Expressing the potential of metal Additive Manufacturing (AM) for components of industrial interest means the ability to produce complex geometries in high-performance materials. AMed components present several notches, both on external and internal surfaces, such as blunt notches, introduced by the designer for functional requirements of the component, or local severe notches and cracks produced by the AM process. Criteria developed for dealing with notches in traditionally manufactured components, such as the Average Strain Energy Density (ASED), have been successfully extended to AMed components in recent years. In the present work, it is analyzed the High Cycle Fatigue (HCF) notch sensitivity as-built cylindrical specimens, including the local geometry and surface roughness in proximity to the notch region. Four geometries of V-notches featuring a radius ranging from 0.3 to 2 mm were considered. Tests were carried out at room temperature in an axial load configuration with a stress ratio of 0.05 and a loading frequency of about 150 Hz, by using a resonant machine. Fractographic analyses were carried out to identify the nucleation and crack propagation region, as well as the presence of the defects in proximity to the fracture onset. The actual geometry in proximity to the notch root was investigated by optical microscopy to extract the local surface profile, including the notch effective geometry and the surface roughness, which was employed to set up a specimen-specific FE model. The results were investigated in the framework of the ASED approach, comparing the prediction obtained using the nominal and the effective notch geometry. Notwithstanding the severe stress concentration caused by the local irregularities introduce by the L-PBF process, the ASED values were found to be almost insensitive to the actual profile geometry. The method was demonstrated to be a valid tool for the design of AMed complex-shaped components.
HCF assessment of additively manufactured notched specimens in Inconel 718 considering the effective local geometry
Giuseppe Macoretta
Primo
Writing – Original Draft Preparation
;Bernardo Disma MonelliSupervision
2023-01-01
Abstract
Expressing the potential of metal Additive Manufacturing (AM) for components of industrial interest means the ability to produce complex geometries in high-performance materials. AMed components present several notches, both on external and internal surfaces, such as blunt notches, introduced by the designer for functional requirements of the component, or local severe notches and cracks produced by the AM process. Criteria developed for dealing with notches in traditionally manufactured components, such as the Average Strain Energy Density (ASED), have been successfully extended to AMed components in recent years. In the present work, it is analyzed the High Cycle Fatigue (HCF) notch sensitivity as-built cylindrical specimens, including the local geometry and surface roughness in proximity to the notch region. Four geometries of V-notches featuring a radius ranging from 0.3 to 2 mm were considered. Tests were carried out at room temperature in an axial load configuration with a stress ratio of 0.05 and a loading frequency of about 150 Hz, by using a resonant machine. Fractographic analyses were carried out to identify the nucleation and crack propagation region, as well as the presence of the defects in proximity to the fracture onset. The actual geometry in proximity to the notch root was investigated by optical microscopy to extract the local surface profile, including the notch effective geometry and the surface roughness, which was employed to set up a specimen-specific FE model. The results were investigated in the framework of the ASED approach, comparing the prediction obtained using the nominal and the effective notch geometry. Notwithstanding the severe stress concentration caused by the local irregularities introduce by the L-PBF process, the ASED values were found to be almost insensitive to the actual profile geometry. The method was demonstrated to be a valid tool for the design of AMed complex-shaped components.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
