Amplitude-Based Defect Sizing of SAFT Results – From Imaging to Quantitative Measurement

Mooshofer, Hubert; Siemens AG; Germany

Mooshofer, H.; Siemens AG; Germany
Boehm, R.; Federal Institute for Materials Research and Testing (BAM); Germany
Heinrich, W.; Siemens AG; Germany
Fendt, K; Friedrich-Alexander University; Germany
Goldammer, M.; Siemens AG; Germany
Kolk, K.; Siemens AG; Germany
Vrana, J.; Vrana GmbH; Germany

ID: ECNDT-0173-2018
Download: PDF
Session: Imaging - UT 1
Room: R2
Date: 2018-06-14
Time: 15:20 - 15:40

Sizing of indications and the determination of the inspection sensitivity are core tasks in ultrasonic testing. They ensure that critical inhomogenities can be detected and assessed.
For SAFT the sizing of indications is currently performed by evaluating the spatial extent in the reconstruction result, i. e. counting the number of voxels belonging to an indication. This limits sizing to the resolution of SAFT, which is in the order of one wavelength. For smaller defects sizing is not possible. Moreover, this method provides no information about the sensitivity of the inspection method.
Compared to classical UT inspection SAFT significantly improves the SNR both, regarding stochastic noise and grain noise. However, this improvement of the sensitivity cannot be utilized without a method for determination of the sensitivity and for sizing small indications.
Similar to classic UT there is a second option to get information about indications: The amplitude sum, which incorporates the echo amplitude, the angle dependent scattering characteristics, the probe parameters and the geometry of the part.
In this publication we show, that the amplitude sum is suitable for sizing small indications and for the determination of sensitivity. The relation between the amplitude sum and the size of indications is explained, and it is shown, that the location of indications and the shape of the object to inspect must be considered. Based on these results a method for sizing of small indications using SAFT is developed which translates the amplitude sum of each voxel in an equivalent reflector size, similarly as done in classical UT by using of DGS diagrams. This sizing method completes SAFT, growing it from an imaging tool to a full-fledged quantitative measurement technique.