A Proof of Concept Study of the Mechanical Behavior of Lattice Structures Used to Design a Shoulder Hemi-Prosthesis

2021 ◽  
Author(s):  
Marinela Peto ◽  
Oscar Aguilar-Rosas ◽  
Erick Erick Ramirez-Cedillo ◽  
Moises Jimenez ◽  
Adriana Hernandez ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Cell Attachment ◽  
Lattice Structure ◽  
Material Model ◽  
Patient Specific ◽  
Hexagonal Prism ◽  
Lattice Structures ◽  
Proof Of Concept

Abstract Lattice structures offer great benefits when employed in medical implants for cell attachment and growth (osseointegration), minimization of stress shielding phenomena, and weight reduction. This study is focused on a proof of concept for developing a generic shoulder hemi-prosthesis, from a patient-specific case of a 46 years old male with a tumor on the upper part of his humerus. A personalized biomodel was designed and a lattice structure was integrated in its middle portion, to lighten weight without affecting humerus’ mechanical response. To select the most appropriate lattice structure, three different configurations were initially tested: Tetrahedral Vertex Centroid (TVC), Hexagonal Prism Vertex Centroid (HPVC), and Cubic Diamond (CD). They were fabricated in resin by digital light processing and its mechanical behavior was studied via compression testing and finite element modeling (FEM). The selected structure according to the results was the HPVC, which was integrated in a digital twin of the biomodel to validate its mechanical performance through FEM but substituting the bone material model with a biocompatible titanium alloy (Ti6Al4V) suitable for prostheses fabrication. Results of the simulation showed acceptable levels of Von Mises stresses (325 MPa max.), below the elastic limit of the titanium alloys, and a better response (52 MPa max.) in a model with equivalent elastic properties, with stress performance in the same order of magnitude than the showed in bone’s material model.

Mechanical Behavior of Lattice Structures Fabricated by Direct Light Processing With Compression Testing and Size Optimization of Unit Cells

2019 ◽  
Author(s):  
Marinela Peto ◽  
Erick Ramirez-Cedillo ◽  
Mohammad J. Uddin ◽  
Ciro A. Rodriguez ◽  
Hector R. Siller
Keyword(s):  
Mechanical Behavior ◽  
Stress Shielding ◽  
Unit Cell ◽  
Compression Testing ◽  
Size Optimization ◽  
Hexagonal Prism ◽  
Lattice Structures ◽  
Dog Bone ◽  
Direct Light ◽  
Unit Cells

Abstract Lattice structures used for medical implants offer advantages related to weight reduction, osseointegration, and minimization of stress shielding. This paper intends to study and to compare the mechanical behavior of three different lattice structures: tetrahedral vertex centroid (TVC), hexagonal prism vertex centroid (HPVC), and cubic diamond (CD), that are designed to be incorporated in a shoulder hemiprosthesis. The unit cell configurations were generated using nTopology Element Pro software with a uniform strut thickness of 0.5 mm. Fifteen cuboid samples of 25mm × 25mm × 15 mm, five for each unit cell configuration, were additively manufactured using Direct Light Printing (DLP) technology with a layer height of 50μm and a XY resolution of 73μm. The mechanical behavior of the 3D printed lattice structures was examined by performing mechanical compression testing. E-silicone (methacrylated silicone) was used for the fabrication of samples, and its mechanical properties were obtained from experimental tensile testing of dog-bone samples. A methodology for size optimization of lattice unit cells is provided, and the optimization is achieved using nTopology Element Pro software. The generated results are analyzed, and the HPVC configuration is selected to be incorporated in the further design of prosthesis for bone cancer patients.

scholarly journals In Silico Performance of a Recellularized Tissue-Engineered Transcatheter Aortic Valve

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Christopher Noble ◽  
Joshua Choe ◽  
Susheil Uthamaraj ◽  
Milton Deherrera ◽  
Amir Lerman ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Heart Valves ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Fe Analysis ◽  
Model Parameters ◽  
Biaxial Testing ◽  
Principal Stresses

Commercially available heart valves have many limitations, such as a lack of remodeling, risk of calcification, and thromboembolic problems. Many state-of-the-art tissue-engineered heart valves (TEHV) rely on recellularization to allow remodeling and transition to mechanical behavior of native tissues. Current in vitro testing is insufficient in characterizing a soon-to-be living valve due to this change in mechanical response; thus, it is imperative to understand the performance of an in situ valve. However, due to the complex in vivo environment, this is difficult to accomplish. Finite element (FE) analysis has become a standard tool for modeling mechanical behavior of heart valves; yet, research to date has mostly focused on commercial valves. The purpose of this study has been to evaluate the mechanical behavior of a TEHV material before and after 6 months of implantation in a rat subdermis model. This model allows the recellularization and remodeling potential of the material to be assessed via a simple and inexpensive means prior to more complex ovine orthotropic studies. Biaxial testing was utilized to evaluate the mechanical properties, and subsequently, constitutive model parameters were fit to the data to allow mechanical performance to be evaluated via FE analysis of a full cardiac cycle. Maximum principal stresses and strains from the leaflets and commissures were then analyzed. The results of this study demonstrate that the explanted tissues had reduced mechanical strength compared to the implants but were similar to the native tissues. For the FE models, this trend was continued with similar mechanical behavior in explant and native tissue groups and less compliant behavior in implant tissues. Histology demonstrated recellularization and remodeling although remodeled collagen had no clear directionality. In conclusion, we observed successful recellularization and remodeling of the tissue giving confidence to our TEHV material; however, the mechanical response indicates the additional remodeling would likely occur in the aortic/pulmonary position.

Mesoscale Lattice Structure Design and Simulation with the Support of a Property Database

2021 ◽  
pp. 247-273
Author(s):  
Guoying Dong ◽  
Yunlong Tang ◽  
Yaoyao Fiona Zhao
Keyword(s):  
Mechanical Performance ◽  
Lattice Structure ◽  
Cellular Materials ◽  
Structure Design ◽  
Lattice Structures ◽  
Strut Thickness ◽  
Design And Optimization ◽  
The Third ◽  
Unit Cells ◽  
The Difference

The lattice structure is a type of cellular materials [1] that has truss-like structures with interconnected struts and nodes in a three-dimensional (3D) space. Compared to other cellular materials such as random foams and honeycombs, the lattice structures exhibit better mechanical performance [2]. Some examples of lattice structures are shown in Figure 8.1. The first one is a randomized lattice structure. Due to the disordered lattice cells, the properties of this type of lattice structures are stochastic and difficult to control. But it can be used as implants in orthopedic surgeries. The second and the third are lattice structures with periodic unit cells. The difference is that the strut thickness of the second one is uniform, which is called homogeneous lattice structures. However, the third one has non-uniform strut thickness for specific loading conditions, which is called heterogeneous lattice structures. By properly adjusting the material in vital parts of the lattice structure, the heterogeneous periodic lattice structure can have a better mechanical performance than the homogeneous one with the same weight. Plenty of design and optimization methods [3-5] have been proposed for lattice structures to pursue better performance in different engineering applications. For example, the lattice structure is applied to achieve lightweight [3, 4], energy absorption [6], and thermal management [7]. Due to the complexity of the geometry, the fabrication of lattice structures had been the most critical issue. However, with the development of Additive Manufacturing (AM) processes, the difficulty in the fabrication was largely relieved.

Finite Element Analysis to Predict the Mechanical Behavior of Lattice Structures Made by Selective Laser Melting Technology

2014 ◽  
Vol 657 ◽  
pp. 231-235 ◽  
Author(s):  
Răzvan Păcurar ◽  
Ancuţa Păcurar ◽  
Anna Petrilak ◽  
Nicolae Bâlc
Keyword(s):  
Finite Element ◽  
Mechanical Behavior ◽  
Selective Laser Melting ◽  
Lattice Structure ◽  
Point Of View ◽  
Mechanical Resistance ◽  
Lattice Structures ◽  
Laser Melting ◽  
Element Analysis ◽  
Medical Implant

Within this article, there are presented a series of researches that are related to the field of customized medical implants made by Additive Manufacturing techniques, such as Selective Laser Melting (SLM) technology. Lattice structures are required in this case for a better osteointegration of the medical implant in the contact area of the bone. But the consequence of using such structures is important also by the mechanical resistance point of view. The shape and size of the cells that are connected within the lattice structure to be manufactured by SLM is critical in this case. There are also few limitations related to the possibilities and performances of the SLM equipment, as well. This is the reason why, several types of lattice structures were designed as having different geometric features, with the aim of analyzing by using finite element method, how the admissible stress and strain will be varied in these cases and what would be the optimum size and shape of the cells that confers the optimum mechanical behavior of lattice structures used within the SLM process of the customized medical implant manufactured from titanium-alloyed materials.

Mechanical Behavior of 3D Printed Stochastic Lattice Structures

2016 ◽  
Vol 258 ◽  
pp. 225-228 ◽  
Author(s):  
Georgios Maliaris ◽  
Elias Sarafis
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Voronoi Tessellation ◽  
Element Model ◽  
Adjacent Cell ◽  
Lattice Structures ◽  
Voronoi Cells ◽  
Compressive Loads ◽  
3D Printed ◽  
Irregular Cell

Stochastic lattice structures are modeled using a generative algorithm. In particular, the voronoi tessellation technique is applied for modeling cellular solids with irregular cell geometry and variable strut sections. The ligaments are formed considering the volume and shape characteristics of the voronoi cells. This way, the strut cross section variability is linked to the adjacent cell topology. The developed geometry is used for 3D printing the structures through a high accuracy SLA 3D printer. The mechanical properties of the photosensitive resin were determined by conducting tension experiments on appropriate 3D printed specimens. The printed stochastic structures were subjected to compressive loads in order to investigate their mechanical response. A finite element model of the compressive tests using the generated geometry, is also developed. The calculated results provide a good correlation with the experimental ones and also provide precious insight for the characterization of the mechanical behavior of the tested structures.

A platform for high-fidelity patient-specific structural modelling of atherosclerotic arteries: from intravascular imaging to three-dimensional stress distributions

2021 ◽  
Vol 18 (182) ◽  
Author(s):  
Karim Kadry ◽  
Max L. Olender ◽  
David Marlevi ◽  
Elazer R. Edelman ◽  
Farhad R. Nezami
Keyword(s):  
Mechanical Response ◽  
Plaque Rupture ◽  
Three Dimensional ◽  
Computational Modelling ◽  
Material Model ◽  
Patient Specific ◽  
Plaque Morphology ◽  
High Fidelity ◽  
Structural Behaviour ◽  
Heterogeneous Models

The pathophysiology of atherosclerotic lesions, including plaque rupture triggered by mechanical failure of the vessel wall, depends directly on the plaque morphology-modulated mechanical response. The complex interplay between lesion morphology and structural behaviour can be studied with high-fidelity computational modelling. However, construction of three-dimensional (3D) and heterogeneous models is challenging, with most previous work focusing on two-dimensional geometries or on single-material lesion compositions. Addressing these limitations, we here present a semi-automatic computational platform, leveraging clinical optical coherence tomography images to effectively reconstruct a 3D patient-specific multi-material model of atherosclerotic plaques, for which the mechanical response is obtained by structural finite-element simulations. To demonstrate the importance of including multi-material plaque components when recovering the mechanical response, a computational case study was conducted in which systematic variation of the intraplaque lipid and calcium was performed. The study demonstrated that the inclusion of various tissue components greatly affected the lesion mechanical response, illustrating the importance of multi-material formulations. This platform accordingly provides a viable foundation for studying how plaque micro-morphology affects plaque mechanical response, allowing for patient-specific assessments and extension into clinically relevant patient cohorts.

A Non-Orthogonal Constitutive Material Model for Advanced Woven Fabrics Based on a Mesoscale Unit Cell

2016 ◽  
Author(s):  
Ozan Erol ◽  
Brian M. Powers ◽  
Michael Keefe
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Material Model ◽  
Shear Resistance ◽  
Woven Fabrics ◽  
Unit Cell ◽  
Uniaxial Tensile ◽  
Constitutive Material Model ◽  
Proposed Model ◽  
Constitutive Material

Advanced woven fabrics can provide a wide range of mechanical properties since the yarns can be arranged in different architectural patterns thus allowing the fabric structure to be tuned based on the specific needs. This adjustable nature makes them an attractive material choice for applications where versatility is highly desired. Hence, there is an increasing interest in woven fabrics in the recent years. They have been used in various applications such as deployable structures, protective garments, medical scaffolds and composites. With the increased interest, there is a need for efficient and accurate computational tools to investigate the mechanical behavior and deformation of woven fabrics for specific applications. Although there are several computational models in the literature that can model uniaxial and biaxial behavior of woven fabrics, there are not any commonly accepted material models for woven fabrics due to the complex interaction of trellising and deformation. Here, we propose an easy to implement constitutive material model based on a mesoscale unit cell of the woven fabrics. The proposed model utilizes the two prominent deformation mechanisms affecting the mechanical response at the mesoscale level: (1) Yarn stretching, and (2) shearing. These mesoscale mechanisms are mechanistically implemented within an unit cell by using truss and rotational springs to generate the mechanical response of the woven fabric. The yarns’ nonlinear mechanical behavior is modeled with non-linear trusses and assumed to be pin-jointed at the center of the unit cell. The truss elements are allowed to rotate at the pin-joint reproducing the yarns’ relative rotational motion during shearing. The fabric’s shear resistance involves two components: yarn-to-yarn relative rotation/sliding and yarn locking due to the yarn transverse compression. These components of the fabric shear resistance are modeled as a non-linear rotational spring located at the pin-joint which generates a moment resisting the shear deformation. The developed forces and moments from the trusses and rotational spring within the unit cell structure are then used to determine the continuum stress state of the material point. The material properties and parameters defined in the proposed model are easy to obtain from uniaxial tensile and shear tests on fabrics. To validate the material model, plain weave Kevlar KM2 fabric is modeled by replicating the standard uniaxial tensile and bias extension tests. The results obtained show that the material model provides a good description of the in-plane deformation and mechanical response.

Investigation on Process-Properties Relationship with Mechanical Properties of Lattice-Structured Cellular Material for Lightweight Application

2018 ◽  
Vol 7 (3.17) ◽  
pp. 1
Author(s):  
N A. Rosli ◽  
R Hasan ◽  
W H. Ng ◽  
M K. Baharudin ◽  
M R. Alkahari
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Lattice Structure ◽  
Testing Machine ◽  
Lattice Structures ◽  
Universal Testing ◽  
Lightweight Structure ◽  
Energy Absorbing ◽  
Printing Machine ◽  
Operational Time

Lattice structures possess exceptional mechanical strength resulting in highly efficient load supporting systems. The lattice structure has been receiving interest in a variety of application areas and industries such as automotive, shipping and aeronautic. The metallic or polymer micro lattice structure can be categorized as lightweight and energy-absorbing structure. These characteristics are best applied to transportation part where the lightweight structure will help reduce its overall weight, thus increase the operational time since energy and cost consumption is a big concern in the industry these days. The aim of this study is to investigate relationship between process-properties and mechanical performance of polymer lattice structure. The lattice structure was designed by using SolidWorks software and fabricated using CubePro 3D printing machine. Compression test was performed by Instron 5585 universal testing machine to analyse the strength of the lattice structure. It was found that lattice structure manufactured with the setting of solid print strength, honeycomb print pattern, 70 µm layer thickness and strut diameter of 2.4 mm possesses the optimum mechanical property. 

scholarly journals Energy Absorption and Mechanical Performance of Functionally Graded Soft–Hard Lattice Structures

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1366 ◽  
Author(s):  
Hafizur Rahman ◽  
Ebrahim Yarali ◽  
Ali Zolfagharian ◽  
Ahmad Serjouei ◽  
Mahdi Bodaghi
Keyword(s):  
Cell Size ◽  
Energy Absorption ◽  
Mechanical Performance ◽  
Lattice Structure ◽  
Unit Cell ◽  
Lattice Structures ◽  
Hard Materials ◽  
Unit Cell Size ◽  
Rational Combination ◽  
Dual Material

Today, the rational combination of materials and design has enabled the development of bio-inspired lattice structures with unprecedented properties to mimic biological features. The present study aims to investigate the mechanical performance and energy absorption capacity of such sophisticated hybrid soft–hard structures with gradient lattices. The structures are designed based on the diversity of materials and graded size of the unit cells. By changing the unit cell size and arrangement, five different graded lattice structures with various relative densities made of soft and hard materials are numerically investigated. The simulations are implemented using ANSYS finite element modeling (FEM) (2020 R1, 2020, ANSYS Inc., Canonsburg, PA, USA) considering elastic-plastic and the hardening behavior of the materials and geometrical non-linearity. The numerical results are validated against experimental data on three-dimensional (3D)-printed lattices revealing the high accuracy of the FEM. Then, by combination of the dissimilar soft and hard polymeric materials in a homogenous hexagonal lattice structure, two dual-material mechanical lattice statures are designed, and their mechanical performance and energy absorption are studied. The results reveal that not only gradual changes in the unit cell size provide more energy absorption and improve mechanical performance, but also the rational combination of soft and hard materials make the lattice structure with the maximum energy absorption and stiffness, in comparison to those structures with a single material, interesting for multi-functional applications.

scholarly journals Compressive Behaviour of Additively Manufactured Lattice Structures: A Review

Aerospace ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 207
Author(s):  
Solomon O. Obadimu ◽  
Kyriakos I. Kourousis
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Lattice Structure ◽  
Evolutionary Process ◽  
Lattice Structures ◽  
Compressive Behaviour ◽  
Technology Industry ◽  
Unit Cells ◽  
Superior Mechanical Properties ◽  
And Performance

Additive manufacturing (AM) technology has undergone an evolutionary process from fabricating test products and prototypes to fabricating end-user products—a major contributing factor to this is the continuing research and development in this area. AM offers the unique opportunity to fabricate complex structures with intricate geometry such as the lattice structures. These structures are made up of struts, unit cells, and nodes, and are being used not only in the aerospace industry, but also in the sports technology industry, owing to their superior mechanical properties and performance. This paper provides a comprehensive review of the mechanical properties and performance of both metallic and non-metallic lattice structures, focusing on compressive behaviour. In particular, optimisation techniques utilised to optimise their mechanical performance are examined, as well the primary factors influencing mechanical properties of lattices, and their failure mechanisms/modes. Important AM limitations regarding lattice structure fabrication are identified from this review, while the paucity of literature regarding material extruded metal-based lattice structures is discussed.

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