scholarly journals A Comparative Biomechanical Analysis of Various Rod Configurations Following Anterior Column Realignment and Pedicle Subtraction Osteotomy

Neurospine ◽  
2021 ◽  
Vol 18 (3) ◽  
pp. 587-596
Author(s):  
Muzammil Mumtaz ◽  
Justin Mendoza ◽  
Ardalan Seyed Vosoughi ◽  
Anthony S. Unger ◽  
Vijay K. Goel
Keyword(s):  
Stress Reduction ◽  
Factor Of Safety ◽  
Maximum Stress ◽  
Element Model ◽  
Pedicle Subtraction Osteotomy ◽  
Biomechanical Analysis ◽  
Anterior Column ◽  
Von Mises Stress ◽  
Correction Technique ◽  
Von Mises

Objective: The objective of this study was to compare the biomechanical differences of different rod configurations following anterior column realignment (ACR) and pedicle subtraction osteotomy (PSO) for an optimal correction technique and rod configuration that would minimize the risk of rod failure.Methods: A validated spinopelvic (L1-pelvis) finite element model was used to simulate ACR at the L3–4 level. The ACR procedure was followed by dual-rod fixation, and for 4-rod constructs, either medial/lateral accessory rods (connected to primary rods) or satellite rods (directly connected to ACR level screws). The range of motion (ROM), maximum von Mises stress on the rods, and factor of safety (FOS) were calculated for the ACR models and compared to the existing literature of different PSO rod configurations.Results: All of the 4-rod ACR constructs showed a reduction in ROM and maximum von Mises stress compared to the dual-rod ACR construct. Additionally, all of the 4-rod ACR constructs showed greater percentage reduction in ROM and maximum von Mises stress compared to the PSO 4-rod configurations. The ACR satellite rod construct had the maximum stress reduction i.e., 47.3% compared to dual-rod construct and showed the highest FOS (4.76). These findings are consistent with existing literature that supports the use of satellite rods to reduce the occurrence of rod fracture.Conclusion: Our findings suggest that the ACR satellite rod construct may be the most beneficial in reducing the risk of rod failure compared to all other PSO and ACR constructs.

scholarly journals Tympanic Membrane Collagen Expression by Dynamically Cultured Human Mesenchymal Stromal Cell/Star-Branched Poly(ε-Caprolactone) Nonwoven Constructs

2020 ◽  
Vol 10 (9) ◽  
pp. 3043
Author(s):  
Stefania Moscato ◽  
Antonella Rocca ◽  
Delfo D’Alessandro ◽  
Dario Puppi ◽  
Vera Gramigna ◽  
...  
Keyword(s):  
Tympanic Membrane ◽  
Maximum Stress ◽  
Element Model ◽  
Von Mises Stress ◽  
Type I ◽  
Collagen Types ◽  
Collagen Expression ◽  
Polymerase Chain ◽  
Von Mises ◽  
Membrane Collagen

The tympanic membrane (TM) primes the sound transmission mechanism due to special fibrous layers mainly of collagens II, III, and IV as a product of TM fibroblasts, while type I is less represented. In this study, human mesenchymal stromal cells (hMSCs) were cultured on star-branched poly(ε-caprolactone) (*PCL)-based nonwovens using a TM bioreactor and proper differentiating factors to induce the expression of the TM collagen types. The cell cultures were carried out for one week under static and dynamic conditions. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) were used to assess collagen expression. A Finite Element Model was applied to calculate the stress distribution on the scaffolds under dynamic culture. Nanohydroxyapatite (HA) was used as a filler to change density and tensile strength of *PCL scaffolds. In dynamically cultured *PCL constructs, fibroblast surface marker was overexpressed, and collagen type II was revealed via IHC. Collagen types I, III and IV were also detected. Von Mises stress maps showed that during the bioreactor motion, the maximum stress in *PCL was double that in HA/*PCL scaffolds. By using a *PCL nonwoven scaffold, with suitable physico-mechanical properties, an oscillatory culture, and proper differentiative factors, hMSCs were committed into fibroblast lineage-producing TM-like collagens.

Joint Stress Optimization by the Hybrid Adhesive Lap Joint

2012 ◽  
Vol 445 ◽  
pp. 1000-1004
Author(s):  
Halil Ozer ◽  
Ozkan Oz
Keyword(s):  
Stress Reduction ◽  
Adhesive Joint ◽  
Modulus Of Elasticity ◽  
Three Dimensional ◽  
Element Model ◽  
Von Mises Stress ◽  
Lap Joint ◽  
Joint Stress ◽  
Stress Components ◽  
Von Mises

Hybrid adhesive joint is an alternative stress reduction technique for the adhesively bonded joints. Hybrid adhesive means that it is used dual adhesives in the overlap region. Adhesive having high modulus of elasticity should be located in the middle of the bondline and the other adhesive having low modulus of elasticity at the ends. In this study, the effect of the hybrid adhesive bondline on the distributions of the peeling, shear and von Mises stress components at the single lap joint were investigated by using three-dimensional finite element model. The results show that the considered stress components can be optimized by using hybrid adhesive joint.

scholarly journals Customized Designs and Biomechanical Analysis of Transtibial Prosthetic Leg

2021 ◽  
Vol 2071 (1) ◽  
pp. 012014
Author(s):  
A J M Mubarak ◽  
A M A Rashid ◽  
A A Wahab ◽  
G H Seng ◽  
M H Ramlee
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Body Part ◽  
Biomechanical Study ◽  
Biomechanical Analysis ◽  
Von Mises Stress ◽  
Foot Model ◽  
Definition Of ◽  
Von Mises

Abstract A prosthetic leg is a technical mechanism that is designed as a substitution of the function of a missing limb or body part. This device has been effectively used as an essential tool for amputees. The traditional way of producing the prosthetic leg is very tedious and time consuming. Apart from that, comfortability issue is another problem if using casting method. Therefore, the main purpose of this study is to customize and biomechanically evaluate an prosthetic’s socket to produce a better construct for the improvement of performance. In this paper, the methods started with a definition of the construction of the finite element model which is divided into four parts: amputee leg, sockets model, pylon and socket. Later, modelling of the pylon and three-dimensional foot model was taken into consideration. The focus was on the design of the socket then moving to the biomechanical study using a finite element method which involved several analyses of the effects of socket designs as well as its material properties. The sockets were initially developed from a data of 3D scanning with an estimated uniform thickness of 5 mm. The results of the finite element study showed that the perforated socket configuration had better stability in terms of displacement (0.19 mm) and von Mises stress (1.15 MPa), as compared to the conventional socket (stress of 3.22 MPa), and the displacement of 0.19 mm. Meanwhile, open-sided socket experienced von Mises stress of 1.18 MPa and displacement of 0.22 mm. In conclusion, a customized design is a promising technique that can enhance the performance of user in terms of biomechanical aspect.

scholarly journals Effects of intracorneal ring segments implementation technique and design on corneal biomechanics and keratometry in a personalized computational analysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Niksa Mohammadi Bagheri ◽  
Mahmoud Kadkhodaei ◽  
Shiva Pirhadi ◽  
Peiman Mosaddegh
Keyword(s):  
Clinical Data ◽  
Three Dimensional ◽  
Element Model ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Average Error ◽  
Constant Thickness ◽  
Arc Length ◽  
Implementation Techniques ◽  
Von Mises

AbstractThe implementation of intracorneal ring segments (ICRS) is one of the successfully applied refractive operations for the treatment of keratoconus (kc) progression. The different selection of ICRS types along with the surgical implementation techniques can significantly affect surgical outcomes. Thus, this study aimed to investigate the influence of ICRS implementation techniques and design on the postoperative biomechanical state and keratometry results. The clinical data of three patients with different stages and patterns of keratoconus were assessed to develop a three-dimensional (3D) patient-specific finite-element model (FEM) of the keratoconic cornea. For each patient, the exact surgery procedure definitions were interpreted in the step-by-step FEM. Then, seven surgical scenarios, including different ICRS designs (complete and incomplete segment), with two surgical implementation methods (tunnel incision and lamellar pocket cut), were simulated. The pre- and postoperative predicted results of FEM were validated with the corresponding clinical data. For the pre- and postoperative results, the average error of 0.4% and 3.7% for the mean keratometry value ($$\text {K}_{\text{mean}}$$ K mean ) were predicted. Furthermore, the difference in induced flattening effects was negligible for three ICRS types (KeraRing segment with arc-length of 355, 320, and two separate 160) of equal thickness. In contrast, the single and double progressive thickness of KeraRing 160 caused a significantly lower flattening effect compared to the same type with constant thickness. The observations indicated that the greater the segment thickness and arc-length, the lower the induced mean keratometry values. While the application of the tunnel incision method resulted in a lower $$\text {K}_{\text{mean}}$$ K mean value for moderate and advanced KC, the induced maximum Von Mises stress on the postoperative cornea exceeded the induced maximum stress on the cornea more than two to five times compared to the pocket incision and the preoperative state of the cornea. In particular, an asymmetric regional Von Mises stress on the corneal surface was generated with a progressive ICRS thickness. These findings could be an early biomechanical sign for a later corneal instability and ICRS migration. The developed methodology provided a platform to personalize ICRS refractive surgery with regard to the patient’s keratoconus stage in order to facilitate the efficiency and biomechanical stability of the surgery.

Theoretical analysis of a rolling-sliding elastohydrodynamic lubrication line contact with a subsurface inclusion

2019 ◽  
Vol 233 (8) ◽  
pp. 1197-1207
Author(s):  
Armando Félix Quiñonez ◽  
Guillermo E Morales Espejel
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Element Model ◽  
Von Mises Stress ◽  
Transient Effects ◽  
Mean Velocity ◽  
The Matrix ◽  
Soft Inclusion ◽  
The Mean ◽  
Von Mises ◽  
Fully Coupled

This work investigates the transient effects of a single subsurface inclusion over the pressure, film thickness, and von Mises stress in a line elastohydrodynamic lubrication contact. Results are obtained with a fully-coupled finite element model for either a stiff or a soft inclusion moving at the speed of the surface. Two cases analyzed consider the inclusion moving either at the same speed as the mean velocity of the lubricant or moving slower. Two additional cases investigate reducing either the size of the inclusion or its stiffness differential with respect to the matrix. It is shown that the well-known two-wave elastohydrodynamic lubrication mechanism induced by surface features is also applicable to the inclusions. Also, that the effects of the inclusion become weaker both when its size is reduced and when its stiffness approaches that of the matrix. A direct comparison with predictions by the semi-analytical model of Morales-Espejel et al. ( Proc IMechE, Part J: J Engineering Tribology 2017; 231) shows reasonable qualitative agreement. Quantitatively some differences are observed which, after accounting for the semi-analytical model's simplicity, physical agreement, and computational efficiency, may then be considered as reasonable for engineering applications.

Failure Analysis of Cementless Hip Joint Prosthesis

2013 ◽  
Vol 845 ◽  
pp. 403-407
Author(s):  
Natesan Dhandapani ◽  
A. Gnanavelbabu ◽  
M. Sivasankar
Keyword(s):  
Hip Joint ◽  
Low Cost ◽  
Three Dimensional ◽  
Surface Characteristics ◽  
Element Model ◽  
Von Mises Stress ◽  
Surface Model ◽  
Joint Prosthesis ◽  
Replacement Technique ◽  
Von Mises

In this changing global scenario, modification, transplantation, and replacement can be the eternal solution for most of the problems in the medical field. Hence replacement technique finds a very prominent place in medicine as a remedy having closely tied up with biomechanics. One of the most important joints in the human body is the hip joint, the big and complex joint. Many researches were conducted and many are in progress, but most of these works use simplified models with either 2D or 3D approaches. The hip joint is formed by four components like femoral head cortical bone, stem, and neck. In this system we can find orthotropic and isotropic materials working together. The main objective of this research is to develop a three dimensional surface and solid finite element model of the hip joint to predict stresses in its individual components. This model is a geometric non-linear model, which helps us understand its structural mechanical behavior, seeming to suggest with advanced research in the future new hip joint prosthesis, as well as to prove the prosthesis joint interaction before being implanted in the patient. This research explains a complete human hip joint model without cartilaginous tissue, using ANSYS 10.0 Multiphysics Analysis for nine different postures in hip joint using three different materials (CoCr, Ti6Al4V, and UHMWPE) to calculate fatigue life. The result obtained from the analysis of surface model and solid model serve to help in predicting the life cycle, surface characteristics, shear stress in XY plane, stress concentration and areas that are prone to failure. Von Mises stress on the surface of our model facilitates us to equip and design an optimized prosthesis device having unique materials composition , with a highly bio-compatible and durable alloy at a low cost could be produced. In this way, a first important step towards the structural characterization of human hip joint has been developed.

scholarly journals Mechanical Strength Study of a Cranial Implant Using Computational Tools

2022 ◽  
Vol 12 (2) ◽  
pp. 878
Author(s):  
Pedro O. Santos ◽  
Gustavo P. Carmo ◽  
Ricardo J. Alves de Sousa ◽  
Fábio A. O. Fernandes ◽  
Mariusz Ptak
Keyword(s):  
Structural Integrity ◽  
Mechanical Performance ◽  
Skull Fracture ◽  
Human Head ◽  
Element Model ◽  
Von Mises Stress ◽  
Cranial Implant ◽  
Von Mises ◽  
Two Parameters ◽  
The Brain

The human head is sometimes subjected to impact loads that lead to skull fracture or other injuries that require the removal of part of the skull, which is called craniectomy. Consequently, the removed portion is replaced using autologous bone or alloplastic material. The aim of this work is to develop a cranial implant to fulfil a defect created on the skull and then study its mechanical performance by integrating it on a human head finite element model. The material chosen for the implant was PEEK, a thermoplastic polymer that has been recently used in cranioplasty. A6 numerical model head coupled with an implant was subjected to analysis to evaluate two parameters: the number of fixation screws that enhance the performance and ensure the structural integrity of the implant, and the implant’s capacity to protect the brain compared to the integral skull. The main findings point to the fact that, among all tested configurations of screws, the model with eight screws presents better performance when considering the von Mises stress field and the displacement field on the interface between the implant and the skull. Additionally, under the specific analyzed conditions, it is observable that the model with the implant offers more efficient brain protection when compared with the model with the integral skull.

SuperMeshing: A Deep Learning Method for Boosting Mesh Density in Numerical Computation Within 2D Domain

2021 ◽  
Author(s):  
Handing Xu ◽  
Zhenguo Nie ◽  
Qingfeng Xu ◽  
Xinjun Liu
Keyword(s):  
Numerical Computation ◽  
Spatial Resolution ◽  
Maximum Stress ◽  
Linear Mapping ◽  
Stress Fields ◽  
Von Mises Stress ◽  
Full Detail ◽  
Mesh Density ◽  
Novel Method ◽  
Von Mises

Abstract Due to the limit of mesh density, the improvement of the spatial resolution of numerical computation always leads to a decrease in computing efficiency. Aiming at this inability of numerical computation, we propose a novel method for boosting the mesh density in finite element method (FEM) within 2D domain. Based on the von Mises stress fields of 2D plane-strain problems computed by the FEM, this method utilizes a deep neural network named SuperMeshingNet to learn a non-linear mapping from low mesh-density to high mesh-density in stress fields, and realizes the improvement of numerical computation accuracy and efficiency simultaneously. We adopt residual dense blocks into our mesh-density boost model – SuperMeshingNet to extract abundant local features and enhance the prediction capacity. The results indicate that SuperMeshingNet is able to effectively increase the spatial resolution of the von Mises stress fields under the multiple scaling factors: 2X,4X,and8X. Compared with the targets, the relative error of SuperMeshingNet is 2.44%, which shows better performance than the interpolation methods. Besides, SuperMeshingNet reveals an astonishing strength in predicting the maximum stress value. We publicly share our work with full detail of implementation at https://github.com/zhenguonie/2021_SuperMeshing_2D_Plane_Strain.

An Improved Control Arm Design for a Commercial Vehicle

2021 ◽  
Author(s):  
Sinan Yıldırım ◽  
Ufuk Çoban ◽  
Mehmet Çevik
Keyword(s):  
Finite Element ◽  
Cost Effective ◽  
Element Model ◽  
Tensile Tests ◽  
The Body ◽  
Von Mises Stress ◽  
Driving Safety ◽  
Design Development ◽  
Element Analysis ◽  
Von Mises

Suspension linkages are one of the fundamental structural elements in each vehicle since they connect the wheel carriers i.e. axles to the body of the vehicle. Moreover, the characteristics of suspension linkages within a suspension system can directly affect driving safety, comfort and economics. Beyond these, all these design criteria are bounded to the package space of the vehicle. In last decades, suspension linkages have been focused on in terms of design development and cost reduction. In this study, a control arm of a diesel public bus was taken into account in order to get the most cost-effective design while improving the strength within specified boundary conditions. Due to the change of the supplier, the control arm of a rigid axle was redesigned to find an economical and more durable solution. The new design was analyzed first by the finite element analysis software Ansys and the finite element model of the control arm was validated by physical tensile tests. The outputs of the study demonstrate that the new design geometry reduces the maximum Von Mises stress 15% while being within the elastic region of the material in use and having found an economical solution in terms of supplier’s criteria.

Contact Analysis of a Soft-Coated Asperity During Loading–Unloading Process in Consideration of Strain Hardening Effects

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Yi Wang ◽  
Yi Cui ◽  
Shuo Liu ◽  
Xinhui Wang ◽  
Xinwei Tian ◽  
...  
Keyword(s):  
Power Law ◽  
Material Properties ◽  
Element Model ◽  
Von Mises Stress ◽  
Main Bearing ◽  
Plastic Properties ◽  
Medium Speed ◽  
Wide Range ◽  
Dimensional Finite Element ◽  
Von Mises

Abstract In this paper, the flattening process of a coated single asperity by a rigid flat is studied based on a two-dimensional finite element model under different contact interferences. The soft coating and hard substrate materials of the main bearing shell in a medium-speed vehicle diesel engine are both considered to follow the power-law hardening elastic-plastic properties. For both loading and unloading processes, the effects of geometrical and material properties, including the coating thickness, Young’s modulus, Poisson’s ratio, yielding stress, and hardening exponent, on the contact behaviors are studied in a wide range to cover the real material properties. The von Mises stress on the interface is also analyzed in order to improve the bonding strength between coating and substrate. The main contribution of this paper is to provide a method to determine the contact properties caused by different material and geometric properties of soft coating and substrate materials, which follow the power-law hardening properties.

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