scholarly journals Derivation of a finite-element model of lingual deformation during swallowing from the mechanics of mesoscale myofiber tracts obtained by MRI

2010 ◽  
Vol 109 (5) ◽  
pp. 1500-1514 ◽  
Author(s):  
Srboljub M. Mijailovich ◽  
Boban Stojanovic ◽  
Milos Kojic ◽  
Alvin Liang ◽  
Van J. Wedeen ◽  
...  
Keyword(s):  
Finite Element ◽  
Connective Tissue ◽  
Diffusion Tensor ◽  
Element Model ◽  
Out Of Plane ◽  
Posterior Direction ◽  
Elastic Constraints ◽  
The Relationship ◽  
Passive Muscle ◽  
Anterior Posterior

To demonstrate the relationship between lingual myoarchitecture and mechanics during swallowing, we performed a finite-element (FE) simulation of lingual deformation employing mesh aligned with the vector coordinates of myofiber tracts obtained by diffusion tensor imaging with tractography in humans. Material properties of individual elements were depicted in terms of Hill's three-component phenomenological model, assuming that the FE mesh was composed of anisotropic muscle and isotropic connective tissue. Moreover, the mechanical model accounted for elastic constraints by passive and active elements from the superior and inferior directions and the effect of out-of-plane muscles and connective tissue. Passive bolus effects were negligible. Myofiber tract activation was simulated over 500 ms in 1-ms steps following lingual tip association with the hard palate and incorporated specifically the accommodative and propulsive phases of the swallow. Examining the displacement field, active and passive muscle stress, elemental stretch, and strain rate relative to changes of global shape, we demonstrate that lingual reconfiguration during these swallow phases is characterized by (in sequence) the following: 1) lingual tip elevation and shortening in the anterior-posterior direction; 2) inferior displacement related to hyoglossus contraction at its inferior-most position; and 3) dominant clockwise rotation related to regional contraction of the genioglossus and contraction of the hyoglossus following anterior displacement. These simulations demonstrate that lingual deformation during the indicated phases of swallowing requires temporally patterned activation of intrinsic and extrinsic muscles and delineate a method to ascertain the mechanics of normal and pathological swallowing.

Dynamic stiffness formulation for the vibrations of stiffened plate structures with consideration of in-plane deformation

2017 ◽  
Vol 24 (20) ◽  
pp. 4825-4838 ◽  
Author(s):  
Xuewen Yin ◽  
Wenwei Wu ◽  
Kuikui Zhong ◽  
Hui Li
Keyword(s):  
Finite Element ◽  
Dynamic Stiffness ◽  
Plane Deformation ◽  
Element Model ◽  
The Finite Element Method ◽  
Plate Structures ◽  
Beam Elements ◽  
Stiffness Model ◽  
Out Of Plane ◽  
The Relationship

A dynamic stiffness method is presented for the vibrations of plate structures that are reinforced by eccentric stiffeners. The model incorporates both out-of-plane and in-plane deformations of the plates and the stiffeners. Based on the relationship between the forces and displacements along the common edges of the plate or beam elements, the dynamic stiffness formulae for the plate and the beam elements are derived, respectively. The globally assembled dynamic stiffness matrix is then obtained using the finite element method so that the dynamics of built-up stiffened plates can be readily addressed by using the present method. Compared to the conventional finite element model, the dynamic stiffness model can provide very accurate solutions using only one element over each uniform plate and beam member, regardless of its geometry.

Finite Element Analysis of the ESTELA M1 Airplane Firewall (Representative Specimen)

2011 ◽  
Author(s):  
V. Ramirez-Elias ◽  
E. Ledesma-Orozco ◽  
H. Hernandez-Moreno
Keyword(s):  
Finite Element ◽  
Federal Aviation Administration ◽  
Element Model ◽  
Maximum Load ◽  
Load Factor ◽  
Representative Specimen ◽  
Maximum Displacement ◽  
Element Analysis ◽  
Element Simulation ◽  
The Relationship

This paper shows the finite element simulation of a representative specimen from the firewall section in the AEROMARMI ESTELA M1 aircraft. This specimen is manufactured in glass and carbon / epoxy laminates. The specimen is subjected to a load which direction and magnitude are determined by a previous dynamic loads study [10], taking into account the maximum load factor allowed by the FAA (Federal Aviation Administration) for utilitarian aircrafts [11]. A representative specimen is manufactured with the same features of the firewall. Meanwhile a fix is built in order to introduce the load directions on the representative specimen. The relationship between load and displacement is plotted for this representative specimen, whence the maximum displacement at the specific load is obtained, afterwards it is compared with the finite element model, which is modified in its laminate thicknesses in order to decrease the deviation error; subsequently this features could be applied to perform the whole firewall analysis in a future model [10].

The Dynamic Strength of a Representative Double Layer Prismatic Core: A Combined Experimental, Numerical, and Analytical Assessment

2010 ◽  
Vol 77 (6) ◽  
Author(s):  
Enrico Ferri ◽  
V. S. Deshpande ◽  
A. G. Evans
Keyword(s):  
Finite Element ◽  
Double Layer ◽  
Dynamic Compression ◽  
Dynamic Strength ◽  
Element Model ◽  
Free Standing ◽  
The Core ◽  
Impulsive Loads ◽  
Back Face ◽  
Out Of Plane

Dynamic out-of-plane compressive testing was used to characterize the dynamic strength of stainless steel prismatic cores with representative double layer topology to be employed in sandwich panels for blast protection. Laboratory-scaled samples of the representative core unit cell were manufactured (relative density of 5.4%) and tested at constant axial impact velocities (ranging from quasi-static to 140 ms−1). The dynamic strength was evaluated by measuring the stresses transmitted to a direct impact Hopkinson bar. Two-dimensional, plane strain, finite element calculations (with a stationary back face) were used to replicate the experimental results upon incorporating imperfections calibrated using the observed dynamic buckling modes. To infer the response of cores when included in a sandwich plate subject to blast loading, the finite element model was modified to an unsupported (free-standing) back face boundary condition. The transmitted stress is found to be modulated by the momentum acquired by the back face mass and, as the mass becomes larger, the core strength approaches that measured and simulated for stationary conditions. This finding justifies the use of a simple dynamic compression test for calibration of the dynamic strength of the core. An analytical model that accounts for the shock effects in a homogenized core and embodies a simple dual-level dynamic strength is presented and shown to capture the experimental observations and simulated results with acceptable fidelity. This model provides the basis for a constitutive model that can be used to understand the response of sandwich plates subject to impulsive loads.

scholarly journals Curvature reduces bending strains in the quokka femur

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3100 ◽  
Author(s):  
Kyle McCabe ◽  
Keith Henderson ◽  
Jess Pantinople ◽  
Hazel L. Richards ◽  
Nick Milne
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Linear Relationship ◽  
Strain Gradient ◽  
Stance Phase ◽  
Element Model ◽  
Knee Extensors ◽  
Bending Strain ◽  
Biarticular Muscles ◽  
The Relationship

This study explores how curvature in the quokka femur may help to reduce bending strain during locomotion. The quokka is a small wallaby, but the curvature of the femur and the muscles active during stance phase are similar to most quadrupedal mammals. Our hypothesis is that the action of hip extensor and ankle plantarflexor muscles during stance phase place cranial bending strains that act to reduce the caudal curvature of the femur. Knee extensors and biarticular muscles that span the femur longitudinally create caudal bending strains in the caudally curved (concave caudal side) bone. These opposing strains can balance each other and result in less strain on the bone. We test this idea by comparing the performance of a normally curved finite element model of the quokka femur to a digitally straightened version of the same bone. The normally curved model is indeed less strained than the straightened version. To further examine the relationship between curvature and the strains in the femoral models, we also tested an extra-curved and a reverse-curved version with the same loads. There appears to be a linear relationship between the curvature and the strains experienced by the models. These results demonstrate that longitudinal curvature in bones may be a manipulable mechanism whereby bone can induce a strain gradient to oppose strains induced by habitual loading.

Characterization of the Dynamical Response of a Micromachined G-Sensor to Mechanical Shock Loading

2007 ◽  
Author(s):  
Daniel E. Jordy ◽  
Mohammad I. Younis
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Squeeze Film ◽  
Dynamical Response ◽  
Mems Devices ◽  
Damping Coefficients ◽  
Squeeze Film Damping ◽  
Out Of Plane ◽  
Gap Width

Squeeze film damping has a significant effect on the dynamic response of MEMS devices that employ perforated microstructures with large planar areas and small gap widths separating them from the substrate. Perforations can alter the effect of squeeze film damping by allowing the gas underneath the device to easily escape, thereby lowering the damping. By decreasing the size of the holes, the damping increases and the squeeze film damping effect increases. This can be used to minimize the out-of-plane motion of the microstructures toward the substrate, thereby minimizing the possibility of contact and stiction. This paper aims to explore the use of the squeeze-film damping phenomenon as a way to mitigate shock and minimize the possibility of stiction and failure in this class of MEMS devices. As a case study, we consider a G-sensor, which is a sort of a threshold accelerometer, employed in an arming and fusing chip. We study the effect of changing the size of the perforation holes and the gap width separating the microstructure from the substrate. We use a multi-physics finite-element model built using the software ANSYS. First, a modal analysis is conducted to calculate the out-of-plane natural frequency of the G-sensor. Then, a squeeze-film damping finite-element model, for both the air underneath the structure and the flow of the air through the perforations, is developed and utilized to estimate the damping coefficients for several hole sizes. Results are shown for various models of squeeze-film damping assuming no holes, large holes, and assuming a finite pressure drop across the holes, which is the most accurate way of modeling. The extracted damping coefficients are then used in a transient structural-shock analysis. Finally, the transient shock analysis is used to determine the shock loads that induce contacts between the G-sensor and the underlying substrate. It is found that the threshold of shock to contact the substrate has increased significantly when decreasing the holes size or the gap width, which is very promising to help mitigate stiction in this class of devices, thereby improving their reliability.

Rotor optimization for the improvement of ultrasonic motor performance

2019 ◽  
Vol 233 (19-20) ◽  
pp. 7089-7100 ◽  
Author(s):  
Zhangfan Xu ◽  
Sisi Di ◽  
Song Pan ◽  
Lei Chen ◽  
Weiqing Huang
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Shell Structure ◽  
Motor Performance ◽  
Thin Shell ◽  
Element Model ◽  
Ultrasonic Motor ◽  
Comsol Multiphysics ◽  
New Approach ◽  
The Relationship

The rotor deformation of an ultrasonic motor is an important factor affecting its performance. However, little research focuses on the relationship between the rotor deformation and motor performance. This paper provides an approach to improve the ultrasonic motor's output properties by changing the rotor's size from the view of proper rotor deformation and better stress distribution on the interface. First, a thin shell structure is introduced to study the deformation of the rotor. A finite element model of the motor is built in COMSOL Multiphysics software for the contact analysis of the stress distribution. Then, the optimized ranges of parameters are determined by simulation. Frictional experiments are conducted to verify the feasibility of the rotor under the optimized size. Finally, the performance experiments of a stator corresponding to different sizes of rotor are carried out. The experimental results show that the speed, the power and the efficiency of the optimized rotor are all increase. These results prove the effectivity of the new approach to improving the performance of the ultrasonic motor.

Comparison Between Single Level and Bi-Level Dynamic Stabilization in Lumbar Spondylolisthesis: A Finite Element Study

2007 ◽  
Author(s):  
A. S. Khere ◽  
A. Kiapour ◽  
J. Jangra ◽  
V. K. Goel ◽  
A. Biyani ◽  
...  
Keyword(s):  
Finite Element ◽  
Severe Pain ◽  
Element Model ◽  
Dynamic Stabilization ◽  
Single Level ◽  
Pars Interarticularis ◽  
Lumbar Spondylolisthesis ◽  
Older Populations ◽  
The Finite Element Model ◽  
Anterior Posterior

Lumbar spondylolisthesis is an extension of spondylolysis in which breakage of the vertebrae occurs at the pars interarticularis causing the vertebrae to slip forward. Spondylolisthesis is seen in both younger and older populations with most lesions occurring at the L4-L5 or L5-S1 level. Although the forward slippage of the vertebra does not usually exceed 30% of the body’s anterior-posterior width, possible spinal stenosis and nerve impingement may lead to severe pain and other complications. The purpose of this study is to determine the effect of single level and bi-level dynamic stabilization in reducing the spondylolisthesis. We used the finite element model for this purpose since it is not practical to procure specimens with spondylolisthesis for an experimental investigation.

Forming limit diagrams by including the M–K model in finite element simulation considering the effect of bending

2016 ◽  
Vol 232 (8) ◽  
pp. 625-636 ◽  
Author(s):  
Mostafa Habibi ◽  
Ramin Hashemi ◽  
Ahmad Ghazanfari ◽  
Reza Naghdabadi ◽  
Ahmad Assempour
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Metal Forming ◽  
Forming Limit Diagram ◽  
Element Model ◽  
Forming Limit ◽  
Finite Element Models ◽  
Element Simulation ◽  
Simple Tension ◽  
Out Of Plane

Forming limit diagram is often used as a criterion to predict necking initiation in sheet metal forming processes. In this study, the forming limit diagram was obtained through the inclusion of the Marciniak–Kaczynski model in the Nakazima out-of-plane test finite element model and also a flat model. The effect of bending on the forming limit diagram was investigated numerically and experimentally. Data required for this simulation were determined through a simple tension test in three directions. After comparing the results of the flat and Nakazima finite element models with the experimental results, the forming limit diagram computed by the Nakazima finite element model was more convenient with less than 10% at the lower level of the experimental forming limit diagram.

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