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Journal of Rock Mechanics and Geotechnical Engineering 2021年第2期13卷 446-456页

作者： Ehsan yazdani Jiayao Wang T.Matthew Evans School of Civil and Construction Engineering Oregon State UniversityCorvallisOR97331USA

This paper presents the results from a case study highlighting the difficulties of pile driving in diatomaceous *** the companion(first)paper to this article,results of an extensive laboratory and in situ testing program were presented while the results from pile driving and further analysis of field observations were presented *** high pile rebound(HPR)was observed during driving of a closed-end pipe pile,with refusal occurring at a depth of less than 5 *** open-ended piles were thus *** and case pile wave analysis program(CAPWAP)data were collected during driving of both closed-and open-end *** data indicated that negative pore water pressures(PWPs)were generated while the closed-ended pile exhibited high *** from in situ tests indicated change in material stiffness and strong dilative tendencies near the depth of refusal.A hypothesis for observed behavior was proposed that considers the soil beneath the pile as a medium with an effectively infinite bulk modulus.

关键词： Diatomaceous soil Problematic soil Site characterization Laboratory testing

Characterization of NbSi_2–Al_2O_3 nanocomposite coatings prepared with plasma spraying mechanically alloyed powders

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International Journal of Minerals,Metallurgy and Materials 2015年第7期22卷 748-754页

作者： Zohreh yazdani Fathallah Karimzadeh Mohammad-Hasan Abbasi Abbas Amini Department of Materials Engineering Isfahan University of Technology

The present study characterized NbSi2-Al2O3 nanocomposite powders plasma-sprayed on Ti-6Al-4Vsubstrates. The powders were agglomerated to obtain suitable particle sizes for spraying. The agglomerated powders were then plasma-sprayed using atmospheric plasma spraying. The structural transformations of the powders along with the morphological and mechanical changes of the coatings were examined by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and hard- ness testing. The results showed that after plasma spraying, the grain size increased, and the lattice strain decreased. However, the grain size of this compound after spraying was still in the nanometer range. The coating was uniform and exhibited good adhesion to the substrate. The microhardness and fracture toughness of the nanocomposite coating were higher than those of a nanostructured NbSi2 coating.

关键词： nanocomposites coatings plasma spraying mechanical alloying

Effect of loading direction on interaction of two pre-existing open and closed flaws in a rock-like brittle material

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Underground Space 2020年第3期5卷 242-257页

作者： Mahtab Alitalesh Mahmoud yazdani Ahmadali Fakhimi Marjan Naeimabadi School of Civil and Environmental Engineering Tarbiat Modares UniversityTehranIran Department of Mineral Engineering New Mexico TechSocorroNMUSA

Investigations of the growth,interaction,and coalescence of cracks are important because they help to provide tools for the more realistic modeling of rock masses containing low persistence discontinuities and better estimations of the strength and stiffness of a rock *** the coalescence mechanism is useful for justifying the mechanism of continental crustal deformation,evaluating the structural failure of slopes with rock bridges,and analyzing the stability of tunnels when a mode I or mix mode failure mechanism is *** evaluation of crack growth can provide valuable information about the mechanism for the formation of new geological structures,and the formation,evolution,and growth of *** paper reports the results of diametrical compression tests on rocklike disk-shaped *** specimen contained two pre-existing open or closed *** growth,interaction,and coalescence of the pre-existing flaws were investigated both physically and numerically.A hybrid bonded particle-finite element system was used in the numerical *** results of the physical and numerical studies were in good *** particular,the induced crack patterns showed close agreement in the physical and numerical *** microscope image processing was used in the physical tests to study the dislocations along the initial *** was shown that wing crack formation was responsible for the failure of the specimen when flaws were inclined with respect to the loading *** crack growth and linkage were shown to be affected by the friction between faces of the *** addition,the slip distributions at the flaws surfaces were illustrated and examined to understand the crack propagation *** effects of the flaws on the disk failure loads were assessed both numerically and experimentally as well.

关键词： Pre-existing flaws Brazilian disk Fracture mechanics Crack propagation Coalescence Bonded particle simulation

Case study of a driven pile foundation in diatomaceous soil.I:Site characterization and engineering properties

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第2期13卷 431-445页

作者： Jiayao Wang Ehsan yazdani T.Matthew Evans School of Civil and Construction Engineering Oregon State UniversityCorvallisOR97331USA

Diatomaceous soils are comprised of the silica frustules of diatom microalgae that are present in marine and lacustrine environments throughout the *** to their unique origin,diatomaceous soils are typically characterized by high intraparticle porosity,complex particle shapes,and uniform mineralogy,causing them to exhibit atypical physical and engineering behaviors.A substantial deposit of diatomaceous silt was observed during site exploration for construction of the Buck Creek Bridge on OR140 near Klamath Falls,OR,USA.A comprehensive laboratory and in situ testing program indicated that the diatomaceous soil possessed“non-textbook”engineering ***,tested samples had high liquid limits(≈100%-140%)with natural water contents at or near the liquid ***,the soil is expected to be normally consolidated,yet high apparent overconsolidation ratios(OCR)(≈15-40)were observed both in oedometric consolidation tests and through cone penetration test(CPT)*** penetration test(SPT)results show a corrected standard penetration resistance consistent with a medium-dense sand(i.e.(N1)_(60)≈25).CPT results include corrected tip resistances(qt)of approximately 7-10 MPa and excess pore pressures(u_(2))of up to 4 *** CPT dissipation tests,pore water pressures(PWPs)returned to hydrostatic pressure in less than 1 *** this work,we synthesize these seemingly disparate material properties in an attempt to infer appropriate engineering properties for the diatomaceous deposit at the Buck Creek Bridge and attempt to provide insight into the underlying reasons for the observed behavior.

关键词： Diatomaceous soil Problematic soil Site characterization Laboratory testing

Manufacturing of cast A356 matrix composite reinforced with nano- to micrometer-sized SiC particles

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Rare Metals 2017年第1期36卷 46-54页

作者： Reza Taherzadeh Mousavian Rasoul Azari Khosroshahi Sasan yazdani Dermot Brabazon Faculty of Materials Engineering Sahand University of Technology Tabriz 65175-4171 Iran Advanced Processing Technology Research Centre School of Mechanical and Manufacturing Engineering Dublin City University Dublin 9 Ireland

In this study, large micron-sized Si C particles were fragmented via ball-milling process in the presence of iron and nickel powders, separately, to fabricate composite powders of Fe–Si C and Ni–Si C. Continuous fracturing of brittle Si C powders leads to the formation of multi-modalsized Si C powders with size of from 50 nm to slightly higher than 10 lm after 36-h ball milling. The milled powders were then incorporated into the semisolid melt of A356 aluminum alloy to ease the incorporation of fine Si C particles by using iron and nickel as their carrier *** final as-cast composites were then extruded at 500 °C with a reduction ratio of 9:1. Lower-sized composite powders with slight agglomeration are obtained for the36-h milled Ni–Si C mixture compared to that of Fe–Si C powders, leading to incorporation of Si C particles into the melt with a lower size and suitable distribution for the Ni–Si C mixture. It is found that lower-sized composite particles could release the fine Si C particles into the melt more easily, while large agglomerated composite particles almost remain in its initial form, resulting in sites of stress concentration and low-strength aluminum matrix composites. Ultimate tensile strength(UTS) and yield strength(YS) values of 243 and 135 MPa, respectively, are obtained for the aluminum matrix composite in which nickel acts as the carrier of fine ceramic particles.

关键词： Aluminum matrix composite Semisolid casting Extrusion Ni Fe

Modeling metallurgical responses of coal Tri-Flo separators by a novel BNN:a"Conscious-Lab"development

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International Journal of Coal Science & Technology 2021年第6期8卷 1436-1446页

作者： Mehdi Alidokht Samaneh yazdani Esmaeil Hadavandi Saeed Chehreh Chelgani Tabas Parvardeh Coal Company(TPCCO) BirjandIran Department of Electrical and Computer Engineering Islamic Azad UniversityNorth Tehran BranchTehranIran Department of Industrial Engineering Birjand University of TechnologyBirjandIran Minerals and Metallurgical Engineering Department of CivilEnvironmental and Natural Resources EngineeringLulea University of Technology97187 LuleaSweden

Tri-flo cyclone,as a dense-medium separation device,is one of the most typical environmentally friendly industrial techniques in the coal washery ***,no detailed investigation has been conducted to explore the effectiveness of tri-flo cyclone operating parameters on their representative metallurgical responses(yield and recovery).To fill this gap,this work for the first time in the coal processing sector is going to introduce a type of advanced intelligent method(boosted-neural network"BNN")which is able to linearly and nonlinearly assess multivariable correlations among all variables,rank them based on their effectiveness and model their produced *** assessments and modeling were considered a new concept called"Conscious Laboratory(CL)".CL can markedly decrease the number of laboratory experiments,reduce cost,save time,remove scaling up risks,expand maintaining processes,and significantly improve our knowledge about the modeled *** this study,a robust monitoring database from the Tabas coal plant was prepared to cover various conditions for building a CL for coal tri-flo ***-known machine learning methods,random forest,and support vector regression were developed to validate BNN *** comparisons indicated the accuracy and strength of BNN over the examined traditional modeling *** a sentence,generating a novel BNN within the CL concept can apply in various energy and coal processing areas,fill gaps in our knowledge about possible interactions,and open a new window for plants’fully automotive process.

关键词： Conscious laboratory BNN Tri-flo Random forest Support vector regression

Effect of shot peening process on fatigue behavior of an alloyed austempered ductile iron

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China Foundry 2011年第3期8卷 325-330页

作者： Amir Sadighzadeh Benam Sasan yazdani Behzad Avishan Faculty of Materials Engineering Sahand University of Technology

Shot peening is one of the most common surface treatments to improve the fatigue behavior of metallic parts. In this study the effect of shot peening process on the fatigue behavior of an alloyed austempered ductile iron (ADI) has been studied. Austempering heat treatment consisted of austenitizing at 875℃ for 90 min followed by austempering at three different temperatures of 320, 365 and 400℃. Rotating-bending fatigue test was carried out on samples after shot peening by 0.4-0.6 mm shots. XRD and SEM analysis, micro hardness and roughness tests were carried out to study the fatigue behavior of the samples. Results indicate that the fatigue strengths of samples austempered at 320, 365 and 400℃ are increased by 27.3%, 33.3% and 48.4%, respectively, after shot peening process.

关键词： austempered ductile iron shot peening fatigue strength roughness

Impact of Perlator on the cooling liquid flow and hottest point temperature of superconducting windings in HTS transformer

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Superconductivity 2022年第3期3卷 97-105页

作者： Mahdi Mahamed Mohammad yazdani-Asrami Vahid Behjat Akbar yazdani Mojtaba Sharifzadeh Department of Electrical Engineering Azarbaijan Shahid Madani UniversityTabrizIran Propulsion Electrification&Superconductivity GroupJames Watt School of EngineeringUniversity of GlasgowGlasgowUK Department of Applied Sciences University of Quebec at ChicoutimiChicoutimiCanada Thermal Power Plant Research Center TabrizIran Fondazione Bruno Kessler TrentoItaly

The generated heat by the superconducting windings and the other parts such as current leads in transformer increases the hottest point temperature(HPT)and causes the high temperature superconducting(HTS)windings to *** to the properties of superconducting windings,reducing the HPT is of critical importance for the stable operation of the HTS *** cooling system of HTS transformers,not only provides the cryogenic temperature for the proper operation of the superconductors but also is responsible for dissipating the generated heat by the *** this paper,the effect of the angle of inlet pipes in cooling system was *** was a simple and effective solution which increases the heat transfer in liquid *** was shown that inlet angle has a significant effect on the flow turbulence and the windings *** Perlator is used as a lattice sheet which is installed inside the inlet valve and increases the turbulence of inlet flow of liquid nitrogen to increase heat transfer and reduce *** thermal analysis is obtained by finite element method using ANSYS Fluent *** influence of changing the inlet pipe angle and different structure of Perlator on heat transfer was investigated.

关键词： Cryogenic temperature Finite element method Heat transfer Perlator Superconducting transformer Turbulences

Preparation and characterization of sphere-like Cu_2SnS_3 nanoparticles and their dropcasted thin films

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Journal of Semiconductors 2017年第1期38卷 86-94页

作者： Zohreh Shadrokh Ahmad yazdani Hosein Eshghi Department of Physics Shahrood University of Technology Department of Physics Tarbiat Modares University

Ternary sphere-like Cu2 SnS3（CTS）semiconductor and 2D hexagonal sheets were synthesized via a simple solvothermal method using PVP as the surface ligand at two temperatures of 180 and 220 *** structural,morphological,and chemical compositions as well as optical properties of as-synthesized CTS particles were characterized using X-ray diffraction（XRD）,Raman spectroscopy,energy dispersive X-ray spectrometry（EDS）,field emission scanning electron microscopy（FESEM）,and UV-Vis *** size of sphere-like particles and the side length of hexagonal sheets were within the range of 120-140 nm and 500 nm-2 μm,***,XRD,and EDS were analyzed to investigate the mechanism of the morphological evolution of CTS *** particles showed proliferation of Sn atomic ratio,which is strongly sensitive to reaction temperature and,highly affects the increase of band gap energy from 1.36 to 1.53 eV due to generation metal defects and formation SnS2-The optical analysis via the transmittance and reflectance reveals that the band-gap energy of dropcasted CTS thin films decreases after annealing due to grain growth and change of chemical ***-responses of CTS nanocrystal thin films indicated a considerable increase in the conductivity of the films under light *** these results showed the potential of these films for solar cell applications.

关键词： Cu2SnS3 nanoparticles solvothermal method nanocrystal thin films

Effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron

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China Foundry 2007年第2期4卷 120-123页

作者： S. yazdani M. Ardestani Faculty of Materials Engineering Sahand University of TechnologyTabrizIRAN

The effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron has been investigated. Austempering of samples was performed at 325℃and 400℃after austenitizing at 875℃and 950℃. The sub-zero treatments were carried out by cooling down the samples to -30℃, -70℃and -196℃. The changes in volume fraction of austenite and mechanical properties were determined after cooling to each temperature. The austenite volume fraction of samples which were austenitized at 875℃and austempered at 325℃remained unchanged, whilst it reduced in samples austenitized at 950℃and 875℃for austempering temperature of 400℃. In these specimens, some austenite transformed to martensite after subzero cooling. Mechanical property measurements showed a slight increase in strength and hardness and decrease in elongation and toughness due to this transformation behavior.

关键词： austempered ductile iron austenite sub-zero cooling martensitic transformation ausferrite