Figure captions

Figure 1 Cross-sectional view of a aluminum tube specimen and its torched region for repeated welding cycles and cross-sectional view of epoxy molded specimen for hardness measurements
Figure 2 Ten positions of upper and lower regions of aluminum tube specimen for micro‐Vickers hardness (Hv) measurements
Figure 3 Grain size images for multiple welding cycles: (a) 0 cycle, (b) 1 cycle, and (c) 5 cycles
Figure 4 Correlation between hardness and grain size for repeated welding cycles
Figure 5 Finite element model and boundary conditions of aluminum tube specimen for fatigue tests
Figure 6 Results of structural analysis under bending moment condition with cutting thicknesses:
(a) Selection of cutting thickness in the unprocessed state (t=0.94mm ), (b) Designed as a concave test specimen (R200 mm ) whose tube center thickness was reduced to 0.94 mm
Figure 7 Measurement of notch shape and size
Figure 8 Rotary bending fatigue test machine and representative fractured specimen after fatigue tests
Figure 9 (a) Fatigue test results at 25°C (black diamond, ◆) and 125°C (black triangle, ▲) (b) Fatigue test results for smooth specimens (black triangle, ▲) and notched specimens (white triangle, △) at 125 °C
Figure 10 Maximum principal stress of notched tube specimen used to calculate material constant (\(a\)) of the Peterson equation