scholarly journals Integration of reliability-based topology optimization into biomechanics: Application on hollow stems used in cementless total hip arthroplasty

2020 ◽  
Vol 210 ◽  
pp. 06003
Author(s):  
Ghais Kharmanda ◽  
Imad Antypas ◽  
Alexey Dyachenko
Keyword(s):  
Topology Optimization ◽  
Hip Replacement ◽  
High Performance ◽  
Design Space ◽  
Design Stage ◽  
Manufacturing Constraints ◽  
Element Discretization ◽  
Performance Levels ◽  
Total Hip ◽  
Alternative Approaches

The integration of topology optimization into biomechanical applications possesses an important key to increase the performance levels. In literature, two models can be found: Deterministic Topology Optimization (DTO) and Reliability-Based Topology Optimization (RBTO). The DTO leads to a single layout for a given design space. However, the RBTO generates several reliability-based topologies with high performance levels. Topology optimization has been already integrated into biomechanical applications such as prosthesis design. The filter-based approaches being tied to the element discretization, are previously used to control the resulting topologies or to prevent undesirable designs. These are expensive operations for fine meshes or complex domains and numerous numerical difficulties can be met. In this work, the RBTO is integrated at the conceptual design stage of the total hip replacement to control the resulting topologies to meet different constraints such as manufacturing constraints. This can provide several types of hollow stems considering the daily loading cases. Two alternative approaches based on the Optimum Safety Factors (OSF) are developed to provide two categories of solutions. The RBTO model can be integrated into the additive manufacturing technology as a topology generator satisfying several manufacturing constraints. The resulting different configurations can then be provided for various patients.

scholarly journals Nonlinearity investigation of reliability-based topology optimization strategies with application to total hip replacement

2021 ◽  
Vol 273 ◽  
pp. 02004
Author(s):  
Ghais Kharmanda ◽  
Hasan Mulki ◽  
Imad Antypas
Keyword(s):  
Topology Optimization ◽  
Total Hip Replacement ◽  
Hip Replacement ◽  
Random Variable ◽  
Design Stage ◽  
Linear Distribution ◽  
Total Hip ◽  
Input Parameters ◽  
Nonlinearity Effect ◽  
Parameter Values

In literature, the topology optimization can be divided into two main models. The first model is called Deterministic Topology Optimization (DTO) producing a single configuration for a given design space. The second one is called Reliability-Based Topology Optimization (RBTO) generating several layouts. In our previous work, two approaches considering the concept of Inverse Optimum Safety Factors (IOSF) were elaborated and only applied to the normal distribution being linear distribution. In this work, a nonlinearity investigation is presented to compare between the linear and nonlinear distribution. The RBTO developments are applied to the total hip replacement to provide suitable hollow stems at the conceptual design stage. The nonlinearity presented here, is related to the types of the random variable distributions. The most common distributions such as normal, lognormal, uniform and Weibull are considered here to perform the investigation. The results show the nonlinearity effect on the output parameter values, but lead to almost similar layouts of the resulting hollow stems in several cases. In certain types of distributions such as Weibull, the changes on the input parameters are very variant. At certain values of the reliability index, some input parameters of material properties exceeded their limits and the algorithm stopped.

scholarly journals Inverse Optimum Safety Factor Method for Reliability-Based Topology Optimization Applied to Free Vibrated Structures

2019 ◽  
pp. 8-19 ◽  
Author(s):  
Ghias Kharmanda ◽  
Imad R. Antypas ◽  
Alexey G. Dyachenko
Keyword(s):  
Topology Optimization ◽  
Structure Function ◽  
Modal Analysis ◽  
Safety Factor ◽  
Optimization Model ◽  
High Performance ◽  
Structural Type ◽  
Efficient Tool ◽  
Performance Levels ◽  
Reliability Level

Introduction. The classical topology optimization leads to a prediction of the structural type and overall layout, and gives a rough description of the shape of the outer as well as inner boundaries of the structure. However, the probabilistic topology optimization (or reliability-based topology optimization) model leads to several reliability-based topologies with high performance levels. The objective of this work is to provide an efficient tool to integrate the reliability-based topology optimization model into free vibrated structure. Materials and Methods. The developed tool is called inverse optimum safety method. When dealing with modal analysis, the choice of optimization domain is highly important in order to be able to eliminate material taking account of the constraints of fabrication and without affecting the structure function. This way the randomness can be applied on certain boundary parameters. Results. Numerical applications on free vibrated structures are presented to show the efficiency of the developed strategy. When considering a required reliability level, the resulting topology represents a different topology relative to the deterministic resulting one. Discussion and Conclusion. In addition to its simplified implementation, the developed inverse optimum safety factor strategy can be considered as a generative tool to provide the designer with several solutions for free vibrated structures with different performance levels.

scholarly journals Reliability-Based Topology Optimization Using Two Alternative Inverse Optimum Safety Factor Approaches: Application to Bridge Structures

2020 ◽  
Vol 30 (3) ◽  
pp. 498-511
Author(s):  
Ghias Kharmanda ◽  
Imad R. Antypas ◽  
Alexey G. Dyachenko
Keyword(s):  
Topology Optimization ◽  
Safety Factor ◽  
Optimization Model ◽  
High Performance ◽  
Bridge Structure ◽  
Objective Performance ◽  
Bridge Structures ◽  
Alternative Approaches ◽  
Alternative Choice

Introduction. The Deterministic Topology Optimization model provides a single solution for a given design space, while the Reliability-Based Topology Optimization model provides several reliability-based topology layouts with high-performance levels. The objective of this work is to develop two strategies that can provide the designer with two categories of resulting topologies. Materials and Methods. Two alternative approaches based on the Inverse Optimum Safety Factor are developed: the first one is called the Objective-Based IOSF Approach and the second one is called Performance-Based IOSF Approach. When dealing with bridge structures, the uncertainty on the input parameters (boundary conditions, material properties, geometry, etc.) and also output parameters (compliance, etc.) should not be ignored. The sensitivity analysis is the fundamental idea of both developed approaches, identifies the role of each parameter on the structural performance. In addition, the optimization domain choice is important when eliminating material that should not affect the structure functioning. Results. Two numerical examples on a 2D bridge structure are presented to demonstrate the efficiency of the developed approaches. When considering a certain reliability level, the Reliability-Based Topology Optimization leads to two different configurations relative to the Deterministic Topology Optimization one. When increasing the reliability levels, the quantity of materials decreases that leads to an increase in the number of holes in the structures. Discussion and Conclusion. In addition to their simplified implementation, the developed alternative approaches can be considered as two generative tools to produce two different categories (families) of solutions where an alternative choice between two functions (objective/performance) is presented.

Topology and Free Size Optimization With Manufacturing Constraints for Light Weight Die Cast Automotive Backrest Frame

2009 ◽  
Author(s):  
Sreeram Polavarapu ◽  
Lonny L. Thompson ◽  
Mica Grujicic
Keyword(s):  
Finite Element ◽  
Topology Optimization ◽  
Design Space ◽  
Size Optimization ◽  
Manufacturing Constraints ◽  
Material Distribution ◽  
Front Seat ◽  
Die Cast ◽  
Stiffening Ribs ◽  
Multiple Load

Finite element analysis, together with topology and free-size optimization is used to design a lightweight die cast automotive front seat backrest frame when subjected to loads prescribed by ECE R17 European government regulations and additional loads which are predicted in an event of crash. In particular, an effort is made here to study the characteristics of a die cast automotive front seat backrest frame and develop a method for predicting the optimized material and support rib distribution which provides a lightweight seat which satisfies both strength and deflection requirements in a design space which includes the action of multiple load cases. An existing commercially available die cast backrest frame serves as the reference design space. Both 3D surface and solid models are created for representation as shell and solid finite element models for analysis. The objective function for topology optimization of the 3D solid model is to minimize mass of the component subject to stress and deflection constraints and is used as a guide in determining optimal geometric distribution of stiffening ribs. When the shell model of the reference seat is subjected to free-size optimization with this same constraint and objective given, an optimized material distribution measured by shell element thicknesses is obtained. For the topology optimization, manufacturing constraints of preferred draw direction and symmetry are applied in order to obtain an optimized material distribution which can be manufactured in the die-cast process. The procedure followed in this work generated an optimal material distribution and stiffening ribs in a lightweight die cast automotive seat backrest frame when subjected to multiple load cases. An overall reduction in weight of 13% is achieved over a reference commercially available die cast backrest frame component.

The Hemodynamic and Fibrinolytic Response to Low Dose Epinephrine and Phenylephrine Infusions During Total Hip Replacement Under Epidural Anesthesia

1992 ◽  
Vol 68 (04) ◽  
pp. 436-441 ◽  
Author(s):  
Nigel E Sharrock ◽  
George Go ◽  
Robert Mineo ◽  
Peter C Harpel
Keyword(s):  
Heart Rate ◽  
Deep Vein Thrombosis ◽  
Cardiac Index ◽  
Total Hip Replacement ◽  
Epidural Anesthesia ◽  
Hip Replacement ◽  
Low Dose ◽  
Total Hip ◽  
Vein Thrombosis ◽  
Deep Vein

SummaryLower rates of deep vein thrombosis have been noted following total hip replacement under epidural anesthesia in patients receiving exogenous epinephrine throughout surgery. To determine whether this is due to enhanced fibrinolysis or to circulatory effects of epinephrine, 30 patients scheduled for primary total hip replacement under epidural anesthesia were randomly assigned to receive intravenous infusions of either low dose epinephrine or phenylephrine intraoperatively. All patients received lumbar epidural anesthesia with induced hypotension and were monitored with radial artery and pulmonary artery catheters.Patients receiving low dose epinephrine infusion had maintenance of heart rate and cardiac index whereas both heart rate and cardiac index declined significantly throughout surgery in patients receiving phenylephrine (p = 0.0001 and p = 0.0001, respectively). Tissue plasminogen activator (t-PA) activity increased significantly during surgery (p <0.0005) and declined below baseline postoperatively (p <0.005) in both groups. Low dose epinephrine was not associated with any additional augmentation of fibrinolytic activity perioperatively. There were no significant differences in changes in D-Dimer, t-PA antigen, α2-plasmin inhibitor-plasmin complexes or thrombin-antithrombin III complexes perioperatively between groups receiving low dose epinephrine or phenylephrine. The reduction in deep vein thrombosis rate with low dose epinephrine is more likely mediated by a circulatory mechanism than by augmentation of fibrinolysis.

Effects on Coagulation and Fibrinolysis of Desmopressin in Patients Undergoing Total Hip Replacement

1991 ◽  
Vol 66 (06) ◽  
pp. 652-656 ◽  
Author(s):  
Per Anders Flordal ◽  
Karl-Gösta Ljungström ◽  
Jan Svensson ◽  
Brenda Ekman ◽  
Gustaf Neander
Keyword(s):  
Total Hip Replacement ◽  
Hip Replacement ◽  
Bleeding Time ◽  
Antithrombin Iii ◽  
Postoperative Bleeding ◽  
Double Blind ◽  
Total Hip ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Coagulation And Fibrinolysis

SummaryTwelve patients undergoing total hip replacement, with regional anaesthesia and with dextran infusion for plasma expansion and thromboprophylaxis, were given the vasopressin analogue desmopressin (DDAVP) or placebo in a randomized, double-blind prospective study. In controls (n = 6) we found a prolongation of the bleeding time, low factor VIII (FVIII) and von Willebrand factor (vWF) and a decrease in antithrombin III to levels known to be at risk for venous thrombosis. Desmopressin shortened postoperative bleeding time, gave an early FVIII/vWF complex increase, prevented antithrombin III from falling to critically low values and appeared to activate the fibrinolytic system, both by tPA increase and PAI-1 decrease.Thus in the controls we found changes in both coagulation and fibrinolysis indicating a haemorrhagic diathesis as well as a risk for thromboembolism. Desmopressin induced factor changes that possibly reduce both risks.

Low-Dose Heparin and Deep-Vein Thrombosis after Total Hip Replacement

1976 ◽  
Vol 36 (01) ◽  
pp. 157-164 ◽  
Author(s):  
P. M Mannucci ◽  
Luisa E. Citterio ◽  
N Panajotopoulos
Keyword(s):  
Deep Vein Thrombosis ◽  
Total Hip Replacement ◽  
Hip Replacement ◽  
Low Dose ◽  
Control Group ◽  
Total Hip ◽  
Vein Thrombosis ◽  
Dose Heparin ◽  
Deep Vein ◽  
Low Dose Heparin

SummaryThe effect of subcutaneous low-dose heparin on postoperative deep-vein thrombosis (D. V. T.) (diagnosed by the 125I-labelled fibrinogen test) has been investigated in a trial of 143 patients undergoing the operation of total hip replacement. Two randomized studies were carried out: in one the scanning for D.V.T. was carried out daily for 7 days post operatively and in the other for 15 days. In both, the incidence of D.V.T. was significantly lower in the heparin-treated patients (P<0.005). Bilateral D.V.T. was also prevented (P<0.05), through the extension of D.V.T. to the distal veins of the thigh was not significantly reduced. Heparin treatment was, however, followed by a higher incidence of severe postoperative bleeding (P< 0.02) and wound haematoma formation (P< 0.005), and the postoperative haemoglobin was significantly lower than in the control group (P<0.005). A higher number of transfused blood units was also needed by the heparin treated patients (P<0.001).

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