Solid-Lattice Hip Prosthesis Design: Applying Topology and Lattice Optimization to Reduce Stress Shielding From Hip Implants

2018 ◽  
Author(s):  
Yuhao He ◽  
Drew Burkhalter ◽  
David Durocher ◽  
James M. Gilbert
Keyword(s):  
Fatigue Life ◽  
Bone Resorption ◽  
Selective Laser Melting ◽  
Design Process ◽  
Design Methodology ◽  
Hip Prosthesis ◽  
Stress Shielding ◽  
Prosthesis Design ◽  
Optimized Design ◽  
Laser Melting

The goal of this study was to construct a design methodology for a prosthesis which causes less stress shielding and meets fatigue requirements. Stress shielding is the reduction in bone stresses due to the introduction of an implant. Implants may become loose when stress shielding is present because bone resorption occurs as the bone adapts to the reduced bone stresses. Topology and lattice optimization were performed using OptiStruct to design a hip prosthesis where stress shielding and prosthesis fatigue were considered. The optimized design reduced stress shielding by 50+% when compared to a conventional generic implant, and the fatigue life met the ISO standards. Additionally, manufacturability was considered in the design process and a Ti-6Al-4V prototype was printed with an EOS selective laser melting machine.

scholarly journals Design of Customize Interbody Fusion Cages of Ti64ELI with Gradient Porosity by Selective Laser Melting Process

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 307
Author(s):  
Cheng-Tang Pan ◽  
Che-Hsin Lin ◽  
Ya-Kang Huang ◽  
Jason S. C. Jang ◽  
Hsuan-Kai Lin ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Selective Laser Melting ◽  
Stress Shielding ◽  
Simulation Software ◽  
Surrounding Tissue ◽  
Shielding Effect ◽  
Stress And Strain ◽  
Laser Melting ◽  
Flexion Extension ◽  
Intervertebral Cage

Intervertebral fusion surgery for spinal trauma, degeneration, and deformity correction is a major vertebral reconstruction operation. For most cages, the stiffness of the cage is high enough to cause stress concentration, leading to a stress shielding effect between the vertebral bones and the cages. The stress shielding effect affects the outcome after the reconstruction surgery, easily causing damage and leading to a higher risk of reoperation. A porous structure for the spinal fusion cage can effectively reduce the stiffness to obtain more comparative strength for the surrounding tissue. In this study, an intervertebral cage with a porous gradation structure was designed for Ti64ELI alloy powders bonded by the selective laser melting (SLM) process. The medical imaging software InVesalius and 3D surface reconstruction software Geomagic Studio 12 (Raindrop Geomagic Inc., Morrisville, NC, USA) were utilized to establish the vertebra model, and ANSYS Workbench 16 (Ansys Inc, Canonsburg, PA, USA) simulation software was used to simulate the stress and strain of the motions including vertical body-weighted compression, flexion, extension, lateral bending, and rotation. The intervertebral cage with a hollow cylinder had porosity values of 80–70–60–70–80% (from center to both top side and bottom side) and had porosity values of 60–70–80 (from outside to inside). In addition, according to the contact areas between the vertebras and cages, the shape of the cages can be custom-designed. The cages underwent fatigue tests by following ASTM F2077-17. Then, mechanical property simulations of the cages were conducted for a comparison with the commercially available cages from three companies: Zimmer (Zimmer Biomet Holdings, Inc., Warsaw, IN, USA), Ulrich (Germany), and B. Braun (Germany). The results show that the stress and strain distribution of the cages are consistent with the ones of human bone, and show a uniform stress distribution, which can reduce stress concentration.

Selective Laser Melting of Ti42Nb Composite Powder and the Effect of Laser Re-Melting

2019 ◽  
Vol 801 ◽  
pp. 270-275 ◽  
Author(s):  
Sheng Huang ◽  
Swee Leong Sing ◽  
Wai Yee Yeong
Keyword(s):  
Selective Laser Melting ◽  
Composite Powder ◽  
Stress Shielding ◽  
Alloyed Powder ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Implant Materials ◽  
Bio Compatibility ◽  
Alloy Systems

Ti-Nb based alloys have the potential to be used as structural implant materials due to their excellent bio-compatibility and ability to reduce stress shielding. The idea to additively manufacture Ti-Nb based alloys using selective laser melting (SLM) technology can further improve the resultant implant quality. However, the lack of economically sound and readily available pre-alloyed powder has pushed for the usage of composite powder as a means to hasten research pace in fabricating new alloy systems via SLM. The usage of Ti-Nb composite powder can lead to several problems, particularly the issue of macro-segregation. Hence, this paper presents the potential of laser re-melting scanning strategy to address macro-segregation without sacrificing (or even improving) density of parts fabricated by SLM.

Porosity content control of CoCrMo and titanium parts by Taguchi method applied to selective laser melting process parameter

2016 ◽  
Vol 22 (1) ◽  
pp. 20-30 ◽  
Author(s):  
David Joguet ◽  
Sophie Costil ◽  
Hanlin Liao ◽  
Yoann Danlos
Keyword(s):  
Selective Laser Melting ◽  
Design Methodology ◽  
Melting Process ◽  
Research Approach ◽  
Analysis Method ◽  
Laser Melting ◽  
Huge Number ◽  
Energy Estimation ◽  
Content Type ◽  
Potential Applications

Purpose – The purpose of this paper consists in the optimization and understanding of the Selective Laser Melting (SLM) manufacturing process of biomaterials, such as T40 and CoCrMo, as scaffolds. Moreover, process optimization is also challenging, with regards to the huge number of parameters and their influence on the finished product. Design/methodology/approach – The paper opted for an exploratory study using Taguchi analysis method to precisely identify the most relevant parameters and justify the energy estimation. Findings – The study showed that SLM fits perfectly with the T40 and CoCrMo part manufacturing. This method allowed to have a complete overview of all the potential applications of SLM for implant manufacturing. Originality/value – With this research approach, the results may be generalized to other material and showed a good theoretical approach.

scholarly journals Selective laser melting of Ti6Al7Nb with hydroxyapatite addition

2014 ◽  
Vol 20 (4) ◽  
pp. 301-310 ◽  
Author(s):  
Teodora Marcu ◽  
Cinzia Menapace ◽  
Luca Girardini ◽  
Dan Leordean ◽  
Catalin Popa
Keyword(s):  
Selective Laser Melting ◽  
Laser Power ◽  
Design Methodology ◽  
Point Of View ◽  
Medical Applications ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Content Type ◽  
Processing Times ◽  
Scanning Electron

Purpose – The purpose of this paper was to obtain by means of selective laser melting and then characterize biocomposites of medical-grade Ti6Al7Nb with hydroxyapatite (2 and 5 vol.%) and without hydroxyapatite, as reference. Design/methodology/approach – Rectangular samples were manufactured with the same scanning strategy; the laser power was between 50 W and 200 W. Processed samples were analysed by means of optical microscopy, scanning electron microscopy and microhardness. Findings – The results showed that despite the very short processing times, hydroxyapatite decomposed and interacted with the base Ti6Al7Nb material. The decomposition degree was found to depend on the applied laser power. From the porosity and bulk microstructure point of view, the most appropriate materials for the purposed medical applications were Ti6Al7Nb with hydroxyapatite processed with a laser power of 50 W. Originality/value – The originality of the present work consists in the study of the behaviour and interaction of hydroxyapatite additive with the Ti6Al7Nb base powder under selective laser melting conditions, as depending on the applied laser power.

The Effect of Manufacturing Defects on the Fatigue Behaviour of Ti-6Al-4V Specimens Fabricated Using Selective Laser Melting

2014 ◽  
Vol 891-892 ◽  
pp. 1519-1524 ◽  
Author(s):  
Qian Chu Liu ◽  
Joe Elambasseril ◽  
Shou Jin Sun ◽  
Martin Leary ◽  
Milan Brandt ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Selective Laser Melting ◽  
Fatigue Crack Initiation ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Metallic Materials ◽  
Laser Melting ◽  
Manufacturing Defects ◽  
Materials Properties

Additive Manufacturing (AM) technologies are considered revolutionary because they could fundamentally change the way products are designed. Selective Laser Melting (SLM) is a metal based AM process with significant and growing potential for the manufacture of aerospace components. Traditionally a material needs to be listed in the Metallic Materials Properties Development and Standardization (MMPDS) handbook if it is to be considered certified. However, this requires a considerable amount of test data to be generated on the materials mechanical properties. Therefore, the MMPDS certification process does not lend itself easily to the certification of AM components as the final component can have similar mechanical properties to wrought alloys combined with the defects associated with traditional casting and welding technologies. These defects can substantially decrease the fatigue life of a fabricated component. The primary purpose of this investigation was to study the fatigue behaviour of as-built Ti-6Al-4V (Ti64) samples. Fatigue tests were performed on the Ti-6Al-4V specimens built using SLM with a variety of layer thicknesses and build (vertical or horizontal) directions. Fractography revealed the presence of a range of manufacturing defects located at or near the surface of the specimens. The experimental results indicated that Lack-of-Fusion (LOF) defects were primarily responsible for fatigue crack initiation. The reduction in fatigue life appeared to be affected by the location, size and shape of the LOF defect.

scholarly journals Mechanical property of octahedron Ti6Al4V fabricated by selective laser melting

2021 ◽  
Vol 60 (1) ◽  
pp. 894-911
Author(s):  
Yun Zhai ◽  
Sibo He ◽  
Lei Lei ◽  
Tianmin Guan
Keyword(s):  
Mechanical Property ◽  
Elastic Modulus ◽  
Selective Laser Melting ◽  
Mechanical Performance ◽  
Lattice Structure ◽  
Stress Shielding ◽  
Human Bone ◽  
Shielding Effect ◽  
Basic Unit ◽  
Laser Melting

Abstract The stress shielding effect is a critical issue for implanted prosthesis due to the difference in elastic modulus between the implanted material and the human bone. The adjustment of the elastic modulus of implants by modification of the lattice structure is the key to the research in the field of implanted prosthesis. Our work focuses on the basic unit structure of octahedron Ti6Al4V. The equivalent elastic modulus and equivalent density of porous structure are optimized according to the mechanical properties of human bone tissue by adjusting the edge diameter and side length of octahedral lattice. Macroscopic long-range ordered arrangement of lattice structures is fabricated by selective laser melting (SLM) technology. Finite element simulation is performed to calculate the mechanical property of octahedron Ti6Al4V. Scanning electronic microscopy is applied to observe the microstructure of octahedron alloy and its cross section morphology of fracture. Standard compression test is performed for the stress–strain behavior of the specimen. Our results show that the octahedral lattice with the edge diameter of 0.4 mm and unit cell length of 1.5 mm has the best mechanical property which is close to the human bone. The value of equivalent elastic modulus increases with the increase in the edge diameter. The SLM technology proves to be an effective processing way for the fabrication of complex microstructures with porosity. In addition, the specimen exhibits isotropic mechanical performance and homogeneity which significantly meet the requirement of implanted prosthetic medical environment.

Selective Laser Melting Molding of Individualized Femur Implant: Design, Process, Optimization

2021 ◽  
Vol 18 (1) ◽  
pp. 128-137
Author(s):  
Guoqing Zhang ◽  
Junxin Li ◽  
Jin Li ◽  
Xiaoyu Zhou ◽  
Juanjuan Xie ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Process Optimization ◽  
Design Process ◽  
Implant Design ◽  
Laser Melting

scholarly journals Comparative study of cell growth and cellular adhesion on Ti-6Al-4V surfaces made by Selective Laser Melting followed by different surface post processing steps

2021 ◽  
Vol 1135 (1) ◽  
pp. 012028
Author(s):  
Benedikt Adelmann ◽  
Melanie Abb ◽  
Ralf Hellmann
Keyword(s):  
Surface Roughness ◽  
Cell Growth ◽  
Selective Laser Melting ◽  
Hot Isostatic Pressing ◽  
Stress Shielding ◽  
Cellular Adhesion ◽  
Laser Melting ◽  
Sem Images ◽  
Inferior Surface ◽  
Medical Grade

Abstract Selective laser melting is generally considered as to improve the design of medical implants, thus supporting medical treatment and maintaining mobility of invalid and older people. In particular, medical grade titanium alloys are in favour for spinal implants, as being nowadays manufactured by, e.g., milling. Selective laser melting offers the advantage of an adapted elasticity as to avoid stress shielding within the backbone by including complex lattice structures inside the individualized implant. For the integration into the backbone, surface properties, particularly surface roughness, are crucial with respect to biocompatibility and cell growth. Opposite to conventional milling, selective laser melting, however, results in an inferior surface roughness, leading to the necessity of downstream process steps. We report on cell growth and cellular adhesion of human primary fibroblasts on medical grade Ti-6Al-4V fabricated by selective laser melting followed by combinations of milling, hot isostatic pressing, chemical surface treatment and steam-sterilization to generate different surface conditions for cell growth. For example, cell growth is studied for varying milling path spacing on SLM parts exhibiting different surface roughness. Our results reveal good cell growth for milling path spacing lower than 0.18 mm as compared to higher milling path spacing and not milled surfaces. Cell fluorescence images and SEM images show that the cell growth is additionally hampered by the edges of the milling path. Conveniently, process failures such as pores originating from the selective laser melting process do not hamper the cell growth.

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