WS4: Eddy-Current Non-Destructive Testing¶
🔧 This is a hands-on industrial workshop — launch the simulator and open the WS4: Eddy-Current Non-Destructive Testing panel to attempt it interactively. Your score is based on how close each control is set to its optimal (target) value.
Scenario¶
You are a quality-control inspector using eddy-current testing to find hidden cracks in an aluminium aircraft panel without damaging it. Tune the probe's coil frequency and lift-off distance to maximize flaw sensitivity while keeping the background signal noise low enough to avoid false alarms.
Controls to Tune¶
| Control | Unit | Typical Range | Notes |
|---|---|---|---|
| Probe coil frequency | kHz | 1–500 | optimal ≈ 100 kHz |
| Probe lift-off distance | mm | 0.1–5 | optimal ≈ 0.5 mm |
| Signal amplifier gain | dB | 0–60 | optimal ≈ 30 dB |
What You'll Learn¶
- An eddy-current probe induces circulating currents in a conductive sample; a crack disrupts these currents and changes the coil's impedance, which is detected as a signal.
- Higher frequency confines eddy currents nearer the surface (thanks to the skin-depth effect) giving better sensitivity to surface cracks but less penetration depth for buried flaws.
- Increasing the 'lift-off' (probe-to-surface gap) strongly reduces coupling and sensitivity — lift-off variation is one of the most common sources of false signals in the field.
Suggested Approach¶
- Read the scenario carefully and identify which physical principle links each control to the outcome you are trying to achieve.
- Start with each control at its mid-range value and observe the live readout/score.
- Adjust one control at a time, noting how the score changes, before combining adjustments.
- Iterate until your score reaches 100% — the simulator awards a printable completion certificate at this level.
- Once satisfied, note down the final values you converged on and compare them with the underlying formula's prediction of the true optimum.
Safety Note¶
Real eddy-current NDT equipment is low-power and safe, but proper calibration against reference standards is essential before any real inspection.
Reflection Questions¶
- Which control had the largest effect on your score, and why does the underlying physics predict that?
- If two controls both improve the outcome, is their combined effect simply additive, or do they interact? Explain using the relevant formula.
- In a real industrial setting, which of these controls would be easiest to adjust, and which would be fixed by equipment/material constraints?
- What would happen to your result if one control were pushed far outside its optimal range — is the penalty symmetric on both sides?
- How does this workshop's scenario connect to one or more of the 18 experiments in this lab's User Guide?