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The electronic states of Mn2+ are derived from excitation spectra for five green‐emitting phosphors: (i) MgGa2O4:normalMn , (ii) Zn2SiO4:normalMn , (iii) ZnAl2O4:normalMn , (iv) Zn2GeO4:normalMn , and (v) Li2ZnGe3O8:normalMn . Only MgGa2O4:normalMn is found to give a spectrum consistent with octahedral (or tetrahedral) symmetry of Mn2+; the other four phosphors show spectra typical of Mn2+ in symmetry lower than octahedral. Solution of the Tanabe‐Sugano energy matrices using the MgGa2O4:normalMn levels as input gave Racah parameters of B=624 cm−1 and C=3468 cm−1 .

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.

In literature, there are already well‐established thermal methods which allow for the estimation of fatigue limit, in particular for metallic materials such as austenitic steels. These methods are based on heat source generation analysis or on surface temperature evaluation of material subjected to different types of cyclic loading. General application of methodology found limitation in those cases in which temperature changes on material related to fatigue damage were very low and, furthermore, thermal methods require high‐performance equipment and a difficult setup. This is the case, for instance, with brittle materials (such as martensitic steels), welded joints and aluminium alloys. In this work, a new thermal method named Thermoelastic Phase Analysis is used to evaluate the fatigue limit of martensitic steels. This thermal method is based on an empirical approach. The main idea is that phase of thermoelastic response of the material subjected to fatigue loading is influenced by the presence of a heat source due to dissipative phenomena related to damage. Monitoring of the phase parameter provides a more stable setup and an independent means of identifying the fatigue limit of material. The method has also proven to be potentially one order of magnitude faster than traditional thermal methods.

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A study of the Friction Stir Welding (FSW) process was carried out in order to evaluate the influence of process parameters on the mechanical properties of aluminum plates (AA5754-H111). The process was monitored during each test by means of infrared cameras in order to correlate temperature information with eventual changes of the mechanical properties of joints. In particular, two process parameters were considered for tests: the welding tool rotation speed and the welding tool traverse speed. The quality of joints was evaluated by means of destructive and non-destructive tests. In this regard, the presence of defects and the ultimate tensile strength (UTS) were investigated for each combination of the process parameters. A statistical analysis was carried out to assess the correlation between the thermal behavior of joints and the process parameters, also proving the capability of Infrared Thermography for on-line monitoring of the quality of joints.

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