Research On Fretting Fatigue Damage And Its Fatigue Life Influence Factors Of 45 Steel

Fretting fatigue damage lies in machine components widely, which interfaces mostly bear alternate load, such as bolts, axletrees, slots and tenors. The fretting result from alternate load makes fatigue cracks initiation in interfaces and accelerates their propagation, and results in components' failure under the fatigue limits of material. The fatigue life descends greatly and catastrophic accidents may arise.In this study, the fretting fatigue test of 45 steel is executed, the fretting damage process and the influence factors on fretting fatigue life is experimentally studied systemically. Firstly, the surface topography of worn zones, and the abrasive dust layer are investigated by means of microcosmic observation analysis. The change of the fretting wear process during the test and the fretting wear mechanism are discussed. Secondly, the distribution of the stress on the contact surface and the field of the stress under the contact surface are analyzed. A finite element model is set up according to the geometry configuration, the contact type and the boundary conditions of the test contact model. With this finite element model, the contact stress on contact surface is obtained by numerical value calculation. The friction force f, the relativeslippage 5 and the maximal pull stress on the contact surface σ_T are got.Accordingly, the numerical analysis of fretting contact is come true.A test equipment with two fretting bridge is designed and developed to independently control the contact pressure p. Fretting fatigue tests are conducted for five values of contact pressure and seven values of axial stress range Sa. The Sa-N curves are got; the results show that the fretting fatigue life decreases as the contact pressure increases. They are numerically analyzed and formulized.Finally, the sample surfaces under different cycles are investigated by microcosmic observation, the fatigue rupture location and the crack propagation orientation are found, and the results are agree with the ones of ANSYS simulation based on the cracks propagation criterion raised by Ruiz.Based on the experiment research and finite element analysis, the fretting wear mechanism and the influence factors on fatigue life are made clear in this paper.