Synergistic effect of pre-cyclic loading on tensile properties and microstructural changes in low-carbon steel

Five and ten loading cycles were applied within the range of 0 to 30 kN in order to examine the effects of pre-cyclic loading on TMT steel bars. Grain refinement as a barrier to dislocation motion was the outcome of pre-cyclic loading, which greatly reduced plastic deformation and increased strength. The yield strength increased by 57% after 5 cycles and by 45% after 10 cycles as a result of grain refining. Furthermore, this reduced the elongation and impact energy of the pre-cyclic loaded materials by decreasing their ductility. However, crack formation brought on by high cyclic stress (10 cycles of 0 to 30 kN) impairs the steel's overall performance. The existence of cracks negated the strengthening impact of the ten cycles of pre-loading. SEM pictures showed that the pre-loaded samples' fracture surface had dimples, which suggested ductile fracture. The optical microstructure and SEM image show the crack that developed for the ten cycles of pre-loading. Nevertheless, the sample's hardness was unaffected by the fracture creation and appeared to have increased in both situations. The steel's tensile strength, toughness, UTS, ductility, and impact energy were all diminished by the microstructural crack that developed in the 10-cycle preloaded sample. The findings imply that mechanical qualities may deteriorate with increased cyclic loads (such as 10 cycles).