Bearing Damage Research Articles

Geometric Attention Regularization Enhancing Convolutional Neural Networks for Bridge Rubber Bearing Damage Assessment

Rubber bearing condition evaluation is crucial for bridge inspection, and the current practice heavily relies on human-vision inspection. Convolutional neural networks (CNNs) have shown great potential for structured damage recognition tasks in recent years; however, this method usually requires a large training data set, which is difficult to collect in practice for rubber bearings. Therefore, methods to improve the performance of CNN for condition classification for elastomeric bearings are necessary. In this paper, a geometric attention regularization (GAR) method is proposed to enhance the performance of CNN for the condition evaluation of rubber bearings. Firstly, the data set of bearings contains different damages that are collected and labeled where the location of the rubber bearing is presented as a bounding box. Then, the location information is utilized to enhance the loss function of CNN in two aspects. On one hand, the bearing location worked as an attention mechanism to indicate the important part of the input image. Besides, it worked as a regularization method to mitigate the effect of overfitting. Experiments using two CNN architectures, including VGG-11 and ResNet-18 trained with transfer learning techniques, are used to evaluate the efficacy of the proposed method. The results show the proposed method is effective to enhance the performance of the CNN model.

Influence of variability and uncertainty of wind and waves on fatigue damage of a floating wind turbine drivetrain

This study investigates the effect of variability and uncertainty of wind and wave conditions on the short-term fatigue damage of a 10-MW floating wind turbine drivetrain. Global dynamic responses of a semi-submersible wind turbine are calculated by aero-hydro-servo-elastic simulations in various environmental conditions. Then, rotor and generator loads, as well as nacelle motions from the global analysis are provided to a drivetrain model to investigate its dynamics. One-hour fatigue damage of the drivetrain bearings is calculated based on the bearing loads and speeds, and the effect of uncertainties related to wind and waves is assessed. The results indicate that the variations of mean wind speed, turbulence intensity and wind shear have great effects on the studied drivetrain. The effect of uncertainties of irregular waves on the drivetrain fatigue damage is small. Five wind and wave random samples are sufficient for dynamic analysis of the drivetrain to achieve accurate results at a reasonable computational cost. Among the drivetrain components, the main bearings are generally most sensitive to the investigated environmental variables. Finally, this study discusses the variation of environmental variables in terms of their relative importance for drivetrain analysis. The results provide a basis for establishing improved design standards and engineering practice for design and analysis of floating wind turbine drivetrains.

Stochastic Transverse Earthquake-Induced Damage Track Irregularity Spectrum Considering the Uncertainty of Track-Bridge System

The track irregularity spectrum of longitudinally connected ballastless track (LCBT)-bridge systems of high-speed railway was proposed in this paper. First, a simulation model of an LCBT-continuous girder bridge was established by considering the influences of approach bridges and subgrade with track structure. Further, a large number of sample analyses were carried out by taking into account the uncertainty of LCBT-bridge systems and stochastic behaviors of ground motions based on the simulation model. The damage laws of residual deformation of track-bridge system after earthquake actions were studied. Then, an interlayer deformation coordination relationship (IDCR) considering the track irregularity caused by earthquake-induced damage of bearings was developed, and the superposed track irregularity samples were obtained. Finally, by using the improved Blackman–Turkey method and Levenberg–Marquardt algorithm, the LCBT irregularity spectrum, track irregularity spectrogram, track irregularity limit spectrum, and a fitting formula for the track irregularity spectrum on a bridge after the action of earthquakes were obtained. Results obtained from the fitting formula and IDCR were compared, and they indicated that tracks undergone significant high-frequency irregularity diseases after the earthquake action. It was found that the track irregularity spectrum could be roughly divided into three ranges: high-, medium- and low-frequency wavebands. Consequently, this led to an application of a three-segment power function for the fitting of the track irregularity spectrum after the earthquake action. The track irregularity spectrum after the action of earthquakes provides an important theoretical basis for the establishment of seismic design methods for high-speed railway bridges based on the traffic safety performance.

Effects of cleaning detergent/water-in-oil emulsions on elastohydrodynamic lubrication

PurposeThe cleaning of food production equipment using cleaning detergents may contaminate the lubricant of the bearings, thereby reducing the bearing service life. The purpose of this paper is to investigate the cause and mechanism of such damage of bearings lubricated by cleaning detergent/water-in-oil emulsions.Design/methodology/approachThe emulsion was prepared by adding a mixture of cleaning detergent and water in one base oil. A self-designed ball-on-disc optical interference test rig was applied to examine the effect of emulsion on lubrication and wear of bearing contacts under pure sliding conditions.FindingsThe emulsion reduced lubricating film thickness at a relatively low-sliding speed but only when the water concentration (20%) in emulsion was high. Water droplets were trapped around the ball-on-disc contact area under static conditions because of a high capillary force. The emulsion can induce damages on the soft surface in the startup mainly due to the presence of water around the contact.Originality/valueThe basic lubrication behaviour of water/oil emulsions containing cleaning detergent under pure sliding was experimental studied and the mechanism of bearing damage in food production equipment was investigated. Based on the study, the solution to avoid such damage was proposed.

An Enhanced Virtual Space Vector Modulation Scheme of Three-Level NPC Converters for More-Electric-Aircraft Applications

Multilevel converters have been used for aircraft electric starter/generator (ESG) systems due to their high power qualities. One of the desirable topologies is the three-level neutral-point-clamped converter. Our studied ESG system operates at a high speed during its generation mode, which results in high modulation index and puts some specific challenges on neutral-point voltage balance, especially under low power factor load conditions. Moreover, common-mode voltage (CMV) needs to be addressed properly as it leads to irreversible damage of motor shaft bearings, thereby degrading the efficiency and reliability of the entire system. Compared with the conventional nearest-three virtual space vector technique, the proposed modulation scheme employs three adjacent medium vectors to synthesize a new medium vector and two pairs of large vectors to compose new small vectors. This allows the presented modulation scheme to achieve balanced capacitor voltage and reduced CMV at the same time. In addition, the torque ripple of the proposed modulation strategy is thoroughly compared and analyzed. Meanwhile, in order to overcome the heavy computational burden, a fast calculation approach is adopted to simplify the algorithm. Simulation results obtained from Simulink/PLECS and experimental results obtained from a 45 kW, 32 kr/min aircraft ESG system verify the effectiveness of the proposed strategy in more-electric-aircraft applications.

Analisa Kerusakan Pompa OCCWP Pada Pembangkit Listrik Tenaga Uap 2 x 115 MW

The use of pumps in the industrial world, especially in power plants, cannot be separated from problems that arise that can cause losses. The research was conducted at PLTU 2 X 115 MW by taking a case that had happened to the pump, namely the Open Cycle Cooling Water Pump 2A. The analytical method used in this final project is the vibration analysis method, namely by reading the spectrum of the data retrieval results so that it can be seen what happens to the equipment that experiences an increase in vibration.
 Bearing damage can be seen in the spectrum image of the measurement results, where the appearance of the spectrum in the high frequency range is an indication of bearing damage. And the high vibration which reaches 13.06 mm/s and is already in the danger category based on ISO 10816-3.

Early Weak Fault Diagnosis of Rolling Bearings Based on Fiber Bragg Grating Sensing Monitoring

Aiming at the problems of weak dynamic response and difficulty in diagnosis of early damage of rolling bearings, a diagnosis method for early damage of rolling bearings is proposed. Taking radial rolling bearings as the main research object, the load symmetric structure of deep groove ball bearings is analyzed. Based on the mechanical second-order system theory, the sensor monitoring structure is constructed. The generalized resonance principle is used to identify weak signals, and the fiber Bragg grating is used for signal sensing. The signal is obtained through the fiber Bragg grating high-speed demodulator. When a continuous periodic generalized resonance wave appears in the amplitude–frequency analysis of the signal, and there is a high-frequency resonance frequency, it can be proved that the bearing is faulty. The diagnosis method can effectively avoid the interference of low-frequency signals, the frequency spectrum is pure and there is no electromagnetic interference. It fully shows that the fiber Bragg grating sensor is suitable for the monitoring and diagnosis of the early weak fault of the bearing.

A comparative study of fully coupled and de-coupled methods on dynamic behaviour of floating wind turbine drivetrains

Traditionally, drivetrain responses are obtained by a de-coupled analysis, which first involves a global analysis with a simplified representation of the drivetrain, followed by a detailed analysis of the drivetrain with the input of global response on the drivetrain interface. As the wind turbine size increases, it is questionable whether this de-coupled analysis method yields sufficiently accurate results. To address this question, a comparative study of the drivetrain dynamic behaviour obtained by a fully coupled method and a de-coupled one, is conducted and reported in this paper. A 10-MW fully coupled aero-hydro-servo-elastic floating wind turbine dynamic model is developed, including a high-fidelity drivetrain. The developed fully coupled model is assessed to be reasonable via the comparison of drivetrain first-order natural frequency and code-to-code comparisons in terms of global responses between two simulation tools Simpack and Fast. Resonance analysis of the 10-MW drivetrain in the fully coupled model is performed, with focus on rotor-drivetrain-bedplate-tower coupled modes in the low frequency range. Time domain simulations of the drivetrain in the fully coupled and the de-coupled models are carried out in different environmental conditions. One-hour fatigue damage of drivetrain gears and bearings in the fully coupled and de-coupled models are compared. Effect of nacelle motion on drivetrain fatigue damage in the de-coupled analysis is discussed. The results are presented to demonstrate whether the de-coupled method could be confidently used for drivetrain dynamic analysis. This study provides a basis for drivetrain design and dynamic analysis in floating wind turbines.

Fractographic study into the effect of drilling damage on bearing mechanisms and performance in Carbon-Fibre epoxy composites

With the widespread adoption of polymer composites in primary structures, understanding and prediction of the performance of composite to metal hybrid joints is now critical to engineering design of transport structures. This work investigated the damage processes associated with bearing failure of such composite joints, for both pristine holes and holes damaged during drilling. An aerospace grade composite was drilled under three different conditions, tested to failure under quasi-static double bearing loading, and then characterised using fractographic techniques. In the pristine condition, the initial damage process was 0° longitudinal splitting tangential to the lateral extents of the hole which then dictated the extent of the subsequent bearing damage development. Beneath the bearing face of the hole inclined lines of in-plane microbuckled fibres had developed whilst beyond the constraint of the washer there was considerable delamination and massive out-of-plane fibre microbuckling. As the degree of drilling damage increased, 0° longitudinal split development was inhibited, and the local pre-existing damage at the periphery of the hole had extended into the bearing damage zone, directly initiating out-of-plane fibre microbuckling. Consequently, the bearing damage zone exhibited irregular distributions of fibre microbuckles, both across the thickness and depth beneath the bearing face of the hole. The observations in this work provide a means to validate predictive models and offer potential routes to improve bearing performance and the tolerance of laminates with drilling damage when under bearing loads.

Effects of Bearing Steps on Probable Wear Damage of Main Bearings of an IC Engine

When two bearing shells are assembled in the bearing housing, it is possible that the edges of the two shells do not fit in the radial direction completely and have an offset relative to each other. This assembly error, which can have different causes, is called the bearing step in this paper. The bearing step can lead to wear damage in bearings. The effects of bearing step on the lubrication performance of main bearings and the probable wear damage have been investigated. To calculate the bearing lubrication characteristics such as maximum oil film pressure and minimum oil film thickness, elasto-hydrodynamic model, which includes the mass conservation algorithm, has been applied. The objective of this work is to investigate the effects of bearing steps on the lubrication performance of the main bearings and assess the probable wear damage of main bearings due to bearing step. The prediction of elasto-hydrodynamic model is very proximate to what really happened. The results show that for the under-study 12-cyl engine, main bearing No. 2 involved with medium wear damage. Wear damage in this main bearing No. 3 is not a concern, while main bearing No.4, 5 and 6 do not predict the probability of wear damage. For main bearing No.7, it is concluded that considering step and bore relief in simulation has high importance so that the solution without step and bore relief does not predict the wear, but with step and bore relief predicts medium wear damage.

Bearing capacity and damage behavior of HCFTST columns under cyclic loading

This paper conducted a comprehensive study on the bearing capacity and damage behavior of circular high-strength concrete-filled thin-walled steel tubular (HCFTST) columns based on the quasi-static seismic test. The moment-axial force relationship was first analyzed in fiber element method, and the influences of key parameters including the peak strain of concrete, material strengths and diameter-to-thickness (D/t) ratios were investigated to develop a practical design method. Then, a dependent triaxiality fracture criterion of high-strength (HS) steel was introduced to establish the finite element damage model for revealing the seismic damage behavior of HCFTST columns, and subsequently a modified restoring force model based on the truss mechanism and the unified theory of concrete-filled steel tube was established and verified. The result indicates that: increasing the steel yield strength, reducing the concrete strength as well as the D/t ratio could respectively push the moment-axial force curves moving inward; the proposed parabolic moment-axial force curve agreed well with the tested bearing capacity; the HS steel tube generated a deep plasticity accumulation to induce the ductile fracture, and the concrete damage area appeared in a V-shaped distribution; increasing the axial compression ratios and D/t ratios amplified the fracture damage of the steel tube web; the established restoring force model displayed a comparatively reasonable accuracy on the degradation behavior (e.g., bearing capacity and stiffness) and the hysteretic characteristic (e.g. softening platform). The aforementioned study could provide the meaningful references for the design and seismic analysis of HCFTST columns.

Smart Anomaly Detection and Prediction for Assembly Process Maintenance in Compliance with Industry 4.0.

One of the big problems of today’s manufacturing companies is the risks of the assembly line unexpected cessation. Although planned and well-performed maintenance will significantly reduce many of these risks, there are still anomalies that cannot be resolved within standard maintenance approaches. In our paper, we aim to solve the problem of accidental carrier bearings damage on an assembly conveyor. Sometimes the bearing of one of the carrier wheels is seized, causing the conveyor, and of course the whole assembly process, to halt. Applying standard approaches in this case does not bring any visible improvement. Therefore, it is necessary to propose and implement a unique approach that incorporates Industrial Internet of Things (IIoT) devices, neural networks, and sound analysis, for the purpose of predicting anomalies. This proposal uses the mentioned approaches in such a way that the gradual integration eliminates the disadvantages of individual approaches while highlighting and preserving the benefits of our solution. As a result, we have created and deployed a smart system that is able to detect and predict arising anomalies and achieve significant reduction in unexpected production cessation.

Experimental Study on Basic Mechanical Properties of Core-Column Non-mortar Aerated Concrete Block Masonry

Autoclaved aerated concrete (AAC) block masonry has been widely used for bearing walls of multi-story buildings or non-bearing walls of high-rise buildings because of its unique advantages, such as lightweight, low pollution output, and excellent thermal insulation performance. However, traditional AAC block masonry has the disadvantages of high water absorption, poor adhesion to mortar, and low construction efficiency. In order to improve the performance of traditional AAC masonry, this paper proposed a new kind of mortar-free AAC block masonry with concrete core-columns. Fundamental mechanical properties of compression and shear were studied. We divided a total of 16 compression specimens into four groups according to different hollow ratios and strength grades of the block, and eight shear specimens into two groups based on different hollow ratios. Each specimen consists of three-layer blocks with two core columns at the point of quadri-section. The diameters of columns were, respectively, 100 mm and 80 mm. The specimens were loaded at a constant speed to evaluate their bearing capacity, displacement response, crack development, and damage state. The formula of the average values and design values of the compressive and shear strength of masonry were obtained statistically. The stress–strain constitutive relation of masonry expressed by a three-stage curve was presented. Furthermore, the result of numerical analysis using the ABAQUS finite element program aligned well with the experimental results. The compressive strength and shear strength of the new type of masonry are no less than traditional AAC masonry, and new masonry has higher construction efficiency and more stable strength.

Enhancing gearbox vibration signals under time-varying operating conditions by combining a whitening procedure and a synchronous processing method

Condition monitoring is very important to avoid unexpected breakdowns of expensive rotating machines found in the power generation and mining industries. The fault information in vibration signals is often buried in low energy frequency bands. In addition to this, time-varying operating conditions and the presence of impulsive components result in the signal to have time-varying spectral content, which impedes the condition inference process. The instantaneous power spectrum is a powerful method that for bearing and gear damage detection under time-varying operating conditions. In this work, we propose a new method of using the instantaneous power spectrum for improved fault diagnosis under time-varying conditions by enhancing the fault information in the vibration signals. It is shown on experimental datasets that the proposed method enhances the fault information in the signal, whereafter it can be used to obtain reliable condition indicators under time-varying operating conditions.

AE source location of debonding steel-rod inserted and adhered inside rubber

Rubber bearings have been applied worldwide to bridge and building components. However, it comes out a critical issue, since significant amounts of damage and deterioration of the bearings have been reported. Therefore, the authors attempted an experimental study on damage evaluation of rubber bearings, by using acoustic emission (AE) method. In the case, it was found that the velocity of the elastic-wave propagating inside the rubber was slower than those of concrete, steel, and other rigid materials. As a result, one question remains on the location accuracy, where AE sources are generated inside the rubber.In order to clarify an applicability of AE method to damage evaluation of rubber bearings, experimental research was conducted. A steel rod was inserted in a rubber specimen and the tip of the rod was adhered. Then, debonding of the rod was measured with a pull-out test. Even distances from the tip of the steel rod to the rubber surface were investigated. Two types of AE sensors were used, with resonances at 60 kHz and 150 kHz. A three-dimensional location analysis was performed by AE method to identify debonded locations. Thus, both applicability and accuracy of AE method in the rubber bearings are verified, and a good promise to evaluate the damage in the rubber bearings is confirmed.

Experimental investigation of ultra-low-cycle fatigue behaviors of plate bearings in spatial grid structures

Ultra-low-cycle fatigue failure of plate bearings in steel grid structures is likely to occur due to an earthquake, which leads to a failure or even complete grid collapse. In this study, the effects of different variables on the hysteretic behavior, skeleton curves, stiffness degradation, and angles of inclination of the bearings and the anchor bolts were investigated. These variables included the vertical force, diameter of anchor bolts and extra baffles. For these purposes, ultra-low-cycle fatigue tests on six groups of plate bearings were carried out under constant vertical loading and horizontal reciprocating variable loading. In addition, the morphological analysis of fatigue fractures was performed to investigate the failure mechanism of anchor bolts in the bearings. It was found that the anchor bolt is the weakest part of the plate bearings during strong earthquakes. Cracks originate at the root of the anchor bolt and expand as the stress concentration increases and a typical ultra-low-cycle fatigue fracture micro-morphology appears. Also, it was also found that adding a baffle in an appropriate position on the bearings can improve the resistance ability against falling from the base supports providing that the baffle capacity is designed properly. Furthermore, a formula for the relationship between horizontal stiffness degradation and cumulative damage of a plate bearing is established. This formula can provide a reference for the seismic capacity evaluation of plate bearings used in spatial grid structures.

Damage tolerance and toughness of elderly human femora

Observations of elastic instability of trabecular bone cores supported the analysis of cortical thickness for predicting bone fragility of the hip in people over 60 years of age. Here, we falsified the hypothesis that elastic instability causes minimal energy fracture by analyzing, with a micrometric resolution, the deformation and fracture behavior of entire femora. Femur specimens were obtained from elderly women aged between 66 – 80 years. Microstructural images of the proximal femur were obtained under 3 – 5 progressively increased loading steps and after fracture. Bone displacements, strain, load bearing and energy absorption capacity were analyzed. Elastic instability of the cortex appeared at early loading stages in regions of peak compression. No elastic instability of trabecular bone was observed. The subchondral bone displayed local crushing in compression at early loading steps and progressed to 8 – 16% compression before fracture. The energy absorption capacity was proportional to the displacement. Stiffness decreased to near-zero values before fracture. Three-fourth of the fracture energy (10.2 – 20.2 J) was dissipated in the final 25% force increment. Fracture occurred in regions of peak tension and shear, adjacent to the location of peak compression, appearing immediately before fracture. Minimal permanent deformation was visible along the fracture surface. Elastic instability modulates the interaction between cortical and trabecular bone promoting an elastically stable fracture behavior of the femur organ, load bearing capacity, toughness, and damage tolerance. These findings will advance current methods for predicting hip fragility.

Experimental investigation on bearing behavior and failure mechanism of double-lap thin-ply composite bolted joints

Thin-ply laminated composites have recently gained increasing attention in the aerospace engineering field, due to enhanced design possibilities and positive size effects with regard to decreasing ply thickness. In this paper, the mechanical behavior of thin-ply laminate and TC21 titanium alloy hybrid joints with double-lap bolted structure under quasi-static loading was studied experimentally. X-ray computed tomography (CT) scanning and SEM microcosmic imaging at special stages of the whole loading process were used to clarify the progression of bearing damage and fastening hole deformation characteristics of laminates. A more gradual damage and failure in bearing was observed in all specimens from the stress-displacement curves. The final failure of hybrid joints is a combined mode of bolt tensile cracking and hole bearing deformation. More importantly, the common delamination of standard-ply composite laminated plates in the bearing failure plane and tensile failure plane was suppressed in thin-ply laminates, resulting in higher bearing failure strength and more damage accumulation. Therefore, the novelty of this work contributes to detailed experimental observations of the bearing failure mechanisms, which provide valuable information for developing accurate mechanism-based failure models to be used in simulations.

Bearing Damage Detection of a Bridge under the Uncertain Conditions Based on the Bayesian Framework and Matrix Perturbation Method

The bearing of a bridge, as a critical component, is important in the force transformation of the superstructure; however, due to the service condition and repeated impact load, the bearing is prone to be damaged but difficult to detect the damage; the present research has few studies that focused on the damage detection of the structural bearing. Meanwhile, practical engineering is always surrounded by variational environmental conditions, and sometimes, the element and bearing damage both exist in the structure. Thus, these uncertain conditions all cause inaccurate damage identification results using the vibration‐based damage detection method. In order to detect the damage of the structural bearing and improve the precision, firstly, the structural dynamic characteristic equation considering uncertain conditions has been deduced; then, a damage detection framework constructed by the Bayesian theory and perturbation method has been developed in this article; a numerical example of an 8‐span concrete continuous beam and a practical example of I‐40 steel‐concrete composite bridge are utilized to validate the feasibility of the proposed method, and single type and two types of damage cases are studied. The outcomes demonstrate that the damage of structural elements and bearings can be detected with high accuracy. The proposed method is of great applicability and good potential.

Analysis of Contact Mechanical Characteristics of Flexible Parts in Harmonic Gear Reducer

Harmonic gear reducer is widely used in industrial robots, aerospace, optics, and other high‐end fields. The failure of harmonic gear reducer is mainly caused by the damage of flexible bearing and flexspline of thin‐walled vulnerable components. To study the contact mechanical characteristics of flexible components such as flexible bearing and flexspline in harmonic gear reducer, the contact mechanical model of flexible bearing, vibration differential equation of flexspline, and finite element model of each component in harmonic gear reducer were established. Based on the established model of harmonic gear reducer, the influence of the length of flexspline cylinder and the thickness of cylinder bottom on the stress of flexspline is discussed, respectively, and the motion characteristics of flexible bearing are studied. At the same time, the spatial distribution of the displacement of the flexspline and the axial vibration response of the flexspline are studied. The correctness of the model established in this paper is verified by experiments. The results show that the increase of cylinder length can improve the stress of flexspline in harmonic gear reducer; the wall thickness of cylinder bottom mainly affects the stress at the bottom of flexspline but has little effect on the stress of gear ring and smooth cylinder. Along the axis direction of the flexspline, the radial displacement, circumferential displacement, and angular displacement increase linearly with the increase of the axial distance between the cylinder and the bottom. When the excitation frequency is high, the vibration mode of flexspline shell is mainly axial vibration. The research results will provide a theoretical reference for the optimal design of harmonic gear reducer and improving the service life of flexible parts.