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A series of bending fretting fatigue tests of 18CrNiMo7-6 alloy steel were carried out, the bending fretting fatigue S-N curve was built up, and an analysis was made on the test results. The results show that, the S-N curve of 18CrNiMo7-6 alloy steel presents a shape of "ε" curve, which is different from the medium carbon steel, and also different from the plain bending fatigue. With the increase of the bending fatigue stress, the fretting regime transforms from partial slip regime to mixed regime and slip regime. The wear mechanisms of fretting damage zones mainly are delaminated, abrasive wear and oxidative wear. In the mixed regime, the cracks are easy to initiate and propagate, and the cracks all originate from the subsurface of contact zone. Due to the different influence levels of the contact stress and bending fatigue stress, the initiation and propagation of the bending fretting fatigue cracks can be divided into three stages. Firstly, the cracks initiate from subsurface under the control of contact stress; then propagate to a larger angle direction under the joint control of contact stress and bending fatigue stress; lastly the cracks propagate vertically to contact surface until fracture failure under the control of bending fatigue stress.

The blends with higher damping performance was prepared based on nitrile butadiene rubber(NBR) with addition of graphene oxide(GO) and modified graphene oxide(MGO) prepared by improved Hammer method. Meanwhile, the damping property and the anti-aging property of the blends were investigated by DMA, AFM, SEM and so forth. The results show that after the addition of the GO and MGO, the tangent of loss angle(tanδ) increases and also the anti-aging property is improved. When adding less amount of GO in the matrix, the anti-aging property is better; when adding MGO in the matrix, the amount of addition is not obviously related with the anti-aging property of the blends. The dispersion of GO and MGO has positive correlation with its anti-aging property. By microscopic analysis, the main reason for the decrease of anti-aging property of the blends is the agglomeration of the GO. The interface effect formed by the addition of MGO and GO is the main reason for its high damping property and anti-aging property.

Bonded MoS2solid lubricant coatings are widely used in tribology for their friction-reducing and antiwear properties. However, such coatings have been rarely investigated in complex fretting conditions, such as dual-rotary fretting (DRF). DRF is a complex fretting wear mode that combines torsional fretting with rotational fretting. In this work, the antiwear properties of bonded MoS2solid lubricant coating under dual-rotary fretting conditions were studied. Results indicated that the MoS2coating had better friction-reducing and antiwear properties than the substrate for alleviating DRF wear. The coating can greatly influence the fretting regimes and reduce the coefficient of friction. Furthermore, the service life of the coating was strongly dependent on the competition of the two fretting components and was reduced as the rotational fretting component increased. [ABSTRACT FROM PUBLISHER]