Several immersion systems have recently been installed or are currently in manufacture. Of all the different applications for USL systems, the most widespread is the inspection of titanium alloy parts for aero-engine applications, particularly fan blades in their various forms, with more than 25 or these units in operation on various sites throughout the world. The latest of these installations is a five axis machine for testing the bond at the root section of these blades.
The probe is mounted on a swinging arm which scans across the arc of the blade root. The angle and position of the probe has to be controlled so that the sound beam is refracted at the water/root interface, generating a beam which meets the bond line at right angles. The position of all axes and gates is pre-programmed for various fan blade types so that scan plans are easily recalled and implemented.
Two further systems are in progress for testing the blade and other similar diffusion bonded parts. These are 6 axis machines with full complex contour following facilities, coupled with high frequency ultrasonic and data acquisition electronics.
A further system has been completed for inspection of a titanium allow sandwich structure made by brazing thin sheets. After brazing and before final forming the resulting product is inevitably slightly distorted in a random way, so a contact probe follower is used to ensure that the sound beam is maintained normal to the surface. This results in a very simple 2 axis scanning mechanism, but the ultrasonics and data acquisition required to inspect thin sheets is very demanding.
Two sheets are inspected simultaneously using a PM30 Pulser Receiver and multiplexer with focussed 20MHz probes.