Study On Bending Fretting Fatigue Damages Of CuMg0.4 Alloy

Fretting fatigue has always been an invisible killer in the mechanical field.It promotes the initiation and propagation of cracks in the contact area of fretting damage and greatly shortens the service life of the components.In the era of mechanical structure and mechanical connection covering various fields,it has undoubtedly become the focus of quality and safety.In this paper,under the different parameters,the bending fretting fatigue test in the conventional environment was carried out on the self-designed bending fretting fatigue device with High-speed railway contact net overall hanging string material(CuMg0.4 alloy).The S~N curve was built up,and the damage area was analyzed according to a series of microscopic analysis equipment,such as scanning electron probe microscope(SEM),white light interferometer(WLI),electron microprobe(EPMA),stereomicroscope,etc.Then the bending fretting fatigue characteristics and damage related laws of the material were discussed.Finally,the following conclusions were drawn:(1)Running characteristics of bending fretting fatigue of CuMg0.4 alloyThe fatigue life S~N curve established by the bending fatigue fretting test results of a series of CuMg0.4 alloys shows that the fretting fatigue life of the material tends to decrease with the increase of bending stress,and then tends to increase.It also shows a decreasing trend.The jog runs in sequence on the PSR(partial slip zone),MFR(mixing zone),and SR(complete slip zone).(2)Damage mechanisms of bending fretting fatigue of CuMg0.4 alloyThe contact damage areas of the three regions of the curved fretting fatigue part,the mixing zone and the complete slip zone were found to have oxidative wear,abrasive wear,fatigue wear and adhesive wear by microscopic morphology analysis and composition analysis.There are four kinds of damage mechanisms,and the wear end wear is relatively serious.(3)Mechanism of initiation and propagation of fatigue cracksThe damage morphology of the contact area appears as an asymmetrical ellipse as a whole,and the fretting fatigue cracks are initiated on the subsurface of the contact area which is about 60~70μm deep from the loading end side.After section crack analysis and fracture morphology results It is shown that the bending fretting fatigue fracture process of CuMg0.4 alloy material is mainly divided into three stages: 1 crack initiation: stress concentration and contact area wear phenomenon cause microcracks to start at the subsurface near the loading end side.And gradually expand to the surrounding;2 Accelerated expansion of crack: As the crack continues to expand,after reaching the bending stress control depth,the combined effect of normal stress and bending stress causes the crack to continue to accelerate and expand,and its expansion direction is 45° to the surface of the material.3 The final extension of the crack: After the crack propagates to get rid of the influence of the contact stress,it continues to expand under the bending stress until the sample breaks,and its expansion direction is 90° to the surface of the material.