Analysis and development of inspection procedures based on X-Ray Computed Tomography and Digital Radiography on Aerospace Additive Manufactured Parts

Transcription

1 More info about this article: Analysis and development of inspection procedures based on X-Ray Computed Tomography and Digital Radiography on Aerospace Additive Manufactured Parts Carlos GALLEGUILLOS 1, Antonio PERIÑÁN 1, Fernando LASAGNI 1 1 Materials & Processes department, CATEC Advanced Center for Aerospace Technologies, C/Wilbur y Orville Wright 19, E La Rinconada (Seville), Spain, cgalleguillos@catec.aero; aperinan@catec.aero; flasagni@catec.aero Abstract The aerospace industry is increasingly demanding complex geometries to obtain low weight structures. At the same time, Additive Manufacturing (AM) is a powerful technology which allows a high degree of geometrical optimization. However, requirements on the inspection of the entire volume, including inner surfaces, restrict very often the design process. In this context, X-Ray computed Tomography (XCT) is capable to measure both inner (lack of fusion, voids, cracks, etc) and outer indication (cracks and also geometrical deviations). On the other hand, although Digital Radiography (DR) presents reduced information if compared with XCT, this technique can reduce both lead time and costs. This work presents a detectability analysis by XCT and DR of typical AM defects. The detectability of voids and cracks is investigated on AM samples, including an analysis of the influence of part thickness on the inspection contrast. At the same time, standards for DR inspection have been developed including induced indications fabricated directly by the variation of AM processing parameters (voids) and through design (cracks), which have been contrasted with XCT. Finally, dimensional analyses of complex geometries are presented as well. 1. Introduction Cracks and voids are most common defectology in AM metallic parts and XCT has become the most suitable technique for the detection of inner flaws in complex geometries. However DR could be more competitive in processes with pass-not pass criteria. In this context, this work presents a detectability comparison of cracks and voids between XCT and Rx techniques in a Standard (1) manufactured by AM with induced inner defects. On the other hand, dimensional verification in samples manufactured by AM can become a complex process due to the inaccessibility in inner geometries. XCT is a powerful technique for metrology with results easy to interpret. However, porosity analysis is also required in a component where inspection resolution and sample thicknesses have a big influence in quality results. In this context, this work presents both deviation analyses in AlSi12 real component with complex geometries (2-3) and a study of the influence of the material thickness on the detection of voids. Creative Commons CC-BY-NC licence

2 2. Experimental methods Non destructive testing has been carried out in the following samples: Test A: Cylindrical sample with octagonal section designed and manufactured in Ti64 with 48 narrow notches representative of cracks. Test B: Rectangular section bar (5x5x20mm 3 ) manufactured in AlSi10Mg. Test C: Connector support base AR5 VEGA AVUM in AlSi12. Inspections have been performed with a X-ray computed tomography system model VJT-225 μ-ct manufactured by VJ Technologies, with the following technical characteristics: X-Ray tube 3 ma, 320W, GE 2,048x2,048pixels, shielded vault of 4,000x3,032x2,827mm 3 (lwh), VGStudio software for reconstruction. 3. Results and discussion First, a comparative on the cracks detection between DR and XCT is presented. Later, influence of the part thickness in XCT results and a deviation analysis of a real component are exposed Crack detection by XCT and DR Test A-crack reference sample has been manufactured by means of AM in Ti64 with 48 induced cracks with different defect dimension and position in deepness (Figure 1.a). All the defects are 5 mm high and with variable deepness (from 0.2 to 3mm) and wide from 0.1 mm to 3mm. Figure 1.b and 1.c show results of the inspection performed by Digital Radiography and Computed Tomography consecutively. XCT has been capable to detect every crack with the inspections resolution, even those induced by design but, because of limitation of the manufacturing process, have created voids instead of cracks (Figure 1.d). On the other hand, only cracks above 500 microns depth and 200 microns wide have been detected by DR. 2

3 Figure 1. (a) Schematic view, (b) X-Ray image, (c) cross section XCT image of Test A and (d) cross section of induced voids instead of 10 microns wide crack. 3

4 3.2 Dimensional analysis and influence of part thickness on the inspection contrast Figure 2. (a) Cross section and (b) 3D deviation analysis of AlSi10Mg connector support; (c) cross section with different geometrical configuration. Figure 2.b present all the indications obtain in XCT deviation analysis performed in test C-connector support such as interface machined deviation (B, Figure 2.b) and deformation produced during manufacturing process (A, Figure 2.a). Also complex geometry like reticular structure (C, Figure 2.b) has been analyzed. Additionally, it can be observed in Figure 2.a a cross section of a detected void of 300 µm diameter. However, the detection of other indication in region were the influence of the thickness is more relevant (D, Figure 2.a) is not viable. In order to establish the influence of the material thickness, an additional study has been performed in an Aluminum sample with different configuration: 1-10 µm/vx resolution, 5mm thickness, 800 projections µm/vx resolution, 5mm thickness, 800 projections µm/vx resolution, 30mm thickness, 800 projections µm/vx resolution, 30mm thickness, 1200 projections. Results of this study (Figure2.c) confirm how the detectability decreases with the distance (1-2, Figure 2.c), but also shows the influence of the thickness (2-3, Figure 2.c). 4. Conclusions 4

5 Lead time and cost are variables that very often define a process as suitable. and although XCT is a powerful technique that present easy to interpret results, digital radiography has demonstrated in this study a good relationship between flaws detectability (86% of all induced cracks were detected) and productivity (30min@DR, 120min@XCT). On the other hand, this study has also presented the influence of the thickness for void detection. In this case, the increase in part thickness from 5 to 30mm has shown a larger influence on void detectability than decreasing voxel resolution from 10 to 70 µm/vx. References 1. C. Galleguillos, A Periñán, J. Vilanova, F. Lasagni, Inspeccionabilidad de componentes fabricados por additive manufacturing, 13 er Cogreso Nacional de Ensayos No Destructivos, F. Lasagni, A. Zorrilla, A. Periñán, S. Tudela, J. Vilanova, On the Investigation of Processing Parameters and NDT Inspection on Additive Manufacturing Materials for Future Launchers, Additive Manufacturing for Space Applications, ESA-ESTEC, Oct J. Vilanova, P. Romera., F. Lasagni., A. Zorrilla., A. Periñán, Additive Layer Manufacturing for Launcher s Applications, 13th European Conference on Spacecraft Structures, Materials & Environmental Testing, Braunschweig, Germany, April