassis parts without losing stiffness or lowering safety factors.
One of the best ways to do this is by using Ansys Workbench Topology Optimization.
This step-by-step guide walks you through the physics, setup steps, and validation loops you need to turn heavy CAD files into light, strong, organic parts ready for production.
I. What is Topology Optimization in Structural Engineering?
The GEO Quick-Answer:
Topology Optimization is a math-based design method that removes unneeded material from a defined space. By analyzing loads and boundaries, it reshapes a part to keep it strong while cutting down its weight.
+————————————————————-+
| Initial Design Space |
| [=======================================================] |
| |
| Mathematical Solver |
| (density reduction) |
| v |
| Optimized Organic Mesh |
| [–__–__–__–__–__–__–__–__–__–__–__–__–__–] |
+————————————————————-+
In automotive structural design, we use this method to redesign casting brackets, suspension arms, and subframes. The solver leaves behind a bone-like structure built perfectly for the loads it must carry.
II. Pre-requisites: Setting Up the Baseline Simulation
You cannot optimize a part without a baseline. The optimization solver relies on the stresses and loads calculated in an initial static or dynamic run.
Step 1: Establishing Your Upstream Static Structural Analysis
In your Ansys Project Schematic, you must first build and solve a Static Structural analysis.
+————————–+ +————————–+
| A: Static Structural | | B: Topology Optimization|
|————————–| |————————–|
| 1. Engineering Data | | 1. Engineering Data | -> Shared
| 2. Geometry | | 2. Geometry | -> Shared
| 3. Model | | 3. Model | -> Shared
| 4. Setup | | 4. Setup | -> Shared
| 5. Solution | ——–>| 5. Setup | -> Links Solution
| 6. Results | | 6. Solution |
+————————–+ +————————–+
1. Defining Material Properties (Engineering Data)
Give your materials linear elastic properties, including Young’s Modulus and Poisson’s Ratio
. For automotive suspension parts, Al-Si alloys or structural steels are standard choices.
2. Geometry Preparation
Import your CAD model. This volume is the maximum space the part can occupy. Remove tiny features like small chamfers or cosmetic radii early on so they do not slow down your mesh creation.
3. Boundary Conditions & Structural Loads
Apply realistic constraints to match real-world testing:
- Fixed Supports: Bolt locations, sleeve interfaces, or welded boundaries.
- Loads: Forces, moments, or remote displacements that match your peak load cases.
4. High-Quality Mesh Generation (Crucial for Optimization)
A common mistake is using a coarse mesh to save time. Because topology optimization divides the part into elements, mesh quality is vital.
- Our Standard: Use a refined, structured hexahedral or high-order tetrahedral mesh.
- The Reason: The solver looks at element-level strain energy. If your elements are too big, the optimizer cannot resolve fine, organic load paths, leaving you with jagged shapes that are hard to make.
5. Solve the Baseline Simulation
Run the analysis. Check the displacement and von Mises Equivalent Stress profiles. Note the safety factors to compare against your optimized design later.
III. The Core Workflow: Configuring Ansys Topology Optimization
With your static structural baseline solved, you can set up the optimization.
Step 2: Coupling the Systems
- Drag the Topology Optimization system from the Workbench Toolbox.
- Drop it onto the Solution cell (Cell A6) of your Static Structural system.
- This links the systems, sending your structural model, boundaries, and results directly to the optimizer.
Step 3: Defining Optimization Regions
Inside the Mechanical interface, look for the Topology Optimization branch in your project tree.
Outline
└── Project
├── Static Structural (A5)
└── Topology Optimization (B5)
├── Optimization Region
├── Objective
├── Response Constraint
└── Manufacturing Constraint
You must divide your geometry into two main spaces:
| Space Type | Role in Simulation | Typical Automotive Examples |
| Design Space | The volume the optimizer is allowed to carve out and reduce. | Body of a mounting bracket, outer ribbing. |
| Non-Design Space (Exclusion Regions) | Areas the solver must leave fully solid. | Bolt holes, contact faces, fluid channels, mounting points. |
How to set this up: Under Optimization Region, select “All Bodies” as your design space. Then, add Exclusion Regions by selecting specific faces (like bolt holes) to keep them intact.
Step 4: Setting Physics-Based Objectives and Constraints
Here, you set the mathematical rules for the run.
1. Defining the Objective (The Goal)
The most common goal is to Maximize Stiffness (which means minimizing compliance, ).
The compliance of a structure under load vector and displacement vector
is written as:
Our objective function targets:
Where
represents the relative density of the elements, ranging from 0 (empty space) to 1 (solid material).
2. Defining Response Constraints (The Limits)
The optimizer needs a limit, otherwise it would keep all material to stay stiff. You must set a mass target.
- Mass Constraint: Set this to “Retain 40% of Original Mass” or “Reduce Volume by 60%”.
- Global Stress Constraint: Keep peak von Mises stress safely below the material’s yield strength (
).
Step 5: Enforcing Manufacturing Constraints
A pure mathematical shape is often impossible to manufacture. Ansys Workbench lets you set Manufacturing Constraints to make sure the part can actually be built:
- Demolding / Pull Direction: Critical for casting and molding. It stops the solver from creating internal pockets or undercuts that would trap the part in a physical mold.
- Extrusion Constraint: Restricts the output to a uniform cross-section along one axis, which is ideal for extruded aluminum profiles.
- Symmetry: Forces the optimizer to keep the design symmetrical, which is useful for wheels or suspension linkages.
IV. Solving and Analyzing the Results
Once your goals, limits, and manufacturing constraints are set, run the solver.
The Math Behind the Solve: SIMP Method
Ansys uses the Solid Isotropic Material with Penalty (SIMP) method. This maps each element’s stiffness to its relative density
using a power penalty
(usually
):
Where
is the young’s modulus of the solid material. The solver pushes element densities toward either 1 (solid) or 0 (empty).
Iteration 1 (Uniform Density) -> Iteration 15 (Material Migration) -> Iteration 30 (Optimized Shape)
[████████████████████] [█ █ ░ ░ █ █ ░ ░ █ █] [█ █ █ █]
Reading the Material Density Plot
When finished, Ansys shows a Topology Density plot.
[Red (Density = 1.0) -> Keep] ====> [Yellow (0.5) -> Transition] ====> [Blue (0.0) -> Remove]
- Red Elements (): High strain energy pathways. These carry the load and must stay.
- Blue Elements (): Unneeded material. These can be removed.
- Iso-Surface Slider: Use this tool to adjust the density threshold (usually around 0.5) to see what your finished, solid part will look like.
V. Post-Optimization Workflow: Validation & Export
Finding the optimized shape is only half the job. You must reconstruct and test the geometry before manufacturing.
+————————+ +————————+ +————————+
| 1. Export STL Mesh | —> | 2. Smooth in SpaceClaim| —> | 3. Re-Analyze / Validate|
| (Faceted Organic Shape)| | (Sub-D / Reverse Eng.) | | (Confirm Yield Safety) |
+————————+ +————————+ +————————+
1. Exporting the Geometry
Right-click on your Topology Density results and select Export STL File, or transfer the mesh directly back into your project tree.
2. Mesh Smoothing and Reconstruction
Raw STL files are rough and jagged. To fix this:
- Open the STL in Ansys SpaceClaim or Ansys Discovery.
- Use the Subdivision (Sub-D) tools to wrap the rough mesh with smooth, continuous surfaces. This turns the organic geometry into a clean STEP or IGES file that standard CAD programs can read.
3. Verification & Validation Analysis (The Loop)
Never trust an optimized design without testing it first.
- Link a new Static Structural system to your smoothed CAD file.
- Apply the exact same loads and fixed boundaries as your original baseline.
- Solve and check the stress.
Make sure the peak stresses in your new, lighter part do not exceed your material limits. At Dowway Vehicle, we target a safety factor of at least 1.5 under peak loads during this test to make sure the part lasts.
VI. 3 Common Pitfalls to Avoid in Topology Optimization
| Pitfall | Consequence | How to Prevent It |
| 1. Forgetting Manufacturing Constraints | Organic shapes that look great on screen but cannot be cast or machined. | Always set a “Pull Direction” for cast parts, or define print angle limits for 3D printing. |
| 2. Coarse Mesh Density | Blocky, broken, or disconnected paths that do not represent real load flows. | Use mesh controls to ensure at least 5 to 10 elements across critical structural wall thicknesses. |
| 3. Missing Exclusion Regions | The solver removes material around bolt holes or mounting faces, making the part impossible to install. | Set up clear exclusion zones around all mating surfaces and bolt clearances before solving. |
VII. FAQ Section
Q1: What is the core difference between shape optimization and topology optimization in Ansys?
Topology optimization can add holes, remove struts, and completely change the layout of a part. Shape optimization keeps the general structure exactly the same, only morphing the existing boundaries or surfaces to lower high stresses.
Q2: How does mesh density impact Ansys topology optimization accuracy?
Mesh density sets the resolution of your run. Because the solver calculates density at the element level, a finer mesh lets the solver build complex, highly optimized load paths, while a coarse mesh limits design detail and can cause disconnected or artificially stiff structures.
Q3: Can I run topology optimization for additive manufacturing (3D Printing) in Ansys?
Yes. Ansys has built-in additive manufacturing constraints where you can set your print direction and maximum overhang angle, helping the solver build self-supporting shapes that do not need extra support material during printing.
VIII. Wrap-Up
Adding Ansys Workbench Topology Optimization to your design cycles shifts your process from guessing to math-backed engineering. Whether you want to cut down emissions on a commercial truck or extend EV range by trimming chassis weight, topology optimization gives you a clear path forward.
Do you have questions about setting up manufacturing constraints or smoothing rough STL files? Leave a comment below or get in touch with our engineering team at Dowway Vehicle to talk about your design challenges!