On the effect of geometrical imperfections and defects on the fatigue strength of cellular lattice structures additively manufactured via Selective Laser Melting

Dallago, Michele; Winiarski, B.; Zanini, Filippo; Carmignato, Simone; Benedetti, M.

doi:10.1016/j.ijfatigue.2019.03.019

Cited by 158 publications

(55 citation statements)

References 62 publications

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“…Melancon et al also calculated an increase, to a lesser degree, of 7% to 9% in diagonal and horizontal struts, respectively. Similar observations on strut orientation dependency are also observed in references [60,[65][66][67].…”

Section: Dimensional Inaccuraciessupporting

confidence: 87%

Review of defects in lattice structures manufactured by powder bed fusion

Echeta

Feng

Dutton

et al. 2019

Int J Adv Manuf Technol

159

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Additively manufactured lattice structures are popular due to their desirable properties, such as high specific stiffness and high surface area, and are being explored for several applications including aerospace components, heat exchangers and biomedical implants. The complexity of lattices challenges the fabrication limits of additive manufacturing processes and thus, lattices are particularly prone to manufacturing defects. This paper presents a review of defects in lattice structures produced by powder bed fusion processes. The review focuses on the effects of lattice design on dimensional inaccuracies, surface texture and porosity. The design constraints on lattice structures are also reviewed, as these can help to discourage defect formation. Appropriate process parameters, post-processing techniques and measurement methods are also discussed. The information presented in this paper contributes towards a deeper understanding of defects in lattice structures, aiming to improve the quality and performance of future designs.

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Section: Dimensional Inaccuraciessupporting

confidence: 87%

Review of defects in lattice structures manufactured by powder bed fusion

Echeta

Feng

Dutton

et al. 2019

Int J Adv Manuf Technol

159

View full text Add to dashboard Cite

show abstract

“…10 Influence of geometric defects on static and fatigue properties has been carried out experimentally as well as using finite element modelling. 11,12 Different modelling techniques have been adopted to model geometric defects, like beam elements, 2,11,13 μCT technique, 14 revolution of spine, 15 and merging of spheres of different diameter. 12 However, revolution of spine and beam element techniques was not able to capture deviation of strut centroids and variation of strut cross-sections.…”

Section: Introductionmentioning

confidence: 99%

Effect of strut cross section and strut defect on tensile properties of cubic cellular structure

Raghavendra

Molinari

Fontanari

et al. 2019

Mat Design & Process Comms

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Selective laser melting (SLM) process is used to produce complex geometries for various applications such as biomedical and aerospace industries. However, one of the limitations with respect to this process is the introduction of geometrical defects during the manufacturing process. The presence of these defects makes it difficult to predict their mechanical behaviour. The present work focuses on the cubic lattice structures and their geometrical deviations from the as-designed structures caused by defects like strut oversizing, varying thickness, and strut waviness. The defects were introduced in finite element modelling by using different cross-sections along a strut and joining them to form smooth solid struts. The modelling of defects was validated by comparing with experimental data. The results indicate an appreciable difference between as-designed and as-built structures. It was observed that varying the strut thickness had a major effect on the strength of the structures. Additionally, an elliptical cross-section better matched the tensile behaviour of the as-built structures rather than a rectangular cross-section.

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“…These premises highlight the importance of studying filleted joints in cellular materials as they can be introduced into the design phase to reduce stress concentrations . Indeed, tensile fatigue tests show that fatigue cracks in SLM lattices occur at the joints, indicating that the shape of the joints is critical in determining the fatigue behavior of this type of structures . In fact, the positive effect of filleted joints on the fatigue resistance of cellular structures was shown by Abad et al On the other hand, fillets at junctions can be unwanted, but generated due to the accumulation of parasitic mass at the strut joints in some AM processes such as SLM …”

Section: Introductionmentioning

confidence: 99%

“…1 Indeed, tensile fatigue tests show that fatigue cracks in SLM lattices occur at the joints, 2 indicating that the shape of the joints is critical in determining the fatigue behavior of this type of structures. 3 In fact, the positive effect of filleted joints on the fatigue resistance of cellular structures was shown by Abad et al 1 On the other hand, fillets at junctions can be unwanted, but generated due to the accumulation of parasitic mass at the strut joints in some AM processes such as SLM. 4 In this work, a numerical method is proposed to estimate the SCFs at the cell wall junctions of 2D regular square cell cellular structures.…”

Section: Introductionmentioning

confidence: 99%

Stress concentration factors for planar square cell lattices with filleted junctions

Dallago

Raghavendra

Fontanari

et al. 2019

Mat Design & Process Comms

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The estimation of the fatigue resistance of cellular structures is fundamental in many applications. The maximum stresses in a material determine the fatigue resistance of the component. In this work, a numerical method is proposed for the estimation of the Stress Concentration Factors (SCF) at the cell wall junctions of 2D cellular structures based on square unit cells. The aim is to obtain a model capable of calculating the values of the SCF as a function of the unit cell geometrical parameters, namely the cell‐wall thickness t0 and the fillet radius R at the joints. This was achieved by applying the Finite Elements (FE) method to the unit cell for wide intervals of t0 and R to calculate the SCF for each couple of the parameters. The values of the SCFs were then fitted with some functions.

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On the effect of geometrical imperfections and defects on the fatigue strength of cellular lattice structures additively manufactured via Selective Laser Melting

Cited by 158 publications

References 62 publications

Review of defects in lattice structures manufactured by powder bed fusion

Review of defects in lattice structures manufactured by powder bed fusion

Effect of strut cross section and strut defect on tensile properties of cubic cellular structure

Stress concentration factors for planar square cell lattices with filleted junctions

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