Contact Analysis
When two parts touch and press against each other — finding the contact area and preventing penetration.
1. What is it?
Contact analysis handles the interaction between two bodies that touch:
- Node-to-surface penalty contact: prevents penetration by applying spring-like forces at contact interfaces.
- Hertz contact mechanics: validates the classic sphere-on-flat contact problem.
- Coulomb friction: models sliding friction between surfaces.
"This bolted joint: how does the load transfer between the plates? What's the contact pressure?"
2. When do I use it?
| Use when | Don't use for |
|---|---|
| Two or more parts touching | Single part (use Static Structural) |
| Bolted joints, press fits | Very fast impact (use Explicit Dynamics) |
| Bearing contact, seal compression | Fluid flow (use Multiphysics) |
| Indentation testing | Thermal expansion only (use Thermo-Mechanical) |
3. The flow — every action described
Step 1: Design (geometry)
What you do: Draw two or more parts that touch.
How:
- Click Design tab
- Create or import two separate geometries that overlap or touch
- Define a contact pair: master surface and slave surface
Why: The solver needs to know which surfaces can come into contact.
Step 2: Boundary (material + supports + loads)
What you do: Tell FEA Lab what it's made of, how it's held, and what pushes.
How:
- Click Boundary tab
- Material: Pick from the library or define your own
- Supports (BCs): Fix one part, apply load to the other
- Contact: Define friction coefficient (0 = frictionless, >0 = friction)
- Loads: Apply force or displacement to push parts together
Why: Contact needs both parts to be properly constrained and loaded.
Step 3: Mesh
What you do: Cut the parts into small cells.
How:
- Click Mesh tab
- Adjust mesh size — finer at contact interface
- Click Generate
Why: Contact pressure gradients are steep — you need resolution at the interface.
Step 4: Simulate → Contact
What you do: Run the contact solver.
How:
- Click Simulate tab
- Select Contact
- Set contact stiffness (penalty parameter)
- Click Run
- Wait for convergence (seconds to minutes)
Why: The solver iteratively finds the contact area and prevents penetration.
Step 5: Results
What you do: Read the contact pressure and penetration.
How:
- Click Results tab
- View contact pressure contour — where are they pressing?
- View penetration — is the penalty working?
- View von Mises stress — stress in both parts
Why: The contact pressure shows load transfer. Penetration should be minimal.
4. Reading your results
Contact pressure
| Color | Meaning |
|---|---|
| Blue | No contact |
| Red | High contact pressure |
Good: Contact pressure is smooth and within material limits. Bad: Spikes indicate insufficient mesh resolution or penetration.
Penetration
| Value | Meaning |
|---|---|
| ≈ 0 | Penalty contact working |
| > 0 | Penetration occurred — increase penalty stiffness |
Friction shear
| Color | Meaning |
|---|---|
| Blue | No sliding |
| Red | High shear stress at interface |
5. Boundaries of truth
What's validated
| Case | Reference | Error |
|---|---|---|
| Hertz sphere-on-flat (F-δ) | Hertz theory | < 5% |
| Patch test (pressure transmission) | Exact | Machine precision |
| 2D frictionless contact | Analytical | < 2% |
What's NOT covered
- Self-contact — one part folding onto itself
- Finite sliding — large sliding motions
- Impact contact — dynamic contact (use Explicit Dynamics)
- Thermal contact — heat transfer across interface
- Adhesive contact — bonding between surfaces
Common mistakes
| Mistake | Fix |
|---|---|
| Insufficient mesh at contact | Refine mesh at contact interface |
| Too soft penalty stiffness | Increase penalty — reduce penetration |
| Missing contact pair | Define master and slave surfaces |
| Parts not touching initially | Ensure small overlap or initial gap |
| No friction coefficient | Set μ = 0 for frictionless, μ > 0 for friction |
See also
- [Static Structural](static-structural.md) — for single-part analysis
- [Explicit Dynamics](dynamics.md) — for impact contact
- [Nonlinear](nonlinear.md) — for plastic deformation during contact
Keep exploring
Open the interactive workspace — mesh, solve, validate and export in the browser.
Start a guided solve