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Grinding Process (grinding + process)

Distribution by Scientific Domains
Chemistry50%

Selected Abstracts

Monitoring of Machining Processes Using Sensor Equipped Tools,

ADVANCED ENGINEERING MATERIALS, Issue 7 2010
Ekkard 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]

Enrichment of the thymoquinone content in volatile oil from Satureja montana using supercritical fluid extraction

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 2 2009
Clara Grosso
Abstract Supercritical fluid extraction (SFE) of the volatile oil from Satureja montana L. was performed under different conditions of pressure (90 and 100 bar), temperature (40 and 50°C), mean particle sizes (0.4, 0.6 and 0.8 mm) and CO2 flow rate (0.8, 1.1 and 1.3 kg/h) to understand the influence of these parameters on the composition and yield of this oil. The results were compared with those obtained for the essential oil isolated by hydrodistillation (HD). The volatile and the essential oil were analysed by GC and GC-MS. The main compounds are carvacrol (52.2,62.0% for HD vs. 41.7,64.5% for SFE), thymol (8.6,11.0% for HD vs. 6.0,11.3% for SFE), p -cymene (6.9,12.8% for HD vs. 6.0,17.8% for SFE), ,-terpinene (6.4,9.4% for HD vs. 2.3,6.0% for SFE) and ,-bisabolene (2.0,2.7% for HD vs. 2.2,3.5% for SFE). The major difference between SFE and HD was the relative amount of thymoquinone, an oxygenated monoterpene with important biological activities, which can be ten-fold higher in volatile oil (1.6,3.0 for SFE vs. 0.2% for HD). The morphology of the glandular trichomes of S. montana and the effect of the grinding process on them was also evaluated by SEM. [source]

Nanoparticle Production with Stirred-Media Mills: Opportunities and Limits

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2010
C. Knieke
Abstract Nanoparticles can be produced by wet grinding in stirred-media mills. In the lower nanometer range a true grinding limit exists, where the transferred energy from the grinding media is no longer sufficient to induce further breakage of the particles even after stressing events with high stress energies. Variations in process conditions lead to the conclusion that the grinding limit is hardly affected by most of the investigated process parameters. However, at high solids concentrations and/or small particle sizes, a drastic increase in suspension viscosity occurs, which leads to a dampening of the grinding media motion and to a reduction in the transferred stress energy. Hence, the rheological behavior can limit the grinding process, and a viscous dampening-related grinding limit can be reached prior to the true grinding limit. [source]

Monitoring of Machining Processes Using Sensor Equipped Tools,

ADVANCED ENGINEERING MATERIALS, Issue 7 2010
Ekkard 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]