## 4 Conclusions  
The tensile stress profiles monitored at the strain gauge of the incident bar were interpreted using three types of stress waves: bar (**B**) waves, flange (**F**) waves, and a series of reverberation (**R\({}_{\bf n}\)**) waves. When the flange length (\(L_{\ell}\)) was long (\(L_{\ell}>L_{\rm s}\); \(L_{\rm s}\) is the striker length), the reflected **F** wave from the rear end of the flange reached the impact plane after generation of the waves (**B** and **F**) at the impact plane was completed. When the **F** wave entered the incident bar across the impact plane, reverberation occurred in the flange structure due to mismatch of the general impedance at the impact plane. When the signal was measured at the strain gauge position, the first reverberation wave (**R\({}_{\bf 1}\)**) was fully separated from the **B** wave in the time axis. When the flange length was intermediate (\(\sim\)\(D_{\rm b}<L_{\ell}<L_{\rm s}\); \(D_{\rm b}\) is the bar diameter), the reflected **F** wave from the rear end of the flange reached the impact plane before the simultaneous generation of the waves (**B** and **F**) was finished at the impact plane; this occurred during the period when the waves (**B** and **F**) were being generated at the impact plane. In such a case, the **F** wave coming from the rear end of the flange enters the incident bar across the impact plane without reverberation; the **F** wave is simply superposed to the **B** wave which is being generated, and the superposed magnitude is simply the sum of the interacting waves. When the signal was monitored at the strain gage position, a two-step pulse appeared; the first step was the **B** wave and the second step was the superposed **B** and **F** waves. The magnitude of the second step was twice that of the first step. When the superposition period was over (i.e., when the pulse generation event was over), the rear part of the **F** wave that entered the incident plane experienced reverberation. When the flange length was short (\(L_{\ell}<\sim\)\(D_{\rm b}\)), the reflected **F** wave from the rear end of the flange reached the impact plane a short time after the waves (**B** and **F**) started generation from the moment of impact; the **F** wave from the flange end reached the impact plane at an early stage of the pulse generation period. As the **F** wave from the flange end entered the incident bar without reverberation, when monitored at the strain gauge position, the following **F** wave was practically fully superposed onto the slightly prevenient **B** wave, resulting in a pseudo-one-step pulse. This observation indicates the necessity of a short flange length, from the view of obtaining a neat tensile pulse. The magnitudes and duration periods of the pulse plateaus were also analysed using one-dimensional impact theory, including a recently formulated equation for impact-induced stress when the striker and bar areas are different (Equation (4)), equations for the reflection/transmission ratios of a stress wave (Equations (5) and (6)), and an equation for the pulse duration time (Equation (7)). Consistency of the observed pulses with the one-dimensional theory was found, which verified the flange length-dependent stress transfer mechanism on a quantitative basis. The flange length-dependent stress transfer mechanism revealed above may serve as a solid background for the design of SHTBs. Investigation into the flange length-dependent interactions of the **F** and **B** waves revealed that, if the waves are superimposed while they are being generated under the influence of the area mismatch, the superposed magnitude is simply the sum of the interacting waves, despite the area mismatch, and no reverberation occurred as the **F** wave entered the bar with different cross-sectional area. This phenomenon observed when the impact and reflection surfaces were close may also serve as a background for interpreting wave interactions and its result (impact-induced deformation) at regions near the free surface of a three-dimensional protective structure.