scholarly journals Estimation of the Critical Seismic Acceleration for Three-Dimensional Rock Slopes

2021 ◽  
Vol 11 (24) ◽  
pp. 11625
Author(s):  
Qingfeng Meng ◽  
Xuyue Hu ◽  
Guanghui Chen ◽  
Peng Li ◽  
Zhi Wang
Keyword(s):  
Failure Criterion ◽  
Three Dimensional ◽  
Rock Slopes ◽  
Failure Model ◽  
Seismic Acceleration ◽  
Design Charts ◽  
Simulation Results ◽  
Rotational Failure ◽  
First Time ◽  
Bound Theory

An analytical approach for the estimating of critical seismic acceleration of rock slopes was proposed in this study. Based on the 3D horn failure model, the critical seismic acceleration coefficient of rock slopes was conducted with the modified Hoek–Brown (MHB) failure criterion in the framework of upper-bound theory for the first time. The nonlinear Hoek–Brown failure criterion is incorporated into the three-dimensional rotational failure mechanism, and a generalized tangent technique is introduced and employed to convert the nonlinear Hoek–Brown failure criterion into a linear criterion. The critical seismic acceleration coefficients obtained from this study were validated by the numerical simulation results based on finite element limit analysis. The agreement showed that the proposed method is effective. Finally, design charts were provided for exceptional cases for practical use in rock engineering.

scholarly journals HYPERCHAOTIC DYNAMICS OF A NEW FRACTIONAL DISCRETE-TIME SYSTEM

Fractals ◽  
2021 ◽  
pp. 2140034
Author(s):  
AMINA-AICHA KHENNAOUI ◽  
ADEL OUANNAS ◽  
SHAHER MOMANI ◽  
ZOHIR DIBI ◽  
GIUSEPPE GRASSI ◽  
...  
Keyword(s):  
Discrete Time ◽  
Three Dimensional ◽  
Phase Portraits ◽  
Bifurcation Diagrams ◽  
Discrete Time System ◽  
Time System ◽  
Discrete Time Systems ◽  
Simulation Results ◽  
Time Systems ◽  
First Time

In recent years, some efforts have been devoted to nonlinear dynamics of fractional discrete-time systems. A number of papers have so far discussed results related to the presence of chaos in fractional maps. However, less results have been published to date regarding the presence of hyperchaos in fractional discrete-time systems. This paper aims to bridge the gap by introducing a new three-dimensional fractional map that shows, for the first time, complex hyperchaotic behaviors. A detailed analysis of the map dynamics is conducted via computation of Lyapunov exponents, bifurcation diagrams, phase portraits, approximated entropy and [Formula: see text] complexity. Simulation results confirm the effectiveness of the approach illustrated herein.

scholarly journals Three-dimensional cellular automaton simulation of coupled hydrogen porosity and microstructure during solidification of ternary aluminum alloys

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Cheng Gu ◽  
Yan Lu ◽  
Colin D. Ridgeway ◽  
Emre Cinkilic ◽  
Alan A. Luo
Keyword(s):  
Aluminum Alloys ◽  
Cellular Automaton ◽  
Grain Growth ◽  
Die Casting ◽  
Three Dimensional ◽  
Porosity Formation ◽  
X Ray ◽  
Formation And Evolution ◽  
Simulation Results ◽  
First Time

Abstract Hydrogen-induced porosity formed during solidification of aluminum-based alloys has been a major issue adversely affecting the performance of solidification products such as castings, welds or additively manufactured components. A three-dimensional cellular automaton model was developed, for the first time, to predict the formation and evolution of hydrogen porosity coupled with grain growth during solidification of a ternary Al-7wt.%Si-0.3wt.%Mg alloy. The simulation results fully describe the concurrent nucleation and evolution of both alloy grains and hydrogen porosity, yielding the morphology of multiple grains as well as the porosity size and distribution. This model, successfully validated by X-ray micro-tomographic measurements and optical microscopy of a wedge die casting, provides a critical tool for minimizing/controlling porosity formation in solidification products.

CBN-Kornverschleißmodellierung/Numerical modeling of CBN grain wear during single grain engagement – CBN-grain wear modelling

2021 ◽  
Vol 111 (06) ◽  
pp. 414-418
Author(s):  
Marc Bredthauer ◽  
Patrick Mattfeld ◽  
Sebastian Barth ◽  
Thomas Bergs
Keyword(s):  
Numerical Modeling ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Finite Elemente ◽  
Wear Modelling ◽  
Numerische Modellierung ◽  
Finite Elemente Methode ◽  
Single Grain ◽  
Simulation Results ◽  
First Time

Dieser Beitrag stellt die numerische Modellierung des CBN-Kornverschleißes beim Einkorneingriff mit der Finite-Elemente-Methode vor. Es wird erstmalig eine dreidimensionale Verschleißsimulation unter Verwendung realer CBN- Korngeometrien im Korn-Werkstückkontakt durchgeführt. Dazu werden drei reale Korngeometrien simuliert, um die Verschleißmechanismen des realen Korneingriffs abzubilden. Abschließend werden die Simulationsergebnisse mit empirischen Untersuchungen verglichen.   This article is about the numerical modeling of CBN grain wear in single grain engagement using the finite element method. A three-dimensional wear simulation using real CBN grain geometries in grain-workpiece contact is conducted for the first time. For this purpose, three real grain geometries are simulated to represent the wear mechanisms of the real grain engagement. Finally, the simulation results are compared with empirical investigations.

scholarly journals Cobalt-based magnetic Weyl semimetals with high-thermodynamic stabilities

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Wei Luo ◽  
Yuma Nakamura ◽  
Jinseon Park ◽  
Mina Yoon
Keyword(s):  
Tight Binding ◽  
Three Dimensional ◽  
Interlayer Coupling ◽  
First Principles Calculation ◽  
Optimization Approach ◽  
Binding Model ◽  
Nodal Lines ◽  
Weyl Semimetal ◽  
Topological Quantum ◽  
First Time

AbstractRecent experiments identified Co3Sn2S2 as the first magnetic Weyl semimetal (MWSM). Using first-principles calculation with a global optimization approach, we explore the structural stabilities and topological electronic properties of cobalt (Co)-based shandite and alloys, Co3MM’X2 (M/M’ = Ge, Sn, Pb, X = S, Se, Te), and identify stable structures with different Weyl phases. Using a tight-binding model, for the first time, we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers, while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms, Sn, Ge, and Pb. The Co3SnPbS2 alloy exhibits two distinguished topological phases, depending on the relative positions of the Sn and Pb atoms: a three-dimensional quantum anomalous Hall metal, and a MWSM phase with anomalous Hall conductivity (~1290 Ω−1 cm−1) that is larger than that of Co2Sn2S2. Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.

scholarly journals Shell-crossing in a ΛCDM Universe

2020 ◽  
Vol 501 (1) ◽  
pp. L71-L75
Author(s):  
Cornelius Rampf ◽  
Oliver Hahn
Keyword(s):  
Dark Matter ◽  
Perturbation Theory ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Three Dimensional ◽  
Random Initial Data ◽  
Recursion Relations ◽  
Indispensable Tool ◽  
First Time ◽  
Very High

ABSTRACT Perturbation theory is an indispensable tool for studying the cosmic large-scale structure, and establishing its limits is therefore of utmost importance. One crucial limitation of perturbation theory is shell-crossing, which is the instance when cold-dark-matter trajectories intersect for the first time. We investigate Lagrangian perturbation theory (LPT) at very high orders in the vicinity of the first shell-crossing for random initial data in a realistic three-dimensional Universe. For this, we have numerically implemented the all-order recursion relations for the matter trajectories, from which the convergence of the LPT series at shell-crossing is established. Convergence studies performed at large orders reveal the nature of the convergence-limiting singularities. These singularities are not the well-known density singularities at shell-crossing but occur at later times when LPT already ceased to provide physically meaningful results.

Experimental and numerical studies on failure and energy absorption of composite thin-walled square tubes under quasi-static compression loading

2020 ◽  
Vol 21 (6) ◽  
pp. 623-634
Author(s):  
Haolei Mou ◽  
Zhenyu Feng ◽  
Jiang Xie ◽  
Jun Zou ◽  
Kun Zhou
Keyword(s):  
Finite Element ◽  
Shell Model ◽  
Energy Absorption ◽  
Failure Mode ◽  
Failure Criterion ◽  
Finite Element Models ◽  
Static Compression ◽  
Compression Loading ◽  
Thin Walled ◽  
Simulation Results

AbstractTo analysis the failure and energy absorption of carbon fiber reinforced polymer (CFRP) thin-walled square tube, the quasi-static axial compression loading tests are conducted for [±45]3s square tube, and the square tube after test is scanned to further investigate the failure mechanism. Three different finite element models, i.e. single-layer shell model, multi-layer shell model and stacked shell mode, are developed by using the Puck 2000 matrix failure criterion and Yamada Sun fiber failure criterion, and three models are verified and compared according to the experimental energy absorption metrics. The experimental and simulation results show that the failure mode of [±45]3s square tube is the local buckling failure mode, and the energy are absorbed mainly by intralaminar and interlaminar delamination, fiber elastic deformation, fiber debonding and fracture, matrix deformation cracking and longitudinal crack propagation. Three different finite element models can reproduce the collapse behaviours of [±45]3s square tube to some extent, but the stacked shell model can better reproduce the failure mode, and the difference of specific energy absorption (SEA) is minimum, which shows the numerical simulation results are in better agreement with the test results.

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