The Ultrasonic Shear Wave Tomography (USWT) test method, commercially known as the MIRA test unit, is a flaw detection system capable of generating 2D and 3D tomographic images of structural elements. The basic system consists of a console with 48 transducers aligned in 12 rows of modules containing four shear wave transducers each. The transducers are spring-loaded, dry-point contact (DPC) piezoelectric sensors with a center frequency of 50 kHz, configured as a single antenna array. Each transducer is built with a wear-resistant ceramic tip, which allows testing on rough surfaces without coupling gels.
Once the ultrasonic shear wave signal is emitted, the received signal is processed by the controlling console and the 2D, b-scan, image is immediately displayed on the built-in screen. A modified, synthetic aperture focusing technique (SAFT-C) data processing analysis method is then performed to generate 3D images of the test results.
YAES engineers have extensive experience applying the use of the USWT test method to investigate a variety of concrete related issues. Our engineers participated in the original research and development of the technology with the equipment manufacturer in the late 1990s.
The USWT test method is commonly used in concrete, stone and masonry structures to detect internal flaws such as delaminations, cracks and poorly consolidated or honeycombed concrete, as well as to locate voids in grouted tendon ducts. One key application of the MIRA system is the ability to assess thick concrete structures such as nuclear power containment walls or subterraneous subway shafts. YAES engineers have used the USWT test method to investigate concrete structures up to 2 meters thick.