scholarly journals Construction of mathematical models of the stressed-strained state of a material with a porous water-saturated base under dynamic load

2021 ◽  
Vol 5 (7 (113)) ◽  
pp. 25-35
Author(s):  
Allayarbek Aidossov ◽  
Galym Aidosov ◽  
Saltanat Narbayeva
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Median Plane ◽  
Lower Surface ◽  
Viscoelastic Layer ◽  
Dimensional Problem ◽  
Underground Structures ◽  
Engineering Structures ◽  
Deformable Base ◽  
Water Saturated

Materials of beams, plates, slabs, strips have been commonly applied in various fields of industry and agriculture as flat elements in the structures for machinery and construction. They are associated with the design of numerous engineering structures and facilities, such as the foundations of various buildings, airfield and road surfaces, floodgates, including underground structures. This paper reports a study into the interaction of the material (of beams, plates, slabs, strips) with the deformable base as a three-dimensional body and in the exact statement of a three-dimensional problem of mathematical physics under dynamic loads. The tasks of studying the interaction of a material (beams, plates, slabs, strips) with a deformable base have been set. A material lying on a porous water-saturated viscoelastic base is considered as a viscoelastic layer of the same geometry. It is assumed that the lower surface of the layer is flat while the upper surface, in a general case, is not flat and is given by some equation. Classical approximate theories of the interaction of a layer with a deformable base, based on the Kirchhoff hypothesis, have been considered. Using the well-known hypothesis by Timoshenko and others, the general three-dimensional problem is reduced to a two-dimensional one relative to the displacement of points of the median plane of the layer, which imposes restrictions on external efforts. In the examined problem, there is no median plane. Therefore, as the desired values, displacements and deformations of the points in the plane have been considered, which, under certain conditions, pass into the median plane of the layer. It is not possible to find a closed analytical solution for most problems while experimental studies often turn out to be time-consuming and dangerous processes

scholarly journals Geoecological aspects of civil engineering on the sands

2018 ◽  
Vol 26 (3) ◽  
pp. 346-353
Author(s):  
Tatyana Ivanovna Averkina
Keyword(s):  
Underground Structures ◽  
Civil Structures ◽  
Engineering Structures ◽  
Emergency Situations ◽  
Pressure Water ◽  
Construction Experience ◽  
Liquefied Soils ◽  
The Stability ◽  
Water Saturated ◽  
Reliable Basis

Civil structures are often built on sands, which are widespread in the upper part of the geological section. These soils usually serve as a reliable basis for engineering structures, but under certain conditions can cause large complications and even endanger the life safety. Analysis and generalization of the construction experience allows us educe three groups of problems that need to be identified and addressed timely. Most of the problems are related to water-bearing sands. Water flows, breakthrough of pressure water and quicksand are very common phenomena that complicate the excavation of construction pits and the device of underground structures. To protect against groundwater is often used dewatering, which can disrupt the stability of the surrounding buildings in high-density urban development. The second group of problems is related to the process of suffusion. The most dangerous of its manifestations are suffusion failures, leading to emergency situations and sometimes to the destruction of structures. The third group of problems is caused by specific reaction of sands to dynamic impacts, in particular, by liquefaction of water-saturated sandy soils. The consequences of such a reaction can be very serious: the immersion of the structure in the ground, the uplift of piles or bridge supports, the float up of underground tanks, the uplift of liquefied soils from under the foundation until the formation of a building tilt or overturning of the structure.

scholarly journals Experimental studies on the transformation from firn to ice in the wet-snow zone of temperate glaciers

1997 ◽  
Vol 24 ◽  
pp. 181-185 ◽  
Author(s):  
Katsuhisa Kawashima ◽  
Tomomi Yamada
Keyword(s):  
Experimental Studies ◽  
Ice Formation ◽  
Compression Tests ◽  
Densification Rate ◽  
Overburden Pressure ◽  
Proportionality Constant ◽  
Wet Snow ◽  
Water Saturated ◽  
The Relationship ◽  
Good Agreement

The densification of water-saturated firn, which had formed just above the firn-ice transition in the wet-snow zone of temperate glaciers, was investigated by compression tests under pressures ranging from 0.036 to 0.173 MPa, with special reference to the relationship between densification rate, time and pressure. At each test, the logarithm of the densification rate was proportional to the logarithm of the time, and its proportionality constant increased exponentially with increasing pressure. The time necessary for ice formation in the firn aquifer was calculated using the empirical formula obtained from the tests. Consequently, the necessary time decreased exponentially as the pressure increased, which shows that the transformation from firn in ice can be completed within the period when the firn aquifer exists, if the overburden pressure acting on the water-saturated firn is above 0.12–0.14 MPa. This critical value of pressure was in good agreement with the overburden pressure obtained from depth–density curves of temperate glaciers. It was concluded that the depth of firn–ice transition was self-balanced by the overburden pressure to result in the concentration between 20 and 30 m.

scholarly journals Targeting hepatocyte growth factor in epithelial–stromal interactions in an in vitro experimental model of human periodontitis

Odontology ◽  
2021 ◽  
Author(s):  
Yoko Yamaguchi ◽  
Akira Saito ◽  
Masafumi Horie ◽  
Akira Aoki ◽  
Patrick Micke ◽  
...  
Keyword(s):  
Growth Factor ◽  
Hepatocyte Growth Factor ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Collagen Gel ◽  
Neutralizing Antibody ◽  
Chronic Inflammatory Disease ◽  
Collagen Degradation ◽  
Hepatocyte Growth

AbstractPeriodontitis is a chronic inflammatory disease leading to progressive connective tissue degradation and loss of the tooth-supporting bone. Clinical and experimental studies suggest that hepatocyte growth factor (HGF) is involved in the dysregulated fibroblast–epithelial cell interactions in periodontitis. The aim of this study was to explore effects of HGF to impact fibroblast-induced collagen degradation. A patient-derived experimental cell culture model of periodontitis was applied. Primary human epithelial cells and fibroblasts isolated from periodontitis-affected gingiva were co-cultured in a three-dimensional collagen gel. The effects of HGF neutralizing antibody on collagen gel degradation were tested and transcriptome analyses were performed. HGF neutralizing antibody attenuated collagen degradation and elicited expression changes of genes related to extracellular matrix (ECM) and cell adhesion, indicating that HGF signaling inhibition leads to extensive impact on cell–cell and cell–ECM interactions. Our study highlights a potential role of HGF in periodontitis. Antagonizing HGF signaling by a neutralizing antibody may represent a novel approach for periodontitis treatment.

Mathematical Theory of Transversally Isotropic Shells of Arbitrary Thickness at Static Load

2019 ◽  
Vol 968 ◽  
pp. 496-510
Author(s):  
Anatoly Grigorievich Zelensky
Keyword(s):  
Mathematical Theory ◽  
Three Dimensional ◽  
Nonlinear Problems ◽  
Theory Of Elasticity ◽  
Elastic Plates ◽  
Dimensional Problem ◽  
Boundary Problems ◽  
Complex Boundary ◽  
Plates And Shells ◽  
Basic Equations

Classical and non-classical refined theories of plates and shells, based on various hypotheses [1-7], for a wide class of boundary problems, can not describe with sufficient accuracy the SSS of plates and shells. These are boundary problems in which the plates and shells undergo local and burst loads, have openings, sharp changes in mechanical and geometric parameters (MGP). The problem also applies to such elements of constructions that have a considerable thickness or large gradient of SSS variations. The above theories in such cases yield results that can differ significantly from those obtained in a three-dimensional formulation. According to the logic in such theories, the accuracy of solving boundary problems is limited by accepted hypotheses and it is impossible to improve the accuracy in principle. SSS components are usually depicted in the form of a small number of members. The systems of differential equations (DE) obtained here have basically a low order. On the other hand, the solution of boundary value problems for non-thin elastic plates and shells in a three-dimensional formulation [8] is associated with great mathematical difficulties. Only in limited cases, the three-dimensional problem of the theory of elasticity for plates and shells provides an opportunity to find an analytical solution. The complexity of the solution in the exact three-dimensional formulation is greatly enhanced if complex boundary conditions or physically nonlinear problems are considered. Theories in which hypotheses are not used, and SSS components are depicted in the form of infinite series in transverse coordinates, will be called mathematical. The approximation of the SSS component can be adopted in the form of various lines [9-16], and the construction of a three-dimensional problem to two-dimensional can be accomplished by various methods: projective [9, 14, 16], variational [12, 13, 15, 17]. The effectiveness and accuracy of one or another variant of mathematical theory (MT) depends on the complex methodology for obtaining the basic equations.

scholarly journals Numerical and Experimental Studies on a Three-Dimensional Numerical Wave Tank

IEEE Access ◽  
2018 ◽  
Vol 6 ◽  
pp. 6585-6593 ◽  
Author(s):  
Xiaojie Tian ◽  
Qingyang Wang ◽  
Guijie Liu ◽  
Wei Deng ◽  
Zhiming Gao
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Numerical Wave

Numerical Modeling of Tube Hydropiercing Using Phenomenological and Micro-Mechanical Damage Criteria

2013 ◽  
Vol 549 ◽  
pp. 172-179 ◽  
Author(s):  
Amir Hassannejadasl ◽  
Daniel E. Green
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Equivalent Plastic Strain ◽  
Mechanical Damage ◽  
High Strength ◽  
Dimensional Finite Element ◽  
Steel Dp600 ◽  
Three Dimensional Finite Element ◽  
Jc Model ◽  
Damage Criteria

Hydropiercing is an efficient way of piercing holes in mass produced hydroformed parts with complex geometries. By driving piercing punches radially into a hydroformed and fully pressurized tube, holes will be pierced and extruded into the tube-wall. Recent experimental studies have shown that the formability of advanced high strength steel (AHSS) tubes can be increased with the application of internal pressure. In this study, three-dimensional finite element simulations of a tube hydropiercing process of a dual phase steel (DP600) were performed in LS-DYNA, using phenomenological, micromechanical and combined damage criteria. Damage was included in the numerical analysis by applying constant equivalent plastic strain (CEPS), the Gurson-Tvergaard-Needleman (GTN), and the Extended GTN (GTN+JC) model. In order to calibrate the parameters in each model, a specialized hole-piercing fixture was designed and piercing tests were carried out on non-pressurized tube specimens. Of the various ductile fracture criteria, the results predicted with the GTN+JC model, such as the punch load-displacement, the roll-over depth, and the quality of the clearance zone correlated the best with the experimental data.

Fracture Mechanics of Thin Plates and Shells Under Combined Membrane, Bending, and Twisting Loads

2005 ◽  
Vol 58 (1) ◽  
pp. 37-48 ◽  
Author(s):  
Alan T. Zehnder ◽  
Mark J. Viz
Keyword(s):  
Fracture Mechanics ◽  
Plate Theory ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Crack Tip ◽  
Thin Plates ◽  
Element Analysis ◽  
Crack Tip Fields ◽  
Plates And Shells ◽  
Membrane Bending

The fracture mechanics of plates and shells under membrane, bending, twisting, and shearing loads are reviewed, starting with the crack tip fields for plane stress, Kirchhoff, and Reissner theories. The energy release rate for each of these theories is calculated and is used to determine the relation between the Kirchhoff and Reissner theories for thin plates. For thicker plates, this relationship is explored using three-dimensional finite element analysis. The validity of the application of two-dimensional (plate theory) solutions to actual three-dimensional objects is analyzed and discussed. Crack tip fields in plates undergoing large deflection are analyzed using von Ka´rma´n theory. Solutions for cracked shells are discussed as well. A number of computational methods for determining stress intensity factors in plates and shells are discussed. Applications of these computational approaches to aircraft structures are examined. The relatively few experimental studies of fracture in plates under bending and twisting loads are also reviewed. There are 101 references cited in this article.

Noninvasive three-dimensional electrocardiographic imaging of ventricular activation sequence

2005 ◽  
Vol 289 (6) ◽  
pp. H2724-H2732 ◽  
Author(s):  
Xin Zhang ◽  
Indiresha Ramachandra ◽  
Zhongming Liu ◽  
Basharat Muneer ◽  
Steven M. Pogwizd ◽  
...  
Keyword(s):  
Surface Potential ◽  
Body Surface ◽  
Cardiac Arrhythmias ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Electrocardiographic Imaging ◽  
Ventricular Activation ◽  
Body Surface Potential ◽  
Life Threatening ◽  
Activation Sequence

Imaging the myocardial activation sequence is critical for improved diagnosis and treatment of life-threatening cardiac arrhythmias. It is desirable to reveal the underlying cardiac electrical activity throughout the three-dimensional (3-D) myocardium (rather than just the endocardial or epicardial surface) from noninvasive body surface potential measurements. A new 3-D electrocardiographic imaging technique (3-DEIT) based on the boundary element method (BEM) and multiobjective nonlinear optimization has been applied to reconstruct the cardiac activation sequences from body surface potential maps. Ultrafast computerized tomography scanning was performed for subsequent construction of the torso and heart models. Experimental studies were then conducted, during left and right ventricular pacing, in which noninvasive assessment of ventricular activation sequence by means of 3-DEIT was performed simultaneously with 3-D intracardiac mapping (up to 200 intramural sites) using specially designed plunge-needle electrodes in closed-chest rabbits. Estimated activation sequences from 3-DEIT were in good agreement with those constructed from simultaneously recorded intracardiac electrograms in the same animals. Averaged over 100 paced beats (from a total of 10 pacing sites), total activation times were comparable (53.3 ± 8.1 vs. 49.8 ± 5.2 ms), the localization error of site of initiation of activation was 5.73 ± 1.77 mm, and the relative error between the estimated and measured activation sequences was 0.32 ± 0.06. The present experimental results demonstrate that the 3-D paced ventricular activation sequence can be reconstructed by using noninvasive multisite body surface electrocardiographic measurements and imaging of heart-torso geometry. This new 3-D electrocardiographic imaging modality has the potential to guide catheter-based ablative interventions for the treatment of life-threatening cardiac arrhythmias.

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