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A crystal plasticity based approach to establish role of grain size and crystallographic texture in the Tension–Compression yield asymmetry and strain hardening behavior of a Magnesium–silver–Rare Earth alloy

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Journal of Magnesium and Alloys 2022年第9期10卷 2546-2562页

作者： sourav Mishra F.khan s.K.Panigrahi Department of Mechanical Engineering Indian Institute of Technology MadrasChennai 600036Tamil NaduIndia Applied Magnesium Research Group Centre for Materials and Manufacturing for Futuristic MobilityIndian Institute of Technology MadrasChennai 600036Tamil NaduIndia school of Mechanical Engineering Vellore Institute of TechnologyVellore 632014Tamil NaduIndia

Existence of tension–compression yield asymmetry is a serious limitation to the load bearing capablities of Magnesium alloys in a number of light weight structural applications.The present work is aimed at nullifying the tension to compression asymmetry problem and strain hardening anomalies in a Magnesium–silver–Rare Earth alloy by engineering different levels of microstructural conditions via friction stir processing and post process annealing.The existence and extent of yield asymmetry ratio in the range of microstructural conditions was experimentally obtained through quasistatic tensile and compression tests.The yield asymmetry problem was profoundly present in specimens of coarse grained microstructures when compared to their fine grained and ultra fine grained counterparts.The impact of the microstructure and associated mechanisms of plasticity on the macroscopic strain hardening behavior was established by Kock–Mecking’s analysis.Crystal plasticity simulations using Viscoplastic self Consistency approach revealed the consequential role of extension twinning mechanism for the existence of yield asymmetry and anomalies in strain hardening behavior.This was especially dominant with coarsening of grain size.Electron Microscopy and characterization were conducted thoroughly in partially deformed specimens to confirm the predictions of the above simulations.The role of crystallographic texture for inducing the polarity to Tension–Compression yield asymmetry was corroborated.A critical grain size in Magnesium–silver–Rare earth alloy was hereby established which could nullify influences of extension twinning in yield asymmetry ratio.

关键词： Magnesium silver rare earth alloy Friction stir processing Ultrafine-grained microstructure Tension to compression yield strength asymmetry Crystallographic texture strain hardening Kock mecking plots Visco plastic self consistency

A framework for coupled consolidation-desiccation behaviour of clay slurries

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International Journal of Mining science and Technology 2018年第2期28卷 275-280页

作者： Faseel s.khan shahid Azam Faculty of Engineering and Applied science University of Regina

A framework is proposed to understand coupled consolidation-desiccation in clay slurries using effective stress and soil suction as state variables. Constitutive surfaces were derived from best-fit equations for reference curves where one state variable was kept at 1 kPa and the other was varied up to 10~6 kPa.Results indicated that volume compressibility comprises of apparent pre-consolidation up to 100 kPa beyond which a single best-fit curve is valid. similarly, the theoretical virgin compression line(specific gravity dependant), indicated that both state variables have the same effect up to the air entry value(1000 kPa at a void ratio of 1.8) beyond which void ratio reduces more readily under effective stress than under soil suction. Likewise, hydraulic conductivity remained saturated up to the air entry value and varied from 10^(-9)m/s to 10^(-12)m/s. Finally, the unsaturated hydraulic conductivity correlated well with empirical relationship up to 10^(-14) m/s bevond which vapor flow became dominant.

关键词： Clay slurries Volume compressibility Hydraulic conductivity Constitutive surfaces

On the detection of closed orbits in time-dependent systems by using double-pulse lasers

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Communications in Theoretical Physics 2020年第9期72卷 111-117页

作者： s U khan M L Du Institute of Theoretical Physics Chinese Academy of Sciences.Beijing 100190China University of Chinese Academy of sciences Beijing100049China

In the photodetachment of atoms or negative ions by a double-pulse laser, the first pulse of the double-pulse laser generates waves and the delayed second pulse may detect them. The phenomenon of the excitation and detection of waves by a double-pulse laser can be used to identify the closed orbits in the system. We demonstrate this phenomenon with a negative hydrogen ion(H^-) by analyzing the total population excited by a double-pulse laser in a timedependent field for different physical parameters. By analyzing the total excited population using a double-pulse laser, we can uncover all the closed orbits existing in the system. We demonstrate that this can be realized by scanning the first pulse position and the time delay between the two pulses.

关键词： double-pulse laser detection of closed orbits photodetachment spectra time-dependent systems

The development of ultralightweight expanded perlite-based thermal insulation panel using alkali activator solution

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Frontiers of structural and Civil Engineering 2022年第11期16卷 1486-1499页

作者： Damla Nur CELIK Gökhan DURMUŞ Civil Engineering Department Technology FacultyGazi UniversityAnkara 06500Turkey

The International Energy Agency(IEA)states that global energy consumption will increase by 53%by 2030.Turkey has 70%of the world’s perlite reserves,and in order to reduce energy consumption a thermal insulation panel was developed in Turkey using different particle sizes of expanded perlite(EP).In this study,0–1.18 mm(powder)and 0–3 mm(granular)EP particle sizes were selected,since they have the lowest thermal conductivity coefficients among all the particle sizes.In addition,an alkali activator solution was used as a binder in the mixtures.The alkaline activator solution was obtained by mixing sodium hydroxide solution(6,8,10,and 12 mol·L−1)and sodium silicate(Module 3)at the different ratios of Na2siO3 to NaOH of 1,1.5,2,and 2.5.This study aimed to experimentally determine the optimum binder and distribution ratio of EP,with the lowest coefficient of thermal conductivity and the lowest density.The lowest thermal conductivity and the lowest density were determined as 0.04919 W·m−1·K−1 and 133.267 kg/m3,respectively,in the sample prepared with 83.33%powder-size EP,6 mol·L−1 sodium hydroxide solution,and ratio of Na2siO3 to NaOH of 1.5.The density,thermal conductivity,and compressive strength of the sample showed the same trends of behavior when the Na2siO3 to NaOH ratio was increased.In addition,the highest compressive strength was measured in 12 mol·L−1 NaOH concentration regardless of particle size.In conclusion,the study predicts that the EP-based thermal insulation panel can be used as an insulation material in the construction industry according to the Ts825 Thermal Insulation standard.

关键词： expanded perlite alkali activator thermal insulation panel thermal conductivity

Heat Transfer of Casson Fluid over a Vertical Plate with Arbitrary shear stress and Exponential Heating

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Computers, Materials & Continua 2022年第4期71卷 1025-1034页

作者： Dolat khan Gohar Ali Arshad khan Ilyas khan Department of Mathematics City University of Science and Information TechnologyPeshawar25000Pakistan Institute of Computer sciences and Information Technology The University of AgriculturePeshawarPakistan Faculty of Mathematics and statistics Ton Duc Thang UniversityHo Chi Minh City72915Vietnam

The basic objective of this work is to study the heat transfer of Casson fluid of non-Newtonian nature.The fluid is considered over a vertical plate such that the plate exhibits arbitrary wall shear stress at the boundary.Heat transfers due to exponential plate heating and natural convection are due to buoyancy force.Magnetohydrodynamic(MHD)analysis in the occurrence of a uniform magnetic field is also considered.The medium over the plate is porous and hence Darcy’s law is applied.The governing equations are established for the velocity and temperature fields by the usual Boussinesq approximation.The problem is first written in dimensionless form using some useful non-dimensional quantities and then solved.The exact analysis is performed and hence solutions via integral transform are established.The analysis of various pertinent parameters on temperature distribution and velocity field are reported graphically.It is found that pours medium permeability parameter retards the fluid motion whereas,velocity decreases with increasing magnetic parameter.Velocity and temperature decrease with increasing Prandtl number whereas the Grashof number enhances the fluid motion.Further,it is concluded from this study that the results obtained here are more general and in a limiting sense several other solutions can be recovered.The Newtonian fluid results can be easily established by taking the Casson parameter infinitely large i.e.,whenβ→∞.

关键词： Heat transfer casson fluid shear stress natural convection

Mathematical modeling of mixed convective MHD Falkner-skan squeezed sutterby multiphase flow with non-Fourier heat flux theory and porosity

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Applied Mathematics and Mechanics(English Edition) 2023年第11期44卷 2005-2018页

作者： shuguang LI M.I.khan F.ALI s.s.ABDULLAEV s.sAADAOUI HABIBULLAH school of Computer science and Technology Shandong Technology and Business UniversityYantai 264005Shandong ProvinceChina Department of Mechanics and Engineering science Peking UniversityBeijing 100871China Department of Mechanical Engineering Lebanese American UniversityBeirut 11020Lebanon Department of Mathematical sciences Federal Urdu University of ArtsSciences&TechnologyGulshan-e-IqbalKarachi 75300Pakistan Faculty of Chemical Engineering New Uzbekistan UniversityTashkent 100070Uzbekistan Department of science and Innovation Tashkent State Pedagogical University named after NizamiTashkent 100070Uzbekistan Department of Physics Faculty of Science and ArtsMohayel AserKing Khalid UniversityAbha 61421Saudi Arabia state Key Laboratory of Turbulence and Complex system Collaborative Innovative Center for Advanced Aero-EnginesPeking UniversityBeijing 100871China

In a wide variety of mechanical and industrial applications,e.g.,space cooling,nuclear reactor cooling,medicinal utilizations(magnetic drug targeting),energy generation,and heat conduction in tissues,the heat transfer phenomenon is involved.Fourier’s law of heat conduction has been used as the foundation for predicting the heat transfer behavior in a variety of real-world contexts.This model’s production of a parabolic energy expression,which means that an initial disturbance would immediately affect the system under investigation,is one of its main drawbacks.Therefore,numerous researchers worked on such problem to resolve this issue.At last,this problem was resolved by Cattaneo by adding relaxation time for heat flux in Fourier’s law,which was defined as the time required to establish steady heat conduction once a temperature gradient is imposed.Christov offered a material invariant version of Cattaneo’s model by taking into account the upper-connected derivative of the Oldroyd model.Nowadays,both models are combinedly known as the Cattaneo-Christov(CC)model.In this attempt,the mixed convective MHD Falkner-skan sutterby nanofluid flow is addressed towards a wedge surface in the presence of the variable external magnetic field.The CC model is incorporated instead of Fourier’s law for the examination of heat transfer features in the energy expression.A two-phase nanofluid model is utilized for the implementation of nano-concept.The nonlinear system of equations is tackled through the bvp4c technique in the MATLAB software 2016.The influence of pertinent flow parameters is discussed and displayed through different sketches.Major and important results are summarized in the conclusion section.Furthermore,in both cases of wall-through flow(i.e.,suction and injection effects),the porosity parameters increase the flow speed,and decrease the heat transport and the influence of drag forces.

关键词： sporosity Cattaneo-Christov(CC)heat flux model Falkner-skan sutterby nanofluid mixed convection stagnation point

Dynamic trip point categorisation using manufacturing process for polycrystalline diamond compact bits as case study

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Journal of Control and Decision 2022年第3期9卷 311-321页

作者： Zubair Ahmad khan Khalid khan shuja Ahmad khan shahbaz khan Muhammad Tufail Abdel Nasser Mechatronics Department University of Engineering and Technology PeshawarPeshawarPakistan Materials for Energy storage and Conversion US Pakistan Centre for Advanced Studies in Energy University of Engineering and Technology PeshawarPeshawarPakistan Bakar Hughes HoustonGermany Jacobs DallasTXUSA

Disruptions in the manufacturing process cast substantial impacts on the consumer’s centric values,cost,and overall efficiency.The ripple effect of these disruptions is observed in the whole assembly line.The proper analysis and mitigation of disruptions is the key to the proficiency of the plant and resource utilisation.The research focuses on the quantitative analysis of the impact of disruptions of the manufacturing process,which is performed by analysing the disruptive workstation dynamically.The disruptive workstations have a significant impact on succeeding and preceding workstations,which have been analysed dynamically,and accordingly,the preset alarm trip points are elevated.The results show that lowering the number of starts and stops decreases the number of rejections of valuable process batches that finally improve efficiency.Finally,the developed model is implemented on a polycrystalline diamond compact drill bit manufacturing plant.The results are compared with the research work of other researchers,showing a 60%reduction in the number of start/stop events,60%reduction in downtime,while a 75%reduction in the number of rejections is noted.

关键词： Disruptions dynamic assessment downtime alarm tripoints

Determination of consolidation behaviour of clay slurries

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International Journal of Mining science and Technology 2016年第2期26卷 277-283页

作者： khan Faseel s. Azam shahid Environmental systems Engineering University of Regina

The main objective of this study was to determine the consolidation behaviour of clay slurries.A finegrained clay with high consistency limits(W_L = 180%,w_P= 120%) was investigated using conventional oedometer and bench-top centrifuge tests.Results indicated that the slurry had an apparent preconsolidation(due to initial conditions,electrochemical interactions,tortuous drainage,and thixotropic strength) from e = 5.7 to e = 5.5 followed by virgin compression.Likewise,the low hydraulic conductivity(10^(-10)-10^(-12) m/s) was due to low porosity(small pore throats) and high tortuosity(long flow paths).Unlike consolidation of soils,the c_v and m_v decreased with increasing σ' but increased with increasing e and k.The data from the two tests correlated well in the range of σ' = 10-65 kPa,e = 5.5-3.86,k= 1.7 × 10^(-10)-5×10^(-11) m/s,F_c = 1-40 MN.New equations were developed to correlate the consolidation parameters(e,σ',k) with F_c.The deviation of k beyond 40 MN(e = 4.65) was due to deviation from the initial straight line portion of the settlement curve in the centrifuge test.

关键词：固结特性粘土泥浆测定先期固结压力水力传导系数离心试验电化学作用孔隙喉道

Adipose-derived regenerative therapies for the treatment of knee osteoarthritis

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World Journal of stem Cells 2024年第4期16卷 324-333页

作者： Ilias E Epanomeritakis Wasim s khan Division of Trauma and Orthopaedic surgery Addenbrooke’s HospitalCambridge University Hospitals NHS Foundation TrustCambridge CB20QQUnited Kingdom Division of Trauma and Orthopaedic surgery Department of SurgeryUniversity of CambridgeCambridge CB20QQUnited Kingdom

Knee osteoarthritis is a degenerative condition with a significant disease burden and no disease-modifying therapy.Definitive treatment ultimately requires joint replacement.Therapies capable of regenerating cartilage could significantly reduce financial and clinical costs.The regenerative potential of mesenchymal stromal cells(MsCs)has been extensively studied in the context of knee osteoarthritis.This has yielded promising results in human studies,and is likely a product of immunomodulatory and chondroprotective biomolecules produced by MsCs in response to inflammation.Adipose-derived MsCs(AsCs)are becoming increasingly popular owing to their relative ease of isolation and high proliferative capacity.stromal vascular fraction(sVF)and micro-fragmented adipose tissue(MFAT)are produced by the enzymatic and mechanical disruption of adipose tissue,respectively.This avoids expansion of isolated AsCs ex vivo and their composition of heterogeneous cell populations,including immune cells,may potentiate the reparative function of AsCs.In this editorial,we comment on a multicenter randomized trial regarding the efficacy of MFAT in treating knee osteoarthritis.We discuss the study’s findings in the context of emerging evidence regarding adipose-derived regenerative therapies.An underlying mechanism of action of AsCs is proposed while drawing important distinctions between the properties of isolated AsCs,sVF,and MFAT.

关键词： Knee osteoarthritis Mesenchymal stromal cells Adipose tissue stromal vascular fraction Micro-fragmented adipose tissue Regeneration