Quantitative tomographic non-destructive testing for flaw size measurement and life time prediction

Modern digital non destructive testing (NDT) techniques achieved an extraordinary improvement of measurement accuracy after transition from classical manual testing to computerized technology during the last decade. X-ray computed tomography (CT) is the most accurate NDT technology, but it was earlier restricted to in house laboratory applications. During the last 10 years a variety of CT systems has been installed in different production facilities for quantitative measurements of flaws, dimensions of inner structures and product integrity. Mobile and in-line CT is applied for casting inspection, aircraft and pipe weld analysis. A mobile Planar CT scanner enables the evaluation of pipe weld undercuts, lack of fusion and crack dimensions for in-service inspection. The quantitative measurement of flaw depth (ligament) and length for in-service inspection enables the prediction of life time for chemical plants and installations in power stations. The technique was qualified by open and blind trails on basis of the European Network of Inspection and Qualification. Tomographic inspections of aircraft components were carried out for evaluation of stringer integrity in carbon fibre reinforced components. New computerized ultrasound techniques on basis of a phased array design enable the 3D reconstruction of flaw dimension. The reconstruction technique is based on the synthetic aperture focusing technique (SAFT), which is similar to the unfiltered planar X-ray CT. The accuracy and presentation of flaw structure and dimension have been significantly improved. SAFT-B-Scan slices are combined in a data cube visualizing the flaws in 3D. Flaw sizing examples of steel castings and CFRP components of aircraft structures are presented. During the last years the thermographic testing was enhanced from simple heat imaging to flaw detection with lateral and depth measurement. New cameras provide more detailed information. Fourier techniques and phase analysis of active heat pulse induced time response measurements enable the 3D tomographic reconstruction of flaws and structure details with enhanced accuracy. New reconstruction results of pulse excited thermography for defect sizing are presented.