Time-dependent mechanical behaviour of the periodontal ligament

2000 ◽  
Vol 214 (5) ◽  
pp. 497-504 ◽  
Author(s):  
W D van Driel ◽  
E J van Leeuwen ◽  
J W Von den Hoff ◽  
J C Maltha ◽  
A M Kuijpers-Jagtman
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Mechanical Behaviour ◽  
Periodontal Ligament ◽  
Alveolar Bone ◽  
Element Model ◽  
Time Dependent ◽  
Step Response ◽  
In Vivo Experiments

The process of tooth displacement in response to orthodontic forces is thought to be induced by the stresses and strains in the periodontium. The mechanical force on the tooth is transmitted to the alveolar bone through a layer of soft connective tissue, the periodontal ligament. Stress and/or strain distribution in this layer must be derived from mathematical models, such as the finite element method, because it cannot be measured directly in a non-destructive way. The material behaviour of the constituent tissues is required as an input for such a model. The purpose of this study was to determine the time-dependent mechanical behaviour of the periodontal ligament due to orthodontic loading of a tooth. Therefore, in vivo experiments were performed on beagle dogs. The experimental configuration was simulated in a finite element model to estimate the poroelastic material properties for the periodontal ligament. The experiments showed a two-step response: an instantaneous displacement of 14.10 ± 3.21 μm within 4 s and a more gradual (creep) displacement reaching a maximum of 60.00 ± 9.92 μm after 5 h. This response fitted excellently in the finite element model when 21 per cent of the ligament volume was assigned a permeability of 1.0 × 10−14m4/Ns, the remaining 97 per cent was assigned a permeability of 2.5 × 10−17 m4/N s. A tissue elastic modulus of 0.015 ± 0.001 MPa was estimated. Our results indicate that fluid compartments within the periodontal ligament play an important role in the transmission and damping of forces acting on teeth.

Finite-Element Simulations and Probabilistic Fracture Assessments of the Response of Alternate Rifling Geometries

2007 ◽  
Author(s):  
A. E. Segall ◽  
R. Carter
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Thermal Stresses ◽  
Rotational Symmetry ◽  
Element Model ◽  
Time Dependent ◽  
Uniform Heating ◽  
Thermal Pressure ◽  
Single Firing ◽  
Hoop Stresses

A 3-D finite-element model was used to simulate the severe and localized thermal/pressure transients and the resulting stresses experienced by a rifled ceramic-barrel with a steel outer-liner; the focus of the simulations was on the influence of non-traditional rifling geometries on the thermoelastic- and pressure-stresses generated during a single firing event. In order to minimize computational requirements, a twisted segment of the barrel length based on rotational symmetry was used. Using this simplification, the model utilized uniform heating and pressure across the ID surface via a time-dependent convective coefficient and pressure generated by the propellant gasses. Results indicated that the unique rifling geometries had only a limited influence on the maximum circumferential (hoop) stresses and temperatures when compared with more traditional rifling configurations because of the compressive thermal stresses developed at the heated (and rifled) surface.

Personalized finite element model of the knee joint in vivo

2006 ◽  
Vol 39 ◽  
pp. S501
Author(s):  
M. Sangeux ◽  
F. Marin ◽  
F. Charleux ◽  
L. Dürselen ◽  
M.-C. Ho Ba Thoa
Keyword(s):  
Finite Element ◽  
Knee Joint ◽  
Finite Element Model ◽  
Element Model

scholarly journals ACCOUNTING FOR EFFECTS OF DECREASING BOND BETWEEN CONCRETE AND REBARS ON SEISMIC RESISTANCE OF REINFORCED CONCRETE STRUCTURAL ELEMENTS

2005 ◽  
Vol 11 (3) ◽  
pp. 163-168
Author(s):  
Andrey V. Benin
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Finite Element Model ◽  
Functional Dependence ◽  
Element Model ◽  
Strain Ratio ◽  
Time Dependent ◽  
Strain Diagram ◽  
System Components ◽  
Non Linear

This study reviews an alternative of reinforced concrete finite element model as a system, where physical conditions for system components are recorded independently and, in addition, conditions for interaction of system components on their contact are also introduced. In this case, we are able to take into account all specific features of reinforcement, to trace the history of loading and destruction for each rebar. Basic specific feature of reviewed problem ascertains the necessity to use non‐linear stress‐strain ratio in reinforced concrete with consideration of specific features of reinforced concrete activity after cracking. Naturally, functional dependence describing this ratio varies along with the progress of rebars corrosion. Exactly, corrosion of rebars is the key reason for time‐dependent quality degrading of reinforced concrete structures. This problem stands for more urgency with respect to structures in seismic sensitive zones since such corrosion of rebars leads to deviations of the structure rigidity characteristics and, in turn, it may lead to an reduction of bearing capability in certain elements or to an increase of displacements to intolerable high values. This study proposes a clarified procedure to solve plane‐stressed problem for reinforced concrete. The specific feature of this procedure assumes an application of new approximation for non‐linear concrete strain diagram, development of a detailed finite element model for reproduction of effect generated under concrete/rebar bond forces, as well as such considerable time‐dependent factors as concrete creep and rebar corrosion.

Sign in / Sign up

Export Citation Format

Share Document