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Machining Process (machining + process)
Selected AbstractsMonitoring of Machining Processes Using Sensor Equipped Tools,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Ekkard Brinksmeier A different to conventional monitoring systems sensor equipped tools give the possibility to gain information about the process status directly from the contact zone between tool and component to be machined. For example this can be realized by the integration of small temperature sensors into grinding wheels. The transmitting of the process data is performed by a telemetric unit attached to the grinding wheel's core. In this paper, the development of a new thin film thermocouple sensor concept is described. The unique feature of this sensor is the continuous contacting of the thermocouple through the grinding process inherent wear which leads to smearing of the thermoelectric layers and thus forming the measuring junction of a thermocouple. The system was used in OD grinding processes aiming to detect grinding burn and process instabilities. By reducing the volume of the sensors a fast response and high time resolution can be obtained. By this way, observance of the key parameters of the practical operation as closely as possible to the cutting area is enabled and so observance of process efficiency and tool status independent from workpiece machining conditions can be realized. All sensors used are thermocouples of type K, a combination of Chromel (NiCr) and Alumel (NiAlMnSi) material. The maximum temperature to be measured by this sensor is about 1350,°C, which ensures the applicability in the grinding process. Telemetry components to amplify and send the thermovoltage signals are adjusted to this type of thermocouple. The ability of the set-up to detect thermal influences was demonstrated in grinding processes with a continuously increasing specific material removal rate. The approach serves to measure temperatures between fast sliding surfaces in harsh environments (fluids, high pressure, heat), similar to the grinding process. Therefore their application is not limited to tools but also applicable for other rotating components such as bearings, gears and shafts in powertrains. [source] Crack-healing behaviour and resultant high-temperature fatigue strength of machined Si3N4/SiC composite ceramicFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2008Y.-S. JUNG ABSTRACT The crack-healing behaviour of machining cracks in Si3N4/20 wt% SiC composite was investigated. The machining cracks were introduced by a heavy machining process, during the creation of a semicircular groove. The machined specimens were healed at various temperatures and times in air. The optimized crack-healing condition of the machined specimens was found to be a temperature of 1673 K and a time of 10 h. The specimens healed by this condition exhibited almost the same strength as the smooth specimens healed. Moreover, the bending strengths and the fatigue limits of the machined specimens healed were systematically investigated at temperatures from room temperature to 1673 K. The machined specimens healed at the optimized condition exhibited an almost constant bending strength (,700 MPa) up to 1673 K. Also, the specimens exhibited considerably high cyclic and static fatigue limits at temperatures from 1073 to 1573 K. These results demonstrated that the crack-healing could be an effective method for improving the structural integrity and reducing machining costs of the Si3N4/SiC composite ceramic. [source] Thermal and mechanical numerical modelling of electric discharge machining processINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2008Nizar Ben Salah Abstract In electric discharge machining (EDM), the heat gradients caused by the electric discharge create a non-uniform local thermal expansion on the level of the surface layers of machined materials from where genesis of thermal stresses takes place. These thermal stresses, if exceeding yield stress, can remain and become residual after the cooling of the part. The modelling of these phenomena, during the heating by the electric discharge and the cooling by the dielectric liquid, requires a heat transfer model, the material behaviour identification, a thermo-mechanical model for the thermal and the residual stress models. This paper presents numerical results concerning the temperature distribution, the thermal and residual stresses of a stable steel material (AISI316L) machined by EDM. Comparison of numerical results with experimental data and numerical results from the literature shows good agreement and is hence quite satisfactory. Copyright © 2008 John Wiley & Sons, Ltd. [source] Residual stress analysis of an autofrettaged compound cylinder under machining processMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 3 2009E.-Y. Lee Autofrettage; Schrumpfpassung; Verbundzylinder; Bearbeitungsprozess Abstract The autofrettage process is used to manufacture pressure vessels and cylinders that can withstand high internal pressure. A multi-layered cylinder was assembled by a shrink fit. Autofrettaged compound cylinder can resist higher internal pressure than a thick cylinder having the same dimension and extend its life time. Inner and outer surfaces of the autofrettaged compound cylinder have to be manufactured into exact dimensions. The distribution of residual stress can change after the machining process. The machining procedure of inner and outer surfaces also affects the distribution of residual stress as a function of the machining procedure. In this study, the distribution of residual stresses of an autofrettaged compound cylinder as machining procedure was investigated using analytical and numerical analyses. [source] Effect of the Machining Method on the Catalycity and Emissivity of ZrB2 and ZrB2,HfB2 -Based CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2008Luigi Scatteia The emissivity and the catalytic efficiency related to atomic oxygen recombination were investigated experimentally in the range 1000,2000 K for ZrB2 and ZrB2,HfB2 -based ceramics. In order to evaluate the effect of the machining method, two series of samples, one prepared by electrical discharge machining and the other machined by diamond-loaded tools, were tested. High emissivity (about 0.7 at 1700 K) and low recombination coefficients (on average 0.08 at 1800 K) were found for all the materials. The experimental data showed an effect of the surface machining on the catalytic behavior only on the ZrB2 -based composite; conversely, small variations were found in the recombination coefficients of ZrB2,HfB2 -based samples for the different machining processes. The surface finish affected the emissivity at lower temperatures in both compositions, with the effect becoming negligible at temperatures above 1500 K. [source] Parametric optimization of magnetic-field-assisted abrasive flow machining by the Taguchi methodQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 4 2002Sehijpal Singh Abstract Some hybrid-machining processes have been developed in the recent past with a view to devising composite machining processes, which are able to overcome the limitations of one process with the help of advantageous features of another similar process. The present paper identifies the parameters of abrasive flow machining (AFM) that significantly affect the material removal when a magnetic field is applied around the workpiece. The Taguchi method has been adopted for studying the effect of magnetic-field-assisted AFM parameters, individually, on the abrasion rate of work materials. Optimization of the process parameters has been carried out for the purpose of off-line monitoring of the process. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||