## 5 Simulation Results and Model Validation  
The simulation model was set up to replicate the experimental procedure in terms of geometrical boundaries and material properties. For the implemented simulation sequence, refer to Figure 5. The initial configuration of the simulation model was significantly less dense then the experimental configuration at around 53 % to 54 % due to the different filling process of the particles into the simulation environment compared to the manual filling in the experimental procedure. In order to obtain a comparable packed bed configuration with similar packing factor, the simulated packed bed was compressed / decompressed for 100 cycles instead of only six cycles. The simulated particles for the reference case were 14 mm in diameter, the same as in the experiment. In addition to the reference case with a uniform particle distribution, three supplementary simulations were conducted with the size distributions visualized in Figure 8. These simulations were carried out to gather insight about the influence of different particle size distributions regarding the resulting loads and to approximate the natural variances in size of the particles used in the experiment. It also highlights the advantage of the DEM model, since those straightforward simulations replace the otherwise required tedious experimental efforts. The results for the simulated packing factors at a temperature of 20 \({}^{\circ}\)C are displayed in Figure 9a. The packing factor increases drastically for early cycles, which mean the initial packed bed configuration is much looser then in the experimental run, where the increase in packing factor over multiple cycles is negligible (see Figure 7). Polydisperse distributions of particle sizes lead to a slightly denser packed bed configuration. The increase in packing factor slows down significantly with an increasing number of compression cycles, indicating the approach of a maximum dense packed bed configuration. The uniform particle size distribution and the distributions 1 and 2 show a parallel curve progression, whereas the slope of distribution 3 is slightly steeper. The reason for this is the broad particle size distribution, which takes more cycles to reach a maximum dense configuration of the packed bed. The stress-strain results for the final cycle are shown in Figure 9b. Only minor differences are observable between the different particle size distributions. While the maximum stresses of distribution 1 and distribution 2 are almost identical with the maximum stress of the uniform particle size distribution, distribution 3 is about 0.1 MPa lower. Again, the reason for this is the looser packed bed configuration of distribution 3 due to broader distribution. Figure 8: Particle size distribution of additional simulations: (**a**) distribution 1; (**b**) distribution 2; (**c**) distribution 3. Since the overall insignificant influence of the particle size distribution, simulations at elevated packed bed temperature levels were conducted only for the uniform particle distribution. In Figure 10, the simulated stress-strain relations for 20 \({}^{\circ}\)C and 600 \({}^{\circ}\)C particle temperature and a uniform particle size distribution are compared to the obtained experimental data. Here, the error bars of the experimental result represent the standard deviation of the mean values of four conducted experimental runs. For the simulation results, the error bars are not shown due to low stochastical differences between them. The simulated results conform quite well to the experimental data, both in quality and quantity, although the simulation curve appears to be smoother overall, and stresses at higher strains slightly fall off compared to the experimental results. Those differences are the direct consequence of simplified modelling assumptions, such as perfect sphericity and smoothness of the particles.