Determining fatigue limits with thermal analysis of static traction tests

This work evaluates the limit stress of the thermo-elastic phase of deformation by thermo-analysing the surface of a specimen during a static traction test. By adding a temperature curve measured over a small area of the surface to the classical stress-strain curve, it is possible to evaluate a limit temperature T-0 that is coincident with the beginning of the curve's nonlinear trend. The corresponding stress value is as estimation of the fatigue limit of the component under analysis. The authors derive an expression to evaluate temperature during a mono-axial static traction test. As an example, temperature curves recorded during traction tests performed on two notched steel specimens are reported and compared with this proposed expression. The change to the linearity in the temperature curve during the static traction test is evident in these examples and the corresponding stress value is an estimation of the fatigue limit of the component under analysis.