检索结果-南通市图书馆

Journal of Materials Science & Technology 2013年第5期29卷 423-428页

作者： Ali Mazahery mohsen Ostad Shabani Department of Materials Science Lenjan BranchIslamic Azad UniversityIsfahanIran

Aluminum alloyed with magnesium and silicon has been used as the matrix material owing to its excellent mechanical properties coupled with good formability and its wide applications in industrial sector. An extrusion process was developed to consolidate AI 6061-SiCp composites from mixed powders. The results show that the composites were fully densified, with no sign of pores or oxide layers observable in the optical microscope. The SiC particles were distributed uniformly in the matrix. As compared with 6061 alloys, the composites demonstrated a smaller elongation, but exhibited a higher Young＇s modulus and a larger work hardening capacity. These composites possessed much higher elongation at the same strength level. The present study also addressed the dry wear behavior of the composites at different sliding speeds and applied loads. Values of the friction coefficient of the matrix alloy and composite materials were in expected range for light metals in dry sliding conditions. All of these improvements were attributed to the merits, including full densification of the bulk, uniform dispersion of the SiC particles in the matrix, and strong binding between the SiC particles and the matrix resulting from the extrusion.

关键词： Aluminum Strength Wear Extrusion Metal matrix composites

Delamination analysis of woven fabrication laminates using cohesive zone model

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2016年第1期23卷 27-38页

作者： mohsen Moslemi Mohammadreza Khoshravan azar Department of Mechanical Engineering University of Tabriz

A new test method was proposed to evaluate the cohesive strength of composite laminates. Cohesive strength and the critical strain energy for Mode-II interlamiar fracture of E-glass/epoxy woven fabrication were determined from the single lap joint(SLJ) and end notch flexure(ENF) test, respectively. In order to verify their adequacy, a cohesive zone model simulation based on interface finite elements was performed. A closed form solution for determination of the penalty stiffness parameter was proposed. Modified form of Park-Paulino-Roesler traction-separation law was provided and conducted altogether with trapezoidal and bilinear mixed-mode damage models to simulate damage using Abaqus cohesive elements. It was observed that accurate damage prediction and numerical convergence were obtained using the proposed penalty stiffness. Comparison between three damage models reveals that good simulation of fracture process zone and delamination prediction were obtained using the modified PPR model as damage model. Cohesive zone length as a material property was determined. To ensure the sufficient dissipation of energy, it was recommended that at least 4 elements should span cohesive zone length.

关键词： cohesive zone model delamination cohesive strength finite element prediction

Effect of seismic wave propagation in massed medium on rate-dependent anisotropic damage growth in concrete gravity dams

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2021年第2期15卷 346-363页

作者： Alireza DANESHYAR Hamid MOHAMMADNEZHAD mohsen GHAEMIAN Civil Engineering Department Sharif University of TechnologyTehran11155-9313Iran Faculty of Civil Water and Environmental EngineeringShahid Beheshti UniversityTehran11155-9313Iran

Seismic modeling of massive structures requires special caution,as wave propagation effects significantly affect the *** becomes more crucial when the path-dependent behavior of the material is *** coexistence of these conditions renders numerical earthquake analysis of concrete dams ***,a finite element model for a comprehensive nonlinear seismic simulation of concrete gravity dams,including realistic soil-structure interactions,is introduced.A semi-infinite medium is formulated based on the domain reduction method in conjunction with standard viscous *** representation of radiation damping in a half-space medium and wave propagation effects in a massed foundation are verified using an analytical solution of vertically propagating shear waves in a viscoelastic half-space domain.A rigorous nonlinear finite element model requires a precise description of the material ***,a microplane-based anisotropic damage-plastic model of concrete is formulated to reproduce irreversible deformations and tensorial degeneration of concrete in a coupled and rate-dependent ***,the Koyna concrete gravity dam is analyzed based on different assumptions of foundation,concrete response,and reservoir *** between responses obtained based on conventional assumptions with the results of the presented comprehensive model indicates the significance of considering radiation damping and employing a rigorous constitutive material model,which is pursued for the presented model.

关键词： soil-structure interaction massed foundation radiation damping anisotropic damage

An efficient aerodynamic shape optimization of blended wing body UAV using multi-fidelity models

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2018年第6期31卷 1165-1180页

作者： Parviz MOHAMMAD ZADEH mohsen SAYADI Faculty of New Sciences and Technologies University of Tehran

This paper presents a novel optimization technique for an efficient multi-fidelity model building approach to reduce computational costs for handling aerodynamic shape optimization based on high-fidelity simulation models. The wing aerodynamic shape optimization problem is solved by dividing optimization into three steps—modeling 3D（high-fidelity） and 2D（lowfidelity） models, building global meta-models from prominent instead of all variables, and determining robust optimizing shape associated with tuning local meta-models. The adaptive robust design optimization aims to modify the shape optimization process. The sufficient infilling strategy—known as adaptive uniform infilling strategy—determines search space dimensions based on the last optimization results or initial point. Following this, 3D model simulations are used to tune local meta-models. Finally, the global optimization gradient-based method—Adaptive Filter Sequential Quadratic Programing（AFSQP） is utilized to search the neighborhood for a probable optimum point. The effectiveness of the proposed method is investigated by applying it, along with conventional optimization approach-based meta-models, to a Blended Wing Body（BWB） Unmanned Aerial Vehicle（UAV）. The drag coefficient is defined as the objective function, which is subjected to minimum lift coefficient bounds and stability constraints. The simulation results indicate improvement in meta-model accuracy and reduction in computational time of the method introduced in this paper.

关键词： Adaptive filter sequential quadratic programing(AFSQP) Adaptive robust meta-model Aerodynamic shape optimization Blended wing body(BWB) Move limit strategy Unmanned aerial vehicle(UAV)

Flow correction control with electromagnetically induced preform resting process

在线全文

学校读者我要写书评

暂无评论

Advances in Manufacturing 2019年第2期7卷 199-208页

作者： mohsen Poorzeinolabedin Kemal Levend Parnas Department of Mechanical Engineering Middle East Technical University Ankara Turkey Leopar Composite Engineering and Consulting Services Ltd. Ankara Turkey Department of Mechanical Engineering TED University Ankara Turkey

Resin flow correction control with electromagnetic field source, a new variation of the vacuum-assisted resin transfer molding (VARTM) process called electromagnetically induced preform resting (EIPR) for dynamical resin flow controlling is introduced to manipulate the flow front and local permeability to prevent the formation of dry spots. This paper proposes an active and real-time flow control approach that is implemented during the composite laminate infusion. The EIPR process applies an electromagnetic field source to pinch (raise) and vibrate the upper flexible mold to rest the fiber preform and increase the local permeability. Vibration action delivers the fluid through the preform. The EIPR process includes a new and creative upper flexible vacuum bag with embedded elements to lift and create local vibrations via an automated gantry system. The control methodology is performed by tracking the flow front with a real-time correction. System capability is demonstrated with three configurations of preform of different preform permeabilities in each experiment. A low permeability preform is employed in these configurations to disturb the flow pattern and cause an artificial problem or pseudo problem during the filling process. The results indicate that this system fills the mold completely and reduces the filling time without any dry spots and therefore creates no waste material.

关键词： Resin flow Process monitoring On-line flow control Vacuum-assisted resin transfer molding

Influence of welding speed on microstructure formation in friction-stir-welded 304 austenitic stainless steels

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2020年第11期27卷 1517-1524页

作者： mohsen Hajizadeh Sajjad Emami Tohid Saeid Faculty of Mechanical Engineering Sahand University of TechnologyTabrizIran Faculty of Materials Engineering Sahand University of TechnologyTabrizIran

The influence of welding speed on the joint microstructures of an austenitic stainless steel(ASS)produced by friction stir welding(FSW)was *** FSW process was conducted using a rotational speed of 400 r/min and welding speeds of 50 and 150 mm/*** study was carried out using electron backscattered diffraction(EBSD)technique in different regions of the resultant stir zones(SZs).The results show that the texture of the advancing side(AS)was mainly composed of C{001}〈110〉and cube{001}〈100〉texture components along with partial B/B{112}〈110〉*** from the AS toward the center and the retreating side(RS),the cube texture component disappeared and the A;/A*{111}(112)component developed and predominated the other *** welding speed greatly affected and decreased the intensity of the textures in the resultant ***,higher welding speed(lower heat input)resulted in lower frequency of cube texture in the AS.

关键词： friction stir welding stainless steels welding speed dynamic recovery shear texture continuous dynamic recrystallization

Controlling Thermodynamic Properties of Ferromagnetic Group-Ⅳ Graphene-Like Nanosheets by Dilute Charged Impurity

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2017年第5期67卷 569-576页

作者： mohsen Yarmohammadi Kavoos Mirabbaszadeh Department of Energy Engineering and Physics Amirkabir University of Technology Tehran Iran

Using the Kane-Mele Hamiltonian, Dirac theory and self-consistent Born approximation, we investigate the effect of dilute charged impurity on the electronic heat capacity and magnetic susceptibility of two-dimensional ferromagnetic honeycomb structure of group-Ⅳ elements including silicene, germanene and stanene within the Green's function approach. We also find these quantities in the presence of applied external electric field. Our results show that the silicene(stanene) has the maximum(minimum) heat capacity and magnetic susceptibility at uniform electric fields. From the behavior of theses quantities, the band gap has been changed with impurity concentration, impurity scattering strength and electric field. The analysis on the impurity-dependent magnetic susceptibility curves shows a phase transition from ferromagnetic to paramagnetic and antiferromagnetic phases. Interestingly, electronic heat capacity increases(decreases) with impurity concentration in silicene(germanene and stanene) structure.

关键词： ferromagnetic group-Ⅳ elements Green's function electronic heat capacity magnetic susceptibility phase transition

Modelling the spatial distribution of snake species in northwestern Tunisia using maximum entropy(Maxent) and Geographic Information System(GIS)

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2018年第1期29卷 233-245页

作者： mohsen Kalboussi Hammadi Achour Institut Sylvo-pastoral de Tabarka Universit6 de Jendouba8110 Tabarka Tunisia Unite de recherche 《Geomatique des Geosystemes》 02/UR/10-01 Universite de la Mannouba Campus universitaire B.P. 95 2010 Mannouba Tunisia

We used GIS and maximum entropy to predict the potential distribution of six snake species belong to three families in Kroumiria（Northwestern Tunisia）： Natricidae（Natrix maura and Natrix astreptophora）, Colubridae（Hemorrhois hippocrepis, Coronella girondica and Macroprotodon mauritanicus）, and Lamprophiidae（Malpolon insignitus）. The suitable habitat for each species was modelled using the maximum entropy algorithm, combining presence field data（collected during 16 years：2000–2015） with a set of seven environmental variables（mean annual precipitation, elevation, slope gradient,aspect, distance to watercourses, land surface temperature and normalized Differential Vegetation Index. The relative importance of these environmental variables was evaluated by jackknife tests and the predictive power of our models was assessed using the area under the receiver operating characteristic. The main explicative variables of the species distribution were distance from streams and elevation, with contributions ranging from 60 to 77 and from 10 to 25%,respectively. Our study provided the first habitat suitability models for snakes in Kroumiria and this information can be used by conservation biologists and land managers concerned with preserving snakes in Kroumiria.

关键词： Species distribution modelling Maxent Snakes Kroumiria Tunisia

An Approximate Approach for Systems of Singular Volterra Integral Equations Based on Taylor Expansion

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2018年第8期69卷 145-152页

作者： mohsen Didgar Alireza Vahidi Department of Mathematics Guilan Science and Research Branch Islamic Azad University Department of Mathematics Rasht Branch Islamic Azad University Department of Mathematics College of Science Yadegar-e-Emam Khomeyni (RAH) Shahr-e-Rey Branch Islamic Azad University

In this article, an extended Taylor expansion method is proposed to estimate the solution of linear singular Volterra integral equations systems. The method is based on combining the m-th order Taylor polynomial of unknown functions at an arbitrary point and integration method, such that the given system of singular integral equations is converted into a system of linear equations with respect to unknown functions and their derivatives. The required solutions are obtained by solving the resulting linear system. The proposed method gives a very satisfactory solution,which can be performed by any symbolic mathematical packages such as Maple, Mathematica, etc. Our proposed approach provides a significant advantage that the m-th order approximate solutions are equal to exact solutions if the exact solutions are polynomial functions of degree less than or equal to m. We present an error analysis for the proposed method to emphasize its reliability. Six numerical examples are provided to show the accuracy and the efficiency of the suggested scheme for which the exact solutions are known in advance.

关键词： systems of singular Volterra integral equations (SSVIEs) systems of generalized Abel's integral equations error analysis Taylor expansion

A Consistency Check for the Free Scalar Field Theory Realization of the Doubly Spacial Relativity

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2019年第6期71卷 677-684页

作者： mohsen Khodadi Kourosh Nozari Young Researchers and Elite Club Firoozkooh BranchIslamic Azad UniversityFiroozkoohIran Department of Physics Faculty of Basic SciencesUniversity of MazandaranP.O.Box47416-95447BabolsarIran Research Institute for Astronomy and Astrophysics of Maragha(RIAAM) P.O.Box55134-441MaraghaIran

We study a free scalar field theory in the framework of the Magueijo-Smolin model of the 'Doubly Special Relativity'(DSR) which is a non-linear realization of the action of the Lorentz group on momentum space admitting an invariant energy cutoff. We show that unlike the standard quantum field theory, the Klein-Gordon equation obtained via Euler-Lagrange field equation and Heisenberg picture equation of motion of the field are not equivalent in this framework,at least up to the first order of the Planck length scale.

关键词： quantum gravity phenomenology doubly special relativity quantum field theory Klein-Gordon equation