A Methodology for Predicting Surface Crack Nucleation in Additively Manufactured Metallic Components

Chan, Kwai S.; Peralta-Duran, Alonso

doi:10.1007/s11661-019-05309-7

Cited by 16 publications

(5 citation statements)

References 24 publications

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“…AR: aspect ratio (must be ≥ 1, where 1 indicates a perfect circle) of the ellipse that approximates the defect, i.e. AR= a b (3) where, b, is the semi-minor axis, and, a, is the semi-major axis of the ellipse. Jag, J: represents the jaggedness of the defect and is defined in terms of the ratio between the perimeter (Perim) of the defect and that of a classical ellipse approximated by:…”

Section: Characterising the Critical Defectsmentioning

confidence: 99%

“…In this respect, the defect population characteristics, microstructural anisotropy, complex residual stress, and surface roughness of AM processed metals [2] can all contribute to the scatter in their high cycle fatigue (HCF) performance. In practice, the residual stresses can be mitigated and an acceptable surface finish can be achieved, by a proper combination of preheating, post-AM heat treatment, peening, vibratory grinding and/or micro machining [3] . Furthermore, the fatigue resistance of AM processed metals has generally been found to be more sensitive to the intrinsic manufacturing defects than the underlying microstructural inhomogeneity [4] .…”

Section: Introductionmentioning

confidence: 99%

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The potency of defects on fatigue of additively manufactured metals

Peng

Qian

et al. 2022

International Journal of Mechanical Sciences

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Section: Characterising the Critical Defectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The potency of defects on fatigue of additively manufactured metals

Peng

Qian

et al. 2022

International Journal of Mechanical Sciences

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“…As is well known, surface roughness is one of the important surface conditions determining the fatigue performance of engineering materials [ 12 , 13 ]. In other words, high surface roughness will feature height peaks and deep valleys, which are potential stress concentration zones resulting in crack formation and consequent propagation [ 14 , 15 ]. Therefore, it is important to reduce the surface roughness of the parts manufactured by PBF, especially for applications in need of long fatigue life.…”

Section: Introductionmentioning

confidence: 99%

Contact-Free Support Structures for the Direct Metal Laser Melting Process

Çelik

Tekoğlu²,

Yasa

et al. 2022

Materials

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Although Direct Metal Laser Melting (DMLM), a powder bed fusion (PBF) Additive Manufacturing (AM) for metallic materials, provides many advantages over conventional manufacturing such as almost unlimited design freedom, one of its main limitations is the need for support structures beneath overhang surfaces. Support structures are generally in contact with overhang surfaces to physically prop them up; therefore, they need to be removed after manufacturing due to not constituting a part of the main component design. The removal of supports is a process sequence adding extra time and cost to the overall manufacturing process and could result in damaging the main component. In this study, to examine the feasibility of contact-free supports for overhang surfaces in the DMLM process, coupons with these novel types of supports were prepared from CoCrMo alloy powder. This study aims to understand the effect of two parameters: the gap distance between supports and overhang surfaces and the inclination angle of overhang surfaces, on the surface topography and microstructural properties of these surfaces. Visual inspection, roughness measurements, and optical microscopy were utilized as characterization methods The roughness parameters (Ra, Rq, and Rz) were obtained using the focus variation method, and optical microscope analysis was performed on the cross-sections of the overhang surfaces to investigate the sub-surface microstructure and surface topology. Results showed that contact-free supports have a positive effect on decreasing surface roughness at all build angles when the gap distance is correctly set to avoid sintering of the powder in between the overhang and supports or to avoid too large gaps eliminating the desired effect of the higher thermal conductivity.

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“…On closer inspection of their stress‐life (S‐N) graphs it can be clearly seen that surface machining alone has a greater improvement than HIPping alone, but when both operations were performed the improvement was greater than might be assumed from summing the improvements from the two individual effects. In another example, Chan and Peralta‐Duran 21 consider fatigue in AM parts, and use an analytical model to treat surface notches as fatigue crack nucleation sites. Their measured fatigue life results for as‐built AM parts do not seem to follow the trend lines of their predictions, whereas the equivalent results for surface machined (SM) AM parts do.…”

Section: Reviewmentioning

confidence: 99%

Combined effect of both surface finish and sub‐surface porosity on component strength under repeated load conditions

McMillan

Jones

2020

Engineering Reports

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High duty engineering component life is usually demonstrated through extensive testing and statistical analysis applied to empirical curve-fit equations. Because of this, the extent of the testing required is huge and costly: it must consider the load cycle range and test to high numbers of cycles. Additive Manufacturing (AM) for high duty components has brought to the fore the question of the effect of porosity and surface roughness on fatigue life, and how the true life of a critical component can be assessed conservatively. The authors propose the first step toward the development of a fatigue model based on well-established engineering physics principles, by creating computational specimens with modeled surface roughness and porosity, and subjected to cyclic loading using Finite Element Analysis. They show that the combination of roughness features and sub-surface pores leads to an equivalent plastic strain distribution pattern that suggests an emergent physical process that has not been reported before, and which indicates that the component strength and life reduction arising from surface roughness can be made significantly worse by the presence of porosity. The development of such phenomenological understanding should lead to improved life prediction techniques, more cost effective test procedures, and the development of better AM methods.

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A Methodology for Predicting Surface Crack Nucleation in Additively Manufactured Metallic Components

Cited by 16 publications

References 24 publications

The potency of defects on fatigue of additively manufactured metals

The potency of defects on fatigue of additively manufactured metals

Contact-Free Support Structures for the Direct Metal Laser Melting Process

Combined effect of both surface finish and sub‐surface porosity on component strength under repeated load conditions

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