The Mechanical Behavior of a Mammalian Lung Alveolar Duct Model

1995 ◽  
Vol 117 (3) ◽  
pp. 254-261 ◽  
Author(s):  
E. Denny ◽  
R. C. Schroter
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Collagen Fiber ◽  
Fiber Bundles ◽  
Published Data ◽  
The Finite Element Method ◽  
Dependent Relationship ◽  
Alveolar Duct ◽  
Mammalian Lung ◽  
Air Liquid Interface

A model for the mechanical properties of an alveolar duct is analyzed using the finite element method. Its geometry comprises an assemblage of truncated octahedral alveoli surrounding a longitudinal air duct. The amounts and distributions of elastin and collagen fiber bundles, modeled by separate stress-strain laws, are based upon published data for dogs. The surface tension of the air-liquid interface is modeled using an area-dependent relationship. Pressure-volume curves are computed that compare well with experimental data for both saline-filled and air-filled lungs. Pressure-volume curves of the separate elastin and collagen fiber contributions are similar in form to the behavior of saline-filled lungs treated with either elastase or collagenase. A comparison with our earlier model, based upon a single alveolus, shows the duct to have a behavior closer to reported experimental data.

A model for mechanical structure of the alveolar duct

1982 ◽  
Vol 52 (4) ◽  
pp. 1064-1070 ◽  
Author(s):  
T. A. Wilson ◽  
H. Bachofen
Keyword(s):  
Surface Tension ◽  
Lung Volume ◽  
Published Data ◽  
Scanning Electron Micrographs ◽  
Fiber System ◽  
Lung Capacity ◽  
Alveolar Duct ◽  
Tissue System ◽  
Line Elements ◽  
Air Liquid Interface

The appearance of the microstructure of the lung as revealed in transmission and scanning electron micrographs of perfusion-fixed air- and saline-filled lungs suggests the following model for the structure of the alveolar duct. There are two networks of force-bearing elements. The first is an interdependent part of the peripheral connective tissue system that starts from the pleura and extends into the interlobar and interlobular fissures. At the sublobular level, its geometry is not yet fully clear. This network is extended by changes in lung volume and is insensitive to surface tension. The second network is composed of the line elements that form the rims of the alveolar openings. This network is the terminal part of the axial fiber system that surrounds bronchi, bronchioli, and arteries. The line elements of this network are extended by the outward force of surface tension. The two-dimensional alveolar walls that form the alveoli are negligible mechanical components except as platforms for surface tension at the air-liquid interface. An analysis of the mechanics of this model yields relations among surface area, recoil pressure, lung volume, and surface tension that are consistent with published data for lung volumes below 80% of total lung capacity.

Interpretation of Mechanical Testing Measurements for Pastes

2002 ◽  
Author(s):  
Robert A. Basterfield ◽  
Chris J. Lawrence ◽  
Michael J. Adams
Keyword(s):  
Experimental Data ◽  
Numerical Models ◽  
Experimental Methods ◽  
Published Data ◽  
The Finite Element Method ◽  
Material Parameters ◽  
Simulation Techniques ◽  
Manufacturing Sectors ◽  
Product Forms ◽  
Computer Simulation Techniques

Pastes occur as intermediates or final product forms in many industrially important manufacturing sectors. The use of computer simulation techniques, such as the finite element method, is becoming more common in the design of paste processing operations. A major problem in the application of this approach is the development of sufficiently representative materials models. It has been established that pastes may be described as elasto-viscoplastic materials with the plastic flow being governed by the Herschel-Bulkley relationship. This paper describes the development of analytical and numerical models that can be used as a basis for deriving the material parameters from experimental data obtained using extrusion, compression and bending procedures. Measurements have also been carried out on a model paste and the derived material parameters are compared with published data for the same paste. The merits of the three experimental methods are compared on this basis.

scholarly journals Surface Instability of Sheared Soft Tissues

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
M. Destrade ◽  
M. D. Gilchrist ◽  
D. A. Prikazchikov ◽  
G. Saccomandi
Keyword(s):  
Experimental Data ◽  
Collagen Fiber ◽  
Soft Tissues ◽  
Surface Instability ◽  
Fiber Bundles ◽  
Parallel Fibers ◽  
Naked Eye ◽  
The Matrix ◽  
Use Values ◽  
Biological Soft Tissue

When a block made of an elastomer is subjected to a large shear, its surface remains flat. When a block of biological soft tissue is subjected to a large shear, it is likely that its surface in the plane of shear will buckle (appearance of wrinkles). One factor that distinguishes soft tissues from rubberlike solids is the presence—sometimes visible to the naked eye—of oriented collagen fiber bundles, which are stiffer than the elastin matrix into which they are embedded but are nonetheless flexible and extensible. Here we show that the simplest model of isotropic nonlinear elasticity, namely, the incompressible neo-Hookean model, suffers surface instability in shear only at tremendous amounts of shear, i.e., above 3.09, which corresponds to a 72deg angle of shear. Next we incorporate a family of parallel fibers in the model and show that the resulting solid can be either reinforced or strongly weakened with respect to surface instability, depending on the angle between the fibers and the direction of shear and depending on the ratio E∕μ between the stiffness of the fibers and that of the matrix. For this ratio we use values compatible with experimental data on soft tissues. Broadly speaking, we find that the surface becomes rapidly unstable when the shear takes place “against” the fibers and that as E∕μ increases, so does the sector of angles where early instability is expected to occur.

Relationships Between Alveolar Size and Fibre Distribution in a Mammalian Lung Alveolar Duct Model

1997 ◽  
Vol 119 (3) ◽  
pp. 289-297 ◽  
Author(s):  
E. Denny ◽  
R. C. Schroter
Keyword(s):  
Static Pressure ◽  
Collagen Fibre ◽  
Element Model ◽  
Volume Density ◽  
Fibre Volume ◽  
Published Data ◽  
Liquid Interfaces ◽  
Tension Properties ◽  
Alveolar Duct ◽  
Mammalian Lung

A finite element model, comprising an assemblage of tetrakaidecahedra or truncated octahedra, is used to represent an alveolar duct unit. The dimensions of the elastin and collagen fibre bundles, and the surface tension properties of the air-liquid interfaces, are based on available published data. Changes to the computed static pressure-volume behavior with variation in alveolar dimensions and fibre volume densities are characterized using distensibility indices (K). The air-filled lung distensibility (Ka) decreased with a reduction in the alveolar airspace length dimensions and increased with a reduction of total fibre volume density. The saline-filled lung distensibility (Ks) remained constant with alveolar dimensions and increased with decreasing total fibre volume density. The degree of geometric anisotropy between the duct lumen and alveoli was computed over pressure-volume cycles. To preserve broadly isotropic behavior, parenchyma with smaller alveolar airspace length dimensions required higher concentrations of fibres located in the duct and less in the septa in comparison with parenchyma of larger airspace dimensions.

Numerical Modeling of Thermobonded Nonwovens

2004 ◽  
Vol os-13 (1) ◽  
pp. 1558925004os-13 ◽  
Author(s):  
Dieter H. Mueller ◽  
Markus Kochmann
Keyword(s):  
Experimental Data ◽  
Nonlinear Behavior ◽  
Fiber Material ◽  
Tensile Behavior ◽  
Fiber Bundles ◽  
The Finite Element Method ◽  
Technological Parameters ◽  
Numerical Effort ◽  
Production Techniques ◽  
Temperature And Pressure

In thermobonded nonwovens, the design of the bond point geometry is of major importance to the desired mechanical behavior. Despite the geometry's significance the selection is subject to a trial and error approach. This paper describes a numerical method for the prediction of the nonwovens tensile behavior depending on the bond point geometry and process parameters. The tensile behavior of thermobonded nonwovens is modeled in a numerical model using the Finite Element Method (FEM). The approach covers the influence of the shape and size of the bonded area as well as the properties of the non-woven. The influence of the technological parameters during the bonding process such as process temperature and pressure, are also covered. The solidified area within the bond point is represented using solid elements. The connection between the bonded areas is modeled using link elements, representing the connecting fibers. This approach covers the nonlinear behavior caused by the fiber material properties and geometry. Sets of fibers are combined into fiber bundles in order to reduce the numerical effort. The fiber orientation within the nonwoven is taken into account in order to represent the different fiber distributions caused by the nonwovens production techniques. The mechanical properties of fibers and fiber bundles are taken from experimental data and are mapped onto the model. The model is verified using experimental data from tensile testing.

scholarly journals Strength Parameters Of Masonry Walls In Modelling Historic Constructions

2015 ◽  
Vol 18 (3) ◽  
pp. 55-64 ◽  
Author(s):  
Michał Gołębiewski ◽  
Izabela Lubowiecka ◽  
Marcin Kujawa
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Material Properties ◽  
Experimental Studies ◽  
Basic Material ◽  
Masonry Walls ◽  
The Finite Element Method ◽  
Strength Parameters ◽  
Element Size

Abstract The paper presents the determination of the basic material properties of a historic brickwork. Experimental studies were used to identify the basic material properties of bricks. The mechanical properties of the masonry, as an orthotropic homogenized material, were calculated. Then, numerical simulations using the Finite Element Method (FEM) were performed to verify the experimental outcomes. Macromodels with element sizes of 40, 20, 10 and 5 mm, and a micromodel with an element size of 5 mm were applied. The results were compared with experimental data and results available in literature.

scholarly journals An Additive Model to Predict the Rheological and Mechanical Properties of Polypropylene Blends Made by Virgin and Reprocessed Components

Recycling ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 2
Author(s):  
Francesco Paolo La Mantia ◽  
Maria Chiara Mistretta ◽  
Vincenzo Titone
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Additive Model ◽  
Industrial Process ◽  
Theoretical Predictions ◽  
Experimental Values ◽  
Polypropylene Blends ◽  
Polypropylene Sample

In this work, an additive model for the prediction of the rheological and mechanical properties of monopolymer blends made by virgin and reprocessed components is proposed. A polypropylene sample has been reprocessed more times in an extruder and monopolymer blends have been prepared by simulating an industrial process. The scraps are exposed to regrinding and are melt reprocessed before mixing with the virgin polymer. The reprocessed polymer is, then, subjected to some thermomechanical degradation. Rheological and mechanical experimental data have been compared with the theoretical predictions. The results obtained showed that the values of this simple additive model are a very good fit for the experimental values of both rheological and mechanical properties.

scholarly journals Simulative investigation of ring creep on a planetary bearing of a wind turbine gearbox

2021 ◽  
Author(s):  
Jonas Gnauert ◽  
Felix Schlüter ◽  
Georg Jacobs ◽  
Dennis Bosse ◽  
Stefan Witter
Keyword(s):  
Experimental Data ◽  
Finite Element Method ◽  
Sensitivity Analysis ◽  
Planetary Gear ◽  
The Finite Element Method ◽  
Relative Movement ◽  
Wind Turbine Gearbox ◽  
Interference Fit ◽  
Planetary Gears ◽  
Module Coefficient

AbstractWind turbines (WT) must be further optimized concerning availability and reliability. One of the major reasons of WT downtime is the failure of gearbox bearings. Some of these failures occur, due to the ring creep phenomenon, which is mostly detected in the planetary bearings. The ring creep phenomenon describes a relative movement of the outer ring to the planetary gear. In order to improve the understanding of ring creep, the finite element method (FEM) is used to simulate ring creep in planetary gears. First, a sensitivity analysis is carried out on a small bearing size (NU205), to characterize relevant influence parameters for ring creep—considered parameters are teeth module, coefficient of friction, interference fit and normal tooth forces. Secondly, a full-scale planetary bearing (SL185030) of a 1MW WT is simulated and verified with experimental data.

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