A Poroelastic Finite Element Model to Describe the Time-Dependent Response of Lumbar Intervertebral Disc

2011 ◽  
Vol 1 (3) ◽  
pp. 246-251 ◽  
Author(s):  
M. Nikkhoo ◽  
M. Haghpanahi ◽  
J. L. Wang ◽  
M. Parnianpour
PLoS ONE ◽  
2017 ◽  
Vol 12 (5) ◽  
pp. e0177088 ◽  
Author(s):  
Gloria Casaroli ◽  
Fabio Galbusera ◽  
René Jonas ◽  
Benedikt Schlager ◽  
Hans-Joachim Wilke ◽  
...  

2016 ◽  
Vol 34 (7) ◽  
pp. 1264-1273 ◽  
Author(s):  
Brent L. Showalter ◽  
John F. DeLucca ◽  
John M. Peloquin ◽  
Daniel H. Cortes ◽  
Jonathon H. Yoder ◽  
...  

Author(s):  
A. E. Segall ◽  
R. Carter

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.


2005 ◽  
Vol 11 (3) ◽  
pp. 163-168
Author(s):  
Andrey V. Benin

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.


Author(s):  
MD Waquar Alam

Large displacements during excavation are regularly observed in Squeezing ground condition and Rock-burst condition with high overburden. The expected displacement has to be estimated prior to excavation to provide enough allowance for the displacements. The support system need to be well-suited through the estimated imposed strains. As the estimated displacements and thus the strains in the support depend upon the load-bearing capacity of support. The ratio of uniaxial compressive strength of rock mass to maximal insitu stress determines tunnel integrity in the weak region.This ratio estimates the requirements of initial lining to control strain to a stipulated level. The elasto-plastic theory may deliver definitive forecasts providing the strength limitations of rock masses are identified accurately. With the help of empirical analysis, the development of displacements for diverse advance rates and supports can be concluded. As a consequence, a quantitative finite element model based on an advanced built-in model is designed to analyse the load-bearing efficiency of initial lining although taking into consideration the time-dependent and non-linear material behaviour of initial lining. The time-dependent excavation mechanism of the drill-and-blast approach for tunnels guided by full face excavation is considered in the finite element model. The material parameters for the initial lining were computed based on case studies- (A Chibro-Khodri Hydropower Tunnel).


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