# Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography
## 2 Materials and Methods  
In this investigation various testing systems have been utilized comprising of both MTS 250 kN Landmark servo-electric and servo-hydraulic load frames. Focusing on the heating and temperature control systems employed, these include IC, RLF, pyrometers, thermocouples and infra-red thermography cameras. The heating systems and their associated temperature control techniques investigated and compared in this investigation are listed in Table 1.  
The 12 kW RLF comprises of two longitudinally divided half cylinders hinged at the centre, with each half containing six lamps. The 12 high-power, vertically mounted quartz lamps heat the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**ID** & **TMF Test Type** & **Heating System** & **Temperature Control Technique** \\ \hline
1 & Strain Control & Non-Uniform multi-turn longitudinal field helical coil & Pyrometer \\
2 & Load Control & 12 kW Infra-red radiant lamp furnace & Non-contact thermocouple \\
3 & Crack Growth & Non-uniform multi-turn longitudinal field helical coil & Thermocouple \\
4 & Load Control & 12 kW Infra-red radiant lamp split furnace & Thermography \\  & & (6\(\times\) blubs, horizontal configuration) & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Heating and temperature control techniques employed and compared within this investigation. specimen to the test temperature. Behind each lamp is a parabolic reflector, which focuses the radiant light toward the centre of the furnace. The infra-red camera was mounted on the front of the RLF, positioned to image the specimen through the extensometer portal, shown in Figure 1a. A second generation RLF furnace was designed in collaboration with Severn Thermal Solutions Ltd. with thermography temperature control at the forefront of the design specification. The 12 kW RLF is a standard split body design with each half containing three horizontally mounted lamps. The external surface of the RLF is coated black with analdite to avoid any reflective radiation complications with the infra-red thermography temperature control. Example images of the bespoke setup are given in Figure 2, with a schematic representation shown in Figure 3. The furnace has been specifically designed to accommodate both an extensometer and a non-invasive temperature measurement device, through two opposing furnace windows. Three independently controllable heating zones allow for accurate temperature control and profiling, wrist built-in internal compressed air cooling delivers the rapid cooling rates required by the complex TMF waveforms. Figure 1: A 1 st generation 12 kW vertically mounted quartz lamp infra-red radiant lamp furnace (**a**) Furnace overview with infra-red camera externally mounted, aimed at the test specimen through the extensometer furnace window; (**b**) Internal furnace view, displaying a side mounted extensometer between the arms the ceramic housing for the non-contact control thermocouple. Figure 2: A 2 nd generation 12 kW horizontally mounted quartz lamp infra-red radiant lamp furnace (**a**) Front view, displaying externally mounted pyrometer aimed at the test specimen through a furnace window; (**b**) Rear view, the temperature controlling infra-red camera aimed at the test specimen through the rear furnace window is visible. As previously mentioned, induction heating is an established method of providing rapid and reliable dynamic heating and as such in this investigation a Trueheat 10 kW induction coil (IC) heater is used to deliver an effective method of heating metallic specimens to temperatures up to 1200 \({}^{\circ}\)C. Peak temperatures and heating rates are dependent on the material, coil design and specimen geometries employed. Metallic materials were heated directly with tailored IC design, ensuring uniform heating over the entire gauge section of the test piece. Depending on the coil design used, this system enabled an infra-red camera to be mounted in various positions around the test piece to enable a 360\({}^{\circ}\) view of both heating and cooling effects.