Laser ultrasonic testing (UT) systems provider PaR Systems’ LaserUT product has been used to perform nondestructive inspections (NDIs) on over 35 000 parts produced by Joint Strike Fighter military aircraft vendors and suppliers, including US aerospace and defence company Lockheed Martin, reports GM Carel Swart.
The company’s LaserUT system was developed and built by PaR Systems, in Texas, over the past 25 years, in collaboration with Lockheed Martin, says LaserUT programme manager Alan Norris.
“LaserUT is the only laser in the world that is optimised for doing laser UT for composite materials, owing to the high quality of the signal” states Norris.
In the past, structures were built essen- tially as flat metal surfaces, which could easily be inspected using X-ray machines and water-jet systems, besides others.
However, in recent years, more complex components are being built using lighter, stronger composite materials, which are difficult to inspect using traditional methods, he says.
Norris adds that laser UT is an enabling tech- nology, allowing the inspection of part configu- rations previously considered uninspectable by automated systems.
Swart explains that PaR’s LaserUT system uses a pulse-echo implementation of laser ultra- sonics to inspect the integrity of the surfaces of composite structures.
With Laser NDI, a pulse is sent into the metal or composite surface, which sends a signal to another laser that enters the signal into a diagnostic system. “Using that signal, one can determine whether there is interference in terms of the structure’s integrity,” he says.
Swart notes that Lockheed Martin needed a system such as the one provided by PaR so that the composite structures could be certified as safe.
Meanwhile, Norris points out that laser ultrasonic NDI has several advantages over water-based NDI.
Firstly, the LaserUT system does not have to be close to the part it is testing, and the laser beam does not have to strike the surface of the component directly, as with water testing. “It can strike the surface off-angle up to about 45º,” he says.
Laser systems are also effective in the inspec- tion of complex-shaped composite aircraft parts, such as F-35 skins and nacelles, adds Norris.
“LaserUT is highly advantaged for applications with challenging structures that would typically require rigid tooling and custom transducer assemblies, and can be up to ten times faster than state-of-the-art traditional UT systems,” he says.
Further, this laser system requires a lower operator skill level than water-based testing systems. “The system is easy to use and acquires the same high-quality data, whether the operator has just been qualified, or has years of experience in ultrasonic technology,” Norris points out.
The process of positioning the component and the lasers is also automated, which means that the pathway for the lasers to test a specific component need only be created once.
“The next time that specific part comes in, the barcode on the part’s paperwork is read and the system guides the operator in placing the component in the correct position,” he explains.