Loading Capacity Research Of Thin Solid Film On The Surface Of Bearing Steel Based On The Analysis Of Interfacial Mechanics

Thin solid films are widely used for space and aerospace,such as the near earth,interstellar space,and even the deep sea.The key point is the work performances and lifespan of the solid films.In this dissertation,thin solid film was designed and implemented on the lubrication surface of close-packed ball bearing for the lunar exploration program's mechanical device.Here,the failure process and interfacial mechanics characteristic were studied for typical solid film lubrication on the surface of bearing steel.This will be a basis for mechanical structure and lubrication design.The element solutions were deduced of the two-and three-dimensional concentrated forces which were applied on the surface of thin solid film.With the method of image in the complex variable theory,the two boundary conditions – free surface and continuous interface – were equivalently transformed into different mirror orders as the cumulative form.The boundary conditions were satisified when the recursive coefficients of every mirror order were precisely selected for the film and the substrate.Thereby,the stresses and deformations inside the two materials and along the interface were gained analytically.With the integration of concentrated surface force,distribution force with the normal load and tangential friction force were taken into account.So the interfacial mechanics model was built in two-and three-dimensional.For the Hertz's point contact,the integrating process of the element forces could be simplified by the transversely isotropic stress potential function solutions.Again the solutions for stress and deformation under the effects of Hertz's point contact were gained according to the method of image.By comparison with the finite element method,this model had the same accuracy but faster computing speed and better adaptability for different input variations or parameters.Based on the typical laminated Mo S2(Molybdenum disulfide)and hard brittle DLC(Diamond-like Carbon)solid films,the tribological and failure characteristics were analyzed and evaluated by using ball on disc tester,and nano / micro scratch tester.Combined with the interfacial mechanical calculations,the stress-respose feature and the boundary of failure parameter were analyzed.For Mo S2 solid film,it behaved layer-slip inside solid film under low stress level,and peeling off into sheets under high stress level.While for the DLC film,cracks inside the solid film initiated and propagated along the end of the sliding direction and interfacial dislocation at the front of the sliding direction.With the required load-carry capacity in the drill device,the structural design and load-distribution analysis were fulfilled for the close-packed ball bearing system.The interfacial stress conditions were verificated for MoS2 and DLC films according to the boundary of failure parameter.Finally,the lubrication performance of thin solid films was experimented on the bearing bench under simulation conditions.