## 3 Results and Discussion
### Damage Prediction Based on Impact Parameters  
The study of potato tuber damage from the working units of machines for the harvesting or the post-harvest processing of potatoes is usually challenging; the measurements of peak acceleration and changes in impact speed recorded with the IRD 400 electronic device should facilitate the prediction of damage. Based on the developed mathematical model, surface graphs were drawn up linking the tuber damage index DI of the Saturna and Hermes potato varieties with the acceleration and changes in velocity \(\Delta v\) of the impacts of the IRD 400 device with various surfaces (Figure 3). Based on the comparative graphs, it can be concluded that significantly lower values of damage indices were characteristic of Saturna potato tubers than those of the Hermes variety. The average values for these varieties were 21.0% and 28.4%, respectively (  
The results confirm research on tuber damage conducted by [PERSON] and [PERSON] [24], who found that steel surfaces and coated steel bars caused more extensive damage than the two-layer potato surface. Moreover, the absorbed energy required to obtain the minimum breakage or fracture surface volume on the tested tubers was higher for the two-layer potato surface than for the other surfaces. The highest values on the tuber damage index were calculated for their free-fall onto a rod conveyor (Figure 3c,d) and a steel plate (Figure 3g,h); for the Saturna and Hermes varieties, these values were 68% and 99%, and 76% and 96%, respectively. The minor differences in the tuber damage index values (12%) between the Saturna and Hermes varieties were recorded during the free-fall of samples onto a concrete surface (Figure 3g,h); the maximum values for this index were 60% and 72%, respectively. Based on all the research results in this field, it can be concluded that the IRD 400 device impacts, characterized by low peak acceleration values a, up to 50 \(g\), and velocity changes \(\Delta v\), up to 2.5 m\(\cdot\)s\({}^{-1}\), and the corresponding free-falls of tubers onto bulk potatoes or a rod conveyor, generated tuber damage in which the index did not exceed values of 2% and 5%, respectively (Figure 3a-d). [PERSON] et al. [2] and [PERSON] [10] also found a positive correlation between increasing impact acceleration and damage severity. [PERSON] et al. [2] reported that the potential for damage to potato tubers was high when the peak acceleration exceeded  
Figure 3: Tuber damage index \(DI\) for potato varieties: Saturna (**a,c,e,g**); and Hermes (**b,d,f,h**) from peak acceleration \(a\) and the change in velocity \(\Delta v\) of the IRD 400 device during impacts with: bulk potatoes (**a,b**); a rod conveyor (**c,d**); a concrete plate (**e,f**); and a steel plate (**g,h**). 100 \(g\), and that peak accelerations above 375 \(g\) were likely to cause visible damage. The authors used these threshold values (from 100 to 375 \(g\)) in their study to determine the risk of bruising depending on the type of packaging material, drop height, and impact force. In a study by [PERSON] and [PERSON] [7], accelerations exceeding 196 \(g\) on a sorting line caused damage of at least 10 mm in diameter. During the impacts on samples with a concrete or steel plate, the minimum peak acceleration exceeded the value of 200 \(g\). The change in the impact velocity \(\Delta v\) was greater than 3.4 m\(\cdot\)s\({}^{-1}\), resulting in damage to the tubers, in which the index value was at least 10% (Figure 3e-h). This means that even the lowest height of the free-fall of the tubers (0.30 m) onto the concrete or steel plate was too high. To not exceed the permissible damage index of 10%, falls onto this type of surface should be reduced, or the external surfaces should be covered with an elastic material, e.g., rubber or soft plastic, characterized by a high value for the elasticity coefficient. In a similar study, [PERSON] and [PERSON] [24] reported that single-tuber drop heights exceeding 15 cm on steel surfaces caused damage.