Axial distortion of airways in the lung

1983 ◽  
Vol 54 (1) ◽  
pp. 185-190 ◽  
Author(s):  
M. J. Kallok ◽  
S. J. Lai-Fook ◽  
M. A. Hajji ◽  
T. A. Wilson
Keyword(s):  
Elastic Tube ◽  
Shear Stresses ◽  
Coupling Mechanism ◽  
Airway Wall ◽  
Axial Loads ◽  
Elastic Continuum ◽  
Airway Lumen ◽  
Axial Forces ◽  
Mathematical Analyses ◽  
The Continuum

Axial loads were applied around the circumference of an airway lumen by pulling on a cup-shaped anchor that embedded itself in the airway wall. Axial displacements were measured as a function of distance from the load, and the data were compared to the results of mathematical analyses of continuum mechanics models. In the modeling it was assumed that the elastic tube representing the airway is bonded to the surrounding elastic continuum representing the parenchyma and that axial forces are transmitted between the tube and the continuum by shear stresses at the interface. The agreement between the measured and computed axial displacements supports the hypothesis that the shear stresses are the dominant coupling mechanism. The following quantitative relations between force and displacement were obtained. The axial displacement produced by the load L was approximately 0.05 L/pi alpha mu, where alpha is the airway radius and mu is the shear modulus of the parenchyma. The displacement decayed to approximately one-half this maximal value at two diameters from the load.

scholarly journals Stress Monitoring on GFRP Anchors Based on Fiber Bragg Grating Sensors

Sensors ◽  
2019 ◽  
Vol 19 (7) ◽  
pp. 1507 ◽  
Author(s):  
Hai-Lei Kou ◽  
Wang Li ◽  
Wang-Chun Zhang ◽  
Yuan Zhou ◽  
Xiao-Long Zhou
Keyword(s):  
Fiber Bragg Grating ◽  
Field Test ◽  
Weight Ratio ◽  
Electromagnetic Properties ◽  
Bragg Grating ◽  
Shear Stresses ◽  
Stress Profile ◽  
Stress Monitoring ◽  
Axial Forces ◽  
Fbg Sensors

Glass fiber-reinforced polymer (GFRP) bolts have been widely used in some applications of grouted anchors because of the advantages of better resistance to corrosion, high strength-to-weight ratio, low electromagnetic properties, and so on. This study presents a field test to assess the feasibility of fiber Bragg grating (FBG) sensors in monitoring the stress profile of GFRP anchors during pulling test. Two GFRP anchors were fully instrumented with FBG sensors and then installed into the ground using a drilling and grouting method. To measure the stress profile along test anchors, seven bare FBG sensors were arranged in a single optical fiber and then embedded in the middle of GFRP bolts in the process of extrusion molding. The procedure for embedding bare FBG sensors into GFRP bolts is introduced first. Then, the axial forces and shear stresses that were calculated from the measurements of the FBG sensors are discussed. The field test results indicate that the embedded FBG technology was feasible to monitor the stress state of GFRP anchors during pulling.

DYNAMIC PERFORMANCE OF POST-BUCKLED PRECOMPRESSED PIEZOELECTRIC ACTUATOR ELEMENTS

2012 ◽  
Vol 12 (05) ◽  
pp. 1250042 ◽  
Author(s):  
GEORGIOS GIANNOPOULOS ◽  
MARK GROEN ◽  
ROELOF VOS ◽  
RON BARRETT
Keyword(s):  
Finite Element ◽  
Damping Ratio ◽  
Dynamic Performance ◽  
Past Research ◽  
Element Model ◽  
Axial Loads ◽  
New Class ◽  
Axial Forces ◽  
Bimorph Actuators ◽  
Full Force

Post-buckled precompressed (PBP) piezoelectric elements have recently been used to enable a new class of actuators that are able to provide far higher deflections compared to the traditional bimorph piezoelectric actuators while maintaining full force and moment generating capabilities. Past research has proven that PBP actuators are capable of generating deflections three times higher than conventional bimorph actuators. In this paper, this work has been extended to the dynamic response realm and the performance of PBP actuators is investigated under various axial loads, at various actuation frequencies. Both analytical and finite element models have been developed in order to evaluate the performance of the actuator regarding the natural frequency shift under increased axial loads. Experimental verification has shown that the overall damping ratio of the structure is a function of the axial forces. Values derived from experiments have been used in the Finite Element model to predict the displacement output, phase angle shifting and end rotation. Numerical and analytical results correlate very well with the experiments and thus give credit to the formulation presented in this work.

scholarly journals Stress Equations for Adhesive in Twodimensional Adhesively Bonded Joints/ Równania Naprężn W Plaskich Dwuwymiarowych Spoinach Klejowych

2014 ◽  
Vol 14 (3) ◽  
pp. 75-94
Author(s):  
Piotr Rapp
Keyword(s):  
Shear Stress ◽  
Shear Stresses ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Adhesive Layers ◽  
Axial Forces ◽  
Joint Plane ◽  
Base Functions ◽  
The Subject

Abstract The subject of this paper is formulation of shear stress equations for plane twodimensional adhesive layers present in adhesively bonded joints. The adherends are assumed to have the same thickness and be made of an isotropic material. The shape of the adherends in the joint plane is arbitrary. The adhesive joint can be subjected to a shear stress arbitrarily distributed on the adherends surfaces as well as normal and shear stresses arbitrarily distributed along the adherends edges. A set of two partial differential equations of the second order with shear stresses in the adhesive as unknowns has been formulated. For a particular case of rectangular joints a set of 12 base functions has been derived; their appropriate linear combinations uniquely define shear stresses in the adhesive for a joint loaded arbitrarily by a set of axial forces, bending moments and shear forces.

scholarly journals Longitudinal shape irregularity of airway lumen assessed by CT in patients with bronchial asthma and COPD

Thorax ◽  
2015 ◽  
Vol 70 (8) ◽  
pp. 719-724 ◽  
Author(s):  
Tsuyoshi Oguma ◽  
Toyohiro Hirai ◽  
Motonari Fukui ◽  
Naoya Tanabe ◽  
Satoshi Marumo ◽  
...  
Keyword(s):  
Bronchial Asthma ◽  
Ct Images ◽  
Wall Thickening ◽  
Airway Remodelling ◽  
Healthy Controls ◽  
Airway Wall ◽  
Cross Sectional ◽  
Airway Lumen ◽  
Luminal Area ◽  
Shape Irregularity

BackgroundAirway remodelling in bronchial asthma (BA) and COPD has been quantitatively assessed by analysing the airway wall area and the luminal area on cross-sectional CT images. To date, there have been no reports on assessment of the longitudinal structure of the airway lumen.MethodsQuantitative airway analysis using CT was performed on three groups consisting of 29 patients with BA, 58 patients with COPD and 59 healthy controls. To assess the longitudinal shape irregularity of the airway lumen, new quantitative CT parameters, validated by a phantom study, were established. The internal radii of imaginary inscribed spheres in the airway lumen were measured as a function of distance from the level of the carina to the fifth-order branches of the right posterior basal bronchus. The gaps of these radii from the regression line were calculated as parameters to reflect the longitudinal airway lumen shape irregularity. These new parameters were compared among the study groups as well as with the conventional parameters of airway wall thickening and luminal area.ResultsLongitudinal airway lumen shape irregularity was significantly greater in patients with COPD than in those with BA and healthy controls. Wall thickening was significantly greater, and luminal area smaller, in patients with BA than in those with COPD and healthy controls. These results were consistent even among the BA and COPD subgroups with similar airflow limitation.ConclusionsThe combination of cross-sectional and longitudinal airway structure analyses using CT images may suggest differences in the characteristics of airway remodelling between COPD and asthma.

scholarly journals Axial creeping flow in the gap between a rigid cylinder and a concentric elastic tube

2016 ◽  
Vol 806 ◽  
pp. 580-602 ◽  
Author(s):  
S. B. Elbaz ◽  
A. D. Gat
Keyword(s):  
Fluid Layer ◽  
Elastic Shell ◽  
Gravity Current ◽  
Travelling Wave ◽  
Elastic Tube ◽  
Creeping Flow ◽  
Shear Stresses ◽  
Length Scales ◽  
Rigid Cylinder ◽  
Viscous Forces

We examine transient axial creeping flow in the annular gap between a rigid cylinder and a concentric elastic tube. The gap is initially filled with a thin fluid layer. We employ an elastic shell model and the lubrication approximation to obtain governing equations for the elastohydrodynamic interaction. At long axial length scales viscous forces are balanced by elastic tension, while at shorter length scales the viscous–elastic balance is achieved by means of an interplay between elastic bending, tension and shear stresses. Based on a viscous gravity current analogy in the tensile–viscous regime, we devise propagation laws for displacement flows which are induced by a variety of boundary conditions and examine different limits of the prewetting thickness. Next we focus on the moving elastohydrodynamic contact line at the edge of a penetrating film. A uniform matched asymptotic solution connecting the interior tension-based region with a boundary layer region near the propagation front is presented. Finally, a constructive example is shown in which isolated moving deformation patterns are created and superimposed to form a travelling wave displacement field. The presented interaction between viscosity and elasticity may be applied to fields such as soft robotics and micro-scale or larger swimmers by allowing for the time-dependent control of an axisymmetric compliant boundary.

Evaluation of Cement-Casing & Cement-Rock Bond Integrity During Well Operations

2021 ◽  
Author(s):  
Abdelfattah Lamik ◽  
Gerhard Pittino ◽  
Michael Prohaska-Marchried ◽  
Ravi Krishna ◽  
Gerhard Thonhauser ◽  
...  
Keyword(s):  
Steam Injection ◽  
Shear Stresses ◽  
Ambient Conditions ◽  
Axial Loads ◽  
Water Steam ◽  
Rock System ◽  
Testing Procedures ◽  
Testing Method ◽  
Geothermal Wells ◽  
Stress Ratios

Abstract This paper presents the results of laboratory static and dynamic tests on casing-cement-rock systems exposed to axial loads under ambient conditions. A new testing method has been developed. The casing-cement-rock system mostly fails due to tension and shear stresses. In various applications such as HPHT, deep-water, (steam) injection or geothermal wells, the cement-casing bond is exposed to cyclic thermomechanical loads resulting in casing elongation, contraction, expansion and subsequently in cyclic radial and axial stresses at the cement-casing-rock system. Cement is a brittle material which can fail when subjected to repeated application of stresses lesser in magnitude than the statically determined strength. A novel atmospheric test cell has been designed and constructed. In order to achieve the fatigue limits of the cement-casing bond, a set of testing procedures has been established. Several tests are conducted to evaluate de-bonding. The focus on de-bonding is achieved by allowing the casing to move through the test while preventing any cement movement. Thus, when a force is applied in the axial z-direction - either the casing is pulled out (tension) or pushed down (compression) - the casing has enough space to move in both directions. The advantage of this testing method is that different stress ratios can be applied during the test.

On the mechanism of mucosal folding in normal and asthmatic airways

1997 ◽  
Vol 83 (6) ◽  
pp. 1814-1821 ◽  
Author(s):  
Barry R. Wiggs ◽  
Constantine A. Hrousis ◽  
Jeffrey M. Drazen ◽  
Roger D. Kamm
Keyword(s):  
Smooth Muscle ◽  
Muscle Activation ◽  
Composite Model ◽  
Chronic Obstructive ◽  
Airway Wall ◽  
Element Analysis ◽  
Obstructive Pulmonary Disease ◽  
Folding Pattern ◽  
Airway Lumen ◽  
Layer Composite

Wiggs, Barry R., Constantine A. Hrousis, Jeffrey M. Drazen, and Roger D. Kamm. On the mechanism of mucosal folding in normal and asthmatic airways. J. Appl. Physiol. 83(6): 1814–1821, 1997.—Previous studies have demonstrated that the airway wall in asthma and chronic obstructive pulmonary disease is markedly thickened. It has also been observed that when the smooth muscle constricts the mucosa buckles, forming folds that penetrate into the airway lumen. This folding pattern may influence the amount of luminal obstruction associated with smooth muscle activation. A finite-element analysis of a two-layer composite model for an airway is used to investigate the factors that determine the mucosal folding pattern and how it is altered as a result of changes in the thickness or stiffness of the different layers that comprise the airway wall. Results demonstrate that the most critical physical characteristic is the thickness of the thin inner layer of the model. Thickening of this inner layer likely is represented by the enhanced subepithelial collagen deposition seen in asthma. Other findings show a high shear stress at or near the epithelial layer, which may explain the pronounced epithelial sloughing that occurs in asthma, and steep gradients in pressure that could cause significant shifts of liquid between wall compartments or between the wall and luminal or vascular spaces.

Vibration and Frequency Analysis of Non-Uniform Timoshenko Beams Subjected to Axial Forces

2003 ◽  
Author(s):  
A. R. Ohadi ◽  
H. Mehdigholi ◽  
E. Esmailzadeh
Keyword(s):  
Stability Analysis ◽  
Boundary Conditions ◽  
Axial Force ◽  
Frequency Equation ◽  
Axial Loads ◽  
Various Boundary Conditions ◽  
Axial Forces ◽  
First Case ◽  
The Stability ◽  
Elastically Supported

Dynamic and stability analysis of non-uniform Timoshenko beam under axial loads is carried out. In the first case of study, the axial force is assumed to be perpendicular to the shear force, while for the second case the axial force is tangent to the axis of the beam column. For each case, a pair of differential equations coupled in terms of the flexural displacement and the angle of rotation due to bending was obtained. The parameters of the frequency equation were determined for various boundary conditions. Several illustrative examples of uniform and non-uniform beams with different boundary conditions such as clamped supported, elastically supported, and free end mass have been presented. The stability analysis, for the variation of the natural frequencies of the uniform and non-uniform beams with the axial force, has also been investigated.

Centrifuge Testing of Plumb and Battered Pile Groups in Sand

1997 ◽  
Vol 1569 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Paulo Pinto ◽  
Michael McVay ◽  
Marc Hoit ◽  
Peter Lai
Keyword(s):  
Pile Groups ◽  
Axial Loads ◽  
Pile Head ◽  
Dead Load ◽  
Centrifuge Testing ◽  
Centrifuge Tests ◽  
Axial Forces ◽  
Lateral Forces ◽  
Lateral Resistance ◽  
Better Than

Pile groups are generally used under structures subject to heavy axial loads or large lateral forces with or without scour. The focus in this paper is only on pile groups subject to large lateral forces. Currently, little, if any, full-scale lateral load data exist on pile groups that vary pile head fixity or batter. Reported here is the summary of a series of centrifuge tests on free- and fixed-head plumb and battered pile groups. Influence of pile head constraint, pile spacing, soil density, and vertical dead load is reported for groups ranging from 3 × 3 to 3 × 7 in size. Results reveal a significant lateral resistance of fixed- over free-head pile groups; fixed-head piles develop significant axial forces; battered piles without vertical dead loads are generally no better than plumb piles; and in the case of plumb piles, the use of multipliers to represent group interaction is valid.

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