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Semantic and Syntactic Matching of Heterogeneous e-Catalogues
Publication . Mehrbod, Ahmad; Grilo, António
In e-procurement, companies use e-catalogues to exchange product infor-mation with business partners. Matching e-catalogues with product requests helps the suppliers to identify the best business opportunities in B2B e-Marketplaces. But various ways to specify products and the large variety of e-catalogue formats used by different business actors makes it difficult.
This Ph.D. thesis aims to discover potential syntactic and semantic rela-tionships among product data in procurement documents and exploit it to find similar e-catalogues. Using a Concept-based Vector Space Model, product data and its semantic interpretation is used to find the correlation of product data. In order to identify important terms in procurement documents, standard e-catalogues and e-tenders are used as a resource to train a Product Named Entity Recognizer to find B2B product mentions in e-catalogues.
The proposed approach makes it possible to use the benefits of all availa-ble semantic resources and schemas but not to be dependent on any specific as-sumption. The solution can serve as a B2B product search system in e-Procurement platforms and e-Marketplaces.
Laser welding of precipitation strengthened Ni-rich NiTiHf high temperature shape memory alloys: Microstructure and mechanical properties
Publication . Oliveira, J. P.; Schell, N.; Zhou, N.; Wood, L.; Benafan, O.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; Elsevier
High temperature shape memory alloys are currently attracting significant attention by the aerospace industry due to the potential use of shape memory and superelastic properties at temperatures above 100 °C. Virtually any advanced engineering material must, at some point, be joined either to itself, to create complex shaped structures, or to other materials to increase its potential applications. In this work, laser welding of a precipitation strengthened Ni-rich NiTiHf high temperature shape memory alloy is reported for the first time. Starting with a base material aged at 500 °C for 3 h and air cooled, defect-free joints with a conduction weld mode were obtained. Microstructural characterization, facilitated via microscopy and synchrotron X-ray diffraction, revealed that the fusion zone contained a single-phase martensitic structure at room temperature, compared to a mixture of martensite and H-phase precipitates in the base material. Isothermal loading in both the martensite (at 30 °C) and austenite (at 200 °C) phases revealed equivalent strength and near-perfect superelasticity in the welded and un-welded reference material.
Effect of ultrasonic spot welding on the mechanical behaviour of NiTi shape memory alloys
Publication . Zhang, W.; Ao, S. S.; Oliveira, J. P.; Zeng, Z.; Luo, Z.; Hao, Z. Z.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; IOP Publishing
NiTi shape memory alloy joints were obtained using ultrasonic spot welding and the effect of this manufacturing process on the mechanical behaviour was investigated. Comparing to the as-received NiTi, the welded material presented increasing austenite transformation temperatures and decreasing martensite finish transformation temperatures. No detrimental intermetallic compounds were found at the weld interface due to the advantages of this solid-state welding technology. A typical interfacial fracture mode was observed at the fracture surface with numerous cleavage planes and micro cracks. Additionally, plastically deformed regions were observed in the weld spot. Ultrasonic welding can be used to effectively join NiTi shape memory alloys.
Microstructural characterization and mechanical behavior of NiTi shape memory alloys ultrasonic joints using Cu interlayer
Publication . Zhang, Wei; Ao, Sansan; Oliveira, Joao Pedro; Zeng, Zhi; Huang, Yifei; Luo, Zhen; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; Molecular Diversity Preservation International (MDPI)
NiTi shape memory alloys (SMAs) are a class of functional materials which can be significantly deformed and recover their original shape via a reversible martensitic phase transformation. Developing effective joining techniques can expand the application of SMAs in the medical and engineering fields. In this study, ultrasonic spot welding (USW), a solid-state joining technique, was used to join NiTi sheets using a Cu interlayer in between the two joining sheets. The influence of USW process on the microstructural characteristics and mechanical behavior of the NiTi joints was investigated. Compared with conventional fusion welding techniques, no intermetallic compounds formed in the joints, which is extreme importance for this particular class of alloys. The joining mechanisms involve a combination of shear plastic deformation, mechanical interlocking and formation of micro-welds. A better bonding interface was obtained with higher welding energy levels, which contributed to a higher tensile load. An interfacial fracture mode occurred and the fracture surfaces exhibited both brittle and ductile-like characteristics with the existence of tear ridges and dimples. The fracture initiated at the weak region of the joint border and then propagated through it, leading to tearing of Cu foil at the fracture interface.
Non-destructive microstructural analysis by electrical conductivity: Comparison with hardness measurements in different materials
Publication . Sorger, Gonçalo L.; Oliveira, J. P.; Inácio, Patrick L.; Enzinger, Norbert; Vilaça, Pedro; Miranda, R. M.; Santos, Telmo G.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; Elsevier
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 Ti6Al4V, 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.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
5876
Número da atribuição
PEst-OE/EME/UI0667/2014