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  • 1
    Electronic Resource
    Electronic Resource
    A simplified method for accuracy estimation of nuclear magnetic resonant imaging (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3300-3307 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Multi-dimensional tomographic-based data sets are now being used to calculate physical properties and transport coefficients. This article presents a method, based upon the propagation of uncertainties, for determining the valid range of values for the property calculated. The example used to demonstrate the method is the application of nuclear magnetic resonance imaging (NMRI) to measure fluid velocity profiles for the calculation of fluid viscosities. The resolution of the velocity data is shown to be the most important factor for implementation of the NMRI-based viscometry technique. Uncertainties in the velocity measurement are propagated through the shear viscosity calculation to estimate the standard deviation of the shear viscosities. Two data sets, experimental velocity resolutions of 0.6 and 1.5 mm/s, demonstrate that when the shear viscosity standard deviation exceeds 30% of the predicted shear viscosity value we observe a discrepancy between the data and viscosities obtained using conventional rheometrical instruments. Removal of those data points with a standard deviation exceeding 30% of the shear viscosity value provided data that agreed to within 6% of conventional rheometry data. The estimation methodology for property uncertainty can be applied prior to experimental measurements to design for accuracy over a specific range of the property to be determined. These findings are not restricted to NMRI and should hold for other tomography-based viscometers © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149113
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  • 2
    Electronic Resource
    Electronic Resource
    The failure of amalgam dental restorations due to cyclic fatigue crack growth (1999)
    Springer
    Journal of materials science 10 (1999), S. 319-327 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract In this study a restored mandibular molar with different Class II amalgam preparations was examined to analyze the potential for restoration failure attributed to cyclic fatigue crack growth. A finite element analysis was used to determine the stress distribution along the cavo-surface margin which results from occlusal loading of each restoration. The cyclic crack growth rate of sub-surface flaws located along the dentinal cavo-surface margin were determined utilizing the Paris law. Based on similarities in material properties and lack of fatigue property data for dental biomaterials, the cyclic fatigue crack growth parameters for engineering ceramics were used to approximate the crack growth behavior. It was found that flaws located within the dentine along the buccal and lingual margins can significantly reduce the fatigue life of restored teeth. Sub-surface cracks as short as 25 μm were found capable of promoting tooth fracture well within 25 years from the time of restoration. Furthermore, cracks longer than 100 μm reduced the fatigue life to less than 5 years. Consequently, sub-surface cracks introduced during cavity preparation with conventional dental burrs may serve as a principal source for premature restoration failure. ©©1999©Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026435821960
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of simultaneous mechanical and thermal loads on the stress distribution in molars with amalgam restorations (2000)
    Springer
    Journal of materials science 11 (2000), S. 133-140 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A finite element analysis (FEA) of a mandibular molar restored with Class II amalgam restoration was conducted to determine the stress distribution which results from a superposition of simultaneous mechanical and thermal loading. A fully crossed three-level four-factor experimental design was used to evaluate the relative influence of crown temperature, time of thermal loading, occlusal force, and cavo-surface margin adhesion on the stress distribution. It was found that occlusal force and temperature had significant influence on the stress distribution and particularly on the maximum principal stress. Over the range in oral conditions considered, thermal loading contributed for over 35% of the stress within the restored molar subjected to simultaneous mechanical and thermal loads. Furthermore, thermal loading had significant effects on the magnitude of normal stress that develops parallel to the pulpal floor. Although marginal bonding of amalgam reduces the stress resulting from occlusal forces, thermal loading promotes the development of significant interfacial shear stresses along the bonded margin. Stresses related to the thermal component of loading concentrate near the pulpal floor and lingual surface margin, the site most prominent in cusp fracture. Hence, results from this study clearly indicate that an evaluation of new dental materials and/or restorative designs should consider the effects from a superposition of simultaneous mechanical and thermal loads on fracture resistance ©©2000©Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008905423584
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  • 4
    Electronic Resource
    Electronic Resource
    Net shape manufacturing and the performance of polymer composites under dynamic loads (1997)
    Springer
    Experimental mechanics 37 (1997), S. 379-385 
    Details
    ISSN: 1741-2765
    Keywords: Composite materials ; impact strength ; machining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental investigation was conducted to determine the influence of postmold trimming and resultant edge quality on the performance of fiber-reinforced plastics (FRP) under dynamic loads. Graphite/epoxy and graphite/bismaleimide laminates were machined using three state-of-the-art industrial techniques and subjected to three-point bend impact to failure. The load load-line displacement records were used to obtain the load, bend deflection and energy absorbed to fracture. High-speed photography was also employed to identify the initiation and progression of failure and record the time dependent fracture process. From a comparison of edge quality and subsequent material performance for both polymeric composites, it was found that the impact response of FRPs is highly process dependent. In general, the load and energy absorbed to fracture decreases with increasing surface roughness. Reductions in the load and energy to the onset of fracture with degrading surface quality were as high as 20 percent. The dynamic response was also found to be dependent on the constituents, stacking sequence and impact velocity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02317300
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    Paper (German National Licenses)
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