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Achieving superior strength-ductility synergy in a heterostructured magnesium alloy via low-temperature extrusion and low-temperature annealing

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Journal of Materials Science & technology 2023年第32期163卷 32-44页

作者： H.Wang d.t.Zhang c.Qiu W.W.Zhang d.L.chen Guangdong Key Laboratory for Advanced Metallic Materials Processing and Forming National Engineering Research Center of Near-net-shape Forming for Metallic MaterialsSouth China University of TechnologyGuangzhou 510640China department of Mechanical and Industrial Engineering Toronto Metropolitan University(formerly Ryerson University)350 Victoria StreetTorontoON M5B 2K3Canada

A low-alloyed Mg-1.2Zn-0.1ca(wt.%)alloy was fabricated via low-temperature extrusion and annealing at 250℃for different times(10,30,and 90 min)to attain heterostructures with different fine-grained fractions,focusing on the effect of heterostructure on the mechanical *** dynamic recrystallization(RX)occurred during extrusion at 150℃,and a lamellar structure consisting of fine RX grains and coarse unRX grains was *** subsequent annealing promoted static RX in the as-extruded alloy,leading to an increased fine-grained fraction from 67%to 95%.Meanwhile,the co-segregation of Zn and ca atoms impeded the migration of grain boundaries,thus achieving a fine grain size of 0.8–1.6μ*** sample annealed for 10 min with a fine-grained fraction of 73%and an average RX grain size of 0.9μm exhibited a superior combination of high yield strength(305 MPa)and good ductility(20%).In comparison,an excellent elongation of 30%was achieved in the alloy with a nearly fully-RXed microstructure and an average grain size of 1.6μm after 90 min annealing,despite a lower yield strength of 228 *** unRX grains,the hard orientation with(01–10)parallel to the extrusion direction and high-density dislocations made it more difficult to deform compared with the RX grains,thus producing hetero-deformation induced(HdI)*** fine grains and high-density dislocations,HdI strengthening is the key to achieving the superior mechanical properties of the low-alloyed Mg alloy.

关键词： Low-alloyed magnesium alloy Low-temperature extrusion Annealing Heterostructure Mechanical properties

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Retrospective analysis of eFASt ultrasounds performed on trauma activations at an academic level-1 trauma center

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World Journal of Emergency Medicine 2020年第1期11卷 12-17页

作者： Samantha Shwe Lauren Witchey Shadi Lahham Ethan Kunstadt Inna Shniter John c.fox School of Medicine University of CaliforniaIrvine 92697USA department of Emergency Medicine University of CaliforniaIrvineOrangeCA 92868USA

BAcKGROUNd:Point-of-care ultrasound(POcUS)has become increasingly integrated into the practice of emergency medicine.A common application is the extended focused assessment with sonography in trauma(eFASt)*** American college of Emergency Physicians has guidelines regarding the scope of ultrasound in the emergency department and the appropriate *** objective of this study was to conduct a review of performed,documented and billed eFASt ultrasounds on trauma activation ***:this was a retrospective review of all trauma activation patients during a 10-month period at an academic level-one trauma center.A list comparing all trauma activations was crossreferenced with a list of all billed eFASt *** records were reviewed to determine whether an eFASt was indicated,performed,and appropriately ***:We found that 1,507 of 1,597 trauma patients had indications for eFASt,but 396(27%)of these patients did not have a billed *** these 396 patients,87(22%)had documentation in the provider note that an eFASt was performed but there was no separate procedure *** remaining 309(78%)did not have any documentation of the eFASt in the patient’s chart although an eFASt was recorded and reviewed during ultrasound quality ***:A significant proportion of trauma patients had eFASt exams performed but were not documented or *** of documentation was *** ultrasound programs require appropriate reimbursement to support training,credentialing,equipment,quality assurance,and device *** study demonstrates a significant absence of adequate documentation leading to potential revenue loss for an emergency ultrasound program.

关键词： Point-of-care ultrasound Emergency medicine Focused assessment withsonography in trauma trauma activation Blunt trauma

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Precision measurements of strangeness photoproduction at threshold energies with the crystal Ball at MAMI-c

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chinese Physics c 2009年第12期33卷 1358-1361页

作者： t. c. Jude d. I Glazier d. P. Watts the University of Edinburgh Edinburgh EH9 3JZ UK

the photoproduction of K＋ mesons from the nucleon provides important constraints on the nucleon excitation spectrum and at threshold energies challenges effective field theories based on chiral perturbation in the strange quark sector. Preliminary cross-section measurements for γ（P, K＋）A are presented at an unprecedented beam energy resolution. the data was collected at the MAMI-c facility in Mainz using the crystal Ball detector. A new method of K＋ detection was used in which the K＋ is tagged from its weak decay products in the detector crystals. this technique has application with other calorimeters at present and future hadron facilities.

关键词： crystal Ball detector strange meson photoproduction

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cleaning properties of dry adhesives

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Science china(technological Sciences) 2010年第11期53卷 2942-2946页

作者： J. P. díAZ téLLEZ d. SAMEOtO c. MENON MENRVA Group School of Engineering Science Simon Fraser University department of Mechanical Engineering University of Alberta

In this paper we present a study into the cleaning properties of synthetic dry adhesives. We have manufactured the adhesive micro-fibres through a low-cost, high yield fabrication method using Sylgard 184 Polydimethylsiloxane (PdMS) as the structural material. We deliberately contaminated the adhesive samples with different sized particles in the micro and macro scales and tested different cleaning methods for their efficacy with respect to each particle size. We investigated different cleaning methods, which included the use of wax moulding, vibration and pressure sensitive adhesives. For adhesion testing we used a custom system with a linear stage and a force sensor indenting a hemispherical probe into the adhesive surface and measuring the pull-off force. to characterize the cleaning efficacy we visually inspected each sample in a microscope and weighed the samples with a microgram-accuracy analytical balance. Results showed that the moulding method induced adhesion recovery in a greater percentage than the other cleaning methods and even helped with the recovery of collapsed posts in some cases. On the other hand pressure sensitive adhesives seem to have the upper hand with regards to certain particle sizes that can potentially pose problems with the moulding method.

关键词： biomimetic dry adhesive PdMS self-cleaning gecko climbing

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Mathematical modeling and numerical computation of the effective interfacial conditions for Stokes flow on an arbitrarily rough solid surface

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Applied Mathematics and Mechanics(English Edition) 2021年第5期42卷 721-746页

作者： A.t.tRAN H.LE QUANG Q.c.HE d.H.NGUYEN Research and Application center for technology in civil Engineering University of Transport and CommunicationsHanoi 10000Vietnam Laboratoire Modelisation et Simulation Multi-Echelle Unite Mixte de Recherche 8208Centre National de la Recherche ScientifiqueUniversite Gustave EiffelMarne-la-Vallee F-77454France School of Mechanical Engineering Southwest Jiaotong UniversityChengdu 610031China

the present work is concerned with a two-dimensional(2d)Stokes flow through a channel bounded by two parallel solid *** distance between the walls may be arbitrary,and the surface of one of the walls can be arbitrarily *** main objective of this work consists in homogenizing the heterogeneous interface between the rough wall and fluid so as to obtain an equivalent smooth slippery fluid/solid interface characterized by an effective slip *** solve the corresponding problem,two efficient numerical approaches are elaborated on the basis of the method of fundamental solution(MFS)and the boundary element methods(BEMs).they are applied to different cases where the fluid/solid interface is periodically or randomly *** results obtained by the proposed two methods are compared with those given by the finite element method and some relevant ones reported in the *** comparison shows that the two proposed methods are particularly efficient and accurate.

关键词： effective slip length method of fundamental solution(MFS) boundary element method(BEM) Stokeslet micro-channel fluid/solid interface

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Micro-scaled plastic yielding and shear-banding dynamics in metallic glasses

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Journal of Materials Science & technology 2023年第21期152卷 237-246页

作者： d.X.Han G.Wang Q.Wang R.Feng X.d.Ma K.c.chan c.t.Liu Institute of Materials Shanghai UniversityShanghai 200444China department of Industrial and Systems Engineering The Hong Kong Polytechnic UniversityHong KongChina Neutron Scattering division Oak Ridge National LaboratoryOak RidgeTN 37831United States department of Material Science and Engineering College of Science and EngineeringCity University of Hong KongHong KongChina center for Advanced Structural Materials College of Science and EngineeringCity University of Hong KongHong KongChina

Shear-banding behavior in metallic glasses plays a key role in the operation of plastic deformation,which is associated with yield *** a micro-scale,the shear-banding behavior must be affected by many factors from the test machine and the ***,in this study,comprehensively considering a machine compliance,a geometry imperfection of micro-pillar,and a substrate sink-in the machine-sample-substrate system,we developed a plastic-strength model at a micrometer scale in this study,which is evidenced by the microscale compressive properties of 18 kinds of metallic *** the-oretical model provides a guidance for the elastic limits and shear-banding dynamics of metallic glasses at the micro-scale,which can be applicable to characterize the microscale deformation behavior of other amorphous materials.

关键词： Metallic glasses Shear-banding dynamics Micro-compression Plastic deformation

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Energy principle of ferroelectric ceramics and single domain mechanical model

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Acta Mechanica Sinica 2007年第5期23卷 531-543页

作者： t.c.Wang LNM Institute of MechanicsChinese Academy of SciencesBeijing 100080China

Many physical experiments have shown that the domain switching in a ferroelectric material is a complicated evolution process of the domain wall with the variation of stress and electric field. According to this mechanism, the volume fraction of the domain switching is introduced in the constitutive law of ferroelectric ceramic and used to study the nonlinear constitutive behavior of ferroelectric body in this paper. the principle of stationary total energy is put forward in which the basic unknown quantities are the displacement ui, electric displacement di and volume fraction pI of the domain switching for the variant I. Mechanical field equation and a new domain switching criterion are obtained from the principle of stationary total energy. the domain switching criterion proposed in this paper is an expansion and development of the energy criterion. On the basis of the domain switching criterion, a set of linear algebraic equations for the volume fraction PI of domain switching is obtained, in which the coefficients of the linear algebraic equations only contain the unknown strain and electric fields. then a single domain mechanical model is proposed in this paper. the poled ferroelectric specimen is considered as a transversely isotropic single domain. By using the partial experimental results, the hardening relation between the driving force of domain switching and the volume fraction of domain switching can be calibrated. then the electromechanical response can be calculated on the basis of the calibrated hardening relation. the results involve the electric butterfly shaped curves of axial strain versus axial electric field, the hysteresis loops of electric displacement versus electric filed and the evo- lution process of the domain switching in the ferroelectric specimens under uniaxial coupled stress and electric field loading. the present theoretic prediction agrees reasonably with the experimental results given by Lynch.

关键词： Ferroelectric ceramic domain switching the volume fraction of domain switching Single domain mechanical model

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Non-parasitic splenic cysts: A report of three cases

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World Journal of Gastroenterology 2005年第43期11卷 6884-6887页

作者： Macheras A Misiakos EP Liakakos t Mpistarakis d Fotiadis c Karatzas G 3rd department of Surgery

Primary splenic cyst is a relatively rare disease, and the majority of cases are classified as epithelial cysts. three cases with nonparasitic splenic cysts are presented: two epithelial and one pseudocyst. All cases had an atypical symptomatology, consisted mainly of fullness in the left upper abdomen and a palpable mass. Preoperative diagnosis was established with ultrasonography and computerized tomography. two cases with large cysts located in the splenic hilum were treated with open complete splenectomy. the most recent case, a pseudocyst, was managed laparoscopically with partial cystectomy. All cases did not have any problems or recurrence during follow-up. Laparoscopic partial cystectomy is an acceptable procedure for the treatment of splenic cysts, because it cures the disease preserving the splenic tissue. complete splenectomy is reserved for cases in which cyst excision cannot be done otherwise.

关键词： Spleen Epithelial cyst Surgery Laparoscopy

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Bulk nanocrystalline W-ti alloys with exceptional mechanical properties and thermal stability

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Journal of Materials Science & technology 2022年第19期114卷 16-28页

作者： H.X.Xue X.c.cai B.R.Sun X.Shen c.c.du X.J.Wang t.t.Yang S.W.Xin t.d.Shen clean Nano Energy center State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China cSSc 723rd Research Institute China State Shipbuilding Corporation LimitedYangzhou 225000China

Nanocrystalline(Nc)W metals and alloys often exhibit higher radiation tolerance and strength than their coarse-grained ***,their thermal stability is low,making it difficult to achieve bulk Nc W metals and alloys by consolidation using conventional techniques such as pressure-less sintering,hot-explosive-compaction sintering,and spark plasma *** we report the synthesis and mechanical properties of bulk Nc W_(100-x)ti_(x)(x=10 at.%-30 at.%)alloys prepared by consolidating mechanically alloyed Nc powders under a high-temperature/high-pressure *** 20 at.%-30 at.%ti largely improves the sinterability of Nc W-ti alloy *** room-temperature microhardness and compressive yield strength of consolidated bulk Nc W_(80)ti_(20) alloy are∼16.9 and 6.0 GPa,respectively,which are mainly caused by grain boundary strengthening and significantly higher than those of previously reported W and W *** ultimate compressive strength of bulk Nc W_(80)ti_(20) measured between 900 and 1100°c deceases with increasing *** behavior can be explained by the activation of Rachinger grain boundary *** grain growth is observed in bulk Nc W_(80)ti_(20) after compression at 1000°*** calculation suggests that it is the segregation of ti at grain boundaries that decreases the specific grain boundary free energy and makes the Nc W_(80)ti_(20) alloy thermodynamically stable.

关键词： Nanocrystalline W-ti alloys Segregation Grain boundary energy Strength Hardness

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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

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