A spatial-temporal method for early prediction of fatigue crack region and orientation in metallic cellular materials using in-situ infrared thermography (IRT)

The key contributions of this paper are as follows: • A novel approach for early prediction of crack region and orientation in AM Metallic Cellular materials • A spatial-temporal method for detecting local plastic deformation and heating using IRT • New insights into detecting wall failures due to low cycle fatigue in AM metallic cellular materials. This study seeks an early prediction method of crack failure location and orientation due to low cycle fatigue in additively manufactured metallic cellular materials by leveraging experimentally observed accumulation of plastic deformation. To study this, a novel spatial-temporal approach for analyzing Infrared Thermographic (IRT) video was developed to detect heat generated by local plastic deformation. The method was validated experimentally by conducting fully reversed low cycle fatigue tests of Inconel 718 (IN718) honeycomb specimens manufactured using Laser Powder Bed Fusion (LPBF). Using the approach developed, results showed that localized heating due to plastic work could be detected and used for early prediction of the most probable path, and orientation of crack propagation. Furthermore, the method developed was found to be able to predict these results within the first 1.5% of the total life of the specimen apriori to crack initiation.