Semi-Destructive Testing Methods
ESPI hole-drilling is a semi-destructive testing method that measures residual stresses by introducing a small drilled hole and using electronic speckle pattern interferometry (ESPI) to capture the resulting surface deformation.
| Feature | Barkhausen noise analysis | X-ray diffraction | ESPI hole drilling |
|---|---|---|---|
| Can measure/detect | ✔ Heat treatment defects ✔ Hardness changes ✔ Grinding burns ✔ Residual stress ✔ Microstructure analysis ✔ Material characterization | ✔ Heat treatment defects ✔ Hardness changes ✔ Grinding burns ✔ Residual stress ✔ Retained austenite content ✔ Microstructure analysis ✔ Material characterization | ✔ Residual stress |
| Materials | Ferromagnetic materials | Crystalline materials | Solid materials |
| Results | Qualitative with numerical scale | Quantitative | Quantitative |
| Measurement depth | Near surface (~100 μm depth) | Surface (~5 μm depth) | Sub-surface (starting from 30 μm) |
| Surface spatial resolution | ~1 mm | Down to ~0.3 mm | 4–7 mm |
| Depth profile resolution | – | ~5 μm (electropolishing limited) | Resolution/sensitivity ~30 μm with smallest bits |
| Depth profile measurement duration | – | 1.5 h | 10 min |