Development of individual medical implants with specific mechanical properties manufactured by Laser Powder Bed Fusion

Laser Powder Bed Fusion (LPBF) is an additive manufacturing process, which enables the generation of complex geometries such as lattice structures, using metallic powder. Lattice structures are being used increasingly in medical technology to adapt the stiffness of individualized implants which can lead to faster bone healing. Lattice structures are also used to adjust the contact surface between the bone and implant to adapt the osseointegrative behavior. The goal of this work is to create lattice structures with local adaption of the stiffness (modulus of elasticity) for individual vertebral body replacement implants and their automated design based on patient data.To form the lattice structure a diamond cell type is used, which is common in medical technology. For the later adaptation of the bone stiffness, the stiffness of the lattice structure with different strut diameters are determined. The calculation of the stiffness is done by numerical simulations using Finite Element Methods (FEM). The simulations are validated with tensile and compression tests. Finally, the automated design of the implants is carried out with an in-house generated tool to adjust the strut diameters based on the bone density from patient data.Parts of this work have been funded by the German ministry of education and research (BMBF) under grant number 13GW0116.

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Compressive Properties of Al-Si Alloy Lattice Structures with Three Different Unit Cells Fabricated via Laser Powder Bed Fusion

Materials ◽

10.3390/ma13132902 ◽

2020 ◽

Vol 13 (13) ◽

pp. 2902 ◽

Cited By ~ 1

Author(s):

Xiaoyang Liu ◽

Keito Sekizawa ◽

Asuka Suzuki ◽

Naoki Takata ◽

Makoto Kobashi ◽

...

Keyword(s):

Strain Rate ◽

Lattice Structure ◽

Unit Cell ◽

Lattice Structures ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Compressive Properties ◽

Powder Bed ◽

Unit Cells ◽

Indentation Tests

In the present study, in order to elucidate geometrical features dominating deformation behaviors and their associated compressive properties of lattice structures, AlSi10Mg lattice structures with three different unit cells were fabricated by laser powder bed fusion. Compressive properties were examined by compression and indentation tests, micro X-ray computed tomography (CT), together with finite element analysis. The truncated octahedron- unit cell (TO) lattice structures exhibited highest stiffness and plateau stress among the studied lattice structures. The body centered cubic-unit cell (BCC) and TO lattice structures experienced the formation of shear bands with stress drops, while the hexagon-unit cell (Hexa) lattice structure behaved in a continuous deformation and flat plateau region. The Hexa lattice structure densified at a smaller strain than the BCC and TO lattice structures, due to high density of the struts in the compressive direction. Static and high-speed indentation tests revealed that the TO and Hexa exhibited slight strain rate dependence of the compressive strength, whereas the BCC lattice structure showed a large strain rate dependence. Among the lattice structures in the present study, the TO lattice exhibited the highest energy absorption capacity comparable to previously reported titanium alloy lattice structures.

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Influence of relative density on quasi-static and fatigue failure of lattice structures in Ti6Al4V produced by laser powder bed fusion

Scientific Reports ◽

10.1038/s41598-021-98631-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Markel Alaña ◽

Antonio Cutolo ◽

Sergio Ruiz de Galarreta ◽

Brecht Van Hooreweder

Keyword(s):

Relative Density ◽

Fatigue Failure ◽

Lattice Structure ◽

Yield Criterion ◽

Fatigue Properties ◽

Face Centered Cubic ◽

Lattice Structures ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

AbstractLattice structures produced by additive manufacturing have been increasingly studied in recent years due to their potential to tailor prescribed mechanical properties. Their mechanical performances are influenced by several factors such as unit cell topology, parent material and relative density. In this study, static and dynamic behaviors of Ti6Al4V lattice structures were analyzed focusing on the criteria used to define the failure of lattices. A modified face-centered cubic (FCCm) lattice structure was designed to avoid the manufacturing problems that arise in the production of horizontal struts by laser powder bed fusion. The Gibson–Ashby curves of the FCCm lattice were obtained and it was found that relative density not only affects stiffness and strength of the structures, but also has important implications on the assumption of macroscopic yield criterion. Regarding fatigue properties, a stiffness based criterion was analyzed to improve the assessment of lattice structure failure in load bearing applications, and the influence of relative density on the stiffness evolution was studied. Apart from common normalization of S–N curves, a more accurate fatigue failure surface was developed, which is also compatible with stiffness based failure criteria. Finally, the effect of hot isostatic pressing in FCCm structures was also studied.

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Effect of Build Orientation on the Microstructure, Mechanical and Corrosion Properties of a Biodegradable High Manganese Steel Processed by Laser Powder Bed Fusion

Metals ◽

10.3390/met11060944 ◽

2021 ◽

Vol 11 (6) ◽

pp. 944

Author(s):

Martin Otto ◽

Stefan Pilz ◽

Annett Gebert ◽

Uta Kühn ◽

Julia Hufenbach

Keyword(s):

Electron Backscatter Diffraction ◽

Longitudinal Axis ◽

Manganese Steel ◽

Compressive Yield Strength ◽

Powder Bed Fusion ◽

Compression Tests ◽

Laser Powder Bed Fusion ◽

Corrosion Properties ◽

Powder Bed ◽

Manufacturing Technologies

In the last decade, additive manufacturing technologies like laser powder bed fusion (LPBF) have emerged strongly. However, the process characteristics involving layer-wise build-up of the part and the occurring high, directional thermal gradient result in significant changes of the microstructure and the related properties compared to traditionally fabricated materials. This study presents the influence of the build direction (BD) on the microstructure and resulting properties of a novel austenitic Fe‑30Mn‑1C‑0.02S alloy processed via LPBF. The fabricated samples display a {011} texture in BD which was detected by electron backscatter diffraction. Furthermore, isolated binding defects could be observed between the layers. Quasi-static tensile and compression tests displayed that the yield, ultimate tensile as well as the compressive yield strength are significantly higher for samples which were built with their longitudinal axis perpendicular to BD compared to their parallel counterparts. This was predominantly ascribed to the less severe effects of the sharp-edged binding defects loaded perpendicular to BD. Additionally, a change of the Young’s modulus in dependence of BD could be demonstrated, which is explained by the respective texture. Potentiodynamic polarization tests conducted in a simulated body fluid revealed only slight differences of the corrosion properties in dependence of the build design.

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Understanding and suppressing shear band formation in strut-based lattice structures manufactured by laser powder bed fusion

Materials & Design ◽

10.1016/j.matdes.2020.109416 ◽

2021 ◽

Vol 199 ◽

pp. 109416

Author(s):

Xiaoyang Liu ◽

Takafumi Wada ◽

Asuka Suzuki ◽

Naoki Takata ◽

Makoto Kobashi ◽

...

Keyword(s):

Shear Band ◽

Lattice Structures ◽

Shear Band Formation ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Band Formation ◽

Powder Bed

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Manufacturability of lattice structures fabricated by laser powder bed fusion: a novel biomedical application of the beta Ti-21S alloy

Additive Manufacturing ◽

10.1016/j.addma.2021.102556 ◽

2021 ◽

pp. 102556

Author(s):

A. Jam ◽

A. du Plessis ◽

C. Lora ◽

S. Raghavendra ◽

M. Pellizzari ◽

...

Keyword(s):

Biomedical Application ◽

Lattice Structures ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

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On the manufacturability of Inconel 718 thin-walled honeycomb structures by laser powder bed fusion

Rapid Prototyping Journal ◽

10.1108/rpj-04-2021-0098 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

José M. Zea Pérez ◽

Jorge Corona-Castuera ◽

Carlos Poblano-Salas ◽

John Henao ◽

Arturo Hernández Hernández

Keyword(s):

Mechanical Properties ◽

Inconel 718 ◽

Dimensional Accuracy ◽

Honeycomb Lattice ◽

Lattice Structures ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Content Type ◽

Powder Bed ◽

Thin Walled

Purpose The purpose of this paper is to study the effects of printing strategies and processing parameters on wall thickness, microhardness and compression strength of Inconel 718 superalloy thin-walled honeycomb lattice structures manufactured by laser powder bed fusion (L-PBF). Design/methodology/approach Two printing contour strategies were applied for producing thin-walled honeycomb lattice structures in which the laser power, contour path, scanning speed and beam offset were systematically modified. The specimens were analyzed by optical microscopy for dimensional accuracy. Vickers hardness and quasi-static uniaxial compression tests were performed on the specimens with the least difference between the design wall thickness and the as built one to evaluate their mechanical properties and compare them with the counterparts obtained by using standard print strategies. Findings The contour printing strategies and process parameters have a significant influence on reducing the fabrication time of thin-walled honeycomb lattice structures (up to 50%) and can lead to improve the manufacturability and dimensional accuracy. Also, an increase in the young modulus up to 0.8 times and improvement in the energy absorption up to 48% with respect to those produced by following a standard strategy was observed. Originality/value This study showed that printing contour strategies can be used for faster fabrication of thin-walled lattice honeycomb structures with similar mechanical properties than those obtained by using a default printing strategy.

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