Issue 43

N. Montinaro et alii, Frattura ed Integrità Strutturale, 43 (2018) 231-240; DOI: 10.3221/IGF-ESIS.43.18 239 Figure 12 : Experimental/numerical comparison of the Mean temperature plot results for the sample 2. Furthermore, the experimentally detected MT decreases along the laser trajectory, contrary to the numerical prediction. This is due to the different initial thermal conditions of the sample which tend to accumulate the heat from different successive scanning. It is though pointed out that even if the general trends are different, both numerical and experimental curves are able to identify the defects in a very similar manner, and this is considered as a sign of robustness of the proposed approach. C ONCLUSIONS dditive manufacturing allows to create 3D complex geometries whose inspection is a big challenge for non- destructive testing methods. The present work demonstrates suitability of a recently proposed laser thermography technique, called “Flying Laser Inner Probing Thermography”, for the on-line detection of typical micro flaws in additive manufactured components. A FEA has been employed to first demonstrate and understand the mechanism of detection in AM components. The same model has been used to adequately tune the parameters of the technique to enhance defect sensitivity. The outcome of the numerical analysis has also been used to identify the optimum size of the ROI to be used for the processing of experimental thermograms. Numerical and experimental results indicate how the technique is able to generate signatures in both tested samples. In particular, this work has demonstrated the advantage of employing a numerical simulation as an aid toward an optimized tuning of experimental parameters. One benefit of the laser thermography as compared to other NDTs is the easy, fast, non-contact, full-field set-up. Some drawbacks may be represented by the need to prepare the surface by applying a matt paint, the difficulty to obtain accurate defect extension evaluations, and the need to use high thermal resolution IR detectors. The remote inspection system by optical methods could potentially be linked to the additive manufacturing rig, in order to achieve monitoring of the entire additive process. The inspection should be performed after layer deposition, when the part has reached room temperature since the equipment cannot stand the heat generated by the process. The technique allows a non-contact and remote inspection showing a potential for in-line automated inspection and processing. R EFERENCES [1] Lewis, G. K., Schlienger, E., Practical considerations and capabilities for laser assisted direct metal deposition, Mater. Des., 21 (2000) 417-423. DOI: 10.1016/S0261-3069(99)00078-3. [2] Ahsan, M. N., Bradley, R., Pinkerton, A. J., Microcomputed Tomography Analysis of Intralayer Porosity Generation in Laser Direct Metal Deposition and its Causes, J. Laser Appl., 23 (2011) 022009. DOI: 10.2351/1.3582311. [3] Thompson, A., Maskery, I., Leach, R. K., X-ray computed tomography for additive manufacturing: a review, Meas. Sci. Technol., 27 (2016) 072001. DOI: 10.1088/0957-0233/27/7/072001. [4] Nilsson, P., Appelgren, A., Henrikson, P., Runnemalm, A., Automatic ultrasonic testing for metal deposition, Proc. 18th World Conference on Nondestructive Testing, Durban, South Africa (2012). 278 280 282 284 286 288 290 292 305,0 305,5 306,0 306,5 307,0 307,5 308,0 308,5 309,0 5 10 15 20 25 30 35 40 45 MT  Experimental scale  [K] Distance [mm] MT Comparison Experimental Numerical MT Numerical  scale [K] Defect 1/2 Defect 2/2 Defect 3/2 A