## 4 Results and Discussion  
The influence of imperfections shown in Figure 2 for the case using a copper pulse shaper is shown in Figures 6-9. Figures 6 and 7 show the curves for an imperfection in the form of an inclination angle \(\alpha\) in the range of 0 to 1.5\({}^{\circ}\) for both the incident and reflected signals, respectively. The next figures present the same curves as related to an imperfection in the form of a neutral axis offset (\(\delta\) = 0-1.5 mm) of the incident bar and the striker.  
Only a small part of the energy was transmitted through direct contact between the striker and the input bar.  
Figure 8: Incident-disturbed pulses for SHPB using a pulse shaper for an imperfection in the form of neutral axis offset \(\delta\).  
Figure 6: Incident-disturbed pulses for SHPB using a pulse shaper for an imperfection in the form of an inclination angle \(\alpha\) between the striker and input bar.  
Figure 7: Reflected disturbed pulses for SHPB using a pulse shaper for an imperfection in the form of inclination angle \(\alpha\) between the striker and input bar.  
In contrast, in all the analyzed cases of an imperfection related to the displacement of the neutral axes of the striker and the bar, the level of the disturbances caused by a bending wave was much lower not only in the case of the incident pulse (Figure 8) but also for the reflected pulse (Figure 9). This imperfection had a very small influence on the pulse rise time. The pulse disturbances that occurred in the plateau stage for the largest displacement (\(\delta\) = 1.5 mm) also had a lower amplitude when compared to the data from the previously analyzed case of imperfection. The shape of the disturbance was also different; in the case of the displaced neutral axes, the disturbance had a sinusoid shape with comparable amplitudes. However, when an inclination angle occurred, large differences in the disturbances amplitude occurred. The difference in the pulses' disturbances resulted from a difference in the position of the contact points between the striker and input bar. The shift of the contact point was greater in the case of an imperfection related to the inclination angle.  
A similar situation occurred when a pulse-shaping technique in the form of a striker with a rounding radius of 120 mm (Figures 10-13) was applied. In this case, the effects of the imperfection were much smaller. This was especially visible in the case of reflected pulses and the imperfections related to an inclination angle (Figure 11), where the occurring disorder only slightly affected the impulse course. In contrast, in the case of an imperfection related to the displacement of the neutral axes, the influence of the existing axis shift was negligible in the considered range of the parameter \(\delta\) (Figures 12 and 13). It should be noted that this disorder amplitude was related to the distance between the end of the barrel and the occurrence of clearance between the striker and the input bar. If these parameters increased, the amplitude of the disturbances in the signals increased.  
Figure 10: Incident-disturbed pulses for SHPB using a rounded striker for an imperfection in the form of inclination angle \(\alpha\) between the striker and input bar.  
Figure 9: Reflected disturbed pulses for SHPB using a pulse shaper for an imperfection in the form of neutral axis offset \(\delta\).  
Both types of the analyzed imperfections, especially the inclination angle, significantly affected the reduction of the high-frequency Pochhammer-Chree oscillations.