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Solid state crack repair by friction stir processing in 304L stainless steel

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Journal of Materials Science & technology 2018年第1期34卷 140-147页

作者： C.Gunter M.P.Miles F.C.Liu t.w.nelson Manufacturing Engineering technology Brigham Young University Department of Mechanical Engineering Brigham Young University

Friction stir processing （FSP） was investigated as a method of repairing cracks in 12 mm thick 304L stainless steel plate. Healing feasibility was demonstrated by processing a tapered crack using a PCBN/w- Re tool with a 25 mm diameter shoulder and a pin length of 6.4 mm. the experiment showed that it was possible to heal a crack that begins narrow and then progressively grows up to a width of 2 mm. Bead on plate experiments were used to find the best parameters for creating a consolidated stir zone with the least amount of hardness difference compared to the base metal. Grain refinement in some specimens resulted in much higher stir zone hardness, compared to base metal, A plot of grain size versus microhardness showed a very strong inverse correlation between grain size and hardness, as expected from the Hall- Perch relationship. Corrosion testing was carried out in order to evaluate the effect of FSP on potential sensitization of the stir zone. After 1000 h of intermittent immersion in 3.5% saline solution at room temperature it was found that no corrosion products formed on the base material controls or on any of the friction stir processed specimens.

关键词： Stainless steel Crack healing Friction stir processing Corrosion resistance

A review of friction stir welding of steels： tool, material flow, microstructure, and properties

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Journal of Materials Science & technology 2018年第1期34卷 39-57页

作者： F.C. Liu Y. Hovanski M.P. Miles C.D. Sorensen t.w. nelson Department of Mechanical Engineering Brigham Young University Provo UT 84602. USA Manufacturing Engineering technology Brigham Young University Provo UT 84602 USA

Considerable progress has been achieved in friction stir welding （FSw） of steels in every aspect of tool fab- rication, microstructure control and properties evaluation in the past two decades. with the development of reliable welding tools and precise control systems, FSw of steels has reached a new level of technical maturity. High-quality, long welds can be produced in many engineering steels. Compared to traditional fusion welding, FSw exhibits unique advantages producing joints with better properties. As a result of active control of the welding temperature and/or cooling rate, FSw has the capability of fabricating steel joints with excellent toughness and strength. For example, unfavorable phase transformations that usu- ally occur during traditional welding can be avoided and favorable phase fractions in advanced steels can be maintained in the weld zone thus avoiding the typical property degradations associated with fusion welding. If phase transformations do occur during FSw of thick steels, optimization of microstructure and properties can be attained by controlling the heat input and post-weld cooling rate.

关键词： Joining Stainless steels Carbon steels High strength low alloy (HSLA) steels Advanced high strength steels (AHSS) Oxide dispersion strengthened (ODS) steels

Assessment of challenges and strategies for driving energy transitions in emerging markets:A socio-technological systems perspective

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Energy Geoscience 2024年第2期5卷 81-100页

作者： nelson S.Chipangamate Glen t.Nwaila wits Mining Institute University of the Witwatersrand1 Jan Smuts Ave.Johannesburg2000South Africa School of Geosciences University of the WitwatersrandPrivate Bag 3Wits2050South Africa

the pursuit of improved quality of life standards has significantly influenced the contemporary mining model in the 21st *** era is witnessing an unprecedented transformation driven by pressing concerns related to sustainability,climate change,the just energy transition,dynamic operating environments,and complex social *** transitions present both opportunities and *** aim of this study is to provide an extensive literature review on energy transition to identify the challenges and strategies associated with navigating transformations in energy *** these transformations is particularly critical in the face of the severe consequences of global warming,where an accelerated energy transition is viewed as a universal *** a socio-technological systems perspective,specifically through the application of Actor Network theory(ANt),this research provides a theoretical foundation while categorising challenges into five distinct domains and outlining strategies across these different *** insights are specifically tailored for emerging market countries to effectively navigate energy transition while fostering the development of resilient ***,our findings highlight that energy transition encompasses more than a mere technological shift;it entails fundamental changes in various systemic socio-economic *** focusing on the role of social structures in transitions,this study makes a significant and innovative contribution to ANt,which has historically been criticised for its limited acknowledgement of social ***,we propose an emerging market energy transition framework,which not only addresses technological aspects,but also integrates social *** framework paves the way for future research and exploration of energy transition *** outcomes of this study offer valuable insights to policymakers,researchers,and practitioners engaged in t

关键词： Actor network theory Energy transition Social innovation technology Actor inclusive policy

transport mechanism in chemically reactive hybrid nanofluid flow containing gyrotactic micro-organisms over a curved oscillatory surface

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Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 177-192页

作者： M.NAVEED M.IMRAN t.ASGHAR Z.ABBAS Department of Mathematics Division of Science and TechnologyUniversity of Education Department of Mathematics The Islamia University of Bahawalpur

this paper examines the transport analysis, including both heat transfer and mass transfer, in hybrid nanofluid flow containing gyrotactic microorganisms towards a curved oscillatory surface. the influence of magnetic fields is also inspected in terms of their physical characteristics. to depict the phenomena of transport, modified versions of both Fick's and Fourier's laws are used. Additionally, the characteristics of both heterogeneous and homogeneous chemical reactions are also incorporated. Utilizing a curvilinear coordinate system, the flow problem is formulated as partial differential equations(PDEs)for momentum, concentration, microorganism field, and energy. An analytical solution to the obtained flow equations is achieved utilizing the homotopy analysis method(HAM).the effects of significant flow parameters on the pressure and microorganism fields, velocity, oscillation velocity, concentration, and temperature distributions are shown via graphs. Furthermore, the variations in skin friction, mass transfer rate, heat transfer rate, and local motile number due to different involved parameters are presented in tables and are analyzed in detail. Graphical results indicate that the curves of velocity and temperature fields are enhanced as the values of the solid volume fraction variables *** is also verified that the concentration rate field decreases as the values of the homogeneous reaction strength parameter and the radius of curvature parameter increase, and it increases with the Schmidt number and the heterogeneous reaction strength *** outcomes show a favorable response of the motile number to advanced values of the Peclet number, the Schmidt number, the microorganism difference parameter, and the bio-convective Lewis number.

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Almost sure stability condition of weakly coupled linear nonautonomous random systems

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Applied Mathematics and Mechanics(English Edition) 2010年第8期31卷 1033-1038页

作者： t．w．MA Department of Civil and Environmental Engineering University of Hawaii at Manoa Honolulu HI 96822 USA

In this study, the sufficient condition of almost sure stability of twodimensional oscillating systems under parametric excitations is investigated. the systems considered are assumed to be composed of two weakly coupled subsystems. the driving actions are considered to be stationary stochastic processes satisfying ergodic properties. the properties of quadratic forms are used in conjunction with the bounds for the eigenvalues to obtain, in a closed form, the sufficient condition for the almost sure stability of the systems.

关键词： almost sure stability ergodic process bound for eigenvalue

Review of the experiments for energetic particle physics on HL-2A

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Plasma Science and technology 2018年第9期20卷 93-105页

作者： X t DING w CHEN Southwestern Institute of Physics Chengdu 610041People＇s Republic of China

this paper reviews the energetic particle（EP） experiments during electron cyclotron resonance heating（ECRH） and neutral beam injection in the HL-2 A tokamak.A number of important results are summarized,which relate to ItER physics,including the behavior of the multi-mode instability,the nonlinear interaction between wave-wave and wave-particles,the losses of EP induced by the instabilities,the effect of the EP instabilities on the thermal plasma confinement and the control of the EP instabilities by means of *** experiments indicate that when the drive is great enough,the nonlinear effects and the multi-mode coexistence may play an important role,which affect the transport both of the EPs and the background plasma confinement,and these instabilities could be *** new phenomena about the EP induced instabilities discovered recently on the device,such as high frequency reversed shear Alfvén eigenmodes,Alfvénic ion temperature gradient modes,the geodesic acoustic mode induced by energetic electrons excited by interaction between tearing mode and beta induced Alfvén eigenmode and double e-fishbone in negative magnetic shear discharges etc,have also been presented in the paper.

关键词： HL-2A tokamak energetic particle Alfven eigenmode plasma confinement

Fecal microbiota transplantation in allergic diseases

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world Journal of Methodology 2025年第2期15卷 83-91页

作者： Ece tüsüzÖnata ÖnerÖzdemir Division of Pediatric Allergy and Immunology Medical FacultySakarya UniversityAdapazarı54100SakaryaTürkiye

Microorganisms such as bacteria,fungi,viruses,parasites living in the human intestine constitute the human intestinal *** refers to composi-tional and quantitative changes that negatively affect healthy gut *** recent years,with the demonstration that many diseases are associated with dysbiosis,treatment strategies targeting the correction of dysbiosis in the treat-ment of these diseases have begun to be *** microbiota trans-plantation(FMt)is the process of transferring faeces from a healthy donor to another recipient in order to restore the gut microbiota and provide a therapeutic *** studies have gained popularity after probiotic,prebiotic,symbiotic studies in the treatment of dysbiosis and related *** has emerged as a potential new therapy in the treatment of allergic diseases as it is associated with the maintenance of intestinal microbiota and immunological balance(t helper 1/t helper 2 cells)and thus suppression of allergic *** this article,the definition,application,safety and use of FMt in allergic diseases will be discussed with current data.

关键词： Microbiota Dysbiosis Faecal microbiota transplantation Allergic diseases

A numerical method based on boundary integral equations and radial basis functions for plane anisotropic thermoelastostatic equations with general variable coefficients

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Applied Mathematics and Mechanics(English Edition) 2020年第4期41卷 551-566页

作者： w.t.ANG X.wANG School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore Department of Mechanical Engineering National University of SingaporeSingapore 117575Singapore

A boundary integral method with radial basis function approximation is proposed for numerically solving an important class of boundary value problems governed by a system of thermoelastostatic equations with variable coe?cients. the equations describe the thermoelastic behaviors of nonhomogeneous anisotropic materials with properties that vary smoothly from point to point in space. No restriction is imposed on the spatial variations of the thermoelastic coe?cients as long as all the requirements of the laws of physics are satis?ed. to check the validity and accuracy of the proposed numerical method, some speci?c test problems with known solutions are solved.

关键词： elliptic partial differential equation variable coefficient boundary element method radial basis function anisotropic thermoelastostatics

Nanofiber–microsphere (nano-micro) matrices for bone regenerative engineering: a convergence approach toward matrix design

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Regenerative Biomaterials 2014年第1期1卷 3-9页

作者： Clarke nelson Yusuf Khan Cato t.Laurencin Raymond and Beverly Sackler Center for Biomedical BiologicalPhysical and Engineering SciencesInstitute for Regenerative EngineeringUniversity of Connecticut Health CenterFarmingtonCT 06030USA Department of Orthopaedic Surgery University of Connecticut Health CenterFarmingtonCT 06030USA Department of Materials Science and Engineering University of ConnecticutStorrsCT 06269USA Department of Chemical and Biomolecular Engineering University of ConnecticutStorrsCT 06269USA

Bone is an essential organ for health and quality of *** to current shortfalls in therapy for bone tissue engineering,scientists have sought the application of synthetic materials as bone graft *** a composite organic/inorganic material with significant extra cellular matrix(ECM),one way to improve bone graft substitutes may be to engineer a synthetic matrix that is influenced by the physical appearance of natural ECM *** this work,the authors evaluate composite,hybrid scaffolds for bone tissue engineering based on composite ceramic/polymer microsphere scaffolds with synthetic ECM-mimetic networks in their pore *** thermally induced phase separation,nanoscale fibers were deposited in the pore spaces of structurally sound microsphere-based scaffold with a density proportionate to the initial polymer *** and mechanical testing indicated no significant changes in overall pore characteristics or mechanical integrity as a result of the fiber deposition *** scaffolds displayed adequate mechanical integrity on the scale of human trabecular bone and supported the adhesion and proliferation of cultured mouse calvarial *** from natural cues,these scaffolds may represent a new avenue forward for advanced bone tissue engineering scaffolds.

关键词： nanobiomaterials bioceramics medical device bone