Issue 43

F. Berto et alii, Frattura ed Integrità Strutturale, 43 (2018) 1-32; DOI: 10.3221/IGF-ESIS.43.01 22 strategic point to fill this knowledge gap allowing future applicants to take full advantage of the unique features of AM, which will be key to integrate AM in every-day manufacturing. Drawing from extensive expertise in the development of modern fatigue assessment criteria, the trend should be to contribute to the fundamental understanding of the mechanical/cracking behavior of AM metals subjected to fatigue loading as well as the integration of this knowledge in an innovative design methodology. The key feature of this unifying approach is the consideration of microstructural features (such as porosity, grain shape, defect morphology, etc.) of the material near crack initiation locations. Due to the geometric complexity of AM advanced components and materials, related structures naturally have large surface to volume ratios. Large areas are exposed to and interact with the surrounding, which is even further enhanced through the typically rough surfaces AM parts exhibit. This can be beneficial, as for example in biomedical applications, where cells tend to easily attach to the porous and rough structure of AM fabricated implants finding proper anchor points. However, this exposure can also lead to detrimental effects such as corrosion, environmental induced embrittlement or wear through friction. Independent from the application, the ability to tailor surface characteristics and surface material properties of these advanced geometric complex components, will allow for the ultimate design freedom. Internal defects are very critical for AM parts and compete in creating provisional crack initiation points (see Fig. 27) competing with geometrical discontinuities due to the complexity of the geometrical features need to be designed. Figure 27: Typical surface intrusions induced by the SLM process.