Study On Wear Behavior Of Material In High Speed Bearing And Sealing Under Impact-sliding Condition

The wear problem of sealing, bearing, gear, pump and valve, caused by severe service conditions, including high temperature, high sliding velocity, extreme low temperature, high load and high frequency vibration, between wear parts, becomes increasingly serious, especially in the application of aviation, aerospace, national defense and high end civilian industry. The life, reliability, extreme performance and stablility of equipments are restricted by these problems. A kind of wear caused by impact-sliding motion between wear parts can induce severe abrasion, which leads to the sudden and abnormal failure of components, and failure of high speed mechanical system. An impact-sliding wear rig was designed and the fully coupled thermal-stress analysis model was constructed for this purpose. The research of mechanics of impact-sliding wear was implemented, using experiment and finite element analysis methods.First, an impact-sliding wear rig was designed and constructed, based on the working conditions of impact-sliding wear in sealing and bearing. This wear rig can display and store the physical parameters. The operation of the testing rig is flexible, the impact load is steady and it can endure long time operation. The results of repeatable tests exhibit good repeatability under the same test conditions. The testing rig meets the demands of the impact-sliding wear researches.To research the distribution of temperature and stress, caused by thermal-stress effect under impact-sliding motion, contact model was established. To increase the efficiency of calculation, a new contact tracking approach was adopted, using virtual contact loading method. The results show that impact-sliding contact causes transient heating and surfacial-tendency of shear stress. The gradient of temperature and surfacial-tendency of shear stress become intensively with the increasing of impact and sliding. The thermal influence area is thin, and the effect of thermal can take effects less than 0.3mm depth only. The thermal effects increase the gradient of mises distribution along depth direction, and the maximum mises stress is closer to contact surface.A four levels orthogonal table-L16(45) was adopted to design the experiments. The impact-sliding wear tests, including 5 sets of typical counterparts, were conducted, using the impact-sliding wear testing rig. The results, processed through multiple element linear regression and range analysis, show that impact motion, including impact frequency and impact load, has greater influence than sliding velocity on wear mass loss of impact specimens. The results of wear volume show clearly that although the titanium alloy TC4 has greater hardness than aluminum bronze, the wear volume of titanium alloy has much greater value compared with aluminum bronze yet. That is the phenomenon of the"the hard worn by the soft". The relationship between average wear loss and experimental factors, including impact frequency, impact load and sliding velocity, is of ternary linear regression, when 20CrNiMo steel and duraluminium alloy wear against GCr15 steel. The quantitative design of wear counterparts can be established, using this conclusion.To research the wear mechanism of materials under impact-sliding interaction, some non-destructive examinations have been performed on worn specimens, including 2D and 3D profilometry, scanning electron microscopy, XRD and EDS technology. The results show that after abrasion, the surface profile of metal specimens changes greatly with large numbers of flaking on worn track. It indicates that material flaking is the main cause of wear of metal impact specimens, under impact-sliding contact, and the wear mechanism of metal impact specimens is delamination wear. When the yield limit of material is high, fatigue flaking is in dominant position, and the flaking becomes serious with the increase of impact frequency. The cracks are of surfacial tendency with the increasing of friction coefficient. When the yield limit of material is low, the wear of impact specimens is caused by mechanical removal and adhesion mainly, and with the increase of experimental factors, the wear mechanism of impact specimens changes from mechanical removal to adhesion. When material is brittle, the particles flake off impact specimen constantly. A portion of these particles fill the interspaces of impact specimen. As a result, the number of micro-crack and porosity is decreased and the wear resistance is improved.Among 5 sets of experiments, the rotational specimen, made of titanium alloy TC4, wears more severely than impact specimen, made of aluminum bronze. This phenomenon can be explained by the behavior of copper-induced embrittlement of titanium alloy. The fracture strength and plastic property of titanium alloy decrease greatly as contacted with certain kinds of metal with low melting point, such as Cu and etc. With the increase of temperature, the diffusion of Cu is accelerated, and copper-induced embrittlement becomes severely. In other experiments of countparts, the wear loss of rotational specimen is not detectable, but the profile and micro-structure changed obviously yet. It can be found that the content of residual austenite increases. This phenomenon can be explained by the decrease of recrystallization temperature, caused by high friction-induced temperature and strain of contact area. This thesis provides the guide line to select wear counterparts properly under high frequency work condition.