This scientific paper presents two approaches, based on the thermographic technique, for fatigue assessment and stress
measurement. The first method, based on the lock-in thermography, is an energy approach; it takes intrinsic dissipation as the fatigue indicator, and evaluates the fatigue limit through a drastic change in the rate of dissipated energy. The second method is the Thermographic Method, which takes temperature increment as the fatigue indicator to assess the fatigue limit of materials and mechanical components. The Energy Approach of the Thermographic Method is based on the energy expression of linear fatigue cumulative damage hypothesis and allows the rapid assessment of the whole S-N curve. This research paper advances this quantitative thermographic method for residual fatigue life assessment. A stress analysis technique, known as SPATE (Stress Pattern Analysis by Thermal Emissions), measures the temperature
variation due to the thermoelastic effect for stress determination, which could be unfaithful when the stress level is relatively high. Thus we proposed to use the Thermographic Method to assess the cyclic stress amplitude σa through the
S-N curve. Good predictions were achieved using all the methods.