A New Approach For Dressing Operation Monitoring Using Voltage Signals Via Impedance-Based Structural Health Monitoring

Among the methods used in structural health monitoring (SHM), the electromechanical impedance technique (EMI), which uses piezoelectric transducers of lead zirconate titanate (PZT), stands out for its low cost. This paper presents a new approach for monitoring of the dressing operation based on structural health monitoring from the digital processing of voltage signals based on the time-domain response of a PZT transducer by EMI method. Experimental tests of the dressing process were performed by using a single-point dresser equipped with a natural diamond. The voltage signals in the time-domain were collected in different damage levels using a measurements EMI System. By using damage metrics, it was possible to qualify different damage levels that the diamond suffered during the dressing operation, observing variations from the magnitude of the signals. The dressing operation is of utmost importance for the grinding process and the dresser wear negatively affects the result of the process, which owns high added value. In this way, this work contributes with a new monitoring tool which aims ensuring a consistent dressing operation.Keywords: Manufacturing process, automation, electromechanical impedance, dressing operation

Contribuição ao Processo de Afiação de Ferramentas Monocortantes de Aço Rápido

Apesar do grande desenvolvimento de ferramentas com insertos de metal duro, material cerâmico e outros nas últimas três décadas, algumas das ferramentas de corte ainda necessitam ser reafiadas após a perda do corte por meio do processo de afiação com rebolos abrasivos. A afiação tem como objetivo gerar as arestas de corte de ferramentas novas ou restabelecer as arestas de corte de ferramentas desgastadas e, para que este processo seja eficiente, ela dependerá da seleção correta dos parâmetros de corte, da máquina ferramenta e habilidade do operador. Se neste processo um parâmetro de corte não for corretamente selecionado a geome-tria poderá ser comprometida e, no pior dos casos, a peça poderá sofrer queima. A queima leva, na maioria dos casos, à perda da dureza da ferramenta, propriedade essencial para que a ferramenta consiga resistir aos esforços durante a usinagem como, por exemplo, quando uma ferramenta monocortante de aço rápido é em-pregada no processo de torneamento cilíndrico de aços ao carbono. A fim de estudar o processo de afiação deste tipo de ferramenta, esta pesquisa aborda o procedimento de afiação com quatro diferentes valores de profundidade de corte, considerado um dos principais parâmetros que afeta a qualidade da geometria gerada. Utilizou-se um rebolo do tipo copo reto de óxido de alumínio branco, típico para esta operação. O material da peça foi o aço rápido (HSS) com dureza de 62 À 2 HRC. As variáveis de saída foram os ângulos de saída, de posição principal e de posição secundário, que foram medidos com o auxílio de um projetor de perfil e um transferidor universal (apenas para o ângulo de saída). Além disso, a incerteza de medição foi calculada para caracterizar a dispersão dos valores atribuídos a cada ângulo medido. Os resultados mostraram que houve variação nas medidas dos ângulos em função da penetração de trabalho, como esperado, e que a maior exati-dão dos ângulos gerados foi obtida após a profundidade de corte igual a 0,06 mm. Não houve formação de rebarba e nem a presença de queima das superfícies usinadas

Surface Quality Evaluation of Various Metals After Grinding with Aluminum Oxide Grinding Wheel

Different metals can respond differently when grinding using the same abrasive grinding wheel, especially in terms of surface quality. In this context, this work aims give a contribution to the metalworking industry by presenting the results of surface finishing after grinding the following metals: VP Atlas steel grade, Gray Cast Iron and two superalloys, Inconel 718 and Ti-6Al-4V. Tests were performed with the aluminum oxide grinding wheel and with following parameters: cutting speed of 37.6 m/s and workspeed of 10 m/min. Two values of depth of cut (15 μm and 30 μm) were tested. The surface roughness (Ra and Rz parameters) were analyzed and SEM images of the machined surfaces were taken and analyzed in order to identify the cutting mechanisms and provide better results discussion. The results showed that the surface roughness increased with the depth of cut; Ra values kept below 0.48 μm for all metals tested. Regarding the machined surface quality, some cracks were observed on the gray cast iron and Ti-6Al-4V surfaces, thereby indicating their relative lower grindability compared to VP Atlas steel under the investigated conditions. No visual thermal damage was observed in the machined surfaces of the samples

Grindability of nickel alloys Inconel 625 and Inconel 718

Nickel-based superalloys are classified as difficult-to-cut materials. This difficulty becomes worse when these materials are processed by grinding, thus requiring more attention in the selection of proper grinding parameters. Among the nickel-based superalloys, the Inconel 718 is the most used alloy, however, the Inconel 625 alloy is also important because of its peculiar properties such as resistance to aqueous and hot corrosions, high strength and resistance to creep. In this sense and motivated by the lack of information about grinding of Inconel 625 alloy, this work evaluates the grindability of this superalloy and compares to the Inconel 718, in several operational conditions. The tests were divided in two stages. In the first stage, the effect of the main input parameters (depth of cut – ae, workspeed – vw, cutting speed – vs, grinding wheel mesh and grinding direction) was evaluated for the Inconel 625 based on surface roughness (Ra and Rz), grinding forces and specific energy in order to determine the statistically significant parameters and then use them for the tests for the evaluation of the grindability of the Inconel 625 and Inconel 718 (second stage). In this stage the ae, vw, vs and grinding wheel mesh were varied. The output parameters used to assess the grindability were the surface roughness (Ra and Rz), images of the ground surfaces obtained by scanning electron microscopy (SEM), microhardness on the surface and below it, grinding forces, specific energy and temperature in the grinding zone. In general, the results showed that the Inconel 625 is harder to grind than the Inconel 718. The surface roughness (Ra and Rz) obtained for Inconel 625 workpieces were higher than those obtained for Inconel 718 for all analyzed conditions. With the higher cutting speed, SEM images indicated a greater presence of plastic deformations on the Inconel 625 surfaces, which led to its work hardening, increasing the microhardness. Grinding forces and specific energy were slightly higher for Inconel 718, while the temperature in the grinding zone was higher for Inconel 625 when compared to Inconel 718.CNPq - Conselho Nacional de Desenvolvimento Científico e TecnológicoTese (Doutorado)As ligas à base de níquel são consideradas como materiais difíceis de usinar, dificuldade que é ainda mais agravada quando elas são submetidas ao processo de retificação, exigindo assim mais atenção para determinar parâmetros de usinagem corretos. Dentre as ligas a base de níquel, a mais emprega é o Inconel 718, contudo, o Inconel 625 também tem se destacado pelas suas propriedades peculiares como a elevada resistência a corrosões aquosas e quentes, alta resistência mecânica e resistência à fluência. Neste sentido, este trabalho buscou avaliar o comportamento desta liga durante o processo de retificação e avaliar a sua retificabilidade em relação ao Inconel 718. Para isso foram testados vários parâmetros operacionais. Os ensaios foram realizados em duas etapas. Na primeira etapa foi avaliado o efeito dos principais parâmetros de entrada (penetração de trabalho – ae, velocidade da peça – vw, velocidade de corte – vs, granulometria do rebolo e sentido de retificação) no processo de retificação do Inconel 625 com base na rugosidade (Ra e Rz), forças de corte e energia específica a fim de determinar os parâmetros estatisticamente significativos e então realizar o ensaios para a avaliação da retificabilidade do Inconel 625 (segunda etapa). Nesta etapa foram variados o ae, vw, vs e a granulometria do rebolo na retificação do Inconel 625 e do Inconel 718. Os parâmetros de saída avaliados foram a rugosidade (Ra e Rz), imagens da superfície retificada obtidas via microscopia eletrônica de varredura (MEV), microdureza na superfície e abaixo dela, forças de retificação, energia específica e temperatura na zona de retificação. Em geral, os resultados indicaram que o Inconel 625 apresenta maiores dificuldades para ser retificado que o Inconel 718. As rugosidades (Ra e Rz) obtidas para as peças de Inconel 625 foram maiores que as obtidas para o Inconel 718, em todas as condições analisadas. Sob velocidade de corte mais elevada, houve uma maior presença de deformações plásticas nas superfícies do Inconel 625, que levou ao encruamento da mesma, elevando a microdureza. As forças de corte, assim como a energia específica foram ligeiramente maiores para o Inconel 718, enquanto a temperatura na zona de retificação foi maior para o Inconel 625 quando comparado ao Inconel 718

Mql With Water In Cylindrical Plunge Grinding Of Hardened Steels Using Cbn Wheels, With And Without Wheel Cleaning By Compressed Air

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Minimum quantity of lubricant (MQL) in grinding is an alternative for reducing abundant fluid flow and both environmental and health hazards when compared with conventional fluid application. In spite of the fact that MQL is considered an innovative cost-effective and environmentally friendly technique, when used in grinding its inadequate application can increase cutting temperature and wheel clogging, worsening surface roughness, and increasing geometric and dimensional errors. The present study aims to evaluate improvements in MQL in grinding using MQL + water (1:1, 1:3, and 1:5 parts of oil per parts of water), when compared to MQL without water and conventional cooling-lubrication technique. Wheel cleaning by compressed air was also tested, aimed for unclogging of the wheel pores. The tests were performed in a plunge cylindrical grinder with CBN wheel and workpieces of AISI 4340 for different feed rates. The ground workpieces were analyzed with respect to the surface roughness, roundness errors, microhardness, and microscopic changes. In addition, tangential cutting force and diametric wheel wear were investigated. The results observed for the MQL plus water in the proportion of 1:5, with wheel cleaning system (at 30A degrees inclination angle of the air nozzle) were the best, when compared to MQL without water, and close to the conventional flood coolant, implying that this technique is a potential alternative for cooling-lubrication when applied properly.901-4329338FAPESP (Sao Paulo Research Foundation) [2009/50965-7, 09/50964-0]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Influence of grinding parameters on inconel 625 surface grinding

Nickel-based alloys have been increasingly employed due to their ability to maintain high mechanical strength and high chemical inertia at high temperatures. However, these outstanding properties can impair their machinability, so they are termed difficult-to-machine materials. Since machining of nickel alloys becomes even more difficult when the grinding process is needed, and because of poor thermal conductivity of both workpiece and the abrasive grinding wheel, more attention from machinists is required to determine proper grinding parameters that should be more moderate than those usually selected for grinding hardened steels. Because of the peculiar properties of Inconel 625 alloy, such as resistance to aqueous solutions, hot corrosion, high strength and resistance to creep, it makes it well suited for a wide range of applications, such as aerospace and marine applications as well as oil and gas industries. The grinding operation is generally the first option to enhance the combinations of narrow dimensional and geometric deviations in most of aeronautical components. In this context and motivated by the lack of information about grindability of this alloy, this work evaluates the influence of the several grinding parameters on surface integrity, grinding forces (Ft and Fn) and specific grinding energy of nickel-based, Inconel 625 alloy. A fractional factorial design of experiments (DOE) was adopted to use the wheel speed, work speed, depth of cut, abrasive mesh and grinding direction (up and down grinding) as measures of variation in the grinding process. Surface integrity was assessed in terms of surface roughness (Ra and Rz), observations of SEM images and microhardness. The results showed that Inconel 625 is highly susceptible to work hardening during grinding. The grinding wheel speed (vs) was the parameter of greatest effect and the best results were obtained when vs=15 m/s55174185CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES141472/2017-0001x superalloysInconel 625Grinding parametersGrinding forcesThe authors thank the Post Graduate Program of Mechanical Engineering of UFUand the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for financial support to this study (process number 141472/2017-0). This study was also financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. The authors thank the Saint-Gobain Abrasives and Villares Metals S.A. by supplying the tools and material used in this work, respectively. The authors also would like to acknowledgements the Multiuser Laboratory of Chemistry Institute at the Universidade Federal de Uberlandia for providing the equipment and technical support for experiments involving the electron microscopic studie

Inferential measurement of the dresser width for the grinding process automation

Dressing is an essential process for the machining industries. The grinding community keeps the slogan “grinding is dressing,” given the importance of this reconditioning process. This paper presents a methodology for forecasting the dresser width one step forward by using indirect monitoring. The dresser width is an important parameter to guarantee the quality of the dressing process and, in many cases, it is monitored directly by the operators. Acoustic emission signals were collected during the dressing process and an estimation neural network was used to correlate the dresser width with the processed signals to estimate the current value of the width. The output of the estimation network was input to a time-delay neural network to predict the next value of the dresser width. By utilizing this procedure, an automatic system would be able to readjust the dressing parameters while avoiding the stops, reducing costs, and maintaining repeatability during the process

MQL with water in cylindrical plunge grinding of hardened steels using CBN wheels, with and without wheel cleaning by compressed air

Minimum quantity of lubricant (MQL) in grinding is an alternative for reducing abundant fluid flow and both environmental and health hazards when compared with conventional fluid application. In spite of the fact that MQL is considered an innovative cost-effective and environmentally friendly technique, when used in grinding its inadequate application can increase cutting temperature and wheel clogging, worsening surface roughness, and increasing geometric and dimensional errors. The present study aims to evaluate improvements in MQL in grinding using MQL + water (1:1, 1:3, and 1:5 parts of oil per parts of water), when compared to MQL without water and conventional cooling-lubrication technique. Wheel cleaning by compressed air was also tested, aimed for unclogging of the wheel pores. The tests were performed in a plunge cylindrical grinder with CBN wheel and workpieces of AISI 4340 for different feed rates. The ground workpieces were analyzed with respect to the surface roughness, roundness errors, microhardness, and microscopic changes. In addition, tangential cutting force and diametric wheel wear were investigated. The results observed for the MQL plus water in the proportion of 1:5, with wheel cleaning system (at 30° inclination angle of the air nozzle) were the best, when compared to MQL without water, and close to the conventional flood coolant, implying that this technique is a potential alternative for cooling-lubrication when applied properly

MQL with water in cylindrical plunge grinding of hardened steels using CBN wheels, with and without wheel cleaning by compressed air

Minimum quantity of lubricant (MQL) in grinding is an alternative for reducing abundant fluid flow and both environmental and health hazards when compared with conventional fluid application. In spite of the fact that MQL is considered an innovative cost-effective and environmentally friendly technique, when used in grinding its inadequate application can increase cutting temperature and wheel clogging, worsening surface roughness, and increasing geometric and dimensional errors. The present study aims to evaluate improvements in MQL in grinding using MQL + water (1:1, 1:3, and 1:5 parts of oil per parts of water), when compared to MQL without water and conventional cooling-lubrication technique. Wheel cleaning by compressed air was also tested, aimed for unclogging of the wheel pores. The tests were performed in a plunge cylindrical grinder with CBN wheel and workpieces of AISI 4340 for different feed rates. The ground workpieces were analyzed with respect to the surface roughness, roundness errors, microhardness, and microscopic changes. In addition, tangential cutting force and diametric wheel wear were investigated. The results observed for the MQL plus water in the proportion of 1:5, with wheel cleaning system (at 30° inclination angle of the air nozzle) were the best, when compared to MQL without water, and close to the conventional flood coolant, implying that this technique is a potential alternative for cooling-lubrication when applied properly901-4329338FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2009/50965-7; 09/50964-