The minimum quantity of lubricant technique in grinding of steel using a wheel cleaning system

The application of minimum quantity of lubricant (MQL) for metal cutting has emerged as an alternative for reducing the abundant flow of cutting fluids, thus achieving cleaner production. Although considered an innovative technique in grinding operations, the widespread application is hindered mainly due to the high heat generation and the clogging of wheel pores caused by machined chips, harming the final product quality and increasing tool wear. This study sought to improve MQL use in grinding. Thus, besides the conventional MQL injected at the wheel/workpiece interface, a compressed air jet was also added, in order to clean the clogged wheel pores from the mixture of MQL oil and machined chips. Experiments were conducted using external cylindrical plunge grinding on AISI 4340 quenched and tempered steel, and a vitrified cubic boron nitrite (CBN) wheel. The lubri-refrigeration methods employed were the conventional with abundant flow, conventional MQL (both without any cleaning air jets) and MQL with the cleaning jet, directed at the surface at different angles of incidence. The main goal of these experiments was to verify the viability of replacing traditional abundance flow with MQL with wheel cleaning. The analyses were conducted by measuring the following output variables of the process: workpiece surface roughness, roundness, diametrical wear of the wheel. Results show the possibility of implementing the cleaning jet technique as a technological improvement of the minimum quantity of and grinding, in order to reduce the usage of cutting fluids. The MQL technique with cleaning compressed air jet, for a specific angle of incidence (30°) proved to be extremely efficient to obtain improved surface quality and accurate workpiece shape, as well as to reduce wear wheel and to prevent thermal damage, when compared to the other lubri-refrigeration methods tested (without cleaning jet).Special thanks to FAPESP (State of São Paulo Research Assistance Foundation) (process 2009/51440-5 (Research Assistance) and 2009/51439-7 (Scientific Initiation)) for the financial resources made available for this study, and to the Schaeffler Group (INA brand) for the support offered in conducting metallographic analyses

Monitoring Single-point Dressers Using Fuzzy Models

AbstractGrinding causes progressive dulling and glazing of the grinding wheel grains and clogging of the voids on the wheel's surface with ground metal dust particles, which gradually increases the grinding forces. The condition of the grains at the periphery of a grinding wheel strongly influences the damage induced in a ground workpiece. Therefore, truing and dressing must be carried out frequently. Dressing is the process of conditioning the grinding wheel surface to reshape the wheel when it has lost its original shape through wear, giving the tool its original condition of efficiency. Despite the very broad range of dressing tools available today, the single-point diamond dresser is still the most widely used dressing tool due to its great versatility. The aim of this work is to predict the wear level of the single-point dresser based on acoustic emission and vibration signals used as input variables for fuzzy models. Experimental tests were performed with synthetic diamond dressers on a surface-grinding machine equipped with an aluminum oxide grinding wheel. Acoustic emission and vibration sensors were attached to the tool holder and the signals were captured at 2MHz. During the tests, the wear of the diamond tip was measured every 20 passes using a microscope with 10 to 100 X magnification. A study was conducted of the frequency content of the signals, choosing the frequency bands that best correlate with the diamond's wear. Digital band-pass filters were applied to the raw signals, after which two statistics were calculated to serve as the inputs for the fuzzy models. The results indicate that the fuzzy models using the aforementioned signal statistics are highly effective for predicting the wear level of the dresser

The HERMES Dual-Radiator Ring Imaging Cerenkov Detector

The construction and use of a dual radiator Ring Imaging Cerenkov(RICH) detector is described. This instrument was developed for the HERMES experiment at DESY which emphasizes measurements of semi-inclusive deep-inelastic scattering. It provides particle identification for pions, kaons, and protons in the momentum range from 2 to 15 GeV, which is essential to these studies. The instrument uses two radiators, C4F10, a heavy fluorocarbon gas, and a wall of silica aerogel tiles. The use of aerogel in a RICH detector has only recently become possible with the development of clear, large homogeneous and hydrophobic aerogel. A lightweight mirror was constructed using a newly perfected technique to make resin-coated carbon-fiber surfaces of optical quality. The photon detector consists of 1934 photomultiplier tubes for each detector half, held in a soft steel matrix to provide shielding against the residual field of the main spectrometer magnet.Comment: 25 pages, 23 figure

Analysis of the influence of the different times of polymerization by incandescent light in composite resins by evaluation of its abrasive wear

No mercado atual a qualidade é necessária na fabricação dos produtos. No mercado odontológico, as resinas compostas são cada vez mais utilizadas para substituir materiais tradicionais, como amalgama, nas restaurações estéticas e funcionais, apresentando boa estética e funcionalidade. A composição química destes materiais é variável e os resultados das reações químicas do processo de polimerização são bastante desconhecidos. O objetivo deste trabalho era medir a resistência do desgaste abrasivo de seis resinas compostas vendidas no mercado brasileiro polimerizadas com tempos de 10, 20 e 40 segundos. O método do disco retificado modificado para aplicações em odontologia foi usado para tornar esta proposta viável. Neste banco de ensaios um disco dinâmico, revestido por porcelana, desgasta um disco estático revestido do tipo de resina que se pretende avaliar, que foi polimerizada durante um tempo pré-estabelecido. Com a determinação do desgaste de material, num determinado tempo, determinava-se a agressividade (capacidade de um material para desgastar outro material) do disco dinâmico sobre o disco estático. Utilizando-se para isso um programa computacional (LabView). Posteriormente era feita a regressão linear dos valores obtidos e determinado o coeficiente angular, utilizado no cálculo de agressividade. Valores elevados de agressividade indicam uma maior agressão do disco dinâmico contra o disco estático. Os resultados mostraram um comportamento variável para cada material que foi polimerizado nos diferentes tempos de polimerização utilizado, mostrando que o método para fazer estudos de desgaste é prático e rápido para testar materiais novos antes da sua utilização.1317787Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Não temIn the current market an increasing quality is demanded to manufacture products. At the odontologic market the composed resins are becoming more and more used to replace old materials, like amalgamates in the aesthetic and functional restorations, since they present a better appearance and easier manuscript. The chemical composition of these materials varies and the results of the chemical reactions of polymerization processes are quite unknown. The aim of this work was to measure the resistance of the abrasive wear of six composed resins sold in Brazilian market when displayed to polymerization periods of 10, 20 and 40 seconds. The grinding disc method appropriated for odontology was used to make this process possible. For this a bank of assays in which a porcelain covered dynamic disc consumes a static disc recovered by the polymerized resin is used to demonstrate the method in a pre-established time. The abrasive wear was determined by the calculation of the aggressiveness (capacity of a material to consume another). This aggressiveness is determined by an initial graph of displacement for time, through the computational method (LabView program). After they have passed through a linear regression the results give as a possibility the angular coefficient, considered a parameter at the calculation of aggressiveness. Higher values of aggressiveness which means a higher aggression suffered by the resin disc indicate worse resistance to the abrasive consuming of this resin in relation to porcelain. The results showed a variable comportment for each material ahead the different polymerization time, which prove the importance in create a practical and fast analyses method to test new materials before their us

Menus for Feeding Black Holes

Black holes are the ultimate prisons of the Universe, regions of spacetime where the enormous gravity prohibits matter or even light to escape to infinity. Yet, matter falling toward the black holes may shine spectacularly, generating the strongest source of radiation. These sources provide us with astrophysical laboratories of extreme physical conditions that cannot be realized on Earth. This chapter offers a review of the basic menus for feeding matter onto black holes and discusses their observational implications.Comment: 27 pages. Accepted for publication in Space Science Reviews. Also to appear in hard cover in the Space Sciences Series of ISSI "The Physics of Accretion onto Black Holes" (Springer Publisher

The Q2Q^2-dependence of the generalised Gerasimov-Drell-Hearn integral for the deuteron, proton and neutron

The Gerasimov-Drell-Hearn (GDH) sum rule connects the anomalous contribution to the magnetic moment of the target nucleus with an energy-weighted integral of the difference of the helicity-dependent photoabsorption cross sections. The data collected by HERMES with a deuterium target are presented together with a re-analysis of previous measurements on the proton. This provides a measurement of the generalised GDH integral covering simultaneously the nucleon-resonance and the deep inelastic scattering regions. The contribution of the nucleon-resonance region is seen to decrease rapidly with increasing $Q^2$. The DIS contribution is sizeable over the full measured range, even down to the lowest measured $Q^2$. As expected, at higher $Q^2$ the data are found to be in agreement with previous measurements of the first moment of $g_1$. From data on the deuteron and proton, the GDH integral for the neutron has been derived and the proton--neutron difference evaluated. This difference is found to satisfy the fundamental Bjorken sum rule at $Q^2 = 5$ GeV$^2$.Comment: 12 pages, 10 figure

Measurement of the Proton Spin Structure Function g1p with a Pure Hydrogen Target

A measurement of the proton spin structure function g1p(x,Q^2) in deep-inelastic scattering is presented. The data were taken with the 27.6 GeV longitudinally polarised positron beam at HERA incident on a longitudinally polarised pure hydrogen gas target internal to the storage ring. The kinematic range is 0.021<x<0.85 and 0.8 GeV^2<Q^2<20 GeV^2. The integral Int_{0.021}^{0.85} g1p(x)dx evaluated at Q0^2 of 2.5 GeV^2 is 0.122+/-0.003(stat.)+/-0.010(syst.).Comment: 7 pages, 3 figures, 1 table, RevTeX late

Subleading-twist effects in single-spin asymmetries in semi-inclusive deep-inelastic scattering on a longitudinally polarized hydrogen target

Single-spin asymmetries in the semi-inclusive production of charged pions in deep-inelastic scattering from transversely and longitudinally polarized proton targets are combined to evaluate the subleading-twist contribution to the longitudinal case. This contribution is significantly positive for (\pi^+) mesons and dominates the asymmetries on a longitudinally polarized target previously measured by \hermes. The subleading-twist contribution for (\pi^-) mesons is found to be small