# Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography
## 2 Materials and Methods
Both transversal and longitudinal electromagnetic fields are employed. Example images of the ICS setups and thermographic views of the specimen are given in Figure 4.  
Examples of different specimen geometries used to explore the flexibility of thermography are shown in Figure 5. HE23 TP was applied to some specimens to maintain a stable surface emissivity and different coating designs were employed for different applications, for example, for thermography control and complete gauge section temperature assessment the entire surface is coated, see Figure 5a. Specimens were coated leaving small areas of the specimen exposed to enable pyrometer or TC measurements upon oxidised surfaces, (Figure 5b or coated to allow stable pyrometer control (Figure 5c). Polished and pre-oxidised metallic specimen surfaces were also assessed, as well as a non-metallic CMC. An example of complications residing from polished metallic surfaces is given in (Figure 5d), where a lack of adhesion between the TP and polished metallic surface results in spallation of the paint after thermal exposure. Figure 3: (**a**) Schematic representation of the bespoke thermo-mechanical fatigue test setup tailored specifically for non-metallic materials utilising thermography; (**b**) Example overview of thermography view of test specimen temperatures. Figure 4: Example helical induction coil configurations used in this investigation; (**a**) Non-Uniform longitudinal field used for load control crack growth; (**b**) Non-Uniform longitudinal field used for extension control; (**c**) Thermography view of 7 \(\times\) 7 mm crack growth specimen in (**a**); (**d**) Split transversal electromagnetic field; (**e**) Thermography view of 7 \(\times\) 7 mm crack growth specimen in (**d**). Figure 5: Test-piece geometries and HE23 thermal paint coating combination examples used in this investigation. (**a**) Cylindrical specimen with gauge section entirely coated with HE23; (**b**) Cylindrical specimen with gauge section coated in HE23 allowing for thermocouple attachment; (**c**) Hollow cylindrical specimen with circular HE23 coated area for pyrometer measurement; (**d**) Rectangular, feature specimen with HE23 thermal paint spalling from a polished metallic surface. To avoid further spallation complications, prior to coating with TP, the specimen surfaces were lightly grit blasted with 120/220 grit to slightly roughen the surface so to improve the bond between the specimen and the TP as described in previous work [11; 13; 30]. A conventional air spray gun was used to apply the paint to a thickness of approximately 20-25 \(\upmu\)m [11; 13]. The paint was then air dried and cured in a furnace at 300 \({}^{\circ}\)C for 1 h.  
In order to compare the specimen temperatures from the diverse techniques in this investigation, six type N TCs at specific locations along the 25 mm specimen gauge section were used; top gauge face and edge +12.5 mm, centre gauge and face 0 mm and the bottom gauge face and edge \(-\)12.5 mm as shown in Figure 6. thermocouples were used to obtain a baseline temperature due to their low cost, simplicity of use, and because they are the most widely accepted measurement method in most mechanical testing standards [2; 3]. The TCs were used to measure temperature at the test-piece surface from the upper, lower, and centre locations of the gauge section. These temperatures were then used to validate measurements taken from thermography and pyrometer at the same locations on the test piece.