Determining the friction, wear and damage behaviour of aero engine components under realistic operation conditions is important to improve the long-term reliability and efficiency. A special test rig ...for single plain bearing bushes of the variable stator vane (VSV) system was designed to investigate these components under engine-like conditions. It is found that four main wear and failure phenomena occur during the testing of VSV bushes. These include heavy abrasive wear on the inner contact area, wear on the flange contact area, plastic deformation and material failure as well as heavy wear and debris on the spindle. Results from polyimide-based plain bearing bushes show that the operational torque and wear rate remain almost constant, as long as no failure of the bush occurs.
•Novel test rig for single plain bearing bushes of the variable stator vane system under engine-like conditions.•Conditions cover temperature, air pressure and loads for current in-service but also future aero engines.•Four main wear and failure phenomena occur during the testing of VSV bushes.•Until failure, the operating torque and wear after an initial run-in phase remain almost constant for polyimide-based bushes.
A new type bearing named self-lubricating ellipsoidal plain bearing was proposed and successfully prepared by cold extrusion forming technology. Through finite element method and experiment, the ...dynamic distributions of the contact stress, wear depth and the worn morphology of the fabric liner were investigated. Results show that the contact and wear performances can be improved by reasonable design of bearing flatness. When the radial load is 1000 N, the contact stress distribution of the bearing with flatness of 0.005 is the most uniform. Compared with traditional spherical plain bearings, the maximum contact stress is decreased from 32.407 MPa to 26.880 MPa, and the maximum wear depth is decreased from 0.0754 mm to 0.0688 mm after 25000 swings.
•Maximum contact stress is decreased from 32.407 MPa to 26.880 MPa.•Maximum wear depth is decreased from 0.0754 mm to 0.0688 mm.•Suspended structure of the outer ring is constructive to store debris and form PTFE self-lubricating film.•Contact stress distribution of the bearing with flatness of 0.005 is the most uniform.
Wear resistance of dynamic system components is a major challenge in aeronautics. According the usage of the aircraft, off-centred dynamic loads can appear on shafts when rotating bodies are ...unbalanced. In literature, most of the wear studies applied to plain bearing consider static loads centred in the contact area. This article presents a study on the wear of a plain bearing submitted to off-centred dynamic loads in order to look for a better mastering of service life of plain bearing for their usage in severe aeronautic conditions. Boussinesq's equations were used to compute the pressure distribution and Archard's law was used to calculate the wear. The wear coefficients of the running-in and stable wear stages were defined experimentally. The evolution over time of the maximum wear depth and the size of the contact zone were validated with experimental results. The perspective of this work is to feed digital twins of dynamic systems in order to predict wear according aircraft usage.
•Numerical model developed to predict wear of a plain bearing system.•Off-centred and dynamic loads were considered.•Model formulation is based on the equations of Boussinesq and Archard.•A test rig was designed and used to validate results of the model.
The swaging quality of self-lubricating spherical plain bearings (SSPBs) has an important influence on the safety of the aircraft. The roller swaging process has an edge on other swaging processes in ...low swaging load and high swaging quality. The 3D elastic–plastic finite element model of roller swaging and push-out test were developed, and the influence of the roller swaging process loading parameters, such as the swaging time, the swaging load and the rotation speed of the roller tool on the push-out load, the gap between the flanging lip of the V-groove and the housing chamfer, and the radial displacement (the inner surface of the outer ring) after roller swaging were studied. Finally, the roller swaging test was conducted, and the test results were compared with the simulation results. The research shows that the test results are consistent with the results of the simulation model, and with the increase of the swaging time, swaging load, and rotation speed of the roller tool, the gap will be increased as well, resulting in an increase in the push-out load. However, the excessive swaging load and rotation speed of the roller tool will increase the radial displacement, which will result in a reduction in the rotation flexibility of the bearing. Under the conditions of reasonable swaging time and swaging load, a good swaging quality can be obtained by controlling reasonable rotation speed of the roller tool.
Tribological Analysis of a Radial Plain Bearing Vela, Daniel-Gheorghe; Vela, Ion; Miclosina, Calin-Octavian
Robotică şi management (Reșița),
06/2022, Letnik:
27, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The paper presents experimental determination of the friction coefficient variation at a radial plain bearing, depending on the values of the radial force R and the angular speed ω of the spindle at ...a constant lubricant temperature value.
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A stochastic model of the wear process of a thin coating in a radial plain bearing that takes into account random changes in the bearing temperature and external load is described. The results of a ...numerical analysis of the process of bearing wear in relation to the conditions of operation in open space at near-Earth orbital stations are presented. The importance of taking into account random changes in temperature and external load for predicting bearing wear and, in particular, its durability is evaluated.
Wind energy is an important renewable energy source. Rotor main bearings are critical components of wind turbines since a faulty main bearing leads to downtime and high repair costs. Operational ...expenditures amount to 32% of wind energy costs. The use of plain bearings as main bearings can potentially reduce these costs. Plain bearings with segmented sliding elements can be repaired up-tower without dismantling the drivetrain, as damaged segments can be exchanged individually. One such segmented plain bearing design is the conical plain bearing design called FlexPad. For the FlexPad, proof of concept was achieved for the 1 MW range during previous studies. Modern wind turbines—especially for offshore deployment—have increased in size significantly compared with their predecessors. The goal of current studies is to transfer the FlexPad design towards a main bearing unit at a market relevant scale of 8.5 MW. In this work, the identified scaling challenges are presented. A FlexPad model scaled to the 8.5 MW range is presented to illustrate the challenges. The bearing load components, such as radial forces and torque, increase on different scales with increasing rotor size leading to changed load characteristics with increasing size. Increased rotor weight and bearing diameters result in an increase in the breakaway torque required to start turbine rotation. This breakaway torque can exceed the torque generated by the turbine at starting wind speeds. The generally increased loads necessitate stiffer sliding segments leading to the increased weight of the segments, which hampers the ability to easily exchange segments.
The issues of cavitation processes in radial bearings are discussed. The operating conditions of such bearings and the effect of cavitation on their operation are considered.
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•Transfer film in-situ observation is achieved at cryogenic and wide temperature range.•Freezing molecule inhibits reorientation and transfer of PTFE with increased friction.•Brittle ...delaminated PTFE below 190 K forms less-oriented uneven transfer film.•Friction and materials transfer inflect at 190 K due to totally restricted molecules.•Rough counterface benefits materials transfer and low friction at low temperatures.
The time evolution and temperature dependence of friction along with transfer film morphology and composition for the polytetrafluoroethylene (PTFE) fabric composite lubricated spherical plain bearing was unraveled through a home-made cryogenic tribotester integrating in-situ Fourier Transform Infrared (FTIR) microscopy. Specifically, the temperature dependence of which shows two regions divided by 190 K, and PTFE plays a crucial role on the lubrication of the fabric composite. Thin and uniform transfer film generally forms at 323 K, however, with decreasing temperature, friction increases and transfer film formation is suppressed, which is attributed to the freezing molecular chain movement and inhibition of molecular reorientation of PTFE. After reaching the highest value around 190 K, friction coefficient slightly decreases with further decreasing temperature due to the brittle delamination of PTFE fragments and formation of less-oriented and patch-like uneven transfer film. The transition temperature around 190 K is closely related to the γ relaxation of PTFE owing to totally restricted mobility of PTFE molecules. Furthermore, inner ring with a surface roughness of 200–300 nm is found to be beneficial to materials transfer and lower friction by increasing plastic flow of PTFE lubricating material at cryogenic temperatures.
Electron beam physical vapor deposition (EB-PVD) with high power axial EB guns has high deposition rates and therefore is well suited for depositing comparatively thick coatings with high throughput ...in mass production processes. The top sliding layer on bearing shells is a well-known use case for this technology. In low-cost manufacturing, often semi-finished products such as sheets or strips are coated, from which final products with a broad range of dimensions can be manufactured.
The adaptation of related processes such as pretreatment and substrate cooling of three different semi-finished products was the focus of the investigations. All process steps were optimized for high throughput. Deposition with AlSn or AlSnCu alloys was carried out at coating rates up to 1 μm/s. These alloys, containing elements with different vapor pressures, were evaporated out of one continuously fed crucible with long-term stability.
The deposited coatings have finely dispersed tin clusters in the aluminum matrix. The tin clusters have linear dimensions in the range of 200 to 400 nm. This size range is a direct consequence of the high coating rate; it is thus process-specific for EB-PVD. Such coatings are highly beneficial for applications such as plain bearings. Initial load tests have impressively confirmed the advantages for EB-PVD processed bearings.
•Aluminum-tin alloys were deposited by EB-PVD at a static deposition rate of up to 1 μm/s.•The pretreatment process and substrate cooling have been optimized for high throughput.•The technology has been adapted to different types of semi-finished products: bearing shells, metal sheets, and strips.•The AlSn coatings have finely dispersed tin clusters with linear dimensions ranging from 200 to 400 nm.•Initial load tests showed a high load capacity of the manufactured bearings.
