VEGETABLE OIL STRUCTURE AND ANTIOXIDANTS
Five vegetable oils: canola, soybean, corn, cottonseed and sunflower oils were characterized with respect to their composition by gas chromatography and viscosity. The compositions of the vegetable oils suggest that they exhibited substantially different propensity for oxidation following the order of: Canola < corn < cottonseed < sunflower ≈ soybean The effect of molecular structure of five different vegetables oils including: corn, soybean, canola, cottonseed and sunflower oils with no antioxidants added on the oxidative stability was calculated and the following order of oxidative stability would be expected: canola < corn < cottonseed < sunflower ≈ soybean. Soybean oil, which is one of the most commercially interesting of the vegetable oils in Brazil, was determined to be the most susceptible to oxidative degradation of those oils evaluated. Therefore, soybean oil was selected to be used for a study to evaluate the ability of an antioxidant to stabilize a vegetable oil relative to two commercially formulated petroleum quench oils: Micro Temp 157, a conventional oil, and Micro Temp 153B, a fast oil. The antioxidants selected for this study were Irganox L57 and Irganox L109. In addition, the potential for combinations of L57 and L109 to provide a synergistic improvement over either antioxidant individually was also examined. The results of this work showed following order of oxidative stabilization: L109 > L57 over 60 hours of accelerated testing. No synergism using a blend of L109 + L57 was observed with performance increasing with increasing amount of L109. As expected all of the antioxidant combinations evaluated were better than soybean oil with no antioxidant. However, none of the vegetable oils evaluated exhibited the oxidative stability obtained for either petroleum oil. Cooling curve analysis results were surprising since increasing viscosity observed for vegetable oils with deceasing stability did not exhibit any large effect on cooling rates or times. The reasons for this have not been definitively shown thus far.
Effect of surface roughness on metal/quenchant interfacial heat transfer and evolution of microstructure
Abstract In the present work, the effect of surface roughness on heat transfer rates in various quenchants was determined. The heat flux transients at the probe/quenchant interface were estimated by inverse modeling of heat conduction during end quenching of stainless steel probes with three different surface roughness (grooved, R a  = 3.0 and 1 μm). Heat transfer during quenching was correlated with the hardness obtained for medium carbon AISI 1060 steel specimens. The effect of surface roughness on heat transfer rate during quenching in water and brine was significant for rough surface whereas its effect on heat transfer rate is only marginal in high viscosity oil quenchants. A fully martensitic structure was observed with grooved surface subjected to water quenching. With a smooth surface a mixed microstructure was obtained. The oil quenched specimens were found to be less sensitive to surface roughness.
Methodology for Comparison of Inverse Heat Conduction Methods
The inverse heat conduction problem involves the calculation of the surface heat flux from transient measured temperatures inside solids. The deviation of the estimated heat flux from the true heat flux due to stabilization procedures is called the deterministic bias. This paper defines two test problems that show the tradeoff errors having constant variance and zero mean, the second test case gives the standard deviation of the estimated heat flux. A methodology for the quantitative comparison of deterministic bias and standard deviation of inverse methods is proposed. Four numerical inverse methods are compared.