## 2 Materials and Methods
### Experimental Setup  
For our investigation, a simple experimental setup that allows comprehensive observation of a high-speed deformation was necessary. Therefore, it was focused on high-speed tensile tests carried out in a commercial high-speed testing machine, Zwick HTM 16020. The geometric shape of the specimen is shown in Figure 1. This geometry is optimized for use on the high-speed test machine from Zwick and proved to be suitable in previous experiments. The asymmetrical specimen shape results from the test principle of the Zwick/Roell 16020 high-speed materials testing machine used. To achieve the very high test speeds of up to 20 m/s or strain rates of 1000/s, an acceleration distance is required, which is realized over the upper specimen length. Furthermore, there is an end-position damping that must be added to this distance. The thickness of the samples is 1 mm, the measurement length is 20 mm, and the width in the thinning area is 16 mm. Three samples were tested for each of the strain rates considered. In the uniaxial tensile test, the nominal strain rate can be calculated directly from the nominal traverse velocity, v, with knowledge of the measurement length, L, via Equation (1). \[\mathrm{d}\epsilon/\mathrm{d}t=\mathrm{v}/\mathrm{L} \tag{1}\]  
The tests are performed at constant nominal test speeds v = 0.002 m/s (nominal strain rate 0.1/s), v = 0.1 m/s (nominal strain rate 5/s), v = 1 m/s (nominal strain rate 50/s), v = 4 m/s (nominal strain rate 200/s), and v = 20 m/s (nominal strain rate 1000/s). The strain in the measuring area is optically recorded by an extensometer Rudolf 200 XR. Therefore, the front side of the specimen is primed white and the measuring area is painted black, creating sharply defined lines that can be easily detected by the extensometer, as shown in Figure 2 on the left. The corresponding force is determined by a piezo load cell that is integrated into the testing machine. Tests were conducted at room temperature in order to quantify the adiabatic heating in the fracture region of the sample. A thermal camera VarioCam with a maximum frame rate of 1000 was used to measure the temperature change during the test. For this purpose, the back side of the specimen is painted black as shown in Figure 2 in the middle. The maximum acceleration distance to reach the test speed is 150 mm, as the outer cage moves downwards at the start of the test and would otherwise press on the upper specimen grip. The thermal camera allows observing the temperature distribution in the complete measurement area at discrete time steps. The wavelength range for the thermocarora is 3-5 um and emissivity is equal to 0.91. However, for the necessary resolution of the pictures of 640 \(\times\) 480 pixels, the frame rate is limited to 1000 frames per second. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Grade** & **R\({}_{\text{p0,2}}\) (MPa)** & **R\({}_{\text{m}}\) (MPa)** & **A\({}_{\text{80}}\) (\%)** \\ \hline DC06 & 137 & 291 & 41 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mechanical properties of the material sheet at quasistatic load. Figure 1: Schematic drawing of a sample in mm. In preliminary tests, it was found that this frame rate is sufficient to observe the time-dependent development of the temperature distribution for test speeds in the magnitude of up to 1 m/s and corresponding strain rates of up to 50/s. For higher tests speeds, it is no longer possible to obtain a sufficient number of pictures during the test to draw reliable conclusions regarding the temperature development during the test and specifically to observe the temperature during failure of the specimen. To overcome this restriction, a high-speed pyrometer IGA 740 from Lumasense, with a frequency of scanning of about 160 kHz, was used in addition to the thermal camera. It allows observing the time-dependent mean temperature in a small stationary area--a measurement point with a diameter of 1 mm.