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.

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 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.

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 Failure Analysis of the Tree Column Structures Type AlSi10Mg Alloy Branches Manufactured by Selective Laser Melting

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3969
Author(s):  
Peikang Bai ◽  
Pengcheng Huo ◽  
Taotao Kang ◽  
Zhanyong Zhao ◽  
Wenbo Du ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stress Concentration ◽  
Selective Laser Melting ◽  
Fracture Morphology ◽  
Eutectic Structure ◽  
Laser Melting ◽  
Different Shapes ◽  
Si Content ◽  
Elastic Shear ◽  
Tree Type

AlSi10Mg alloy branches were fabricated by selective laser melting (SLM), and the branches were employed to evaluate their effect on the mechanical properties. When the porous branches were compressed along its building direction, the tree column structures-type AlSi10Mg alloy branches collapsed twice, which had typical elastic, shear, collapse, and densification stages. The compressive stress concentration at the interface between the support and the porous body caused the fracture of the tree column structures-type AlSi10Mg alloy branches. The fracture surface indicated that the prepared tree-type branches were distributed with different shapes of dimples, and the Si content inside the dimples was higher than that of the edge. The morphology of the Al-Si eutectic structure formed by SLM and the stress concentration at the Al/Al-Si-eutectic interface affected the fracture morphology and Si content distribution.

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.

scholarly journals A Further Analysis on Ti6Al4V Lattice Structures Manufactured by Selective Laser Melting

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Saverio Maietta ◽  
Antonio Gloria ◽  
Giovanni Improta ◽  
Maria Richetta ◽  
Roberto De Santis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mass Transport ◽  
Selective Laser Melting ◽  
Mechanical Performance ◽  
Stress Shielding ◽  
Lattice Structures ◽  
Laser Melting ◽  
Tissue Ingrowth ◽  
Architectural Features ◽  
Bone Atrophy

Mechanical and architectural features play an important role in designing biomedical devices. The use of materials (i.e., Ti6Al4V) with Young’s modulus higher than those of natural tissues generally cause stress shielding effects, bone atrophy, and implant loosening. However, porous devices may be designed to reduce the implant stiffness and, consequently, to improve its stability by promoting tissue ingrowth. If porosity increases, mass transport properties, which are crucial for cell behavior and tissue ingrowth, increase, whereas mechanical properties decrease. As reported in the literature, it is always possible to tailor mass transport and mechanical properties of additively manufactured structures by varying the architectural features, as well as pore shape and size. Even though many studies have already been made on different porous structures with controlled morphology, the aim of current study was to provide only a further analysis on Ti6Al4V lattice structures manufactured by selective laser melting. Experimental and theoretical analyses also demonstrated the possibility to vary the architectural features, pore size, and geometry, without dramatically altering the mechanical performance of the structure.

scholarly journals Selective Laser Melting and Electron Beam Melting of Ti6Al4V for Orthopedic Applications: A Comparative Study on the Applied Building Direction

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5584
Author(s):  
Paola Ginestra ◽  
Rosalba Monica Ferraro ◽  
Keren Zohar-Hauber ◽  
Andrea Abeni ◽  
Silvia Giliani ◽  
...  
Keyword(s):  
Electron Beam ◽  
Selective Laser Melting ◽  
Electron Beam Melting ◽  
Cell Attachment ◽  
Dimensional Accuracy ◽  
Surrounding Tissue ◽  
Laser Melting ◽  
Implant Surface ◽  
Whole Process

The 3D printing process offers several advantages to the medical industry by producing complex and bespoke devices that accurately reproduce customized patient geometries. Despite the recent developments that strongly enhanced the dominance of additive manufacturing (AM) techniques over conventional methods, processes need to be continually optimized and controlled to obtain implants that can fulfill all the requirements of the surgical procedure and the anatomical district of interest. The best outcomes of an implant derive from optimal compromise and balance between a good interaction with the surrounding tissue through cell attachment and reduced inflammatory response mainly caused by a weak interface with the native tissue or bacteria colonization of the implant surface. For these reasons, the chemical, morphological, and mechanical properties of a device need to be designed in order to assure the best performances considering the in vivo environment components. In particular, complex 3D geometries can be produced with high dimensional accuracy but inadequate surface properties due to the layer manufacturing process that always entails the use of post-processing techniques to improve the surface quality, increasing the lead times of the whole process despite the reduction of the supply chain. The goal of this work was to provide a comparison between Ti6Al4V samples fabricated by selective laser melting (SLM) and electron beam melting (EBM) with different building directions in relation to the building plate. The results highlighted the influence of the process technique on osteoblast attachment and mineralization compared with the building orientation that showed a limited effect in promoting a proper osseointegration over a long-term period.

scholarly journals Prediction of Model Distortion by FEM in 3D Printing via the Selective Laser Melting of Stainless Steel AISI 316L

2021 ◽  
Vol 11 (4) ◽  
pp. 1656 ◽  
Author(s):  
Marek Pagac ◽  
Jiri Hajnys ◽  
Radim Halama ◽  
Tariq Aldabash ◽  
Jakub Mesicek ◽  
...  
Keyword(s):  
Stainless Steel ◽  
3D Printing ◽  
Selective Laser Melting ◽  
Base Plate ◽  
Simulation Software ◽  
Aisi 316L ◽  
Laser Melting ◽  
Stress Prediction ◽  
Steel Aisi ◽  
Prediction And Simulation

This paper deals with an experimental analysis of stress prediction and simulation prior to 3D printing via the selective laser melting (SLM) method and the subsequent separation of a printed sample from a base plate in two software programs, ANSYS Addictive Suite and MSC Simufact Additive. Practical verification of the simulation was performed on a 3Dprinted topologically optimized part made of AISI 316L stainless steel. This paper presents a typical workflow for working with metallic 3D printing technology and the state-of-the-art knowledge in the field of stress analysis and simulation of printed components. The paper emphasizes the role of simulation software for additive production and reflects on their weaknesses and strengths as well, with regard to their use not only in science and research but also in practice.

Tension-compression asymmetric mechanical behaviour of lattice cellular structures produced by selective laser melting

2020 ◽  
Vol 234 (16) ◽  
pp. 3241-3256 ◽  
Author(s):  
Sunil Raghavendra ◽  
Alberto Molinari ◽  
Vigilio Fontanari ◽  
Michele Dallago ◽  
Valerio Luchin ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Stress Shielding ◽  
Tensile Tests ◽  
Porous Titanium ◽  
Cellular Structures ◽  
Compression Tests ◽  
Laser Melting ◽  
Broad Array ◽  
Cell Topology ◽  
Titanium Alloy Ti6al4v

Additive manufacturing is an evolving technology for fabricating porous structures used in a broad array of applications, ranging from the aerospace industry to biomedical engineering. Porous titanium alloy (Ti6Al4V) structures play a major role in biomedical implants and are preferred over conventional solid implants because their properties can be tailored to obtain the stiffness required to avoid stress shielding and improve osteointegration. The mechanical properties of these structures are dependent on unit cell topology and overall porosity. In the present work, three open cellular configurations were studied, namely regular (square), irregular (skewed square) and fully random structures, at three different porosity levels. The samples were manufactured using the selective laser melting of spherical Ti6Al4V powder. The deviations of manufactured samples from as designed were assessed using morphological characterisations and porosity analyses. The mechanical characterisations of the samples included monotonic and cyclic tensile tests, along with conventional compression tests under monotonic and cyclic conditions. The results from the study indicate a clear deviation of thickness values from as-designed values. The effect of inclination of the strut with respect to the loading axis has been studied in compression samples. The off-axis loading in compression led to the asymmetry in the Young's modulus in compression and tension. These led to finite element modelling of structures in the elastic regime and its validation using Gibson–Ashby model for cellular structures.

MANUFACTURING NOVEL HEAT TRANSFER DEVICES BY SELECTIVE LASER MELTING

Equipment ◽  
2006 ◽  
Author(s):  
S. Tsopanos ◽  
M. Wong ◽  
I. Owen ◽  
C. J. Sutcliffe
Keyword(s):  
Heat Transfer ◽  
Selective Laser Melting ◽  
Laser Melting
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