Multiscale Design and Multiobjective Optimization of Orthopaedic Cellular Hip Implants

2011 ◽  
Author(s):  
Sajad Arabnejad Khanoki ◽  
Damiano Pasini
Keyword(s):  
Finite Element ◽  
Bone Resorption ◽  
Multiobjective Optimization ◽  
Relative Density ◽  
Homogeneous Medium ◽  
Unit Cell ◽  
Interface Stress ◽  
Optimization Strategy ◽  
Interface Failure ◽  
Nsga Ii

A multiscale design and multiobjective optimization procedure is developed to design a new type of graded cellular hip implant. We assume that the prosthesis design domain is occupied by a unit cell representing the building block of the implant. An optimization strategy seeks the best geometric parameters of the unit cell to minimize bone resorption and interface failure, two conflicting objective functions. Using the asymptotic homogenization method, the microstructure of the implant is replaced by a homogeneous medium with an effective constitutive tensor. This tensor is used to construct the stiffness matrix for the finite element modeling (FEM) solver that calculates the value of each objective function at each iteration. As an example, a 2D finite element model of a left implanted femur is developed. The relative density of the lattice material is the variable of the multiobjective optimization, which is solved through the non-dominated sorting genetic algorithm II (NSGA-II). The set of optimum relative density distributions is determined to minimize concurrently interface stress distribution and bone loss mass. The results show that the amount of bone resorption and the maximum value of interface stress can be reduced by over 70% and 50%, respectively, when compared to current fully dense titanium stem.

scholarly journals Multiscale Design and Multiobjective Optimization of Orthopedic Hip Implants with Functionally Graded Cellular Material

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Sajad Arabnejad Khanoki ◽  
Damiano Pasini
Keyword(s):  
Bone Resorption ◽  
Relative Density ◽  
Titanium Implant ◽  
Functionally Graded ◽  
Interface Instability ◽  
Interface Failure ◽  
Bone Implant ◽  
Multiscale Mechanics ◽  
Cellular Microstructure ◽  
Dense Titanium

Revision surgeries of total hip arthroplasty are often caused by a deficient structural compatibility of the implant. Two main culprits, among others, are bone-implant interface instability and bone resorption. To address these issues, in this paper we propose a novel type of implant, which, in contrast to current hip replacement implants made of either a fully solid or a foam material, consists of a lattice microstructure with nonhomogeneous distribution of material properties. A methodology based on multiscale mechanics and design optimization is introduced to synthesize a graded cellular implant that can minimize concurrently bone resorption and implant interface failure. The procedure is applied to the design of a 2D left implanted femur with optimized gradients of relative density. To assess the manufacturability of the graded cellular microstructure, a proof-of-concept is fabricated by using rapid prototyping. The results from the analysis are used to compare the optimized cellular implant with a fully dense titanium implant and a homogeneous foam implant with a relative density of 50%. The bone resorption and the maximum value of interface stress of the cellular implant are found to be over 70% and 50% less than the titanium implant while being 53% and 65% less than the foam implant.

scholarly journals Optimal Designs of Phononic Crystal Microstructures Considering Point and Line Defects

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1993
Author(s):  
Jingjie He ◽  
Jiamei Sun ◽  
Juncheng Fan ◽  
Zhiyuan Jia ◽  
Xiaopeng Zhang
Keyword(s):  
Finite Element ◽  
Band Gap ◽  
Phononic Crystal ◽  
Hyperelliptic Curves ◽  
Unit Cell ◽  
Optimal Designs ◽  
Finite Element Models ◽  
Optimization Strategy ◽  
Unit Cells ◽  
Line Defects

In this paper, a two-stage optimization strategy for designing defective unit cells of phononic crystal (PnC) to explore the localization and waveguide states for target frequencies is proposed. In the optimization model, the PnC microstructures are parametrically described by a series of hyperelliptic curves, and the optimal designs can be obtained by systematically changing the designable parameters of hyperellipse. The optimization contains two individual processes. We obtain the configurations of a perfect unit cell for different orders of band gap maximization. Subsequently, by taking advantage of the supercell technique, the defective unit cells are designed based on the unit cell configuration for different orders of band gap maximization. The finite element models show the localization and waveguide phenomenon for target frequencies and validate the effectiveness of the optimal designs numerically.

Multiobjective Optimization for Dynamic Umbilical Installation Using Non-Dominated Sorting Genetic Algorithm

2011 ◽  
Author(s):  
Aijun Wang ◽  
Hezhen Yang ◽  
Huajun Li
Keyword(s):  
Genetic Algorithm ◽  
Multiobjective Optimization ◽  
Cost Effective ◽  
Optimization Strategy ◽  
Approximation Model ◽  
Dynamic Nature ◽  
Nsga Ii ◽  
Pareto Solution ◽  
Dynamic Analyses ◽  
Optimal Deployment

This paper presents a method of multiobjective optimization based on approximation model for dynamic umbilical installation. The optimization aims to find out the most cost effective size, quantity and location of buoyancy modules for umbilical installation. Due to the highly geometrically nonlinearity and highly responsive dynamic nature in deepwater, dynamic umbilical analysis is very complex and time-consuming. Approximation Model constructed by design of experiment (DOE) sampling is utilized to solve this problem. Non-linear dynamic analyses considering environmental loadings are executed on these sample points from DOE. Non-dominated Sorting Genetic Algorithm (NSGA-II) is employed to obtain the Pareto solution set through an evolutionary optimization process. The optimization results indicate this optimization strategy with approximation model is valid, and provide the optimal deployment way of buoyancy modules.

scholarly journals Thermo-Viscoelastic Response of 3D Braided Composites Based on a Novel FsMsFE Method

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 271
Author(s):  
Jun-Jun Zhai ◽  
Xiang-Xia Kong ◽  
Lu-Chen Wang
Keyword(s):  
Finite Element ◽  
Cell Model ◽  
Structural Parameters ◽  
Thermal Relaxation ◽  
Viscoelastic Behavior ◽  
Unit Cell ◽  
Time Dependent ◽  
3D Braided Composites ◽  
Equivalent Time ◽  
Representative Unit Cell

A homogenization-based five-step multi-scale finite element (FsMsFE) simulation framework is developed to describe the time-temperature-dependent viscoelastic behavior of 3D braided four-directional composites. The current analysis was performed via three-scale finite element models, the fiber/matrix (microscopic) representative unit cell (RUC) model, the yarn/matrix (mesoscopic) representative unit cell model, and the macroscopic solid model with homogeneous property. Coupling the time-temperature equivalence principle, multi-phase finite element approach, Laplace transformation and Prony series fitting technology, the character of the stress relaxation behaviors at three scales subject to variation in temperature is investigated, and the equivalent time-dependent thermal expansion coefficients (TTEC), the equivalent time-dependent thermal relaxation modulus (TTRM) under micro-scale and meso-scale were predicted. Furthermore, the impacts of temperature, structural parameters and relaxation time on the time-dependent thermo-viscoelastic properties of 3D braided four-directional composites were studied.

scholarly journals A numerical study of a size-dependent finite-element based unit cell with primary and secondary voids

2021 ◽  
pp. 104493
Author(s):  
Vetle Espeseth ◽  
David Morin ◽  
Jonas Faleskog ◽  
Tore Børvik ◽  
Odd Sture Hopperstad
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Unit Cell ◽  
Size Dependent

scholarly journals Multiobjective Optimization Model of Production Planning in Cloud Manufacturing Based on TOPSIS Method with Combined Weights

Complexity ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Zhiru Li ◽  
Wei Xu ◽  
Huibin Shi ◽  
Qingshan Zhang ◽  
Fengyi He
Keyword(s):  
Multiobjective Optimization ◽  
Production Planning ◽  
Mass Customization ◽  
Evaluation Model ◽  
Cloud Manufacturing ◽  
Production Plan ◽  
Topsis Method ◽  
Nsga Ii ◽  
Optimal Production ◽  
Planning Scheme

Combined with the research of mass customization and cloud manufacturing mode, this paper discussed the production planning of mass customization enterprises in the context of cloud manufacturing in detail, analyzed the attribute index of manufacturing resource combination, and given a system considering the characteristics of batch production in mass customization and the decentralization of manufacturing resources in cloud manufacturing environment. Then, a multiobjective optimization model has been constructed according to the product delivery date, product cost, and product quality that customers care most about. The Pareto solution set of production plan has been obtained by using NSGA-II algorithm. This paper established a six-tier attribute index system evaluation model for the optimization of production planning scheme set of mass customization enterprises in cloud manufacturing environment. The weight coefficients of attribute indexes were calculated by combining subjective and objective weights with analytic hierarchy process (AHP) and entropy weight method. Finally, the combined weights calculated were applied to the improved TOPSIS method, and the optimal production planning scheme has been obtained by ranking. This paper validated the effectiveness and feasibility of the multiobjective model and NSGA-II algorithm by the example of company A. The Pareto effective solution has been obtained by solving the model. Then the production plan set has been sorted synthetically according to the comprehensive evaluation model, and the optimal production plan has been obtained.

scholarly journals A theory for bone resorption based on the local rupture of osteocytes cells connections: A finite element study

2015 ◽  
Vol 262 ◽  
pp. 46-55 ◽  
Author(s):  
Hambli Ridha ◽  
Khalid H. Almitani ◽  
Abdessalem Chamekh ◽  
Hechmi Toumi ◽  
Joao Manuel R.S. Tavares
Keyword(s):  
Finite Element ◽  
Bone Resorption ◽  
Finite Element Study ◽  
Element Study

Tuning of Power System Stabilizers using Multiobjective Optimization NSGA II

2015 ◽  
Vol 13 (8) ◽  
pp. 2653-2660 ◽  
Author(s):  
Humberto Verdejo ◽  
Diego Gonzalez ◽  
Jose Delpiano ◽  
Cristhian Becker
Keyword(s):  
Multiobjective Optimization ◽  
Power System ◽  
Power System Stabilizers ◽  
Nsga Ii

The Role of Topology and Tissue Mechanics in Remora Attachment

2014 ◽  
Vol 1648 ◽  
Author(s):  
Michael Culler ◽  
Keri A. Ledford ◽  
Jason H. Nadler
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Tissue Mechanics ◽  
Unit Cell ◽  
Surface Topology ◽  
Finite Element Models ◽  
Cell Geometry ◽  
Critical Step ◽  
Tissue Material

ABSTRACTRemora fish are capable of fast, reversible and reliable adhesion to a wide variety of both natural and artificial marine hosts through a uniquely evolved dorsal pad. This adhesion is partially attributed to suction, which requires a robust seal between the pad interior and the ambient environment. Understanding the behavior of remora adhesion based on measurable surface parameters and material properties is a critical step when creating artificial, bio-inspired devices. In this work, structural and fluid finite element models (FEM) based on a simplified “unit cell” geometry were developed to predict the behavior of the seal with respect to host/remora surface topology and tissue material properties.

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