Development of an experimental setup for metal cutting research

Analytical, numerical and experimental models have been developed over time to try to characterize and understand the metal cutting process by chip removal. A true knowledge of the cutting process by chip removal is required by the increasing production, by the quality requirements of the product and by the reduced production time, in the industries in which it is employed. In this thesis an experimental setup is developed to evaluate the forces and the temperature distribution in the tool according to the orthogonal cutting model conditions, in order to evaluate its performance and its possible adoption in future works. The experimental setup is developed in a CNC lathe and uses an orthogonal cutting configuration, in which thin discs fixed onto a mandrel are cut by the cutting insert. In this experimental setup, the forces are measured by a piezoelectric dynamometer while temperatures are measured by thermocouples placed juxtaposed to the side face of the cutting insert. Three different solutions are implemented and evaluated for the thermocouples attachment in the cutting insert: thermocouples embedded in thermal paste, thermocouples embedded in copper plate and thermocouples brazed in the cutting insert. From the tests performed in the experimental setup it is concluded that the adopted forces measurement technique shows a good performance. Regarding to the adopted temperatures measurement techniques, only the thermocouples brazed in the cutting insert solution shows a good performance for temperature measurement. The remaining solutions show contact problems between the thermocouple and the side face of the cutting insert, especially when the vibration phenomenon intensifies during the cut. It is concluded that the experimental setup does not present a sufficiently robust and reliable performance, and that it can only be used in future work after making improvements in the assembly of the thermocouples.

An investigation of safety design practices of metal machines

BACKGROUND: Machinery safety issues are a challenge facing manufacturers who are supposed to create and provide products in a better and faster way. In spite of their construction and technological advance, they still contribute to many potential hazards for operators and those nearby. OBJECTIVE: The aim of this study is to investigate safety aspects of metal machinery offered for sale on Internet market according to compliance with minimum and fundamental requirements. METHODS: The study was carried out with the application of a checklist prepared on the basis of Directive 2006/42/EC and Directive 2009/104/EC and regulations enforcing them into Polish law. RESULTS: On the basis of the study it was possible to reveal the safety aspects that were not met in practice. It appeared that in the case of minimum requirements the most relevant problems concerned information, signal and control elements, technology and machinery operations, whereas as far as fundamental aspects are concerned it was hard to assure safe work process. CONCLUSIONS: In spite of the fact that more and more legal acts binding in the Member Countries of the European Union are being introduced to alleviate the phenomenon, these regulations are often not fulfilled.

Analysis of polydicyclopentadiene-metal hybrid adhesive joints for automotive exterior body applications

An exterior body panel solution containing a polydicyclopentadiene skin attached to an interior metallic reinforcement through adhesive bonding is being studied to be applied in the MobiCar bonnet. With this solution is expected to achieve lightness, adequate structural integrity and cost-efficiency. However, there is uncertainty regarding to the bonnet adhesiveness since different metallic materials and adhesive types are being considered for its development. Thus, in this paper, several samples are tested through shear loading with the aim of understanding the loading magnitude expected by using polydicyclopentadiene, steel DC04+ZE and aluminum alloy AW5754-H111 as substrates adhesively bonded by an epoxy or a methacrylate. Methacrylate adhesive have shown greater shear strength in all types of adhesive joints. PDCPD joints presented the highest displacements. Surface degradation was considered adequate over abrading once none strength difference was seen between the different surface treatments. Steel treated by cataphoresis has shown the highest joint interface strength.

(Un)suitability of the use of pH buffers in biological, biochemical and environmental studies and their interaction with metal ions - a review

The use of buffers to maintain the pH within a desired range is a very common practice in chemical, biochemical and biological studies. Among them, zwitterionic N-substituted aminosulfonic acids, usually known as Good's buffers, although widely used, can complex metals and interact with biological systems. The present work reviews, discusses and updates the metal complexation characteristics of thirty one commercially available buffers. In addition, their impact on biological systems is also presented. The influences of these buffers on the results obtained in biological, biochemical and environmental studies, with special focus on their interaction with metal ions, are highlighted and critically reviewed. Using chemical speciation simulations, based on the current knowledge of the metal-buffer stability constants, a proposal of the most adequate buffer to employ for a given metal ion is presented.

Search for heavy lepton resonances decaying to a Z boson and a lepton in pp collisions at s√=8 TeV with the ATLAS detector

A search for heavy leptons decaying to a Z boson and an electron or a muon is presented. The search is based on pp collision data taken at s√=8 TeV by the ATLAS experiment at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb−1. Three high-transverse-momentum electrons or muons are selected, with two of them required to be consistent with originating from a Z boson decay. No significant excess above Standard Model background predictions is observed, and 95% confidence level limits on the production cross section of high-mass trilepton resonances are derived. The results are interpreted in the context of vector-like lepton and type-III seesaw models. For the vector-like lepton model, most heavy lepton mass values in the range 114-176 GeV are excluded. For the type-III seesaw model, most mass values in the range 100-468 GeV are excluded.

Search for a Heavy Neutral Particle Decaying to eμ, eτ, or μτ in pp Collisions at s√=8 TeV with the ATLAS Detector

This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, e±μ∓, e±τ∓, or μ±τ∓ using 20.3 fb−1 of pp collision data at s√=8 TeV collected by the ATLAS detector at the LHC. The numbers of observed candidate events are compatible with the Standard Model expectations. Limits are set on the cross section of new phenomena in two scenarios: the production of ν~τ in R-parity-violating supersymmetric models and the production of a lepton-flavor-violating Z′ vector boson.

Search for heavy long-lived multi-charged particles in pp collisions at √s = 8 TeV using the ATLAS detector

A search for heavy long-lived multi-charged particles is performed using the ATLAS detector at the LHC. Data collected in 2012 at s√=8 TeV from pp collisions corresponding to an integrated luminosity of 20.3 fb−1 are examined. Particles producing anomalously high ionisation, consistent with long-lived massive particles with electric charges from |q|=2e to |q|=6e are searched for. No signal candidate events are observed, and 95% confidence level cross-section upper limits are interpreted as lower mass limits for a Drell--Yan production model. The mass limits range between 660 and 785 GeV.

Search for type-III Seesaw heavy leptons in pp collisions at s√=8 TeV with the ATLAS Detector

A search for the pair-production of heavy leptons (N0,L±) predicted by the type-III seesaw theory formulated to explain the origin of small neutrino masses is presented. The decay channels N0→W±l∓ (ℓ=e,μ,τ) and L±→W±ν (ν=νe,νμ,ντ) are considered. The analysis is performed using the final state that contains two leptons (electrons or muons), two jets from a hadronically decaying W boson, and large missing transverse momentum. The data used in the measurement correspond to an integrated luminosity of 20.3fb−1 of pp collisions at s√=8 TeV collected by the ATLAS detector at the LHC. No evidence of heavy lepton pair-production is observed. Heavy leptons with masses below 325--540 GeV are excluded at the 95% confidence level, depending on the theoretical scenario considered.

Search for dark matter in events with heavy quarks and missing transverse momentum in pp collisions with the ATLAS detector

This article reports on a search for dark matter pair production in association with bottom or top quarks in 20.3fb−1 of pp collisions collected at s√=8 TeV by the ATLAS detector at the LHC. Events with large missing transverse momentum are selected when produced in association with high-momentum jets of which one or more are identified as jets containing b-quarks. Final states with top quarks are selected by requiring a high jet multiplicity and in some cases a single lepton. The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter--nucleon cross-section for spin-independent and spin-dependent interactions are also provided. These limits are particularly strong for low-mass dark matter. Using a simplified model, constraints are set on the mass of dark matter and of a coloured mediator suitable to explain a possible signal of annihilating dark matter.

Search for heavy Majorana neutrinos with the ATLAS detector in pp collisions at s√=8 TeV

A search for heavy Majorana neutrinos in events containing a pair of high-pT leptons of the same charge and high-pT jets is presented. The search uses 20.3fb−1 of pp collision data collected with the ATLAS detector at the CERN Large Hadron Collider with a centre-of-mass energy of s√=8 TeV. The data are found to be consistent with the background-only hypothesis based on the Standard Model expectation. In the context of a Type-I seesaw mechanism, limits are set on the production cross-section times branching ratio for production of heavy Majorana neutrinos in the mass range between 100 and 500 GeV. The limits are subsequently interpreted as limits on the mixing between the heavy Majorana neutrinos and the Standard Model neutrinos. In the context of a left-right symmetric model, limits on the production cross-section times branching ratio are set with respect to the masses of heavy Majorana neutrinos and heavy gauge bosons WR and Z′.

Searches for heavy long-lived charged particles with the ATLAS detector in proton--proton collisions at s√ = 8 TeV

Searches for heavy long-lived charged particles are performed using a data sample of 19.8 fb−1 from proton--proton collisions at a centre-of-mass energy of s√ = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. No excess is observed above the estimated background and limits are placed on the mass of long-lived particles in various supersymmetric models. Long-lived tau sleptons in models with gauge-mediated symmetry breaking are excluded up to masses between 440 and 385 GeV for tan(beta) between 10 and 50, with a 290 GeV limit in the case where only direct tau slepton production is considered. In the context of simplified LeptoSUSY models, where sleptons are stable and have a mass of 300 GeV, squark and gluino masses are excluded up to a mass of 1500 and 1360 GeV, respectively. Directly produced charginos, in simplified models where they are nearly degenerate to the lightest neutralino, are excluded up to a mass of 620 GeV. R-hadrons, composites containing a gluino, bottom squark or top squark, are excluded up to a mass of 1270, 845 and 900 GeV, respectively, using the full detector; and up to a mass of 1260, 835 and 870 GeV using an approach disregarding information from the muon spectrometer.

Aplicação de ferramentas Lean e gestão da manutenção numa metalomecânica

Dissertação de mestrado em Engenharia e Gestão da Qualidade

Organic-inorganic hybrid sol-gelcoatings for metal corrosion protection: a review of recent progress

This paper is a review of the most recent and relevant achievements (from 2001 to 2013) on the development of organic–inorganic hybrid (OIH) coatings produced by sol–gel-derivedmethods to improve resistance to oxidation/corrosion of different metallic substrates and their alloys. This review is focused on the research of OIH coatings based on siloxanes using the sol–gel process conducted at an academic level and aims to summarize the materials developed and identify perspectives for further research. The fundamentals of sol–gel are described, including OIH classification, the interaction with the substrate, their advantages, and limitations. The main precursors used in the synthesis ofOIHsol–gel coatings for corrosion protection are also discussed, according to the metallic substrate used. Finally, a multilayer system to improve the resistance to corrosion is proposed, based on OIH coatings produced by the sol–gel process, and the future research challenges are debated.

Electronic structure and optical signatures of semiconducting transition metal dichalcogenide nanosheets

CONSPECTUS: Two-dimensional (2D) crystals derived from transition metal dichalcogenides (TMDs) are intriguing materials that offer a unique platform to study fundamental physical phenomena as well as to explore development of novel devices. Semiconducting group 6 TMDs such as MoS2 and WSe2 are known for their large optical absorption coefficient and their potential for high efficiency photovoltaics and photodetectors. Monolayer sheets of these compounds are flexible, stretchable, and soft semiconductors with a direct band gap in contrast to their well-known bulk crystals that are rigid and hard indirect gap semiconductors. Recent intense research has been motivated by the distinct electrical, optical, and mechanical properties of these TMD crystals in the ultimate thickness regime. As a semiconductor with a band gap in the visible to near-IR frequencies, these 2D MX2 materials (M = Mo, W; X = S, Se) exhibit distinct excitonic absorption and emission features. In this Account, we discuss how optical spectroscopy of these materials allows investigation of their electronic properties and the relaxation dynamics of excitons. We first discuss the basic electronic structure of 2D TMDs highlighting the key features of the dispersion relation. With the help of theoretical calculations, we further discuss how photoluminescence energy of direct and indirect excitons provide a guide to understanding the evolution of the electronic structure as a function of the number of layers. We also highlight the behavior of the two competing conduction valleys and their role in the optical processes. Intercalation of group 6 TMDs by alkali metals results in the structural phase transformation with corresponding semiconductor-to-metal transition. Monolayer TMDs obtained by intercalation-assisted exfoliation retains the metastable metallic phase. Mild annealing, however, destabilizes the metastable phase and gradually restores the original semiconducting phase. Interestingly, the semiconducting 2H phase, metallic 1T phase, and a charge-density-wave-like 1T' phase can coexist within a single crystalline monolayer sheet. We further discuss the electronic properties of the restacked films of chemically exfoliated MoS2. Finally, we focus on the strong optical absorption and related exciton relaxation in monolayer and bilayer MX2. Monolayer MX2 absorbs as much as 30% of incident photons in the blue region of the visible light despite being atomically thin. This giant absorption is attributed to nesting of the conduction and valence bands, which leads to diversion of optical conductivity. We describe how the relaxation pathway of excitons depends strongly on the excitation energy. Excitation at the band nesting region is of unique significance because it leads to relaxation of electrons and holes with opposite momentum and spontaneous formation of indirect excitons.

Imidazo-benzocrown ether functionalised amino acids: synthesis and fluorimetric chemosensing studies with metal cations

Comunicação em painel - P59