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Air-Coupled / Airscan Ultrasonics
Use air as couplant for your ultrasonic inspections
Water, the most commonly used couplant in ultrasonic testing, is not compatible with certain industrial processes. It may cause permanent damage to many materials, especially to some of the advanced materials used by the aerospace industry. Therefore, QMI developed the unique AIRSCAN® instrumentation and technique, which uses the air of the natural environment as couplant. As such, AIRSCAN is considered a noncontact ultrasonic inspection method. The method also allows increasing the scanning speed without being constrained by any couplant.
The SONDA 007CX is the multi-frequency AIRSCAN® instrument for air-coupled ultrasonic testing.
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| SONDA 007CX, Air-Coupled Instrument |
AIRSCAN Transducers |
AIRSCAN TRANSDUCERS Highly attenuative materials are readily tested using 120kHz ceramic transducers (ceramic transducers are more robust than electrostatic transducers). Our new 225kHz transducers provide an optimum combination of good resolution and penetration for general-purpose applications. The high frequency of 400kHz transducers yield the best lateral resolution while still providing good penetration on many materials, while the low frequency 50 kHz transducers are used for the most attenuative materials (thick section foam core & multi-septum parts).
Typical applications include:
| Products Tested | Inspection | Enduse and Application |
| Gr/E Laminates | C/C Aircraft Brake Discs | Production Feedback Control for Pultrusions |
| Solar Panels | Uncured Prepreg Lay-ups | ARALL Panels |
| Honeycombs | Impact Damage Assessment | Composite Fan Blades |
| Perforated Honeycombs | Impact Damage Repair Test | Aerofoils and Components |
| Cork Coated Honeycombs | Multiple Layer Aluminum Sheet Bonding | Composite Aluminum Balsa |
| Solar Cell Bonding | Corrosion Detection (Aged Aircraft) | High-Temp Applications |
| Aircraft Floor Panels | Solid Rocket Propellant | Fiber Reinforced Pressure Vessels |
| Foam Sandwich Panels | Robotics Sound Sight Recognition (Nuclear) | Materials Characterization |
Multifrequency scanning offers an additional tool for defect evalution, as shown in the following C-scans. Two carbon-carbon silicon carbide coated (SiC) panels having a thickness of 1/8 in., which were fabricated during an R&D stage, were tested ultrasonically with air-coupled transducers at two different frequencies. The C-scans were performed at a speed of 6 in./sec, with a step size of 0.030 in.
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| Fig a. C-scan image of a 6 in x 8 in. section of a SiC panel scanned with 400 kHz air-coupled transducers. |
Fig b. C-scan image of a 6 in x 8-in section of a SiC panel scanned with 50 kHz air-coupled transducers. |
The C-scan of figure a. was produced using the 400 kHz focused transducers, while the C-scan of figure b. was produced with the 50 kHz eletrostatic unfocused transducers. Note the dark blue area in the center of figure a. Such an area could be indicative of intermittant voids. The same area, however, appears much lighter and green in figure b. It follows from the applied color code, that the dark blue area of figure a has a transmission of about 10% of the maximum amplitude (white spots), while the same area in figure b has a transmission amplitude of about 25% of the maximum transmitted amplitude (dark red spots). Such a frequency dependant transmssion is indicative of an increased porosity rather than of intermittant voids. The increased porosity was subsequently confirmed through destructive testing.