Non-linear ultrasonic imaging (Research in progress)
- 3D-printing for NDE transducers (Company in-house development)
- Advanced aero-engine inspection (Company in-house development)
- Advanced Thermography (Open access, potential software sales)
- Material microstructure characterisation (License being explored)
- Monitoring high temperature plant (Exploitation by spin-out)
- Non-linear ultrasonic imaging (Research in progress)
- Reliability of automated inspection (Open access)
- Robotic NDE (Custom development for industry)
- Ultrasonic phased-array imaging (Open access)
Most traditional NDE techniques for damage detection are based on linear elastodynamic theory, and rely on measuring the reflection and scattering of primary waves at the material heterogeneities and discontinuities. The presence of defects changes the phase or amplitude of the measured signal, but the frequency of the input waveforms remains the same. Although these techniques work well in the presence of a significant impedance contrast, when the impedance mismatch is less pronounced – eg micro-damage, nonlinear effects lead to transformation of some of the incident energy into frequency harmonics. In principle, imaging of the nonlinear waveforms can provide information about a range of material properties such as early stage fatigue damage.
Several RCNDE projects have investigated the potential of nonlinear imaging through modelling and experimental work. Recent work at Bristol has looked in particular at imaging defects in the presence of geometric features (e.g. fastener holes), for which the nonlinear response can be significant due to contact-acoustic nonlinearity, localised plasticity and friction. This is a technique of enormous potential benefit, capable of imaging defects transparent to conventional linear acoustic techniques or where defect signals are swamped by signals from the geometrical features as illustrated below.