Fatigue life prediction of additively manufactured material: Effects of surface roughness, defect size, and shape

Self Cite

In this study, the crack‐growth approach is used to predict the fatigue life of 17‐4 precipitation hardening (PH) stainless steel (SS) fabricated via an additive manufacturing (AM) system in different orientations (ie, vertical and horizontal) before and after heat treatment. To perform fatigue‐life calculations, the effective stress intensity factor as a function of crack‐growth rate was obtained from testing modified compact specimens with different crack orientations in as‐built and heat‐treated conditions. The plasticity‐induced crack closure model, FASTRAN, was used to calculate fatigue lives based on the size of process‐induced defects. Results indicated that in the presence of large voids (ie, lack‐of‐fusion defects), the total fatigue life of AM 17‐4 PH SS in as‐built and heat‐treated conditions is dominated by crack growth. Effect of build orientation on fatigue life of AM 17‐4 PH SS was also captured based on the size of defects projected on a plane perpendicular to the loading direction.

Section: Introductionmentioning

confidence: 99%

Fatigue‐life prediction of additively manufactured material: Effects of heat treatment and build orientation

Yadollahi

Elwany

Doude

et al. 2020

Self Cite

“…It is well known that small defects, eg, scratches, cavities, and non‐metallic inclusions, can degrade the fatigue life and fatigue limit of various steels and other metallic materials depending on the shape and size. In addition, for Ni‐based superalloys, some researchers have reported the detrimental effect of small defects on the fatigue strength . For example, Yadollahi et al conducted fatigue tests of two types of AMed Alloy 718 specimens with different defect sizes, ie, specimens containing defects due to a lack of fusion ( defective build specimens ) and specimens in which such defects were reduced ( nondefective build specimens ).…”

Section: Introductionmentioning

confidence: 99%

Effect of defects on the fatigue limit of Ni‐based superalloy 718 with different grain sizes

Kevinsanny

Okazaki

Takakuwa

et al. 2019

Tension‐compression fatigue tests were performed on two types of Ni‐based superalloy 718 with different microstructures in which small artificial defects of various sizes and shapes were introduced. The susceptibility of the fatigue strength to the defects varied significantly with the microstructure morphology, ie, a smaller grain size made the alloy more susceptible to defects. The fatigue limit as a small‐crack threshold was successfully predicted using the area parameter model. The evaluation of the fatigue limit was classified into the following three stages depending on the defect size: (a) harmless defect regime, (b) small‐crack regime, and (c) large‐crack regime. Such a classification enabled comprehensive evaluation of the fatigue limit in a wide range of defect size, considering (a) defect size over a range of small crack to large crack and (b) characteristics of matrix represented by grain size and hardness.

“…There are several studies on estimating the fatigue life of AM components based on internal and external defects . Romano et al proposed a model based on internal defects to predict both low‐cycle and high‐cycle fatigue in AlSi10Mg, based on assumptions regarding defect size, geometry, and occurrence.…”

Section: Introductionmentioning

confidence: 99%

“…Romano et al proposed a model based on internal defects to predict both low‐cycle and high‐cycle fatigue in AlSi10Mg, based on assumptions regarding defect size, geometry, and occurrence. Yadollahi et al applied a similar method to describe the effect of surface texture and defect features on the fatigue life of Inconel 718. The latter article suggested using the maximum valley depth of the surface profile ( R v ) as the initial crack length for fatigue life modelling.…”

Section: Introductionmentioning

confidence: 99%

“…There are several studies on estimating the fatigue life of AM components based on internal and external defects. [4][5][6][7][8] Romano et al 4,5 proposed a model based on internal defects to predict both low-cycle and high-cycle fatigue in AlSi10Mg, based on assumptions regarding defect size, geometry, and occurrence. Yadollahi et al 6 applied a similar method to describe the effect of surface texture and defect features on the fatigue life of Inconel 718.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

High cycle fatigue life estimation of materials processed by laser powder bed fusion

Hovig

Azar

Sunding

et al. 2019

The fatigue life of metal components is known to depend on the surface topography. For components made by laser powder bed fusion, the roughness of the as‐built surfaces depends on the orientation of the component surface with respect to the build plate. Surface topographies of AlSi10Mg and Inconel 718 specimens built at 0° to 90° inclination, with 15° increments, were characterised by white light interferometry. Two methods for calculating the stress concentration factor using the surface roughness data are proposed, and the results of each approach are presented and compared. Moreover, a finite element model was developed, in order to analyse the stress field when subsurface porosity is present. The fatigue lifetime estimates suggest that the lifetime of components may differ up to two orders of magnitude, depending on the build orientation.