Abstract
Non-destructive ultrasonic testing is utilized widely by industries for quality assurance. For sensitive materials or surfaces, non-contact, non-destructive testing methods are in demand. The air-coupled ultrasound (ACU) is one possible solution. This can be used to investigate large, panel-like objects for delaminations and other flaws. For a high detectability, fine measurement grids are required (typically < λ is used), which results in extremely long data acquisition times that are only practicable for laboratory applications. This paper aimed at reducing the required measurement grid points for obtaining high detectability evaluations. The novel method presented in this paper allows a measurement grid that is much coarser than the resulting grid. The method combines a software refinement of the measured data with the Rayleigh–Sommerfeld diffraction integral for the calculation of the pressure distribution on the object’s surface. This result allows the precise prediction of delaminations and flaws in the tested object. The presented method shows a decrease in the total investigation time by up to 98%.
Highlights
Piezoelectric ultrasonic transducers have become indispensable in the field of non-destructive material testing, since Sokolov used continuous ultrasonic waves to identify material defects [1].Those are usually used in a liquid medium due to the impedance matching of the transducer and the ambient medium
Piezoelectric ultrasonic transducers can be designed more if they do not require extra protection against liquids. For such kind of materials, air-coupled ultrasound (ACU) has established itself in many areas of non-destructive testing (NDT) after the high impedance difference between solid and gas could be overcome with new developments [4]
Even with a very coarse measuring grid, it is possible to detect flaws
Summary
Piezoelectric ultrasonic transducers have become indispensable in the field of non-destructive material testing, since Sokolov used continuous ultrasonic waves to identify material defects [1]. Those are usually used in a liquid medium due to the impedance matching of the transducer and the ambient medium. Piezoelectric ultrasonic transducers can be designed more if they do not require extra protection against liquids For such kind of materials, air-coupled ultrasound (ACU) has established itself in many areas of non-destructive testing (NDT) after the high impedance difference between solid and gas could be overcome with new developments (e.g., application of a matching layer for impedance matching of piezoceramics to air) [4]. The large, well-known furniture manufacturers want to be able to offer their furniture
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