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Journal of Materials Science & Technology 2019年第2期35卷 231-241页

作者： lawrence e.murr Department of Metallurgical Materials and Biomedical Engineering The University of Texas at El Paso W.M.Keck Center for 3D Innovation The University of Texas at El Paso

Additive manufacturing of porous, open-cellular metal or alloy implants, fabricated by laser or electron beam melting of a powder bed, is briefly reviewed in relation to optimizing biomechanical compatibility by assuring elastic(Young's) modulus matching of proximate bone, along with corresponding pore sizes assuring osseointegration and vasculature development and migration. In addition, associated, requisite compressive and fatigue strengths for such implants are described. Strategies for optimizing osteoblast(bone cell) development and osteoinduction as well as vascularization of tissue in 3 D scaffolds and tissue engineering constructs for bone repair are reviewed in relation to the biology of osteogenesis and neovascularization in bone, and the role of associated growth factors, bone morphogenic proteins, signaling molecules and the like. Prospects for infusing hydrogel/collagen matrices containing these cellular and protein components or surgically extracted intramedullary(bone marrow) concentrate/aspirate containing these biological and cell components into porous implants are discussed, as strategies for creating living implants, which over the long term would act as metal or alloy scaffolds.

关键词： Additive manufacturing Open cellular metal and alloy implants electron beam melting Living implant strategies Vascularization Osseointegration Osteoinduction

Frontiers of 3D Printing/Additive Manufacturing: from Human Organs to Aircraft Fabrication

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Journal of Materials Science & Technology 2016年第10期32卷 987-995页

作者： lawrence e.murr Department of Metallurgical Materials and Biomedical Engineering The University of Texas at El Paso W.M.Keck Center for 3D Innovation The University of Texas at El Paso

It has been more than three decades since stereolithography began to emerge in various forms of additive manufacturing and 3D printing. Today these technologies are proliferating worldwide in various forms of advanced manufacturing. The largest segment of the 3D printing market today involves various polymer component fabrications, particularly complex structures not attainable by other manufacturing *** printer head systems have also been adapted to selectively print various speciated human cells and special molecules in attempts to construct human organs, beginning with skin and various tissue patches. These efforts are discussed along with metal and alloy fabrication of a variety of implant and bone replacement components by creating powder layers, which are selectively melted into complex forms（such as foams and other open-cellular structures） using laser and electron beams directed by CAD software. efforts to create a ＂living implant＂ by bone ingrowth and eventual vascularization within these implants will be discussed briefly. Novel printer heads for direct metal droplet deposition as in other 3D printing systems are briefly described since these concepts will allow for the eventual fabrication of very large and complex products, including automotive and aerospace structures and components.

关键词： 3D printing/additive manufacturing Laser and electron beam melting Organ printing Organ and implant vascularization Metal droplet printing

Vascularization in interconnected 3D printed Ti-6Al-4V foams with hydrogel matrix for biomedical bone replacement implants

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Science China Materials 2018年第4期61卷 565-578页

作者： Victor L.Correa Kristine M.Garza lawrence e.murr Department of Metallurgical Materials and Biomedical Engineering University of Texas at El Paso Department of Biological Sciences University of Texas at El Paso

Vascularization on newly implanted metal orthopedic implants has remained a challenge in the field of tissue engineering. To address this challenge, in this research,an interconnected foam structure of Ti-6 Al-4 V was microfabricated by electron beam melting(eBM) technique. The foam in question has a density of 1.77 g cm-3 with 60% porosity and a tensile strength of 18 GPa. An extracellular matrix based hydrogel was added as an aqueous matrix to the *** mimetic stress has been closely related to many wound healing biomedical applications as it increases survival and proliferation molecular signals. To that end, increased expression of hypoxia-inducible factor-1α(Hif-1α) and vascular endothelial growth factor(VeGF) in the aqueous hydrogel matrix was achieved by the addition of a hypoxia mimetic deferoxamine mesylate(DFM). In this study, the formation of an endothelial network was achieved in a hydrogel matrix in the presence of the before mentioned 3 D printed metal foam. Cellular viability, fluorescent microscopy and scanning electron microscopy imaging analysis demonstrate that pre-osteoblasts undergo proliferation and also attach efficiently to the foam when exposed to DFM. Human umbilical vascular endothelial cells(HUVeCs) were grown in an extracellular matrix-like 3 D hydrogel and a hypoxia-like stress was achieved. This research demonstrates that pre-osteoblast cells undergo cell differentiation and increase the production of hydroxyapatite on exposure to the hypoxia mimetic molecule. This proposed approach encompasses an ideal prototype for a completely living implanted structure for future orthopedic implants.

关键词： Ti-6Al-4V electron beam melting angiogenesis deferoxamine mesylate hydrogel vascularization

Preface to Special Issue: Recent Advances in Additive Manufacturing of Metals and Alloys

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Journal of Materials Science & Technology 2019年第2期35卷 I0001-I0002页

作者： Yufeng Zheng lawrence e.murr Department of Materials Science and engineering College of engineering Peking University Department of Metallurgical Materials and Biomedical Engineering and W.M.Keck Center for 3D Innovation The University of Texas at El Paso

Metal and alloy component fabrication utilizing various forms of additive or layer manufacturing has become the new manufacturing paradigm worldwide. Over the past decade, the development, installation and application of various forms of metal and alloy additive manufacturing (AM) processes have increased exponentially, led in large part by laser and electron beam powder-bed melt technologies. Along with this global proliferation of new manufacturing strategies has been the corresponding proliferation of journals and books describing various aspects of additive manufacturing and 3D printing.

关键词： Special Issue Metal and alloy 3D

Microstructure and mechanical properties of Ti-6Al-4V-5% hydroxyapatite composite fabricated using electron beam powder bed fusion

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Journal of Materials Science & Technology 2019年第2期35卷 309-321页

作者： César A.Terrazas lawrence e.murr Diego Bermudez edel Arrieta David A.Roberson Ryan B.Wicker W.M.Keck Center for 3D Innovation The University of Texas at El PasoEl PasoTX 79968USA Department of Mechanical engineering The University of Texas at El PasoTX 79968USA Department of Metallurgical Materials and Biomedical EngineeringThe University of Texas at El PasoTX 79968USA

A novel, Ti-6 Al-4 V(Ti64)/Hydroxyapatite(HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion(ePBF) additive manufacturing(AM): specifically, the commercial electron beam melting(eBM?) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell(model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm^3, and corresponding Young's moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ~3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. Both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, ePBF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography(OM) and scanning electron microscopy(SeM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha(hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ~5 μm in the ePBF-fabricated Ti64 to ~1.1 m for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 m. This work highlights the use of ePBF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors' knowledge has not been reported before. The results also illu

关键词： Hydroxyapatite (HA) Metal-matrix ceramic composites Open-cellular (mesh) structures electron-beam powder bed fusion (ePBF) Additive manufacturing (AM) Mechanical properties Microstructure characterization

Hybrid post-processing effects of magnetic abrasive finishing and heat treatment on surface integrity and mechanical properties of additively manufactured Inconel 718 superalloys

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Journal of Materials Science & Technology 2022年第33期128卷 10-21页

作者： Kun Li Ruijin Ma Ming Zhang Wen Chen Xiaobin Li David Z.Zhang Qian Tang lawrence e.murr Jinfeng Li Huajun Cao State Key Laboratory of Mechanical Transmission Chongqing UniversityChongqing 400044China Chongqing Key Laboratory of Metal Additive Manufacturing(3D Printing) Chongqing UniversityChongqing 400044China College of engineering Mathematics and Physical SciencesUniversity of ExeterNorth Park RoadExeter EX44QFUK W.M.Keck Center for 3D Innovation University of Texas at El PasoEl PasoTX 79968USA Department of Metallurgical Materials and Biomedical EngineeringUniversity of Texas at El PasoEl PasoTX 79968USA Institute of Materials China Academy of Engineering PhysicsMianyang 621908China

Desired microstructure and surface integrity are critical to achieving the high performance of additively manufactured *** the present work,the hybrid post-processes of magnetic abrasive finishing(MAF)and post-heat treatment(HT)were applied to the additively manufactured Inconel718 *** hybrid effects and influencing mechanism on the surface quality and mechanical properties of the additively manufactured samples have been studied *** results show that the MAF process effectively reduces the surface roughness by more than an order of magnitude due to the flexibility and geometric consistency of the magnetic particles and abrasives with the finished *** proper sequence of MAF and HT obtains enhanced mechanical properties for the homogenized-MAF-aged sample with the yield strength of 1147 MPa,the ultimate tensile strength of 1334 MPa,and the elongation of 22.9%,which exceeds the standard wrought *** surface integrity,compressive residual stress field,and grain refinement induced by the MAF and subsequent aging heat treatment increase the cracking resistance and delay the fracture failure,which significantly benefits the mechanical *** MAF process combined with proper post-heat treatment provides an effective pathway to improve the mechanical properties of additively manufactured materials.

关键词： Magnetic abrasive finishing Additive manufacturing Inconel 718 Microstructure–property relationship Heat treatment

Fatigue behavior of Ti-6Al-4V cellular structures fabricated by additive manufacturing technique

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Journal of Materials Science & Technology 2019年第2期35卷 285-294页

作者： Dechun Ren Shujun Li Hao Wang Wentao Hou Yulin Hao Wei Jin Rui Yang R.Devesh K.Misra lawrence e.murr Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences School of Materials Science and engineering University of Science and Technology of China Department of Metallurgical and Materials engineering The University of Texas at EI Paso

Porous titanium and its alloys have been considered as promising replacement for dense implants, as they possess low elastic modulus comparable to that of compact human bones and are capable of providing space for in-growth of bony tissues to achieve a better fixation. Recently, the additive manufacturing(AM) method has been successfully applied to the fabrication of Ti-6 Al-4 V cellular meshes and *** to traditional fabrication methods, the AM method offers advantages of accurate control of complex cell shapes and internal pore architectures, thus attracting extensive attention. Considering the long-term safety in the human body, the metallic cellular structures should possess high fatigue *** this paper, the recent progress on the fatigue properties of Ti-6 Al-4 V cellular structures fabricated by the AM technique is reviewed. The various design factors including cell shapes, surface properties, post treatments and graded porosity distribution affecting the fatigue properties of additive manufactured Ti-6 Al-4 V cellular structures were introduced and future development trends were also discussed.

关键词： Ti-6Al-4V cellular structures Additive manufacturing Fatigue behavior

Preface to SPeCIAL ISSUe: Advances in Metallic Biomaterials

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Science China Materials 2018年第4期61卷 439-439页

作者： lawrence e.murr Cuie Wen Yufeng Zheng Department of Metallurgical Materials and Biomedical EngineeringUniversity of Texas at El Paso School of engineering RMIT University Department of Materials Science and engineering College of Engineering Peking University

Metallic biomaterials,especially advances in various biodegradable metallic materials and porous or open-cellular metallic materials having important applications as orthopaedic and other biomedical implants or applia... 详细信息

关键词： Advances in Metallic Biomaterials Preface to SPeCIAL ISSUe

Fabrication of open-cellular(porous) titanium alloy implants: osseointegration, vascularization and preliminary human trials

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Science China Materials 2018年第4期61卷 525-536页

作者： Shujun Li Xiaokang Li Wentao Hou Krishna C. Nune R. Devesh K. Misra Victor L. Correa-Rodriguez Zheng Guo Yulin Hao Rui Yang lawrence e. murr Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Department of Orthopedics Xijing Hospital Fourth Military Medical University Xi＇an 710032 China Department of Metallurgical Materials and Biomedical Engineering The University of Texas at El Paso El Paso TX 79968 USA

In this study we describe the fabrication of a variety of open-cellular titanium alloy（Ti-6 Al-4 V） implants,both reticular mesh and foam structures, using electron beam melting（eBM）. These structures allow for the elimination of stress shielding by adjusting the porosity（or density） to produce an elastic modulus（or stiffness） to match that of both soft（trabecular） and hard（cortical） bone, as well as allowing for bone cell ingrowth, increased cell density, and all-matrix interactions; the latter involving the interplay between bone morphogenetic protein（BMP-2） and osteoblast functions. The early formation and characterization of elementary vascular structures in an aqueous hydrogel matrix are *** results for both animal（sheep） and human trials for a number of eBM-fabricated, and often patient-specific Tialloy implants are also presented and summarized. The results, while preliminary, support the concept and development of successful, porous, engineered ＂living＂ implants.

关键词： porous implant fabrication osseointegration vascularization animal and clinical human trials

Segment routing for traffic engineering and effective recovery in low-earth orbit satellite constellations

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Digital Communications and Networks 2024年第3期10卷 706-715页

作者： Shengyu Zhang Xiaoqian Li Kwan lawrence Yeung Department of electrical and electronic engineering The University of Hong KongHKSARChina National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of ChinaChengduSichuan611731China

Low-earth Orbit Satellite Constellations(LeO-SCs)provide global,high-speed,and low latency Internet access services,which bridges the digital divide in the remote *** inter-satellite links are not supported in initial deployment(*** Starlink),the communication between satellites is based on ground stations with radio frequency *** to the rapid movement of satellites,this hybrid topology of LeO-SCs and ground stations is time-varying,which imposes a major challenge to uninterrupted service provisioning and network *** this paper,we focus on solving two notable problems in such a ground station-assisted LeO-SC topology,i.e.,traffic engineering and fast reroute,to guarantee that the packets are forwarded in a balanced and uninterrupted ***,we employ segment routing to support the arbitrary path routing in *** solve the traffic engineering problem,we proposed two source routings with traffic splitting algorithms,Delay-Bounded Traffic Splitting(DBTS)and DBTS+,where DBTS equally splits a flow and DBTS+favors shorter ***-lation results show that DBTS+can achieve about 30%lower maximum satellite load at the cost of about 10%more *** guarantee the fast recovery of failures,two fast reroute mechanisms,Loop-Free Alternate(LFA)and LFA+,are studied,where LFA pre-computes an alternate next-hop as a backup while LFA+finds a 2-segment backup *** show that LFA+can increase the percentage of protection coverage by about 15%.

关键词： Fast reroute Low-earth orbit satellite constellation Segment routing Traffic engineering Traffic splitting