Contribución del tratamiento de shot-peening y el tratamiento térmico en la vida a fatiga de los engranajes

Abstract

Gears are used in transmission systems in many different industries, such as the automotive or aerospace industry, lifting or power generation. Due to their operating conditions, tooth bending fatigue is one of the most common failure modes in gears. In this regard, case hardening and shot-peening treatments are often applied to improve the mechanical properties of the surface and thus the mechanical fatigue resistance of these components. However, the contribution of these treatments is usually taken into account on the basis of standards in a very conservative way, so that their effectiveness and potential are not fully proven. In this work, the contribution of shot peening and heat treatment (case hardening) to the fatigue resistance of gears under single tooth bending fatigue (STBF) conditions is numerically evaluated. This is the first part of a larger study, which will be followed by experimental validation. The case study chosen is a gear of normal modulus 6, made of 16MnCr5 steel. Four different conditions have been analysed: i) virgin (without any treatment), ii) case-hardened, iii) shot-peened, iv) both case-hardened and shot-peened. Firstly, the application of shot-peening on the tooth foot has been modelled to estimate the evolution of the residual stress pattern generated. The same procedure was used for the cementation treatment on the surface layer of the gear. Subsequently, the fatigue strength of the four gears has been numerically predicted considering the residual stresses of each case, for different load cases and considering the multi-axial fatigue parameters. Finally, the contribution of each treatment to the gear strength has been evaluated