scholarly journals Mesure du module en petites déformations d'un sol autour d'une conduite enterrée : présentation d'un nouvel essai in situ

2000 ◽  
Vol 37 (4) ◽  
pp. 909-917 ◽  
Author(s):  
Olivier Thépot ◽  
Roger Frank
Keyword(s):  
Test Procedure ◽  
Three Dimensional ◽  
Longitudinal Direction ◽  
Displacement Curve ◽  
Flexible Pipe ◽  
Soil Stiffness ◽  
Test Soil ◽  
Force Displacement ◽  
Small Deformations

A new method of measurement of backfill stiffness around buried flexible pipe is presented. It consists of using flexible pipe as an expanding pressiometric probe. The pipe dilatation is obtained by an internal jacking test that causes a relatively small three-dimensional "ovalization" around 0.05%. We obtain a force-displacement curve along the force axis as well as the damping of the displacement in the longitudinal direction up to one diameter in range. Knowing the pipe mechanical characteristics, we can calculate Young's modulus of the backfill in the domain of small deformations. The paper describes the test procedure as well as the modulus computation technique, which is based upon a three-dimensional parametric study using the finite element method. The results obtained in a jacking test conducted on iron pipe of 1.4 m in diameter and 8.0 m in length are presented. The computed moduli are compared with the ones obtained in laboratory testing using resonant-column and cyclic triaxial tests.Key words: buried pipes, jacking test, soil stiffness, soil-structure interaction, three-dimensional analysis, finite elements.

scholarly journals Young’s Modulus of Polycrystalline Titania Microspheres Determined by In Situ Nanoindentation and Finite Element Modeling

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Peida Hao ◽  
Yanping Liu ◽  
Yuanming Du ◽  
Yuefei Zhang
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Deformation Mechanisms ◽  
Displacement Curve ◽  
Element Simulation ◽  
Nanoindentation Experiment ◽  
Force Displacement

In situ nanoindentation was employed to probe the mechanical properties of individual polycrystalline titania (TiO2) microspheres. The force-displacement curves captured by a hybrid scanning electron microscope/scanning probe microscope (SEM/SPM) system were analyzed based on Hertz’s theory of contact mechanics. However, the deformation mechanisms of the nano/microspheres in the nanoindentation tests are not very clear. Finite element simulation was employed to investigate the deformation of spheres at the nanoscale under the pressure of an AFM tip. Then a revised method for the calculation of Young’s modulus of the microspheres was presented based on the deformation mechanisms of the spheres and Hertz’s theory. Meanwhile, a new force-displacement curve was reproduced by finite element simulation with the new calculation, and it was compared with the curve obtained by the nanoindentation experiment. The results of the comparison show that utilization of this revised model produces more accurate results. The calculated results showed that Young’s modulus of a polycrystalline TiO2microsphere was approximately 30% larger than that of the bulk counterpart.

Molecular Dynamics Simulation of a Rigid Sphere Indenting a Copper Substrate

2012 ◽  
Author(s):  
Ding Jia ◽  
Longqiu Li ◽  
Andrey Ovcharenko ◽  
Wenping Song ◽  
Guangyu Zhang
Keyword(s):  
Molecular Dynamics ◽  
Md Simulation ◽  
Copper Substrate ◽  
Three Dimensional ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Rigid Sphere ◽  
Displacement Curve ◽  
Loading And Unloading ◽  
Force Displacement

Three-dimensional molecular dynamics (MD) simulation is used to study the atomic-scale indentation process of a spherical diamond tip in contact with a copper substrate. In the indentation simulations, the force-displacement curve is obtained and compared with a modified elastic solution of Hertz. The contact area under different indentation depths is also investigated. The force-displacement curve under different maximum indentation depths is obtained to investigate elastic-plastic deformation during the loading and unloading processes.

Force-displacement relationship modelling of masonry infilled walls with openings in hinged steel frames

2021 ◽  
Author(s):  
Haoran Zuo ◽  
Weiping Zhang ◽  
Baotong Wang ◽  
Xianglin Gu
Keyword(s):  
Three Dimensional ◽  
Steel Frames ◽  
Structural Response ◽  
Displacement Curve ◽  
Initial Stiffness ◽  
Seismic Behaviour ◽  
Infilled Frames ◽  
Aspect Ratios ◽  
Three Dimensional Finite Element ◽  
Force Displacement

Abstract Seismic behaviour of masonry infilled frames has attracted extensive attentions from researchers, and it was found that infills normally experienced a diagonal compression under lateral loading. Infill was therefore assumed as an equivalent diagonal strut in structural response estimations of infilled frames, and a force-displacement curve was adopted to describe the mechanical properties of the strut. However, the influences of infill aspect ratio, vertical load acting on the surrounding frames, and opening were not systematically addressed in establishing the force-displacement relationship of infills. To investigate the effects of these influential parameters on the lateral responses of infilled walls including initial stiffness and strength, detailed three-dimensional finite element (FE) models of masonry infilled hinged steel frames are developed in ABAQUS in the present study, and a wide parametric study with respect to various aspect ratios, vertical loads, and opening sizes and locations is performed. A generalized force-displacement relationship model of infilled walls is proposed based on regression analyses of numerical results. The efficacy of the proposed model is examined by using the existing experimental test results, and it shows that the model can accurately predict the lateral stiffness and load carrying capacity of infilled walls and thus has great potential applications in structural designs and analyses for masonry infilled steel frames.

Comparison Between Stress Obtained by Numerical Analysis and In-Situ Measurements on a Flexible Pipe Subjected to In-Plane Bending Test

2016 ◽  
Author(s):  
Troels Vestergaard Lukassen ◽  
Kristian Glejbøl ◽  
Anders Lyckegaard ◽  
Christian Berggreen
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Performance Optimization ◽  
Three Dimensional ◽  
Element Model ◽  
Bending Test ◽  
Flexible Pipe ◽  
Stress Variation ◽  
Stress Variations

To predict the lifetime and long-term properties of tensile armour wires in a dynamically loaded pipe, it is essential to have a tool which allows detailed prediction of the stress variations in the tensile armour wires during global pipe loading. Furthermore, detailed understanding of the stress variations will allow for performance optimization of the armour layers. To study the detailed stress variations in flexible pipes during dynamic loading, a comprehensive three-dimensional implicit nonlinear finite element model has been developed. The predicted numerical stress variations will be compared to stress patterns obtained during in-situ OMS measurements carried out during an actual experimental inplane bending test. The study showed a good correlation between the stress variation predicted with the finite element model and the measured stress variation.

A Three-Dimensional Finite Element Analysis of Unburied Flexible Flowline: A Case Study

2002 ◽  
Author(s):  
Wenchao Zhang ◽  
Justin Tuohy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Longitudinal Direction ◽  
Flexible Pipe ◽  
Element Analysis ◽  
Upheaval Buckling ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Pipelines in the service of conveying hot fluid will tend to expand due to pressure and differential temperature. However, since the flowline is generally fixed at the end terminations to rigid structures or equipment, such an expansion will be restricted in longitudinal direction. This is particularly the case for the section remote from the pipe ends, and results in an axial compression in the pipe section. In many cases, a subsea flowline has to be trenched or buried for the purposes of protection and thermal insulation. Consequently, the lateral movement of a flexible flowline is greatly limited, and an upward displacement is encouraged that may become excessive. Eventually, the flowline may lift out of the trench when the uplift resistance provided by the backfill cover and self-weight of the flowline is gradually overcome by the strain energy built up in the flowline. For flexible pipe, it is this excessive upward deformation being termed as the Upheaval Buckling, which can be prevented by employing adequate downward restraint, such as sand bag/rock dump or by designing a subsea pipe route to overcome this phenomenon. In this paper a case study of the full three-dimensional finite element analysis of a trenched but unburied 6.0-inch production flowline is presented following a description of Wellstream Finite Element Method (FEM) based methodology for Upheaval Buckling analysis of flexible pipes. The effect Bending Stiffness Hysteresis and Upheaval Creep–unique to flexible pipe characteristics, is considered in addition to the general loads such as the flowline self-weight and backfill, pretension, pressure, temperature distribution and prescribed forces (either concentrated or distributed) and displacements. The effects of environmental loads, such as the action of currents that would result in scouring off the backfill, can also be addressed. The finite element analysis program package ANSYS was chosen for this case study due to its special feature of ANSYS Parametric Design Language (APDL) and contact/target elements; and the general three-dimensional shell and solid elements were used to represent the flexible pipe and trench soil respectively.

Correlated Studies of Cellular Interactions Using TEM, Freeze Etching, and SEM

1974 ◽  
Vol 32 ◽  
pp. 320-321
Author(s):  
J. P. Revel
Keyword(s):  
Developmental Stages ◽  
Three Dimensional ◽  
Cell Movement ◽  
Cellular Interactions ◽  
Serial Sections ◽  
Cell Sheets ◽  
Freeze Etching ◽  
Early Developmental

Movement of individual cells or of cell sheets and complex patterns of folding play a prominent role in the early developmental stages of the embryo. Our understanding of these processes is based on three- dimensional reconstructions laboriously prepared from serial sections, and from autoradiographic and other studies. Many concepts have also evolved from extrapolation of investigations of cell movement carried out in vitro. The scanning electron microscope now allows us to examine some of these events in situ. It is possible to prepare dissections of embryos and even of tissues of adult animals which reveal existing relationships between various structures more readily than used to be possible vithout an SEM.

In vitro and in vivo polysaccharides assembly: ultrastructural and cytochemical study of growing plant cell wall components.

1978 ◽  
Vol 36 (2) ◽  
pp. 434-435
Author(s):  
D. Reis ◽  
B. Vian ◽  
J. C. Roland
Keyword(s):  
Cell Wall ◽  
Self Assembly ◽  
Plant Cell Wall ◽  
Higher Plants ◽  
Three Dimensional ◽  
Cytochemical Study ◽  
Wall Components

Wall morphogenesis in higher plants is a problem still open to controversy. Until now the possibility of a transmembrane control and the involvement of microtubules were mostly envisaged. Self-assembly processes have been observed in the case of walls of Chlamydomonas and bacteria. Spontaneous gelling interactions between xanthan and galactomannan from Ceratonia have been analyzed very recently. The present work provides indications that some processes of spontaneous aggregation could occur in higher plants during the formation and expansion of cell wall.Observations were performed on hypocotyl of mung bean (Phaseolus aureus) for which growth characteristics and wall composition have been previously defined.In situ, the walls of actively growing cells (primary walls) show an ordered three-dimensional organization (fig. 1). The wall is typically polylamellate with multifibrillar layers alternately transverse and longitudinal. Between these layers intermediate strata exist in which the orientation of microfibrils progressively rotates. Thus a progressive change in the morphogenetic activity occurs.

In situ investigation of the primary recrystallization of alpha titanium in HVEM

1978 ◽  
Vol 36 (1) ◽  
pp. 634-635
Author(s):  
S. Naka ◽  
R. Penelle ◽  
R. Valle
Keyword(s):  
Dimensional Analysis ◽  
Texture Evolution ◽  
Cold Work ◽  
Three Dimensional ◽  
Primary Recrystallization ◽  
Thin Foils ◽  
In Situ Investigation ◽  
Grain Growth Model ◽  
Alpha Titanium

The in situ experimentation technique in HVEM seems to be particularly suitable to clarify the processes involved in recrystallization. The material under investigation was unidirectionally cold-rolled titanium of commercial purity. The problem was approached in two different ways. The three-dimensional analysis of textures was used to describe the texture evolution during the primary recrystallization. Observations of bulk-annealed specimens or thin foils annealed in the microscope were also made in order to provide information concerning the mechanisms involved in the formation of new grains. In contrast to the already published work on titanium, this investigation takes into consideration different values of the cold-work ratio, the temperature and the annealing time.Two different models are commonly used to explain the recrystallization textures i.e. the selective grain growth model (Beck) or the oriented nucleation model (Burgers). The three-dimensional analysis of both the rolling and recrystallization textures was performed to identify the mechanismsl involved in the recrystallization of titanium.

Detection and mapping of interactions between chromatin and the nuclear envelope in drosophila embryos

1995 ◽  
Vol 53 ◽  
pp. 764-765
Author(s):  
W.F. Marshall ◽  
A.F. Dernburg ◽  
B. Harmon ◽  
J.W. Sedat
Keyword(s):  
Nuclear Envelope ◽  
Chromatin Condensation ◽  
Three Dimensional ◽  
Physiological Role ◽  
Nuclear Surface ◽  
Intact Cells ◽  
Molecular Determinants ◽  
Surface Harmonic ◽  
Drosophila Embryos

Interactions between chromatin and nuclear envelope (NE) have been implicated in chromatin condensation, gene regulation, nuclear reassembly, and organization of chromosomes within the nucleus. To further investigate the physiological role played by such interactions, it will be necessary to determine which loci specifically interact with the nuclear envelope. This will not only facilitate identification of the molecular determinants of this interaction, but will also allow manipulation of the pattern of chromatin-NE interactions to probe possible functions. We have developed a microscopic approach to detect and map chromatin-NE interactions inside intact cells.Fluorescence in situ hybridization (FISH) is used to localize specific chromosomal regions within the nucleus of Drosophila embryos and anti-lamin immunofluorescence is used to detect the nuclear envelope. Widefield deconvolution microscopy is then used to obtain a three-dimensional image of the sample (Fig. 1). The nuclear surface is represented by a surface-harmonic expansion (Fig 2). A statistical test for association of the FISH spot with the surface is then performed.

Three-Dimensional Subcellular Organization of Hepatocytes in Intact Liver: Simultaneous Visualization of Cytoskeletal and Membrane Markers by Confocal Microscopy

1996 ◽  
Vol 54 ◽  
pp. 288-289
Author(s):  
Greg V. Martin ◽  
Ann L. Hubbard
Keyword(s):  
Three Dimensional ◽  
Integral Membrane Proteins ◽  
Polarized Secretion ◽  
Microscope Images ◽  
Computer Aided ◽  
Intracellular Organelles ◽  
Cytoskeletal Elements ◽  
Simultaneous Visualization

The microtubule (MT) cytoskeleton is necessary for many of the polarized functions of hepatocytes. Among the functions dependent on the MT-based cytoskeleton are polarized secretion of proteins, delivery of endocytosed material to lysosomes, and transcytosis of integral plasma membrane (PM) proteins. Although microtubules have been shown to be crucial to the establishment and maintenance of functional and structural polarization in the hepatocyte, little is known about the architecture of the hepatocyte MT cytoskeleton in vivo, particularly with regard to its relationship to PM domains and membranous organelles. Using an in situ extraction technique that preserves both microtubules and cellular membranes, we have developed a protocol for immunofluorescent co-localization of cytoskeletal elements and integral membrane proteins within 20 µm cryosections of fixed rat liver. Computer-aided 3D reconstruction of multi-spectral confocal microscope images was used to visualize the spatial relationships among the MT cytoskeleton, PM domains and intracellular organelles.

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