Shear Wave Ultrasonic

The Ultrasonic Shear Wave (SW) test method is a concrete flaw detection technique capable of generating 3-D tomographic images of structural elements. The method is based on the analysis of reflected stress waves. Available Shear Wave systems include the MIRA and EYECON units. Based on the principles of reflective ultrasonics, Shear Wave testing requires access to only one side of a structural element. The MIRA system 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 voids in grouted tendon duct systems.

Methodology

Shear Waves are introduced using an array of piezoelectric transducers at the testing surface. Shear waves reflected from changes in acoustic impedance in the material are measured by the transducer array. With knowledge of the propagation velocity through the material, the data can be analyzed to determine the depth to internal flaws or the back surface. Data interpretation and analysis is required by experienced operators.

The MIRA system consists of an array of forty ultrasonic transducers capable of transmitting and receiving ultrasonic shear waves. The transducers are spring-loaded, dry-point contact (DPC) piezoelectric sensors with a center frequency of 50 kHz. Each transducer is built with a wear-resistant ceramic tip, which allows testing on rough surfaces. The received signals are processed by the controlling console and then transferred to a laptop computer for analysis. A synthetic aperture focusing technique (SAFT) data processing method is then performed to generate the 3-D images of the tested element. The reconstructed images are displayed as a plan view, cross-section, and isometric views.

Project Applications

  • Detection of internal flaws in building elements, tunnels, dams, retaining walls, foundations, and other concrete structures

  • Delamination detection of bridge decks

  • Detection and location of embedded insulation and block-outs

  • Verification of grout integrity in embedded post-tensioning ducts and splice sleeves

  • Quality assurance testing of bonded repairs