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Unit cell design: (a) 3D lattice infill pattern, (b) double-pyramid lattice with cross, (c) doublepyramid lattice and face diagonals, (d) octahedral lattice 2, (e) specimens' dimensions.
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The development of medical implants is an ongoing process pursued by many studies in the biomedical field. The focus is on enhancing the structure of the implants to improve their biomechanical properties, thus reducing the imperfections for the patient and increasing the lifespan of the prosthesis. The purpose of this study was to investigate the...
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... parameters were chosen based on the idea of getting a close-in-value porosity percentage for all types in order to make sure that the comparison was as effective as possible by having a small range of porosity among the samples. In Figure 1, the forming unit cell design for each type is shown, with a detailed view of the dimensions of the specimens. ISO standard 13314 was followed in terms of the relationships among the dimensions, where the length, width, and height of each unit cell were equal to or more than 10 times the pore size. ...
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... As shown in Figure 1: (a), a 2 mm-thick shell all over the transparent part of the implant body is to be latticed with three unit-cell types: (b) 3D-lattice infill, (c) double-pyramid lattice and face diagonals, and (d) octahedral lattice 2 (names of the unit-cell types are based on the Ansys SpaceClaim 2021 R2 Canonsburg, Pa, USA software classifications). From a medical point of view, the outer thickness of 2 mm was chosen to be latticed in order to ease the interaction between the bone and implant since the value of Young's modulus for the implant material decreased, as proven in a previous study [39], into a value close to the bone's, which made the integration smoother [40]. ...
... As shown in Figure 1: (a), a 2 mmthick shell all over the transparent part of the implant body is to be latticed with three unit-cell types: (b) 3D-lattice infill, (c) double-pyramid lattice and face diagonals, and (d) octahedral lattice 2 (names of the unit-cell types are based on the Ansys SpaceClaim 2021 R2 Canonsburg, Pa, USA software classifications). From a medical point of view, the outer thickness of 2 mm was chosen to be latticed in order to ease the interaction between the bone and implant since the value of Young's modulus for the implant material decreased, as proven in a previous study [39], into a value close to the bone's, which made the integration smoother [40]. The porosity of lattice structures within the latticed part can be determined by employing a calculation that relies on the volume measurements, as shown in Equation (1). ...
As the name implies, patient-specific latticed hip implants vary in design depending on the properties required by the patient to serve as a valid suitable organ. Unit cells are typically built based on a 3D design of beams, and the properties of unit cells change depending on their geometries, which, in turn, are defined by two main parameters: beam length and beam thickness. Due to the continuous increase in the complexity of the unit cells’ designs and their reactions against different loads, the call for machine learning techniques is inevitable to help explore the parameters of the unit cells that can build lattice structures with specific desirable properties. In this study, a machine learning technique is used to predict the best defining parameters (length and thickness) to create a latticed design with a set of required properties (mainly porosity). The data (porosity, mass, and latticed area) from the properties of three unit-cell types, applied to the latticed part of a hip implant design, were collected based on the random length and thickness for three unit-cell types. Using the linear regression algorithm (a supervised machine learning method) from the scikit-learn library, a machine learning model was developed to predict the value of the porosity for the lattice structures based on the length and thickness as input data. The number of samples needed to generate an accurate result for each type of unit cell is also discussed.
... In addition, various skeletal sites have different mechanical requirements [12,13], and the spine is often subjected to compression and bending loads during exercise [14]. At the same time, the tibia of the knee joint bears not only external pressure load but also specific shear loads [15,16]. ...
The elastic modulus of traditional solid titanium alloy tibial implants is much higher than that of human bones, which can cause stress shielding. Designing them as a porous structure to form a bone-like trabecular structure effectively reduces stress shielding. However, the actual loading conditions of bones in different parts of the human body have not been considered for some trabecular structures, and their mechanical properties have not been considered concerning the personalized differences of other patients. Therefore, based on the elastic modulus of the tibial stem obtained from Quantitative Computed Tomography (QCT) imaging between 3.031 and10.528 GPa, and the load-bearing state of the tibia at the knee joint, a porous structure was designed under compressive and shear loading modes using topology optimization. Through comprehensive analysis of the mechanical and permeability properties of the porous structure, the results show that the Topology Optimization–Shear-2 (TO-S2) structure has the best compressive, shear mechanical properties and permeability and is suitable as a trabecular structure for tibial implants. The Gibson–Ashby model was established to control the mechanical properties of porous titanium alloy. A gradient filling of porous titanium alloy with a strut diameter of 0.106–0.202 mm was performed on the tibial stem based on the elastic modulus range, achieving precise matching of the mechanical properties of tibial implants and closer to the natural structure than uniformly distributed porous structures in human bones. Finally, the new tibial implant was printed by selective laser melting (SLM), and the molding effect was excellent.
... Since FEM is a costeffective method, various FEM methods are used by current researchers to design lattice structures and calculate mechanical properties. However, a slight deviation in outcomes can be observed during FEM analysis compared to real experimentations [10]. Apart from this, FEM analysis for AM parts analysis has a limitation such as it cannot consider the manufacturing parameters during the simulation [9]. ...
... In the literature [55][56][57][58], there are several lattice structure finite element analyses examples and these analysis examples benefited from own mechanical properties of materials such as aluminum alloy, inconel, stainless steel 316L, magnesium alloy, and titanium alloy. General view of this issue includes Young's modulus, yield strength, ultimate strength, and Poisson's ratio. ...
... In order to finite element analysis verification, a numerical comparison and verification was accomplished with a study. In the reference [58], 3D lattice model which has 74% porosity rate and 0.7 mm strut thickness was used as comparison sample in finite element analysis study. Finite element analysis process includes 1.5 mm mesh size and element number between 500,000 and 700,000. ...
Bone tissue loss may occur in bone structures, which are one of the elements that provide the body’s endurance and movement of living things, due to situations such as falling, hitting, or cancer formation. In bad scenarios, applications such as an external plate or internal rod addition are made to regain the old durability of the structure. At the same time, full or semi-prosthesis applications can be made in cases where the original bone structure cannot be preserved. With today’s advanced possibilities, lattice structures can be produced effortlessly with the additive manufacturing (AM) method. Here, the formation of the structure that can show anisotropic behavior depending on the production and the effect of the roughness caused by the production quality should also be seen in the process plan. In this study, it was aimed to compare the durability of titanium (Ti-6Al-4V) and magnesium (ZK60) materials for humeral half prosthesis using cubic-based lattice structure and to show their differences compared to the original bone structure. Maximum stress and deformation values were obtained by performing analyses with the finite element method on the lattice semi-humerus prosthesis obtained with this aim. Reliability analysis was made on the data obtained, and parameter optimization of the lattice structure was aimed. As a result of the study, it was seen that the lattice structure with 65% porosity compared to the reference values is reliable and with the same reliability rate, magnesium provides approximately 60% lightness compared to titanium.
... A lightweight implant can be obtained by changing the materials from 316 L stainless steel to titanium alloy (Ti6Al4V), as well as pore designation [16]. However, the topology optimization of the hip implant is still questionable, thus leading to this study, where an analysis was performed on hip implants with different lattice structure that affect the mass of the hip implant [17]. Therefore, this study was conducted to study the biomechanical effects of the commonly used lattice structures of Gyroid and Voronoi on the uncemented hip implant design through finite element analysis. ...
Total hip arthroplasty (THA) is most likely one of the most successful surgical procedures in medicine. It is estimated that three in four patients live beyond the first post-operative year, so appropriate surgery is needed to alleviate an otherwise long-standing suboptimal functional level. However, research has shown that during a complete THA procedure, a solid hip implant inserted in the femur can damage the main arterial supply of the cortex and damage the medullary space, leading to cortical bone resorption. Therefore, this study aimed to design a porous hip implant with a focus on providing more space for better osteointegration, improving the medullary revascularisation and blood circulation of patients. Based on a review of the literature, a lightweight implant design was developed by applying topology optimisation and changing the materials of the implant. Gyroid and Voronoi lattice structures and a solid hip implant (as a control) were designed. In total, three designs of hip implants were constructed by using SolidWorks and nTopology software version 2.31. Point loads were applied at the x, y and z-axis to imitate the stance phase condition. The forces represented were x = 320 N, y = −170 N, and z = −2850 N. The materials that were used in this study were titanium alloys. All of the designs were then simulated by using Marc Mentat software version 2020 (MSC Software Corporation, Munich, Germany) via a finite element method. Analysis of the study on topology optimisation demonstrated that the Voronoi lattice structure yielded the lowest von Mises stress and displacement values, at 313.96 MPa and 1.50 mm, respectively, with titanium alloys as the materials. The results also indicate that porous hip implants have the potential to be implemented for hip implant replacement, whereby the mechanical integrity is still preserved. This result will not only help orthopaedic surgeons to justify the design choices, but could also provide new insights for future studies in biomechanics.
... The current von Mises stress results from the computational simulation of hard-onhard bearings of total hip prosthesis need to be validated to ensure the accuracy of the results obtained in previous studies under identical conditions and parameters [41]. The highest von Mises stress (in the 7th phase of the gait loading) for the CoCrMo-on-CoCrMo bearing was validated by the previous research by Saputra et al. [24] presented in Figure 5. ...
Due to polymeric wear debris causing osteolysis from polymer, metal ions causing metallosis from metal, and brittle characteristic causing fracture failure from ceramic in the application on bearing of total hip prosthesis requires the availability of new material options as a solution to these problems. Polycrystalline diamond (PCD) has the potential to become the selected material for hard-on-hard bearing in view of its advantages in terms of mechanical properties and biocompatibility. The present study contributes to confirming the potential of PCD to replace metals and ceramics for hard-on-hard bearing through von Mises stress investigations. A computational simulation using a 2D axisymmetric finite element model of hard-on-hard bearing under gait loading has been performed. The percentage of maximum von Mises stress to respective yield strength from PCD-on-PCD is the lowest at 2.47%, with CoCrMo (cobalt chromium molybdenum)-on-CoCrMo at 10.79%, and Al2O3 (aluminium oxide)-on-Al2O3 at 13.49%. This confirms that the use of PCD as a hard-on-hard bearing material is the safest option compared to the investigated metal and ceramic hard-on-hard bearings from the mechanical perspective.
... Under the same density conditions, compared with the disordered structures (such as foam and sponges), it has higher strength, modulus, energy absorption capacity and independently designed structural characteristics [3][4][5]. Lattice materials have become one of the research hotspots in aviation, aerospace, shipbuilding, automobile and biomedicine [6][7][8][9][10][11]. ...
In this study, electroless nickel plating and electrodeposition were used to deposit thin films on the polymer lattice template prepared by 3D printing, then seven Octet hollow nickel lattice materials with different structural parameters were synthesized by etching process at the expense of the polymer backbone. The microstructure and properties of the Octet structure nickel lattice were characterized by X-ray diffraction, Electron backscattering diffraction and transmission electron microscopy. According to the results, the average grain size of the electrodeposition Ni lattice material was 429 nm, and (001) weak texture was found along the direction of the film deposition. The lattice deformation mode changed with the increase of the lattice length-to-diameter ratio, and it shifted from the lattice deformation layer-by-layer and the overall deformation to the shear deformation in the 45° direction. The strength, modulus and energy absorption properties of the Octet lattice increased with the density, and they were exponentially related to density. In the relative density range of 0.7~5%, Octet hollow Ni lattices with the same density conditions but different structural parameters showed similar compressive strength and elasticity modulus; the energy absorption capacity, however, was weakened as the length-to-diameter ratio increased.
In the present work, the influence of defects on the compressive response of octet‐truss AlSi10Mg lattice structure specimens produced with a selective laser melting process is investigated. The defect population in one cell, in two cells, and cubic specimens composed of 27 cells has been assessed with micro‐computed tomography (micro‐CT) analyses. The statistical distributions of the characteristic defect sizes, i.e., the equivalent diameter, the volume, and the surface, assessed in the lattice structure specimens and in volumes randomly extracted from a rectangular bar have been compared. Finally, the compressive behavior of lattice structure specimens has been simulated with a simplified damage‐tolerant finite element model accounting for the influence of defects and compared with experimental results. The analyses have proven that the defect population in volumes extracted from a rectangular bar can provide reliable simulated results, even if micro‐CT inspections of a unit cell or specimens made of several cells are suggested.
