Measurement of the rear-face temperature of metals struck by lightning long-duration currents

This paper presents an experimental investigation of the rear-face temperature rise of different metals struck by lightning long-duration currents on the front face. The experimental investigation simulates the heating effect of one current component of the natural lightning flashes that may strike in-light or landed aircraft and rockets; munitions and nuclear weapons; and storage/collection tanks and pipelines of the petroleum/gas industries. In the case of a lightning strike the rear-face temperature rise must be less than certain limits to avoid catastrophic damage/accidents. A sophisticated high-speed infrared camera, having an image frequency of 50 Hz and a temperature range up to 1200°C, is used to measure the rear-face temperature profiles as a function of the coordinates and time. The results are interpreted in light of the optical observation of the arc motion, physical measurement of the spot diameter, and study of the energy balance at the cathode and anode spots. The results reveal that for constant charge transfer, lightning long-duration currents having higher amplitudes give a higher rear-face temperature rise and hence a higher risk of accidents. Both the maximum rear-face core temperature and the front-face spot diameter exponentially increase with the mean current amplitude. Moreover, the maximum rear-face core temperature varies exponentially with the charge and linearly with the action integral. Current injection with positive polarity of the test electrode gives a lower rear-face temperature for all metals used except for aluminium where the trend is reversed.