Theoretical and Experimental Analysis of the Metal-Based Ignition Propensity Test Thermodynamics

This research analysed in detail the performance of the new alternative ignition propensity test prescribed in the standard ASTM E2187-16, which is based on the utilization of a substrate comprising a thin steel plate along with one filter paper. The analysis was performed both experimentally, by means of infrared temperature measurements, and theoretically by using a comprehensive finite element model that was able to predict the temperature of the substrate with errors of only 7.3% and 15.7% in space and time, respectively. While the new alternative test was able to reduce the variability of the heat absorbance from 33% to only 4% with respect to the conventional tests, it showed several downsides that critically reduce its reliability. The heat absorbance of the alternative test did not correctly emulate the conventional procedure as it absorbed as much heat as twice. The gravity effect on the plate increased the air gap thickness more than twice, thereby decreasing potentially the heat absorbance by 13%. In addition, a mechanical analysis showed that compressive stresses due to high temperature gradients could cause irreversible buckling, creep and yielding of the plate. Experiments showed that in fact the concavity of the plate was prone to increase after testing. Assuming the maximum concavity allowed by the standards, the heat absorbance was halved in respect to a perfectly flat plate. In view of these results, the utilization of the conventional test method still appears clearly more appropriate than the alternative one.