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A data reduction program and ignition model developed for the analysis of data generated by the frictional heating test facility at WSTF is presented. Based on transient temperature data measured from the stationary cylinder, the model can be used to generate an effective friction coefficient, activation energy and reactive flux constant for different metals/alloys at various test conditions. Data of 15 tests conducted for carbon steel are analyzed to illustrate the capability of the present model.
The effective friction coefficient is observed to decrease with increasing oxygen pressure, suggesting that the formation of oxide layer and the oxide's lubrication property have important effects on the ignition process for carbon steel. The activation energy is estimated to be 46600 cal/gmole. The reactive flux constant is observed to increase with oxygen pressure, suggesting that either the diffusion of ions through an oxide layer or the adsorption of oxygen at the oxide-gas interface is the primary physical process controlling the ignition. The Pv product (which is the mechanical energy input into the system) required for ignition is shown to first decrease and then increase with oxygen pressure, suggesting that at low oxygen pressure, the reactive flux constant is the important parameter controlling the energy input required for ignition while at high oxygen pressure, the reduction in friction coefficient due to the formation of oxide is the dominant physical process.
metal, alloy, oxide, ignition, friction coefficient, frictional heating test, oxygen pressure, heat transfer, oxidation
Professor of Mechanical Engineering, University of California at Santa Barbara, Santa Barbara, California