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Non-destructive microstructural analysis by electrical conductivity:Comparison with hardness measurements in different materials

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Journal of Materials Science & Technology 2019年第3期35卷 360-368页

作者： Gon?alo L.Sorger J.P.Oliveira Patrick L.Inácio Norbert Enzinger Pedro Vila? R.M.Miranda Telmo G.Santos Department of Engineering Design and Production School of Engineering Aalto University Department of Materials Science and Engineering The Ohio State University unidemi Departamento de Engenharia Mecanica e Industrial Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa IMAT-Institute of Materials Science Joining and FormingTU Graz

The use of non-destructive evaluation(NDE) techniques for assessing microstructural changes in processed materials is of particular importance as it can be used to assess, qualitatively, the integrity of any material/structure. Among the several NDE techniques available, electrical conductivity measurements using eddy currents attract great attention owing to its simplicity and reliability. In this work, the electrical conductivity profiles of friction stir processed Ti6Al4 V, Cu, Pb, S355 steel and gas tungsten arc welded AISI 304 stainless steel were determined through eddy currents and four-point probe. In parallel, hardness measurements were also performed. The profiles matched well with the optical macrographs of the materials: while entering in the processed region a variation in both profiles was always observed. One particular advantage of electrical conductivity profiles over hardness was evident: it provides a better resolution of the microstructural alterations in the processed materials. Moreover, when thermomechanical processing induces microstructural changes that modify the magnetic properties of a material,eddy currents testing can be used to qualitatively determine the phase fraction in a given region of the material. A qualitative relation between electrical conductivity measurements and hardness is observed.

关键词： Non-destructive evaluation techniques Electrical conductivity Hardness Friction stir processing Gas tungsten arc welding

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Revealing microstructural evolution and mechanical properties of resistance spot welded NiTi-stainless steel with Ni or Nb interlayer

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Journal of Materials Science & Technology 2024年第13期180卷 160-173页

作者： K.Zhang A.Shamsolhodaei A.Ghatei-Kalashami J.P.Oliveira C.Zang N.Schell J.Li A.R.H.Midawi J.G.Lopes J.Yan P.E.J.Rivera-Díaz-del-Castillo P.Peng Y.N.Zhou Department of Mechanical and Mechatronics Engineering University of Waterloo200 University Avenue WestWaterlooONN2L 3G1Canada CENIMAT/I3N Department of Materials ScienceNOVA School of Science and TechnologyUniversidade NOVA de Lisboa2829-516CaparicaPortugal Materials Research Group Department of Mechanical EngineeringUniversity of SouthamptonSouthamptonSO171BJUK Helmholtz-Zentrum Hereon Institute of Materials PhysicsMax-Planck-Str.1Geesthacht21502Germany unidemi Department of Mechanical and Industrial EngineeringNOVA School of Science and TechnologyUniversidade NOVA de Lisboa2829-516CaparicaPortugal

Dissimilar welding of NiTi and stainless steel(SS)for multifunctional device fabrication is challenging due to the brittle nature of intermetallic compounds(IMCs)that are formed in the weld *** this work,Ni and Nb interlayers were applied for the resistance spot welding(RSW)of NiTi and SS to replace the harmful Fe_(2)Ti phase and to restrict the mixing of dissimilar molten metals,*** evolution and mechanical properties of the joints were *** was shown that a conventional weld nugget was created in the absence of any interlayer in the welded joint suffering from traversed cracks due to the formation of brittle IMCs network in the fusion zone(FZ).By the addition of Ni from the interlayer,Fe_(2)Ti dominated weld nugget was efficaciously replaced by Ni_(3)Ti phase;however,the presence of the large pore and cracks reduced the effective joining *** use of a Nb interlayer resulted in a fundamentally different joint,in which FZs at NiTi and SS sides separated by the unmolten Nb would suppress the mixing of dissimilar molten ***-containing eutectic structures with low brittleness formed at the interfaces,contributing to the enhancement of joint strength(increased by 38%on fracture load and 460%on energy absorption).A high-melting-point interlayer showed great potential to realize a reliable and high-performing RSWed NiTi-SS joint.

关键词： NiTi Stainless steel Resistance spot welding Intermetallic compounds Mechanical properties

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Radiotherapy-customized head immobilization masks:from modeling and analysis to 3D printing

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Nuclear Science and Techniques 2019年第9期30卷 103-118页

作者： M.A.R.Loja D.S.Craveiro L.Vieira E.Sousa J.A.Rodrigues R.J.F.Portal CIMOSM Centro de Investigacao em Modelacao e Optimizacao de Sistemas Multifuncionais ISEL IPL Instituto Superior de Engenharia de Lisboa Av. Conselheiro Emidio Navarro 1 1959-007 Lisbon Portugal LAETA IDMEC Instituto Superior Teccnico Universidade de Lisboa Av. Rovisco Pais 1 1049-001 Lisbon Portugal Department of Mechanical and Industrial Engineering Faculty of Science and Technology NOVA UNIDEMI Universidade Nova de Lisboa Caparica Portugal H&TRC -Health &Technology Research Center ESTeSL - Escola Superior de Tecnologia da Saude de Lisboa Av. D. Joao II Lote 4.69.01 1990-096 Lisbon Portugal Instituto de Biofisica e Engenharia Biomedica Faculdade de Ciencias da Universidade de Lisboa Lisbon Portugal

Immobilization devices may be a valuable aid to ensure the improved effectiveness of radiotherapy treatments where constraining the movements of specific anatomical segments is crucial. This need is also present in other situations, specifically when the superposition of various medical images is required for fine identification and characterization of some pathologies. Because of their structural characteristics, existing head immobilization systems may be claustrophobic and very uncomfortable for patients, during both the modeling and usage stages. Because of this, it is important to minimize all the discomforts related to the mask to alleviate patients’ distress and to simultaneously guarantee and maximize the restraint effectiveness of the mask. In the present work, various head immobilization mask models are proposed based on geometrical information extracted from computerized tomography images and from 3D laser scanning point clouds. These models also consider the corresponding connection to a radiotherapy table, as this connection is easily altered to accommodate various manufacturers’ solutions. A set of materials used in the radiotherapy field is considered to allow the assessment of the stiffness and strength of the masks when submitted to typical loadings.

关键词： Computed tomography 3D laser scanning Geometric modeling Head immobilization devices Stiffness and strength analyses 3D printing

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