Fatigue of additively manufactured 316L stainless steel: The influence of porosity and surface roughness

Abstract

The fatigue behaviour of additively manufactured (AM) 316L stainless steel is investigated with the main emphasis on internal porosity and surface roughness. A transition between two cases of failure are found: failure from defects in the surface region and failure from the internal defects. At low applied load level (and consequently a high number of cycles to failure), fatigue is initiating from defects in the surface region, while for high load levels, fatigue is initiating from internal defects. Porosities captured by X‐ray computed tomography (XCT) are compared with the defects initiating fatigue cracks, obtained from fractography. The fatigue data are synthesised using stress intensity factor (SIF) of the internal and surface defects on the fracture surface.

Fatigue assessment of as‐built and heat‐treated Inconel 718 specimens produced by additive manufacturing including notch effects

“…The Murakami model has been frequently employed when analysing AM metals. 7,[31][32][33] The model correlates the fatigue limit, σ w , with the hardness and the critical defect size, ffiffiffiffiffiffiffiffiffi area p . The fatigue limit can be estimated (for R = -1 loading) by the following relation:…”

Ductile fracture locus identification using mesoscale critical equivalent plastic strain

“…The results showed that the maximum MCEPS contributes to a better prediction compared to the homogenized MCEPS. Noted that further validation with different values of stress triaxiality and Lode parameter is recommended. Further research is needed: (i) comparing the identified fracture strain exposed to multiaxial stress status with different uncoupled damage models, (ii) investigating the void number and positions effects on the identified fracture strain and (iii) using the proposed failure index to predict the ductile fracture of additively manufactured materials 42,43 and welded joints 44,45 …”

Resource‐efficient joint fabrication by welding metal 3D‐printed parts to conventional steel: A structural integrity study

“…We used this methodology, and enriched the traditional finite element (FE) modelling procedure by taking into account the powder bed fusion (PBF) part characteristics, where the main challenge was to quantify the mechanical modifications in the heat affected zone (HAZ) due to welding. Among the experimental studies related to the PBF parts, 5,6,23,24,31–33 we referred to the research by Buchanan et al 6 to calibrate the printed SS316L model, and to the works done by Järvinen 5 and Laitinen 23 to calibrate the welded connection.…”