Non-destructive evaluation techniques for the inspection of additive manufacturing

Additive manufacturing (AM) enables the production of complex and lightweight components with properties exceeding traditionally manufactured components. This has fuelled rapid adoption of AM in several industries including aerospace, automotive and biomedical. Despite the growth of the capabilities, these production techniques face. challenges that include the lack of standardized testing methods for AM materials, insufficient standards for in-situ monitoring and the lack of guidelines for how to qualify and certify parts made by AM. The application of inspection techniques, such as destructive and non-destructive evaluation techniques, are proposed in literature as a tool to overcome the current limitations of the AM. The application of these inspection techniques to AM is however challenging. These challenges arise form AM parts or process characteristics, such as the geometrical complexity of the parts or the lack of information related to the characteristic dimension of the defects. Other challenges are related to the inspection techniques, such as the absence of standards or inspection procedures for AM processes or the lack of of probability-of-detection data. Several studies are available in the literature about the application of these investigation techniques to AM. This thesis reviews the literature about the Non-destructive evaluation (NDE) techniques applied to AM. A detailed discussion is devoted to the use of NDE techniques for the inspection of feedstock material and parts produced via additive manufacturing (AM) and the monitoring of the AM process. Attention is also given to the characteristic material and process related defects of the AM and the capability of the NDE techniques to detect these defects.