Lower bound limit and shakedown analysis of orthotropic material

We present in this study a new approach for predicting the plastic and shakedown limits of structures composed of orthotropic materials. In this approach, the Hill yield criterion is introduced to Melan’s theorem. By formulating the problem by means of the finite element method and solving the resulting large-scale nonlinear optimization problem we successfully predict the plastic and shakedown limits of structures having complex geometries made from multi-orthotropic materials. Several numerical examples are elaborated in this study for evaluating the accuracy, general applicability, as well as the efficiency of the established numerical scheme. Overall, the study confirms that the direct method can be extended and adopted as a viable means for design and analysis of structures made of orthotropic materials.

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An effective parameterization of texture-induced viscous anisotropy in orthotropic materials with application for modeling geodynamical flows

10.46298/jtcam.6737 ◽

2021 ◽

Author(s):

Javier Signorelli ◽

Riad Hassani ◽

Andréa Tommasi ◽

Lucan Mameri

Keyword(s):

Large Scale ◽

Materials Science ◽

Yield Criterion ◽

Mathematical Formulation ◽

Shear Zones ◽

Computational Time ◽

Orthotropic Materials ◽

Localized Deformation ◽

Orthorhombic Materials ◽

The Hill

In this article, we describe the mathematical formulation and the numerical implementation of an effective parametrization of the viscous anisotropy of orthorhombic materials produced by crystallographic preferred orientations (CPO or texture), which can be integrated into 3D geodynamic and materials science codes. Here, the approach is applied to characterize the texture-induced viscous anisotropy of olivine polycrystals, the main constituent of the Earth's upper mantle. The parameterization is based on the Hill (1948) orthotropic yield criterion. The coefficients of the Hill yield surface are calibrated based on numerical tests performed using the second order Viscoplastic Self-consistent (SO-VPSC) model. The parametrization was implemented in a 3D thermo-mechanical finite-element code developed to model large-scale geodynamical flows, in the form of a Maxwell rheology combining isotropic elastic and anisotropic non-linear viscous behaviors. The implementation was validated by comparison with results of the analytical solution and of the SO-VPSC model for simple shear and axial compression of a homogeneous anisotropic material. An application designed to examine the effect of texture-induced viscous anisotropy on the reactivation of mantle shear zones in continental plates highlights unexpected couplings between localized deformation controlled by variations in the orientation and intensity of the olivine texture in the mantle and the mechanical behavior of the elasto-viscoplastic overlying crust. Importantly, the computational time only increases by a factor 2-3 with respect to the classic isotropic Maxwell viscoelastic rheology. Comment: 32 pag.; 5 figures; 4 tables

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Die Shape Optimal Design in Bimetal Extrusion by the Finite Element Method

Journal of Manufacturing Science and Engineering ◽

10.1115/1.2831089 ◽

1997 ◽

Vol 119 (2) ◽

pp. 143-150 ◽

Cited By ~ 10

Author(s):

S. M. Byon ◽

S. M. Hwang

Keyword(s):

Finite Element ◽

Optimal Design ◽

Optimization Problem ◽

Element Model ◽

The Finite Element Method ◽

Constrained Optimization Problem ◽

New Approach ◽

The Core ◽

The Finite Element Model

A new approach to die shape optimal design in bimetal extrusion of rods is presented. In this approach, the design problem is formulated as a constrained optimization problem incorporated with the finite element model, and optimization of the die shape is conducted on the basis of the design sensitivities. The approach is applied to the determination of the optimal die shapes for several combinations of the core and sleeve materials.

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Soil/Tire Interaction Analysis Using FEM and FVM

Tire Science and Technology ◽

10.2346/1.2186786 ◽

2005 ◽

Vol 33 (1) ◽

pp. 38-62 ◽

Cited By ~ 17

Author(s):

S. Oida ◽

E. Seta ◽

H. Heguri ◽

K. Kato

Keyword(s):

Large Scale ◽

Interaction Analysis ◽

Yield Criterion ◽

Surrounding Medium ◽

Flow Analysis ◽

Measurement Data ◽

Traction Force ◽

Elastoplastic Material ◽

The Road ◽

Soil Flow

Abstract Vehicles, such as an agricultural tractor, construction vehicle, mobile machinery, and 4-wheel drive vehicle, are often operated on unpaved ground. In many cases, the ground is deformable; therefore, the deformation should be taken into consideration in order to assess the off-the-road performance of a tire. Recent progress in computational mechanics enabled us to simulate the large scale coupling problem, in which the deformation of tire structure and of surrounding medium can be interactively considered. Using this technology, hydroplaning phenomena and tire traction on snow have been predicted. In this paper, the simulation methodology of tire/soil coupling problems is developed for pneumatic tires of arbitrary tread patterns. The Finite Element Method (FEM) and the Finite Volume Method (FVM) are used for structural and for soil-flow analysis, respectively. The soil is modeled as an elastoplastic material with a specified yield criterion and a nonlinear elasticity. The material constants are referred to measurement data, so that the cone penetration resistance and the shear resistance are represented. Finally, the traction force of the tire in a cultivated field is predicted, and a good correlation with experiments is obtained.

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Scientific-methodological approach to the substantiation of the rational seasonal scenario of using combine harvesters by large-scale agricultural producers

Mehanization and electrification of agricultural ◽

10.37204/0131-2189-2020-11-24 ◽

2020 ◽

pp. 205-217

Author(s):

V. Skibchyk ◽

V. Dnes ◽

R. Kudrynetskyi ◽

O. Krypuch

Keyword(s):

Large Scale ◽

System Analysis ◽

Methodological Approach ◽

Production Unit ◽

Agricultural Producers ◽

New Approach ◽

Rational Use ◽

Road Map ◽

Analysis And Synthesis ◽

Combine Harvesters

Аnnotation Purpose. To increase the efficiency of technological processes of grain harvesting by large-scale agricultural producers due to the rational use of combine harvesters available on the farm. Methods. In the course of the research the methods of system analysis and synthesis, induction and deduction, system-factor and system-event approaches, graphic method were used. Results. Characteristic events that occur during the harvesting of grain crops, both within a single production unit and the entire agricultural producer are identified. A method for predicting time intervals of use and downtime of combine harvesters of production units has been developed. The roadmap of substantiation the rational seasonal scenario of the use of grain harvesters of large-scale agricultural producers is developed, which allows estimating the efficiency of each of the scenarios of multivariate placement of grain harvesters on fields taking into account influence of natural production and agrometeorological factors on the efficiency of technological cultures. Conclusions 1. Known scientific and methodological approaches to optimization of machine used in agriculture do not take into account the risks of losses of crops due to late harvesting, as well as seasonal natural and agrometeorological conditions of each production unit of the farmer, which requires a new approach to the rational use of rational seasonal combines of large agricultural producers. 2. The developed new approach to the substantiation of the rational seasonal scenario of the use of combined harvesters of large-scale agricultural producers allows taking into account the costs of harvesting of grain and the cost of the lost crop because of the lateness of harvesting at optimum variants of attraction of additional free combine harvesters. provides more profit. 3. The practical application of the developed road map will allow large-scale agricultural producers to use combine harvesters more efficiently and reduce harvesting costs. Keywords: combine harvesters, use, production divisions, risk, seasonal scenario, large-scale agricultural producers.

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Solid Lipid Nanoparticles: A Promising Drug Delivery Technology

International Journal of Pharmaceutical Sciences and Nanotechnology ◽

10.37285/ijpsn.2009.2.2.3 ◽

2009 ◽

Vol 2 (2) ◽

pp. 509-516

Author(s):

S. Pragati ◽

S. Kuldeep ◽

S. Ashok ◽

M. Satheesh

Keyword(s):

Drug Delivery ◽

Solid Lipid Nanoparticles ◽

Large Scale ◽

Colloidal Particles ◽

Scale Up ◽

Lipid Nanoparticles ◽

Scale Production ◽

Research Activity ◽

New Approach ◽

Solid Lipid

One of the situations in the treatment of disease is the delivery of efficacious medication of appropriate concentration to the site of action in a controlled and continual manner. Nanoparticle represents an important particulate carrier system, developed accordingly. Nanoparticles are solid colloidal particles ranging in size from 1 to 1000 nm and composed of macromolecular material. Nanoparticles could be polymeric or lipidic (SLNs). Industry estimates suggest that approximately 40% of lipophilic drug candidates fail due to solubility and formulation stability issues, prompting significant research activity in advanced lipophile delivery technologies. Solid lipid nanoparticle technology represents a promising new approach to lipophile drug delivery. Solid lipid nanoparticles (SLNs) are important advancement in this area. The bioacceptable and biodegradable nature of SLNs makes them less toxic as compared to polymeric nanoparticles. Supplemented with small size which prolongs the circulation time in blood, feasible scale up for large scale production and absence of burst effect makes them interesting candidates for study. In this present review this new approach is discussed in terms of their preparation, advantages, characterization and special features.

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Modeling Extinction

10.1093/oso/9780195159455.001.0001 ◽

2003 ◽

Author(s):

M. E. J. Newman ◽

R. G. Palmer

Keyword(s):

Evolutionary Biology ◽

Large Scale ◽

Competitive Exclusion ◽

Applied Mathematics ◽

Santa Fe ◽

New Approach ◽

Self Organized ◽

Self Organized Criticality ◽

Extinction Events ◽

Mass Extinction Events

Developed after a meeting at the Santa Fe Institute on extinction modeling, this book comments critically on the various modeling approaches. In the last decade or so, scientists have started to examine a new approach to the patterns of evolution and extinction in the fossil record. This approach may be called "statistical paleontology," since it looks at large-scale patterns in the record and attempts to understand and model their average statistical features, rather than their detailed structure. Examples of the patterns these studies examine are the distribution of the sizes of mass extinction events over time, the distribution of species lifetimes, or the apparent increase in the number of species alive over the last half a billion years. In attempting to model these patterns, researchers have drawn on ideas not only from paleontology, but from evolutionary biology, ecology, physics, and applied mathematics, including fitness landscapes, competitive exclusion, interaction matrices, and self-organized criticality. A self-contained review of work in this field.

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Dynamic output feedback control for nonlinear large-scale interconnected systems

COMPEL The International Journal for Computation and Mathematics in Electrical and Electronic Engineering ◽

10.1108/compel-10-2019-0427 ◽

2020 ◽

Vol 39 (4) ◽

pp. 801-821

Author(s):

Ezzeddine Touti ◽

Ali Sghaier Tlili ◽

Muhannad Almutiry

Keyword(s):

Decentralized Control ◽

Output Feedback ◽

Large Scale ◽

Optimization Problem ◽

Lyapunov Theory ◽

Interconnected Systems ◽

Dynamic Output Feedback ◽

Content Type ◽

Dynamic Output ◽

Control Scheme

Purpose This paper aims to focus on the design of a decentralized observation and control method for a class of large-scale systems characterized by nonlinear interconnected functions that are assumed to be uncertain but quadratically bounded. Design/methodology/approach Sufficient conditions, under which the designed control scheme can achieve the asymptotic stabilization of the augmented system, are developed within the Lyapunov theory in the framework of linear matrix inequalities (LMIs). Findings The derived LMIs are formulated under the form of an optimization problem whose resolution allows the concurrent computation of the decentralized control and observation gains and the maximization of the nonlinearity coverage tolerated by the system without becoming unstable. The reliable performances of the designed control scheme, compared to a distinguished decentralized guaranteed cost control strategy issued from the literature, are demonstrated by numerical simulations on an extensive application of a three-generator infinite bus power system. Originality/value The developed optimization problem subject to LMI constraints is efficiently solved by a one-step procedure to analyze the asymptotic stability and to synthesize all the control and observation parameters. Therefore, such a procedure enables to cope with the conservatism and suboptimal solutions procreated by optimization problems based on iterative algorithms with multi-step procedures usually used in the problem of dynamic output feedback decentralized control of nonlinear interconnected systems.

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