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

Abstract

SUMMARYThis 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-flight 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.

Computation of transient-temperature profiles in objects exposed to simulated lightning currents

“…In this paper a computation of the three-dimension (3-D) transient temperature distribution in metals and composites struck by different lightning currents is introduced using a written computer program based on the finite volume technique. Also, the theoretical results are verified using the previously published experimental works [14,15].…”

“…Fig. 2 shows a comparison between the measured [14] and computed rear-face temperature contour maps ϑ r (x, y) for normal steel [19] at different times due to an LDC (square-like) current with an amplitude I = −93 A and a duration t = 325 ms. A good agreement is found between the measured and the computed ϑ r (x, y) during heating and cooling, too. Since the major part of the absorbed energy by the sample is transferred by heat conduction to the sample rear-face.…”

“…An experimental simulation of the effects of lightning longduration and impulse currents (LDC and IC) striking to metallic plates was performed by measuring the temperature profiles as a function of the rear-face coordinates every 20 ms by using a sophisticated high-speed infrared camera, having an upper temperature limit of 1200 • C [14,15]. The test sample (25 × 25 cm 2 ) is concentrically fixed on an aluminum disc (diameter = 60 cm and thickness = 10 mm).…”

Monte Carlo based lightning risk assessment in oil plant tank farms

“…These parameter are associated with the appearance of hot spots in the metallic structure of the tanks, of induced voltages and with melting phenomena, as shown by specific numerical models and experimental tests (e.g. [10,11]). …”

“…Equation (6) uses this assumption and leads to an overestimate of the melted volume: Basically, the charge to be considered is the sum of the charge of the return stroke and the lightning continuing current. Laboratory experience has revealed that the effects of the return stroke charge may be of minor importance when compared to the effects of the continuing current [11].…”