The equations for fatigue potential energy and the lethargy coefficient are derived from the dynamic fatigue life equation, whilst the static fatigue equation is used in the uniaxial tensile test for a damage accumulation process. Microstructural processes during high-cycle fatigue are investigated according to plastic strain-hardening, crack formation, crack propagation and fracture. It is shown that the fatigue test resembles the uniaxial tensile test. The logarithm of the number of cycles-to-failure is proportional to the elongation in the tensile test, which emerges from the resemblance of the two tests. The proportional constant is a function of Young's modulus. Transformation procedures from the stress-strain curve of tensile test to the SN curve of the fatigue test are illustrated, including finding the fatigue limit. It is shown that the fatigue limit, the ultimate point, the yield point, and the fractured point have a one-to-one correspondence in the tensile test and the SN curve of the fatigue test.