scholarly journals Stress - Strain Response of the Human Spine Intervertebral Disc As an Anisotropic Body. Mathematical Modeling and Computation

Open Physics ◽  
2016 ◽  
Vol 14 (1) ◽  
pp. 426-435
Author(s):  
Mária Minárová ◽  
Jozef Sumec
Keyword(s):  
Intervertebral Disc ◽  
Constitutive Equations ◽  
Outer Part ◽  
Anisotropic Body ◽  
Lumbar Vertebrae ◽  
Basic Unit ◽  
Stress Strain ◽  
Element Analysis ◽  
Annulus Fibrosis ◽  
Motion Segment

AbstractThe paper deals with the biomechanical investigation on the human lumbar intervertebral disc under the static load. The disc is regarded as a two - phased ambient consisting of a fibrous outer part called annulus fibrosis and a liquid inner part nucleus pulposus. Due to the fibrous structure, the annulus fibrosis can be treated by using a special case of anisotropy - transversal isotropy.In the paper the corresponding tensor of material constants is derived. The tensor consequently incomes to the constitutive equations determining the stress - strain relation in the material. In order to study the mechanical behaviour the disc is observed within the motion segment, the basic unit for motion tracing. The motion segment involves two neighbouring vertebrae and the intervertebral disc between them that connect them both.When constitutive equations are accomplished, they can be incorporated in the finite element analysis. The illustrative example of the intervertebral disc L2/L3, the disc between the second and the third lumbar vertebrae the lumbar part of spine, with its computer implementation is performed. Finally the comparison of the results of using anisotropic and homogenized approach is provided. The comparison illustrates the eligibility of such a kind of approach.

Effects of Endplate Curvature on Stresses in a Vertebral Motion Segment: Finite Element Analysis

2004 ◽  
Author(s):  
Shreedhar P. Kale ◽  
Noshir A. Langrana ◽  
Thomas Edwards
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Distribution ◽  
Lumbar Vertebrae ◽  
Lumbosacral Spine ◽  
Human Cadaver ◽  
Element Analysis ◽  
Linear Elastic ◽  
Motion Segment ◽  
Cortical Shell

The vertebral endplates of the lumbosacral spine have various degrees of concavity and/or convexity. Several investigators including Seenivasan G., Goel, V. K., 1994, Liebschner et al, 2003, etc have performed finite element analysis on the vertebral bones, but the endplate curvatures are not included. Therefore, the effect of morphological details of the endplate curvatures on the stress distribution is unknown. Differences in these curvatures will increase stress in some regions and decrease stress elsewhere as the spine is compressed. In our previous study [Kale et al, 2003], lumbar vertebral endplate curvatures in the anterior-posterior and medial-lateral directions on human cadaver lumbar vertebrae were measured. The measurements were carried out using a reverse engineering instrument, built at Rutgers University [Hsieh et al, 2002]. Six sets of measurements (on human male-female L4 lower to S1 upper endplates) were performed. The data was later used in a linear elastic cylindrical model containing cortical shell and trabecular core. The model then was modified to a more accurate model, with more realistic, characteristic kidney shaped cross section (obtained from equation by Mizrahi et al, 1993) and linearly varying height. The endplates were assigned curvatures extracted from our human cadaver data. FEA, done on both the models, showed that the endplate curvatures and their location had significant effect on the stress distribution in the vertebral bone. In the current study we have extended our bone model into a motion segment and have investigated the effects of the curvatures on the stresses in the motion segment.

COMPARATIVE STUDY OF SINGLE CRYSTAL CONSTITUTIVE EQUATIONS FOR CRYSTAL PLASTICITY FINITE ELEMENT ANALYSIS

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5388-5393 ◽  
Author(s):  
MYOUNG GYU LEE ◽  
ROBERT H. WAGONER ◽  
SUNG-JOON KIM
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Single Crystal ◽  
Crystal Plasticity ◽  
Constitutive Equations ◽  
Critical Force ◽  
Stress Strain ◽  
Element Analysis ◽  
Crystal Plasticity Finite Element ◽  
Constitutive Parameters

Two sets of single crystal constitutive equations used for the crystal plasticity finite element analysis are comparatively investigated by simulating simple deformation of oriented single crystals. The first of these consists of conventional constitutive equations, which have been adopted for the prediction of deformation texture and their parameters are generally obtained by back-fitting polycrystalline stress-strain response. The other set uses interactions between moving dislocations on the primary slip system and the corresponding forest dislocations. The idealized Orowan hardening mechanism is adopted for the calculation of the critical force, and constitutive parameters are determined by the geometry of dislocations, thus less fitting procedure is involved. The stress-strain curves of copper single crystal are used to demonstrate how the two models work for the orientation dependent stress-strain responses.

КОНСТРУКТИВНО-ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ХВОСТО-ВИХ БАЛОК СІТЧАСТОГО ТИПУ З ПОЛІМЕРНИХ КОМПО-ЗИЦІЙНИХ МАТЕРІАЛІВ ВЕРТОЛЬОТІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

2020 ◽  
pp. 15-30
Author(s):  
А. Г. Гребеников ◽  
И. В. Малков ◽  
В. А. Урбанович ◽  
Н. И. Москаленко ◽  
Д. С. Колодийчик
Keyword(s):  
Finite Element ◽  
Strain State ◽  
Layer Structure ◽  
Metal Structure ◽  
Element Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Mesh Structure ◽  
Stress Strain State ◽  
Mesh Structures

The analysis of the design and technological features of the tail boom (ТB) of a helicopter made of polymer composite materials (PCM) is carried out.Three structural and technological concepts are distinguished - semi-monocoque (reinforced metal structure), monocoque (three-layer structure) and mesh-type structure. The high weight and economic efficiency of mesh structures is shown, which allows them to be used in aerospace engineering. The physicomechanical characteristics of the network structures are estimated and their uniqueness is shown. The use of mesh structures can reduce the weight of the product by a factor of two or more.The stress-strain state (SSS) of the proposed tail boom design is determined. The analysis of methods for calculating the characteristics of the total SSS of conical mesh shells is carried out. The design of the tail boom is presented, the design diagram of the tail boom of the transport category rotorcraft is developed. A finite element model was created using the Siemens NX 7.5 system. The calculation of the stress-strain state (SSS) of the HC of the helicopter was carried out on the basis of the developed structural scheme using the Advanced Simulation module of the Siemens NX 7.5 system. The main zones of probable fatigue failure of tail booms are determined. Finite Element Analysis (FEA) provides a theoretical basis for design decisions.Shown is the effect of the type of technological process selected for the production of the tail boom on the strength of the HB structure. The stability of the characteristics of the PCM tail boom largely depends on the extent to which its design is suitable for the use of mechanized and automated production processes.A method for the manufacture of a helicopter tail boom from PCM by the automated winding method is proposed. A variant of computer modeling of the tail boom of a mesh structure made of PCM is shown.The automated winding technology can be recommended for implementation in the design of the composite tail boom of the Mi-2 and Mi-8 helicopters.

Application of Computational Mechanics to Tire Design—Yesterday, Today, and Tomorrow

2011 ◽  
Vol 39 (4) ◽  
pp. 223-244 ◽  
Author(s):  
Y. Nakajima
Keyword(s):  
Finite Element ◽  
New Technologies ◽  
Computational Mechanics ◽  
Design Procedure ◽  
Side Wall ◽  
Rolling Resistance ◽  
Optimization Techniques ◽  
Stress Strain ◽  
Element Analysis ◽  
Crown Shape

Abstract The tire technology related with the computational mechanics is reviewed from the standpoint of yesterday, today, and tomorrow. Yesterday: A finite element method was developed in the 1950s as a tool of computational mechanics. In the tire manufacturers, finite element analysis (FEA) was started applying to a tire analysis in the beginning of 1970s and this was much earlier than the vehicle industry, electric industry, and others. The main reason was that construction and configurations of a tire were so complicated that analytical approach could not solve many problems related with tire mechanics. Since commercial software was not so popular in 1970s, in-house axisymmetric codes were developed for three kinds of application such as stress/strain, heat conduction, and modal analysis. Since FEA could make the stress/strain visible in a tire, the application area was mainly tire durability. Today: combining FEA with optimization techniques, the tire design procedure is drastically changed in side wall shape, tire crown shape, pitch variation, tire pattern, etc. So the computational mechanics becomes an indispensable tool for tire industry. Furthermore, an insight to improve tire performance is obtained from the optimized solution and the new technologies were created from the insight. Then, FEA is applied to various areas such as hydroplaning and snow traction based on the formulation of fluid–tire interaction. Since the computational mechanics enables us to see what we could not see, new tire patterns were developed by seeing the streamline in tire contact area and shear stress in snow in traction.Tomorrow: The computational mechanics will be applied in multidisciplinary areas and nano-scale areas to create new technologies. The environmental subjects will be more important such as rolling resistance, noise and wear.

Cord/Rubber Material Properties

1985 ◽  
Vol 58 (4) ◽  
pp. 830-856 ◽  
Author(s):  
R. J. Cembrola ◽  
T. J. Dudek
Keyword(s):  
Finite Element ◽  
Material Model ◽  
Rubber Composites ◽  
Stress Strain ◽  
Element Analysis ◽  
Rubber Layer ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Interlaminar Shear ◽  
Mechanics Of Composite Materials

Abstract Recent developments in nonlinear finite element methods (FEM) and mechanics of composite materials have made it possible to handle complex tire mechanics problems involving large deformations and moderate strains. The development of an accurate material model for cord/rubber composites is a necessary requirement for the application of these powerful finite element programs to practical problems but involves numerous complexities. Difficulties associated with the application of classical lamination theory to cord/rubber composites were reviewed. The complexity of the material characterization of cord/rubber composites by experimental means was also discussed. This complexity arises from the highly anisotropic properties of twisted cords and the nonlinear stress—strain behavior of the laminates. Micromechanics theories, which have been successfully applied to hard composites (i.e., graphite—epoxy) have been shown to be inadequate in predicting some of the properties of the calendered fabric ply material from the properties of the cord and rubber. Finite element models which include an interply rubber layer to account for the interlaminar shear have been shown to give a better representation of cord/rubber laminate behavior in tension and bending. The application of finite element analysis to more refined models of complex structures like tires, however, requires the development of a more realistic material model which would account for the nonlinear stress—strain properties of cord/rubber composites.

Effect of Residual Stress or Plastic Deformation History on Fatigue Life Simulation of Pipeline Dents

2018 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Rick Wang
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Strain History ◽  
Deformation History ◽  
Stress Strain ◽  
Element Analysis ◽  
Fea Model

Mechanical dents often occur in transmission pipelines, and are recognized as one of major threats to pipeline integrity because of the potential fatigue failure due to cyclic pressures. With matured in-line-inspection (ILI) technology, mechanical dents can be identified from the ILI runs. Based on ILI measured dent profiles, finite element analysis (FEA) is commonly used to simulate stresses and strains in a dent, and to predict fatigue life of the dented pipeline. However, the dent profile defined by ILI data is a purely geometric shape without residual stresses nor plastic deformation history, and is different from its actual dent that contains residual stresses/strains due to dent creation and re-rounding. As a result, the FEA results of an ILI dent may not represent those of the actual dent, and may lead to inaccurate or incorrect results. To investigate the effect of residual stress or plastic deformation history on mechanics responses and fatigue life of an actual dent, three dent models are considered in this paper: (a) a true dent with residual stresses and dent formation history, (b) a purely geometric dent having the true dent profile with all stress/strain history removed from it, and (c) a purely geometric dent having an ILI defined dent profile with all stress/strain history removed from it. Using a three-dimensional FEA model, those three dents are simulated in the elastic-plastic conditions. The FEA results showed that the two geometric dents determine significantly different stresses and strains in comparison to those in the true dent, and overpredict the fatigue life or burst pressure of the true dent. On this basis, suggestions are made on how to use the ILI data to predict the dent fatigue life.

Study and Analysis of Mechanical Behavior between Rigid and Dynamic Fixation Systems Analyzed by the Finite Element Method

2017 ◽  
Vol 33 ◽  
pp. 12-31 ◽  
Author(s):  
Samir Zahaf ◽  
Said Kebdani
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Intervertebral Disc ◽  
Spinal Diseases ◽  
Main Role ◽  
Rigid Fixation ◽  
Dynamic Fixation ◽  
Motion Segment ◽  
Fixation Devices ◽  
Element Method

Orthopedic fixation devices are widely used in treatment of spinal diseases. It is expected that application of dynamic stabilization confers valuable movement possibility besides its main role of load bearing. Comparative investigation between pedicle screw model rigid fixation and (B Dyne, Elaspine, Bioflex, Coflexe rivet) models dynamic fixation systems may elucidate the efficacy of each design. The goal of the present study is to evaluate the efficacy of five fixation systems mounted on L4-L5 motion segment. In this numerical study, a 3D precious model of L4, L5 and their intervertebral disc has been employed based on CT images. five fixation devices have been also implanted internally to the motion segment. Finite element method was used to evaluate stress distribution in the disc and determine the overall displacement of the segment as a measure of movement possibility. The results show that The Coflex rivet implantation can provide stability in all motions and reduce disc annulus stress at the surgical segment (L4-L5), on the other hand, Maximum stress in the disc has been observed in dynamic systems but within the safe range. The greater movement of the motion segment has been also appeared in dynamic fixations. Existence of the fixation systems reduced the stress on the intervertebral disc which might be exerted in intact cases. Use of the fixation devices can considerably reduce the load on the discs and prepare conditions for healing of the injured ones. Furthermore, dynamic modes of fixation confer possibility of movement to the motion segments in order to facilitate the spinal activities.

Enhancement of Bone Implants by Substituting Nitinol for Titanium (Ti-6Al-4V): A Modeling Comparison

2014 ◽  
Author(s):  
Narges Shayesteh Moghaddam ◽  
Mohammad Elahinia ◽  
Michael Miller ◽  
David Dean
Keyword(s):  
Tumor Resection ◽  
Stress Shielding ◽  
High Strength ◽  
Standard Of Care ◽  
Mandibular Reconstruction ◽  
Bone Plate ◽  
Segmental Defect ◽  
Stress Strain ◽  
Element Analysis ◽  
Grade 5

Mandibular segmental defect reconstruction is most often necessitated by tumor resection, trauma, infection, or osteoradionecrosis. The standard of care treatment for mandibular segmental defect repair involves using metallic plates to immobilize fibula grafts, which replace the resected portion of mandible. Surgical grade 5 titanium (Ti-6Al-4V) is commonly used to fabricate the fixture plate due to its low density, high strength, and high biocompatibility. One of the potential problems with mandibular reconstruction is stress shielding caused by a stiffness mismatch between the Titanium fixation plate and the remaining mandible bone and the bone grafts. A highly stiff fixture carries a large portion of the load (e.g., muscle loading and bite force), therefore the surrounding mandible would undergo reduced stress. As a result the area receiving less strain would remodel and may undergo significant resorption. This process may continue until the implant fails. To avoid stress shielding it is ideal to use fixtures with stiffness similar to that of the surrounding bone. Although Ti-6Al-4V has a lower stiffness (110 GPa) than other common materials (e.g., stainless steel, tantalum), it is still much stiffer than the cancellous (1.5–4.5 GPa) and cortical portions of the mandible (17.6–31.2 GPa). As a solution, we offer a nitinol in order to reduce stiffness of the fixation hardware to the level of mandible. To this end, we performed a finite element analysis to look at strain distribution in a human mandible in three different cases: I) healthy mandible, II) resected mandible treated with a Ti-6Al-4V bone plate, III) resected mandible treated with a nitinol bone plate. In order to predict the implant’s success, it is useful to simulate the stress-strain trajectories through the treated mandible. This work covers a modeling approach to confirm superiority of nitinol for mandibular reconstruction. Our results show that the stress-strain trajectories of the mandibular reconstruction using nitinol fixation is closer to normal than if grade 5 surgical titanium fixation is used.

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