Line Scan Thermography™ (LST™) in a noncontact inspection method developed by NASA using dynamic thermography in which a heat source scans an object's surface while an infrared camera moves in tandem. LST™ has been previously used for thickness testing of boiler tubes, and it is now being applied to composites. The dynamic heat application allows observation of a variety of subsurface defects. Given the novel heat application and image generation procedures, LST™ lends itself for inspection of large areas. This technique produces a real-time digital image of the section inspected, and it is easily implemented both in the field and in different manufacturing processes, making it easier to deploy than other thermography techniques better suited for laboratory analysis.

LST™ Scanning Cart

Designed to travel over flat surfaces, like a composite deck plating of a ship, to thermographically inspect for imperfections. The system has driven wheels to deliver continuous rolling scans of the deck.

Portable Scanner

This light and portable scanner is equipped with an active suction cup, enabling attachment to flat and slightly curved surfaces like a composite fuselage. Adapted with magnetic wheels to attach to metallic surfaces like boiler tubes, the scanner has stepper motor driven axis to move the camera and heat source over the test object.

Gantry

LST™ isn't just a portable scanning function. Line Scan Thermography™ can also be mechanized and subsequently attached to a Gantry or an existing scanner, which provides one axis of motion. Customized scanners can also be provided to meet any customer requirement.

Advantages of LST™

The capabilities of the LST™ to examine large-scale components make the cutting-edge thermographic technique impressive. Yet its advantages are more than just large-scale testing capacity.

Lateral motion provides heating uniformity and allows image processing capabilities that improve distinction among defect region, image noise, and sound area - providing the clearest representation of any prospective fault or defect. In addition, those large-scale inspections don't cause any loss in resolution - no matter the size of the inspected component. So a scan of a large subject will be no less sharp and provide no less information than a scan of a normal-sized component.

And the image reconstruction procedure provides an intentional in-plane variation in heat disposition that can be used to analyze material with directional properties.

Summary

The LST™ technique has been used successfully for non-destructive testing of laminate composites of different thicknesses, and honeycomb structures with composite skin among other materials.

It can also be utilized on fiber reinforced plastics, concrete surfaces, and in general materials that will react to a thermal excitation evaluation.

The success of LST™ depends on proper optimization of the scanning parameters, but the simplicity of the technique and the apparatus provides significant freedom for inspection of various structures.