## 2 Materials and Methods
### Test Stand  
The test stand utilised for the study comprised the TIRAtest 2803 universal testing machine, operated using MATEST H009N software (Figure 1a), with an accuracy of 1 N [64; 65; 66]. The machine used in the research is built on a frame structure. The working beam is driven by a screw transmission, which in turn is connected via a toothed belt to a worm transmission. The machine is equipped with a modern servo drive [67; 68]. The software allowed the determination of the cutting force-deformation relationship through strength tests with an accuracy of 1 N, which was subsequently used to calculate shear stress and specific cutting energy. Shoot sections, each 200 mm in length, were mounted on a special head, perpendicular to the blade plane. Cutting measurements were taken at a constant speed of 10 mm/min. The basket willlow shoots analysed in the study are shown in Figure 1b.  
Figure 1: Test stand and materials: (**a**) testing machine; (**b**) shoots of the basket willlow analysed in the study.  
Ten repetitions were performed for each combination of variable parameters: shoot moisture content and blade sliding-cutting angle.  
The shear stress \(\tau_{t}\) was calculated for the maximum cutting force:  
\[\tau_{t}=\frac{F_{tmax}}{S_{t}} \tag{2}\]  
where:  
\(\tau_{t}\)--shear stress, MPa;  
\(F_{tmax}\)--maximum cutting force, N;  
\(S_{t}\)--cross-sectional area of the sample at the cutting point, mm\({}^{2}\);  
The specific cutting energy was calculated as the ratio of the total deformation energy to the cross-sectional area of the willow stem, using the following formula:  
\[E_{fit}=\frac{1}{S_{t}}\int F_{t}dx \tag{3}\]  
where:  
\(E_{fit}\)--specific cutting energy, mJ\(\cdot\)mm\({}^{-2}\);  
\(F_{t}\)--cutting force, N;  
\(S_{t}\)--cross-sectional area of the sample at the cutting point, mm\({}^{2}\);  
\(x\)--deformation (blade displacement), mm.  
Experimental results were evaluated using analysis of variance (ANOVA), while [PERSON]'s test was applied to identify and classify groups with homogeneous specific energy values. The analysis was performed using the STATISTICA software package, version 13.3.  
Figure 2: Blades used (variable sliding-cutting angle).  
[PERSON]'s multiple range test is a statistical test used to compare the means of multiple groups. It is a post-hoc test that is used after a significant difference has been found in an analysis of variance (ANOVA) test. The test determines which group means are significantly different from each other and groups them into subsets based on their similarities [69; 70].  
The test works by comparing the differences between the means of all possible pairs of groups. It calculates a critical value based on the number of groups and the number of observations in each group. If the difference between two means is greater than the critical value, then the means are considered significantly different from each other.  
To perform the Duncan test, the first step is to perform the ANOVA test (to determine if there is a significant difference between the means groups), then calculate the means for each group and the standard deviation of each group. The next step is to sort the groups in descending order based on their mean values and calculate the Duncan critical range (Q) based on the number of groups and the number of observations in each group. This will allow you to compare the differences between the means of all possible pairs of groups. If the difference is greater than Q, then the means are significantly different from each other. In the last step necessary to perform the Duncan test, the means should be grouped into subsets based on their similarities.