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- 3D ray tracing (1)
- Anisotropic austenitic steel (1)
- Austenitic welds (1)
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- Ray tracing (1)
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Up to now there is no sufficient technique to detect transverse cracks in austenitic and dissimilar welds which recently are of increasing interest in the integrity surveillance of nuclear power plants as well as in quality control of longitudinally welded pipes. Weld inspection by interpretation of single A-scans will lead to erroneous results due to effects caused by anisotropy and in worst case might leave flaws undetected. Therefore, imaging techniques such as the synthetic aperture focusing technique (SAFT) should be used. If the SAFT algorithm is applied on data taken from austenitic welds, the inhomogeneous, anisotropic structure of these welds has to be taken into account in order to properly attribute amplitudes measured in A-scans to the corresponding coordinates in the region of interest. While this has been investigated in the past, all attempts so far were limited to the imaging of longitudinal cracks which requires a less complicated setup than the imaging of transverse cracks. In this paper we give an outline of our attempts to reconstruct images of transverse cracks in different welds. For this purpose a SAFT program based on ray tracing and a layered structure weld model derived from an empirical model of grain orientations in welds are used. The results of the image reconstruction on experimental data are shown and compared to images obtained by assuming an isotropic homogeneous model. Root reflection and crack tip echo are clearly visible which allows an estimation of size and position of the crack with good accuracy.
Quantitative evaluation of ultrasonic C-scan images in homogeneous and layered anisotropic austenitic materials is of general importance for understanding the influence of anisotropy on wave fields during ultrasonic non-destructive testing and evaluation of these materials. In this contribution, a three dimensional ray tracing method is presented for evaluating ultrasonic C-scan images quantitatively in general homogeneous and layered anisotropic austenitic materials. The directivity of the ultrasonic ray source in general homogeneous columnar grained anisotropic austenitic steel material (including layback orientation) is obtained in three dimensions based on Lamb's reciprocity theorem. As a prerequisite for ray tracing model, the problem of ultrasonic ray energy reflection and transmission coefficients at an interface between (a) isotropic base material and anisotropic austenitic weld material (including layback orientation), (b) two adjacent anisotropic weld metals and (c) anisotropic weld metal and isotropic base material is solved in three dimensions. The influence of columnar grain orientation and layback orientation on ultrasonic C-scan image is quantitatively analyzed in the context of ultrasonic testing of homogeneous and layered austenitic steel materials. The presented quantitative results provide valuable information during ultrasonic characterization of homogeneous and layered anisotropic austenitic steel materials.