A multianalysis thermography‐based approach for fatigue and damage investigations of ASTM A182 F6NM steel at two stress ratios

Abstract

Infrared thermography allows an alternative energy‐based approach for studying the fatigue behaviour of materials to better understand damage phenomena. In particular, the methodology of infrared thermography can explain the complex dissipative mechanisms promoted by the input parameters, such as the loading ratio, can rapidly provide information about the fatigue strength, and has low cost. In this work, analysis of the thermographic sequences of ASTM A 182 grade F6NM steel obtained during fatigue testing provided four thermal indexes that were used to investigate the thermoelastic and plastic behaviour of material. Fatigue tests at two opportunely chosen loading ratios (R = −0.1, R = 0.5) were performed to investigate the relation between the material behaviour and each index at a specific loading ratio. Finally, estimation of the fatigue strength by means of suitable analysis procedures allowed for an investigation of the damage behaviour of materials under specific loading conditions.

The use of nondestructive evaluation methods in fatigue: A review

“…35,79 Reported issues with the use of the IRT method in fatigue investigations, as also mentioned earlier, involve the a priori required knowledge of the damage location to be able to accordingly position the monitoring region, which results in a number of considerations when applying this method in laboratory conditions. 87…”

“…Hence, the passive form of IRT is useful for detecting evolution and damage that is occurring in situ (ie, not for pre‐existing damage) while the active form can detect and, to some extent, produce size estimates of the damage . Reported issues with the use of the IRT method in fatigue investigations, as also mentioned earlier, involve the a priori required knowledge of the damage location to be able to accordingly position the monitoring region, which results in a number of considerations when applying this method in laboratory conditions …”

Monitoring multiple damage mechanisms in crack‐patched structures using optical infrared thermography

“…This short and strongly simplified description of the correlation between mechanical loading and temperature evolution illustrates that the use of temperature‐based inspection methods, such as IrT can be used to monitor the damage procedures of loaded structures. Methods as the thermal stress analysis for instance even provide the potential of correlating cyclic heat and temperature changes with fatigue properties 28,29 . To facilitate the interpretation of the test results, a short introduction into the functionality of IrT is provided.…”

Thermographic approach for high cycle fatigue of seam welded steel joints under variable amplitude loadings

“…• either the initial gradient of temperature is analysed during the beginning of the cycling 17,23,24 by assuming adiabatic condition (on a short duration), or at the end of the loading 25,26 ; • or, recently, De Finis et al 27 show that cyclic variations of temperature is linked with fatigue limit through the phase and amplitude of the first two harmonics; • else, the stabilized temperature after the increasing phase is handled by assuming a steady-state case ( _ T = 0 ), and so neglecting the thermal inertial term ρc _ T.…”