Topology Optimization of Porous Lattice Structures for Orthopaedic Implants

Rodgers, Geoffrey W.; Houten, Elijah E. W. Van; Bianco, Rohan Jean; Besset, Romain; Woodfield, T.

doi:10.3182/20140824-6-za-1003.00924

Cited by 10 publications

(5 citation statements)

References 18 publications

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“…In the third approach, graded structures are obtained through topology optimization (TO) using some pre-defined constraints [4,[14][15][16][17]. In TO, either the density distribution of a solid material block is optimized followed by the material density remapping to a typical cellular structure; or the lattices are designed prior to strut size and wall thickness optimization within the cells.…”

Section: Of 23mentioning

confidence: 99%

Design and Additive Manufacturing of Acetabular Implant with Continuously Graded Porosity

Mukherjee¹,

Dhara²,

Saha³

2023

Preprint

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Porous structured metallic implants are preferable as bone graft substitutes due to their faster tissue integration mediated by bone in-growth and vascularization. The porous scaffolds/ implants should also mimic the graded structure of natural bone to ensure a match of mechanical properties. This article presents a method to design graded porous structured acetabular implant and identifies the suitable parameters for manufacturing the model through additive manufacturing. The design method is based on slice-wise modification to ensure continuity of gradation. Modification of the slices was achieved through the binary image processing route. A geodesic dome type design was adopted for developing the acetabular cup model from the graded porous structure. The model had a solid shell with the target porosity and pore size gradually changing from 65% and 950 µm, respectively, in the inner side to 75% and 650 µm, respectively, towards the periphery. The required dimensions of the unit structures, and the combinations of pore structure and strut diameter to obtain the target porosity and pore size were determined analytically. Suitable process parameters were identified to manufacture the model by Direct Metal Laser Sintering (DMLS) using Ti6Al4V powder after carrying out a detailed experimental study to minimize the variation of surface roughness and warping over different build angles of the strut structures. A dual contour scanning was implemented to simplify the scan strategy. The minimum diameter of struts that could be manufactured using the selected scanning strategy and scanning parameters was found to be 375 µm. Finally, the model was built and from the micro-CT data, the porosities and pore sizes were found to be closely conforming to the designed values. The stiffness of the structures, as found from compression testing, was also found to be well matching with that of human trabecular bone. Further, the structure exhibited compliant bending-dominated behavior under compressive loading.

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Section: Of 23mentioning

confidence: 99%

Design and Additive Manufacturing of Acetabular Implant with Continuously Graded Porosity

Mukherjee¹,

Dhara²,

Saha³

2023

Preprint

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show abstract

“…The resulting displacement of each node of the unit cell is compared to that of the same node in the reference cell. A global deviation is then calculated according to (2), where in the total number of nodes in the unit cell; , , and are the components of the displacement of the th node of the unit cell; and , , and are, respectively, the same values for the same nodes in the reference unit cell. If a unit cell is deformed exactly in the same way as the reference cell, the deviation would then be equal to zero.…”

Section: Effect Of the Boundary Condition Applied To The Unit Cellmentioning

confidence: 99%

“…Porous metals, also called metallic foams, are increasingly used in many different applications, especially in the aerospace and medical fields [1,2]. The main advantage presented by these materials is the possibility of having their properties (stiffness, permeability, thermal resistance, etc.)…”

Section: Introductionmentioning

confidence: 99%

Influence of Boundary Conditions on the Simulation of a Diamond-Type Lattice Structure: A Preliminary Study

Terriault

Braïlovski

2017

Advances in Materials Science and Engineering

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Emergent additive manufacturing processes allow the use of metallic porous structures in various industrial applications. Because these structures comprise a large number of ordered unit cells, their design using conventional modeling approaches, such as finite elements, becomes a real challenge. A homogenization technique, in which the lattice structure is simulated as a fully dense volume having equivalent material properties, can then be employed. To determine these equivalent material properties, numerical simulations can be performed on a single unit cell of the lattice structure. However, a critical aspect to consider is the boundary conditions applied to the external faces of the unit cell. In the literature, different types of boundary conditions are used, but a comparative study is definitely lacking. In this publication, a diamond-type unit cell is studied in compression by applying different boundary conditions. If the porous structure’s boundaries are free to deform, then the periodic boundary condition is found to be the most representative, but constraint equations must be introduced in the model. If, instead, the porous structure is inserted in a rigid enclosure, it is then better to use frictionless boundary conditions. These preliminary results remain to be validated for other types of unit cells loaded beyond the yield limit of the material.

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“…In the third approach, graded structures are obtained through topology optimization (TO) using some pre-defined constraints [ 4 , 27 , 28 , 29 , 30 ]. In TO, either the density distribution of a solid material block is optimized followed by the material density remapping to a typical cellular structure; or the lattices are designed prior to strut size and wall thickness optimization within the cells.…”

Section: Introductionmentioning

confidence: 99%

Design and Additive Manufacturing of Acetabular Implant with Continuously Graded Porosity

Mukherjee¹,

Dhara

Saha

2023

Bioengineering

View full text Add to dashboard Cite

Porous structured metallic implants are preferable as bone graft substitutes due to their faster tissue integration mediated by bone in-growth and vascularization. The porous scaffolds/implants should also mimic the graded structure of natural bone to ensure a match of mechanical properties. This article presents a method for designing a graded porous structured acetabular implant and identifies suitable parameters for manufacturing the model through additive manufacturing. The design method is based on slice-wise modification to ensure continuity of gradation. Modification of the slices was achieved through the binary image processing route. A geodesic dome-type design was adopted for developing the acetabular cup model from the graded porous structure. The model had a solid shell with the target porosity and pore size gradually changing from 65% and 950 µm, respectively, in the inner side to 75% and 650 µm, respectively, towards the periphery. The required dimensions of the unit structures and the combinations of pore structure and strut diameter necessary to obtain the target porosity and pore size were determined analytically. Suitable process parameters were identified to manufacture the model by Direct Metal Laser Sintering (DMLS) using Ti6Al4V powder after carrying out a detailed experimental study to minimize the variation of surface roughness and warping over different build angles of the strut structures. Dual-contour scanning was implemented to simplify the scan strategy. The minimum diameter of struts that could be manufactured using the selected scanning strategy and scanning parameters was found to be 375 µm. Finally, the model was built and from the micro-CT data, the porosities and pore sizes were found to be closely conforming to the designed values. The stiffness of the structures, as found from compression testing, was also found to match with that of human trabecular bone well. Further, the structure exhibited compliant bending-dominated behaviour under compressive loading.

show abstract

Topology Optimization of Porous Lattice Structures for Orthopaedic Implants

Cited by 10 publications

References 18 publications

Design and Additive Manufacturing of Acetabular Implant with Continuously Graded Porosity

Design and Additive Manufacturing of Acetabular Implant with Continuously Graded Porosity

Influence of Boundary Conditions on the Simulation of a Diamond-Type Lattice Structure: A Preliminary Study

Design and Additive Manufacturing of Acetabular Implant with Continuously Graded Porosity

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