Testing and Analysis of Uniaxial Mechanical Fatigue, Charpy Impact Fracture Energy and Microhardness of Two Low-Carbon Steels

The paper presents and analyzes the results of experimental tests performed on two non-alloy low carbon steels (1.1141 and 1.0122) in cases of their exposure to impact fracture energy and uniaxial high cyclic mechanical stress-controlled fatigue. The experimental results provide insight into the changes in the Charpy impact fracture energy of the V-notched test specimen that occur as a result of temperature changes. The experimental results also provide insight into the mechanical response of the tested materials to mechanical uniaxial high-cycle fatigue at room temperature in an air atmosphere and at different applied stress ratios. Material fatigue tests refer to symmetric (R = -1), asymmetric (R = -0.5) and pulsating tensile (R = 0) cycles. The test results are shown in the S-N diagrams and refer to the highest applied stresses in relation to the number of failures at a given stress ratio. Using the modified staircase method, the fatigue limit (endurance limit) was calculated for both tested materials at each prescribed stress ratio. For both tested steel al-loys, and at prescribed stress ratios, the fatigue limit levels (sigma_f) are shown as follows: for steel C15E+C (1.1141)-> sigma(f)[250.8(R)=-1; 345.4(R)=-0.5; 527(R=0)] (MPa); and for steel S235JRC+C (1.0122)-> sigma(f) [202(R)=-1; 310(R)=-0.5; 462(R=0)](MPa). All uniaxial fatigue tests were performed on unnotched, smooth, highly-polished specimens. The microhardness of both materials was also tested.