## 3 Results
### Full-Field DIC Study
#### 3.4.2 Adjustment and Positioning of the Magnet Without Load  
The main purpose of the magnet holder is to ensure precise calibration of the magnet position. This task is studied in detail in the two subsections. First of all the influence of the tightening of the adjusting screws on horizontal deformation of the inner frame was studied. The obtained results (Figure 23) revealed that increasing the tensile force in the adjusting screws does not significantly affect the horizontal deformation of the inner frame.  
The possibilities and the range of positioning of the magnet position are shown in Figure 24. Here, the series of curves describe the location of the points LC and RC in the function of the adjustment of bolt torque \(M_{r}\). The curves were designated for different clamp-bolt-tightening torques \(M_{c}\). The different initial position for \(M_{r}=0\) Nm is caused by clamp-bolt-tightening torque \(M_{c}\). As it was discussed in the previous subsection, larger \(M_{c}\) causes larger movement of the magnet in the positive direction (moving away from the frame). The increase in the adjustment bolt torque \(M_{r}\) results in moving the magnet in the negative direction (into the inner side of the frame). The torque was changed within the range \(M_{r}=0\)-\(10\) Nm in each test and it caused the movement of the magnet by about  
Figure 23: Influence of adjustment bolt torque \(M_{r}\) on horizontal inner frame deformation.  
Figure 22: Deformation of magnet holder and repeatability of measurements.  
0.55-0.60 mm. This is almost two times larger than the required range of the magnet positioning. It should also be noted that the relationship between magnet displacement and torque \(M_{r}\) is linear in the investigated range.  
The accuracy of DIC analyses was evaluated based on the difference in displacements between photos taken at different times but for the same loading conditions. Based on six measurements, the difference in DIC calculation for LC and RC points was in the range of 1-25 \(\upmu\)m, and the average difference was equal to 16 \(\upmu\)m. However, it should be noted that bolts were tightened and loosened during the tests, which might also affect the position of the holder. Summing up, DIC results should be considered sufficiently accurate.  
The next experiment was focused on the assessment of the modification of the magnet face inclination angle. In this case, the clamp-bolt-tightening torque \(M_{c}\) was set as constant, and the measurement was divided into two parts, S1 and S2 (Figure 25). Both series were compared with deformations obtained under the uniform tightening of adjustment bolts (blue line in Figure 25). In the first one (S1), the adjusting bolts on the right-hand side were completely loosened and only bolts on the left-hand side were tightened using torque \(M_{r}\) in the range of 0 Nm-10 Nm. It is obvious that this led to a larger lowering of the magnet on the side where adjusting bolts were tightened (see Figures 25 and 26a). In the second part (S2), the adjusting bolts on the right side were tightened using torque \(M_{r}\) in the same range of 0-10 Nm. In both series S1 and S2, the slope of the curves (orange color) is different on both sides of the magnet and in comparison with the curve for uniform bolt tensioning. This confirms the possibilities of the additional adjustment (but in a smaller range than \(\pm\)0.15 mm) of the magnet's face inclination angle.  
Figure 24: Influence of adjustment bolt torque \(M_{r}\) and clamp-bolt-tightening torque \(M_{c}\) on magnet displacement.  
Figure 25: Influence of adjustment bolt torque \(M_{r}\) on magnet displacement.