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• A contact multi-body dynamics model of an RV reducer is presented. • Vibration properties of RV reducer under excitation of faulty NBRs are studied. • The accuracy of the dynamic model has been confirmed by experimental tests. • Defect excitation has a unique periodic effect on the RV reducer's vibration. • The condition monitoring of RV reducer is supported by simulation and test data. The rotate vector (RV) reducer's needle roller bearings (NRBs) are vulnerable to wear and flaws such as fatigue spalling of the raceway material. Studying the vibration mechanism and the excitation laws of NRB failures is essential to enhancing the RV reducer's performance and comprehending its operating state. This paper presents a dynamic model of the RV reducer based on the theory of contact multibody dynamics. It integrates internal and external raceway defects and takes into account the synchronous contact interaction between NRB groups and the crankshaft and cycloidal gears, as well as the time-varying mesh stiffness in the planetary gear transmission and cycloidal pin transmission. The study demonstrates that the rolling of bearings and the meshing of internal transmission components are the primary causes of vibration in a healthy RV reducer through experimental verification and dynamic simulation analysis of the system with and without NRB failures. Both the crankshaft rotation frequency and the cycloidal gear rotation frequency affect the vibration excitation source's characteristic frequency. The vibration amplitude of the RV reducer is influenced by bearing flaws on a periodic basis. The impact of internal raceway defects is greater than that of external raceway faults, resulting in a notable rise in vibration amplitude. [ABSTRACT FROM AUTHOR]

In this study, an analysis was conducted to investigate how misaligned cardan shaft could result in failure of gearbox in CRH high speed train. The cardan shaft was used to provide rotating motion from motor to gearbox. The study began with an analysis of the failure of a serviced gearbox in CRH train. It was revealed that rotation of misaligned cardan shaft was the most likely candidate for gearbox fracture which led to total failure of the train. To explain how misaligned cardan shaft led to failure, a kinetic analysis of misaligned cardan shaft was first performed by analytically calculating the force acted on gearbox and followed by an experimental test to validate the results. The results from kinematic analysis indicated a small offset of cardan shaft led to huge inertial force and frictional force acting on the universal joints. These forces resulted in bending load acting on bevel gear shaft and led to vibration. The vibration caused excessive rubbing of the connection and resulted in looseness of the fit. Eventually the gearbox was fractured by violent collision. An experiment was conducted to validate the failure process. The experimental results confirmed the rotational misaligned cardan shaft caused impact between shaft and bearing block. Consequently, this paper proposes a detection method to monitor cardan shaft used in CHR high speed train. For the first time this work conforms it was essential to consider transport acceleration when analyzing unbalance force due to misalignment of cardan shaft. • Systematic studies of kinetics and dynamics of misaligned cardan shaft in rotation. • Design of experimental cardan shaft and test set-up to mimic real life operation. • Investigation on looseness of interference fit of flange leading to gearbox failure. • Confirming the inertial force caused by transport acceleration is the main reason leading to looseness. • Study on influence of misalignment on the friction force of cardan shaft. [ABSTRACT FROM AUTHOR]

A new model for mechanical analysis of the main shaft, self-aligning bearing and the cantilever bearingin wellbore trajectory control tool is presented. The theoretical model considered the effects of the parameters of the shell and the main shaft on mechanical analysis. Aiming at the problem of cantilever bearing, a finite element model (FE model) of interaction between cantilever bearing and main shaft is developed. The theoretical model and FE model are verified by experiments. The results show that, the inclination and stress concentration of the needle roller are the main reasons for the failure of the cantilever bearing. The maximum von Mises stress, deformation and inclinationare reduced by 48.62%, 66.19%, 48.09% respectively while changing the fillet radius from 0.25 mm to 0.75 mm. And the stress concentration of the needle roller and the cage in cantileverbearing can also be reduced by changing the distance between the eccentric ring and the bearings, the inner diameter of the shelland others while meeting therequirement of high build-up rate. • Presented a new theoretical model for mechanical analysis of the main shaft • The influence of main shaft parameters was analyzed. • Developed a finite element model to analyze the failure of cantilever bearing • The fillet radius of needle roller have obvious influence on the strength of bearing. • The theoretical model and the FE model were verified by experiments. [ABSTRACT FROM AUTHOR]

This paper presents a new stage of on-going research to fully characterize the rolling contact fatigue (RCF) damage observed in rail axle Compact Tapered roller Bearing Units (CTBUs). The bearings examined in this work have been removed from service, following the identification of degradation using on-board condition monitoring techniques. The running surfaces of the bearings were examined and the damage fully characterized using a mixture of metallographic, surface profilometry and high-resolution micro-Computed Tomography (μ-CT) techniques. In this manner the RCF was categorised by initiation mechanism: sub-surface or surface. This work has led to an increased understanding of the propagation of sub-surface and surface initiated RCF and its implications for life and condition of the bearing once failure has initiated. It was determined that the sub-surface initiated RCF damage was the first to occur in service and produced large craters on the bearing running surface. Once material had been lost in this primary manner, further secondary surface-initiating RCF grew from the edges of the large craters. It was deemed that the deep primary sub-surface RCF craters were more life limiting than the secondary surface damage. Therefore maps of the damage were created allowing the two mechanisms to be examined separately, both visually and by quantitative parameters such as volume loss, area, depth, roughness etc. [ABSTRACT FROM AUTHOR]

Rail axle-bearing failure is a serious issue that can affect passenger safety and generate large costs for operators from penalties, recovery, reduced train availability and repairs. Southeastern have fitted bearing sensors to their Electrostar fleet; these sensors identify rail axle-bearing degradation. In this paper (presented at ICEFA VI) we introduce an on-going study where ex-situ rail axle bearings with recorded vibration histories are being forensically examined. The ultimate aims of this work are (1) to link vibration signatures to levels of physical damage and (2) to identify any common factors that are causing bearing failures. The current work presents results from one removed bearing; this work highlights the methods and techniques being used to measure and quantify the physical damage, which include profilometry, X-ray tomography and metallography. The bearing described herein presented large subsurface white etched layers, rolling contact fatigue crack propagation and evidence of electrical arcing damage. [ABSTRACT FROM AUTHOR]

Highlights: [•] Correlation of noise signal and wear response via air-borne method due to sliding action. [•] Friction coefficient of A7075 bearing alloys against steel was in the range of 0.02–0.13. [•] Three distinct regions in the wear stages; the running-in, the steady state and the severe wear. [•] values were applicable to predict the K′ value with the accuracy of 96–99%. [ABSTRACT FROM AUTHOR]

Highlights: [•] Calculation model for dynamic load capacity of a large roller slewing bearing. [•] 3D FEM-model is used for calculation of internal contact force distribution. [•] Influence of support deformation and clearance on the contact force distribution. [•] Influence of the roller profile on the raceway loading. [ABSTRACT FROM AUTHOR]

Abstract: In present paper the premature failure of journal bearings encountered in sugar mills has been analyzed. The causes of bearing failure are identified by simulating the operating conditions and conducting controlled experiments on a fully automated Journal Bearing Test Rig with provisions for varied combination (i.e. load, speed, and lubricating oil) of operating conditions. The results of performance behavior (i.e. coefficient of friction, change in surface roughness and weight loss) of the bearings as observed in these experiments have been reported. The theoretical and experimental results indicate the existence of boundary lubrication conditions in sugar mill journal bearings. To mitigate the problem of relatively high wear, lubricating oil with boundary additives have been tried and results are reported. [Copyright &y& Elsevier]

Abstract: Multi-layered bearing systems used in the automotive industry show shielding and anti-shielding effects that reduce or amplify the crack driving force under large-scale yielding conditions. Using finite element analysis, it is shown that shielding in such systems results in path deflection and bifurcation despite the absence of mixed-mode loading. As the crack approaches a stiff layer, the tangential strains measured around a blunted crack tip model show a maximum corresponding to the direction of crack propagation. The distribution of such strains indicates the effect of shielding and the likelihood of the tip to deflect or bifurcate. The suitability of bi-layer and tri-layer bearing architectures is assessed through crack path and respective crack driving force predictions. [Copyright &y& Elsevier]

Abstract: This paper presents a failure analysis of a bearing sleeve made from GCr15 steel. The bearing sleeve fractured, when being interference fitted. The fracture surfaces were observed by visual and SEM. The crack initiated from the top end of the bearing sleeve and propagated towards the bottom. Intergranular brittle fracture is the main failure mechanism. Detailed investigation of the microstructure indicates needle-like bainite, with lamellar troostite occuring at grain boundaries as a discontinuous network. A banded structure was observed on the bearing sleeve material, but Charpy impact tests of samples taken from different orientations of the failed sleeve show that the failure of the bearing sleeve has nothing to do with the banded structure. The discontinuous network structure lowers the strength of the grain boundary. Insufficient quenching rate and low quenching temperature are responsible for the formation of the discontinuous grain boundary network. [Copyright &y& Elsevier]

In most machines, the vibration signature of bearing faults extends into a higher frequency range than most other components, and this allows separation. In the case of helicopter gearboxes, there is a very wide range of shaft frequencies between input and output, and the associated gearmesh frequencies cover the whole audio frequency range. Techniques have thus been developed to separate the gear signals from the bearing signals, based on their different statistical properties. Other techniques have been developed to separate gear and bearing effects even when they are combined multiplicatively rather than additively. The techniques are illustrated using case history data obtained from the US Navy, from faults in three helicopter gearboxes. [Copyright &y& Elsevier]

• The calculation methods of crossbeam considering bearings displacement are deduced. • The calculation method of crossbeam considering local failure of bearing are deduced. • The influence of displacement of bearings on the force of crossbeam are compared. • The influence of failure of bearing on the force of crossbeam are considered. • According to different failure modes, corresponding design suggestions are given. Aiming at the problem that the uneven deformation of the crossbeam of the new ground anchor counterfort grille dam under the impact of debris flow is easy to cause the overall damage of the structure, the crossbeam is simplified as a mechanics model of multi − span continuous beam supported on the grille columns, and the internal force calculation formulas of the crossbeam under the displacement and the local failure of the bearings are deduced. Combined with an example, during the process of bearings from the displacement to local failure, the internal force variation of the crossbeam are analyzed. The results show that when the single bearing is displaced, the mid − span bearing has the greatest impact on the internal force of the crossbeam. When the two bearings are displaced at the same time, the two side − span bearings have a greater influence on the internal force of the crossbeam. When three bearings are displaced at the same time, the influence on the internal force of the crossbeam is the smallest. When the single bearing fails, the failure of side − span bearing has the greatest influence on the internal force of the crossbeam, the mid − span bearing failure is second. Therefore, the reinforcement at each bearing of the crossbeam should be considered to meet the force requirements after the internal force redistribution in the design, so as to ensure the safety of the structure after the positive and negative bending moment of bearing are converted. In addition, when displacement or failure of bearings occur, attention should be paid to meet the limit requirements of structural deformation and stability. The research results can provide a theoretical basis for the reliability analysis of the new ground anchor counterfort grille dam. [ABSTRACT FROM AUTHOR]

• Metallurgical analysis was conducted on AISI 440C bearings to address surface distress. • During ground testing, running tracks were noticed on the contact surfaces of the balls. • Loss of hard and coarse carbide particles from the martensitic matrix is observed. • These particles once removed, can contaminate the lubricant. • Contaminated lubricant creates surface distress and progressive damage to the contact surface. Bearing damages in reaction/momentum wheels are detrimental to the life and performance of the spacecraft. The signature of performance degradation in spacecraft ball bearings includes an increase in the bearing friction as evidenced by the increase in wheel current with a simultaneous increase in the wheel bearing temperature. The potential source of the problem should be addressed to avoid the irreversible impact on mission life. This paper presents the details of metallurgical analysis conducted on AISI 440C ball bearings to address the issues which perhaps contribute to the above problem and suggest possible remedial measures to avoid the recurrence of such issues. During ground testing, surface distress/running tracks were noticed on the contact surfaces of the balls. Detailed metallurgical analysis revealed loss of hard/coarse primary carbides from the matrix. In a closed system, these particles once removed, can contaminate the lubricant and cause further surface distress and progressive damage to the contact surface. [ABSTRACT FROM AUTHOR]

• Failure of submarine thrust bearing was analyzed. • Calculations reveal that the maximum load of the bearing was not exceeded. • Engineering calculations point to insufficient oil flow at low temperature as the cause of failure. • Surface inspection and numerical calculations prove this hypothesis. • Possible means of increasing oil flow are presented. This paper presents an analysis of the combined thrust radial bearing of a submarine propulsion shaft. The lubrication system of the bearing is based on a fixed ring. The efficiency of the lubrication system depends on the shaft speed and temperature, which affects oil viscosity. In turn, the thrust bearing load also depends on the rotational speed of the shaft, because as the speed increases, the drag of the ship increases simultaneously, but this increase in load is accompanied by the increase of load capacity of the hydrodynamic thrust bearing. The analysis made it possible to assess the causes of bearing failure and formulate recommendations for bearing operation. [ABSTRACT FROM AUTHOR]