Abstract
The microscopic size and the closed characteristics of zigzag line defects at the root of friction stir welded joints frequently result in a detection inability by off-the-shelf ultrasonic weld inspection techniques. To overcome this problem, we take advantage of a non-linear ultrasonic approach by employing a slanted contact pitch-catch mode scanning using chirp-coded excitation with subsequent pulse-inversion analysis. We validated that the observed nonlinearity correlates well with the micro-crack density along the weld path. Doing so, hot spots in the pulse-inversion chirp-coded weld harmonic images can be interpreted as zones with high concentrations of micro-flaws.
| Original language | English |
|---|---|
| Article number | 75 (2017) |
| Pages (from-to) | 1-10 |
| Number of pages | 10 |
| Journal | Journal of Nondestructive Evaluation |
| Volume | 36 |
| Early online date | 23 Oct 2017 |
| DOIs | |
| Publication status | Published online - 23 Oct 2017 |
Keywords
- Friction stir welding
- Micro-crack density
- Zigzag line defects
- Continuous oxide film
- Pulse-inversion
- Chirp-coded sccitation
- Harmonic imaging
- Non-destructive testing