AIR-COUPLED ULTRASONIC TESTING FOR ADHESIVE BONDS
Non-destructive & coupling agent-free testing of bonds of multi-material components for defects and flaws
Necessity of Testing Adhesive Bonds
In modern production processes, different materials are more and more bonded to each other by means of an adhesive bond in order to reduce the weight of the vehicle in the automotive industry and thus reduce material consumption, for example. Especially plastics are bonded with metals or metals with metals. After manufacturing, it is no longer possible to visually check the correctness of the bond. However, it is of great importance. The ultrasonic inspection system “yoUScan” is ideally suited for a retrospective check.
How an Air-Coupled Ultrasonic Test Works
Without touching the material to be inspected, the yoUScan system can check the bond for defects using air-coupled ultrasound. Two different methods can be used for the inspection:
One is by damping, the other is by the transit time of the sound. Each material attenuates sound to a different extent due to its physical properties. The damping values between the air and a bonded joint are so strong that air pockets in the bonded joint can be clearly detected. As with damping, the transit time also depends on the physical properties of the material. The differences between air and adhesive layer are also clearly distinguishable here.
Practical example: Bonding of steel panels
The photo shows a top view of two bonded steel plates with a thickness of 1.5mm. The bonded joint was tested with CT and ultrasonics (C‑scan) to contrast the images. In both cases the air gap or adhesive is clearly visible.