Browsing by Author "John S. Strenkowski, Committee Member"

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    End Milling of Elastomers
    (2002-10-06) Lewis, Mark Austin; Ron O. Scattergood, Committee Member; Albert J. Shih, Committee Chair; John S. Strenkowski, Committee Member
    The purpose of this study is to identify mechanisms for effective elastomer machining using sharp, woodworking tools and cryogenic cooling. The development of an elastomer machining process could reduce cost and time spent in mold processing as an alternative approach. Thirteen tools of different sizes, tool geometries, materials, and milling configuration are used in this study. Fixture design is identified to be critical to elatomer machining due to material's elastic properties. The finite element method using ANSYS software is used to evaluate the stiffness of the workpiece when machined by different size end mills. The term effective stiffness is defined for the elastomer workpiece and found to increase with increasing tool size. Down milling configuration tools can effectively remove elastomer material at room temperature. Cryogenic cooling to -78.6 degrees C with solid carbon dioxide also improves the machined elastomer surface. A survey of the chip morphology is taken using Scanning Electron Microscopy (SEM). A system of classifying 7 types of chips based on size and morphology is developed. Serrated chip formation with apparent adiabatic shear bands is observed for one end milling test, possibly caused by the low thermal conductivity of elastomers. Other serrated chips exhibit wavy marks on the surface possibly due to vibration during machining. Milling forces were recorded and analyzed and show higher cutting forces for samples cut at the cryogenic condition. Cutting forces also reveal a correlation of the maximum uncut chip thickness with averaged peak cutting forces for different spindle speeds, which may have potential for modeling the elastomer machining process.
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    Infrared-based temperature measurement in ceramics grinding and diesel exhaust aftertreatment filters
    (2004-02-18) Kong, Jian; John S. Strenkowski, Committee Member; Ronald O. Scattergood, Committee Member; Albert J. Shih, Committee Chair; Paul I. Ro, Committee Member
    Non-contact remote-sensing radiation thermometry was used in the applications of temperature measurement in ceramics grinding and diesel exhaust aftertreatment filters. Results of temperature measurements by analysis of the thermal emission spectra generated during grinding and subsequently transmitted through partially stabilized zirconia workpiece are presented. Portions of emitted visible and near-infrared spectra were collected with spectrometers. Source temperatures were determined by fitting the scaled spectrometer output spectra to blackbody curves. Simulations showed that the effective temperatures determined by this method will be strongly biased toward hot-spot (flash) temperatures, which are expected to occur at the grinding grit-workpiece interface. Hot-spot temperatures on the order of 3000 K were obtained for grinding with both SiC and diamond wheels. These high temperatures modify the grinding process and the phase content of grinding chips. The in-situ measurement of the temperature distribution on the cavity wall surface in diesel exhaust aftertreatment filters using the infrared radiation thermometry was developed. The temperature measurement system consists of a sapphire fiber with 45° angled tip, PbS/PbSe two-color sensor, and data conditioning and acquisition device. A calibration technique using the blackbody cavity was developed. Calibration curves were generated between 80 to 400°C, the temperature range of special interest for applications in catalyzed diesel exhaust aftertreatment filters. One-color and two-color radiation thermometry methods were both employed to compare and validate temperature measurement results. The wall surface temperature of a microwave-heated ceramic filter was measured at four locations. This study demonstrates the feasibility of using the infrared thermometry for non-contact temperature measurement at a specific region within the cavity of diesel exhaust aftertreatment filters. Based on the above temperature measurement results, the infrared thermometry method was applied to study the temperature distribution in microwave heating of diesel particulate filters. Temperature measurement tests were conducted in integrated multi-channel fiber optic infrared temperature measurement and microwave heating systems. The silica light-pipes, which are transparent to electromagnetic field, were used to collect the infrared radiation from different locations inside filter cavity. One-color thermometry method was implemented to convert the measured radiation into temperatures. The temporal and spatial distributions of three diesel particulate filters heated by microwave were studied. Experimental results show the non-uniform heating across the filter. The interaction between catalyst, soot loading, and microwave power varies the heating pattern and temperature distribution. During a 600 s heating period, a 1 kW microwave power setting is able to raise the temperatures above 200°C in most area of a catalyzed filter with soot loading.