Main Shaft Research Articles

Destruction Characteristics and Control Countermeasure of Shaft Surrounding Rock Mass in Complex Geological Environment

Increasing construction depth, changeable failure formations, and redistributed stress conditions inevitably make the mechanical response of mining shaft rock mass complicated. The design method and construction technology of deep shaft need to be perfected urgently. We studied the stability and control method of a main shaft from −930 m located in a deep gold mine. It is concluded that the surrounding rock of the shaft faces conditions including non-high-stressed, high-stressed, and possible instabilities. The failure types include structural plane-controlled failure, deep stress induced failure, rock burst, low confining pressure shear failure, spalling, and frequent conversion of multiple failure. The damages of the surrounding rock mass at −930~−1500 m displayed “ear-shaped” damage, with damage ranges of less than 2.5 m. The shaft temporary reinforcement adopted bolt mResh beam support, in which the length of the bolt was 2.5~3 m, and the row spacing was 1.5 m. The steel type and diameter were determined by the on-site bolt pull test. This temporary support countermeasure plays an important role in preventing shaft deformation and is worth promoting in similar mines.

Dynamic reliability analysis of main shaft bearings in wind turbines

Tapered roller bearings (TRBs) are widely employed in large wind turbines as main shaft supports. The reliability of TRBs is directly related to the operational efficiency and safety of wind turbines. In this paper, a method for dynamic reliability analysis of TRBs used for supporting the main shafts of wind turbines is presented. First, a new quasi-static TRB model is established based on the meta-heuristic optimization algorithm. Then, the influence of preload, bearing clearance, and friction on the fatigue life of the TRB is investigated in detail. Moreover, considering the impact of uncertain factors, a dynamic reliability analysis of TRBs under fatigue load is conducted based on the composite limit state and adaptive double-loop Kriging theories. The effect of preload on the dynamic reliability of TRBs is assessed to guide the main shaft bearing assembly of wind turbines. Finally, a practical application example is provided to demonstrate the effectiveness and benefits of the proposed method.

The design of a new type coaxial multilayer rotor helicopter vehicle

Today’s small rotor helicopter vehicles mostly use electric motors and batteries as power sources. Most helicopter power configurations are either front powered or rear powered, causing the center of the helicopter to be offset. This kind of offset should be overcome by structural compensation or by adjusting the angle of attack of the blades, but some lift of the angle of attack will be sacrifice at the same time. This paper proposes a new type of electric helicopter powertrain design. The advantage of new type helicopter design is setting the centre of gravity at the centre position of helicopter. The main shaft of the helicopter through the power transmission method of the electric motor built into the internal gear of the star gear, which improves the design of the center offset of the helicopter. That is improved the flight stability of the helicopter. At the same time, in terms of power transmission, the motor power consumed by the primary gear power of the star gear, while the traditional helicopter power transmission method has three or four gear power losses. The new concept of electric motor with star gear structure proposed in this paper can effectively reduce the transmission power loss of the gear. In addition, the distributed power control system proposed in this paper also reduces the possibility of helicopter crash due to motor failure.

Synaptic branch stability is mediated by non-enzymatic functions of MEC-17/αTAT1 and ATAT-2

Microtubules are fundamental elements of neuronal structure and function. They are dynamic structures formed from protofilament chains of α- and β-tubulin heterodimers. Acetylation of the lysine 40 (K40) residue of α-tubulin protects microtubules from mechanical stresses by imparting structural elasticity. The enzyme responsible for this acetylation event is MEC-17/αTAT1. Despite its functional importance, however, the consequences of altered MEC-17/αTAT1 levels on neuronal structure and function are incompletely defined. Here we demonstrate that overexpression or loss of MEC-17, or of its functional paralogue ATAT-2, causes a delay in synaptic branch extension, and defective synaptogenesis in the mechanosensory neurons of Caenorhabditis elegans. Strikingly, by adulthood, the synaptic branches in these animals are lost, while the main axon shaft remains mostly intact. We show that MEC-17 and ATAT-2 regulate the stability of the synaptic branches largely independently from their acetyltransferase domains. Genetic analyses reveals novel interactions between both mec-17 and atat-2 with the focal adhesion gene zyx-1/Zyxin, which has previously been implicated in actin remodelling. Together, our results reveal new, acetylation-independent roles for MEC-17 and ATAT-2 in the development and maintenance of neuronal architecture.

A new method for contact characteristic analysis of the tapered roller bearing in wind turbine main shaft

Premature failures of TRB in wind turbine remain a significant contributor to high operation and maintenance costs. The analysis of contact characteristics is the premise of the TRB failure investigation. In this paper, a novel five degrees of freedom (5DOF) TRB model which considers bearing clearance and preload, is established. Instead of the Newton-Raphson method, the meta-heuristic optimization is adopted to solve the nonlinear system by the L2-norm minimization control. This improvement can intelligently judge the load region of TRB, avoid the selection of initial values and improve the convergence speed. The load distribution results are compared to the simulation results of the finite element model, Romax model and Harris model to verify the effectiveness of the proposed model. Besides, the proposed method has a higher efficiency than the existing methods. Finally, the influences of bearing clearance and preload on the contact characteristic and fatigue life are discussed.

Microstructure and tribological performances of M50 bearing steel processed by ultrasonic surface rolling

To prolong service life of M50 steel for the main shaft bearing, ultrasonic surface rolling process (USRP) was utilized to improve surface performances. The effects of USRP on surface integrity and tribological behavior were investigated. The results show the effect of USRP parameters on surface performances follows the order: feed rate > load > rolling times. During the USRP treatment, plastic deformation layer with 24 µm thickness is formed, and fine grain strengthening increases the microhardness (15.56%) and residual stress (79.61%) and decreases the surface roughness (−68.09%), respectively. Friction coefficient and wear rate of USRP sample are lower than those of untreated sample, because USRP helps form a smooth tribolayer and changes the main wear mechanism to slight adhesive wear.

Design and testing of a smart rubber stave for marine water-lubricated bearings

Abstract The water-lubricated bearing is mainly installed at the stern of the ship to support the rotation of the main shaft of the ship, which is an important component of the ship’s power plant. The rubber stave of the water-lubricated bearing acts as an elastic body, which can effectively suppress the rotational vibration of the rotating shaft and improve the shaft alignment effect. To monitor the operational status of the water-lubricated bearing at the stern of a ship, a design method of smart rubber stave for water-lubricated bearings is proposed in this article. According to the structure of the rubber stave, the packaging and protection form of the optical fiber, the forming process of the rubber stave, and the mechanical analysis were carried out to determine the distribution design principle of the fiber Bragg grating (FBG) in the rubber stave. Then, FBGs were packaged, protected, and implanted with an uneven distribution into the rubber stave to achieve force sensing in the bearing. With reference to the force state of the water-lubricated bearing during shipbuilding and ship operation, various types of condition monitoring tests were conducted on the smart rubber stave using an elastomer testing machine, which were to analyze the effects of load sizes, frequencies, and ambient temperatures. The tests showed that the FBGs in the rubber stave could monitor the static and dynamic loads of the bearing under the seawater environment or inland water environment below 30°C. This method can be used for the smart designing and online load condition monitoring of water-lubricated bearings.

An integrated maintenance and power generation forecast by ANN approach based on availability maximization of a wind farm

Climate change, global warming and high costs of fossil fuels caused an urgent need to shift from traditional sources of energy generation to renewable ones. Wind energy has been identified as one of the most attractive renewable sources that supply affordable, inexhaustible, and clean energy to the economy. To guarantee wind plant availability, the maintenance downtime has to be minimized. In doing so, a systematic preventive maintenance strategy integrated with wind power generation forecasted by artificial neural network (ANN) technique was developed by selecting the components which maintenance action will be performed upon based on a set minimum reliability margin. In this work, four components of the turbine (bearing, main shaft, gearbox and generator) were selected to represent the reliability of the turbine. An algorithm was developed to automatically select the component whose reliability falls below the minimum selected margin and a perfect maintenance is carried out by replacing the component. We try to develop the model that yields the optimal number of preventive maintenance (PM) actions that minimizes maintenance downtime which yields maximum availability The uniqueness of the work lies with the consideration and integration of the influence of turbine power generation rate into the PM planning strategy. Finally, numerical example was presented and sensitivity analysis was performed by varying some parameters to validate the algorithm.

An on-line monitoring method for the flow excitation in francis hydraulic turbine based on dynamics

During the operation of hydraulic turbine, the vibration often exceeds the standard due to flow excitation, which affects the safe and stable operation of the hydraulic turbine. In this paper, an on-line monitoring method for the flow excitation in Francis hydraulic turbine is proposed based on the dynamic characteristics of Francis hydraulic turbine. Firstly, based on the flow excitation characteristics in Francis hydraulic turbine and the dynamic equation of main shaft system, the internal relationships between the dynamic response of turbine bearing and the flow excitation in the Francis hydraulic turbine are clarified. Secondly, according to these relationships, a method based on wavelet transform (WT), particle swarm optimization (PSO), and variational mode decomposition (VMD) is proposed for extracting the flow excitation features in Francis hydraulic turbine. Then, by this method, the flow excitation features are acquired. Based on the obtained flow excitation features, the flow excitation can be monitored on-line. Finally, the proposed on-line monitoring method for the flow excitation in Francis hydraulic turbine is verified by experiments. Based on the results, the flow excitation components in the signal extracted by this method are about 35 % more than those extracted by the previous methods. The results show that the on-line monitoring method proposed in this paper is convenient and effective.

Numerical Modeling on Blasting Stress Wave in Interbedding Rheological Rockmass for the Stability of the Main Shaft of Mine

High rheological property and strong mining disturbance are prominent conditions in deep rock projects, and often present a coupled process to induce rockbursts, collapse and land subsidence. This paper aims to investigate the effect of surrounding rheological rockmass on the main shaft of mine with interbedding structure under coupled blasting stress wave condition. Based on elastic damage theory and the constitutive equation of rheological rockmass, considering the total strain rate in tensor form, a double-rock model was established. The model was then validated by comparing the numerical simulations with the test results. Matlab was used to develop the COMSOL software, allowing numerical simulation of the failure of shaft rock sequentially subjected to this complex loading path. The results from the rheology-impact numerical simulations show that the double-rock rheology was greatly affected by the dynamic disturbance. Under high creep stress and constant impact stress wave, the last failure of the double-rock with higher creep stress is more severe than that of double-rock with lower creep stress. The numerical simulation of the shaft in situ stress was used to predict the collapse of the rheological rockmass with interbedding structure. The preliminary results suggest that one contribution to this phenomenon is likely related to irreversible damage in the rock during the creep-disturbance process. Dynamic disturbance also promoted the failure of the rock near the interbedding structure, but also increased the strain and stress. This may reflect the initial compaction and elastic phase the rock near the interbedding structure related to the large compressive strength of the hard rock during the dynamic disturbance. The numerical results indicate that a circle-shaped spalling damage zone is prone to develop around the shaft with increased time. We discuss the reason for the decreased stress on point A2 near the interbedding structure of the shaft by visco-elastic theory. The results clearly showed insufficient stability of surrounding rockmass, thus the initial design of shaft is not reasonable. This study has important referential significance for main shaft design for similar mines.

Research on Foundation Deformation and Structural Stress Variation of Shaft Tower under the Influence of Frost Heave and Thaw Settlement

As the laws of structure deformation and structural stress variation under freezing construction around high-rise buildings are not clear and no engineering experience can be referred to, freezing method construction in this situation is paired with huge safety risks. In this paper, freezing construction was successfully carried out around the main shaft tower in Chensilou Coal Mine by taking the following protective measures: symmetrical drilling, local freezing and hot water circulation. The elevation of the shaft tower foundation is continuously measured during the process of drilling, frost heaving and thaw settlement (hereinafter referred to as the DHS process). Benefiting from these protective measures, the maximum inclination value (−0.406 mm/m) of the shaft tower is controlled at well below the allowable value. The observation data informed the settlement and inclination of the tower foundation during the DHS process. A numerical model of the shaft tower is further established based on the observation data to reveal the tower structure’s law of stress variation during the DHS process. In addition, the fitting equation between the tower inclination value and the structural stress is obtained, which can provide a reference for freezing construction of similar high-rise buildings.

Experimental Study and Simulation on the Seal Pressure of a Ferrofluid Seal Using Radial-Charged Magnets

As one of the most mature applications of ferrofluid, the pole shoes of a ferrofluid seal are easily damaged under the situation of the large radial beating of the main shaft. Meanwhile, due to the small size, the pole teeth commonly used in pole shoes harbor problems such as poor processability and low seal pressure under a large gap. In order to solve the aforementioned problems, we proposed a new structure of the ferrofluid seal that uses a radial-charged ring magnet as the magnetic source. Then, considering that the ring magnets have problems of uneven magnetization and installation difficulties, we used split magnets to take the place of ring magnets and proposed the second new structure. According to the study on the distribution of magnetic field in seal gap axially and circumferentially, we obtained the simulation results of the two new structures’ seal pressure. The results revealed that the new structure of the ferrofluid seal with rectangular magnets can solve the aforementioned problems and exhibited a certain amount of sealing pressure.

Research on security technology of tower foundation based on precise control of freezing temperature field

Freezing method is used in the main shaft slotting repair project in Chensilou Coal Mine in China. According to the actual conditions of Chensilou Coal Mine, this paper established a numerical calculation model which included the following influence factors: thermodynamic parameters, borehole layout, original formation temperature, groundwater seepage, hot water circulation protection. The calculation results show that the reasonable brine temperature for the freezing project in Chensilou Coal Mine should be controlled between -30 °C and -25 °C and the reasonable freezing time should be 160 days. When the freezing time extends to 80–120 days, the freezing front has developed to the temperature-control hole. In this case, the hot water circulation of the temperature-control hole needs to be started and the hot water temperature is not lower than 20 °C. The freezing construction was implemented in accordance with the optimized brine temperature and freezing time, and the freezing of tower foundation has been successfully avoided. The measured results show that the tower tilts to the northeast as a whole during formation freezing and the tilt values are all less than the allowable value.

Fluid–Structure Coupling Analysis of the Stationary Structures of a Prototype Pump Turbine during Load Rejection

During the load rejection transient process of the prototype pump turbine units, the pressure fluctuations of the entire flow passage change drastically due to the rapid closing of guide vanes. The extremely unsteady pressure distribution in the flow domains including the crown chamber and the band chamber may cause a strong vibration on the stationary structures of the unit and result in large dynamic stress on the head cover, stay ring and bottom ring. In this paper, the numerical fluid dynamic analysis of the entire flow passage of a reversible prototype pump turbine during load rejection was performed. The flow characteristics in the runner passage, crown chamber, band chamber, seal labyrinths and balance tubes are analysed. The corresponding unsteady flow-induced dynamic behaviour of the head cover, stay vanes and bottom ring was investigated in detail. The analysed results show that the total deformation of the inner edge of the head cover closed to the main shaft is larger than that of other stationary structures of the unit during the load rejection. The maximum stress of the stay ring is larger than that of the head cover and the bottom ring and the maximum equivalent stress is located at the fillet of the stay vane trailing edge. The fluid–structure coupling calculation method and the analysed results can provide guidance for the design of stationary components of hydraulic machinery such as pump turbines, Francis turbines and centrifugal pumps with different heads.

A one-class Shapelet dictionary learning method for wind turbine bearing anomaly detection

Detecting main shaft bearing anomaly is crucial to ensure the safe operation of wind turbines. However, existing anomaly detection methods have a limitation that anomaly samples are required for hyper-parameters tuning. Because of the scarcity of anomaly samples in the real-world scenarios, it is difficult to implement such existing methods in real-world applications. This paper proposes an end-to-end anomaly detection algorithm named one-class Shapelet dictionary learning. Firstly, the loss function of Shapelet dictionary learning is modified by integrating a soft-boundary term, so that the features and decision boundary can be learnt jointly. Then, a hyper-parameter setting strategy is introduced, so that anomaly samples are not needed in the training stage. The proposed method is validated through a case study collected from a real-world wind power farm. Results shown that the proposed method has a better F1 score than all baselines while anomaly samples are totally banded in the training stage.

Application of Fractography and Finite Element Analysis Adopting Elastic Foundation Stiffness to Improve Fatigue Life of Main Shaft in Mechanical Press

The main shaft of a mechanical press inevitably includes significant stress concentrations that can trigger severe mechanical damage and finally lead to failure under repetitive use. In this study, an efficient procedure to quantitatively evaluate the fatigue life of the shaft system including the main shaft and its support bearings, based on the macroscopic failure analysis of the main shaft broken during actual use, was investigated. For this purpose, the bearing support was modeled as an elastic foundation, and the elastic foundation stiffness value was varied to determine the optimal value that best simulates the failure behavior, especially with respect to the failure location and failure sequence, of an actual shaft. While the finite element mesh size was kept the same, only the effect of elastic foundation stiffness was investigated. The optimum value for the main shaft investigated in this study was approximately 60 N/mm³, and the fatigue life of the shaft was evaluated based on the conventional maximum principal stress theory. Based on this, two modified designs to enhance the fatigue life of the existing shaft are proposed.

IFWG-TOPSIS Model for Supporting Infant Failure Assessment in an Offshore Wind Turbine System

Introduction: System failure analysis is an essential aspect of equipment management. This analysis improves equipment reliability and availability. However, to assess infant failure under dynamic criteria, reliability engineers require special models. Method: Hence, this study uses an Intuitionistic Fuzzy Weighted Geometric (IFWG) and Intuitionistic Fuzzy Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) methods to develop an IFWG-TOPSIS model for infant failure assessment. We consider a case study of Offshore Wind (OFW) turbine infant failure assessment. Result: During the model evaluation, this study considered an infant failure of the turbine's main shaft, blade bearings, pitch system, jacket and monopile support structure, and gearbox. Risk factor, spare part weight, technical importance, cost, and complexity criteria were used to evaluate these components’ reliability. The results show that the blade bearings (S2) and main shaft are the most and least reliable components, respectively. To validate the model’s performance, we compared its results with Gümüş and Bali’s and standard VIKOR models results. These models selected the same components as the most and least reliable components, respectively. Thus, the proposed model is suitable for OFW turbine’s infant failure assessment. Discussion: It can be deduced that the use of the modified IFWG operator to calculate the intuitionistic fuzzy distance measure in standard TOPSIS model as the capacity to produce realistic results that can compete with existing decision-making methods. Conclusion: This study has investigated the use of techno-economic criteria for OFW turbine components’ infant failure assessment. A fuzzy-based model was used to establish the connection between the criteria and the components. We developed this model using the Intuitionistic Fuzzy Weighted Geometric (IFWG) and Intuitionistic Fuzzy Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) methods. Using experts’ judgments, data were obtained for the developed model evaluation and validation.

Lifetime fatigue response due to wake steering on a pair of utility-scale wind turbines

Quantifying the impacts on turbine loads during wind farm control is an important consideration in assessing power production benefits. Wake steering controls aim to improve total wind farm performance by coordinating the control actions of individual turbines, wherein an upstream turbine is intentionally yawed at an offset angle from the measured wind direction. Consequently, this redirects its wake for improved power production and potentially reduces fatigue loads of the downstream turbines. This paper studies the lifetime fatigue loads associated with wake steering by using utility-scale wind turbine experimental data to conduct an analysis on a pair of wind turbines. This study was part of a large field experiment in which a group of five GE 1.5-MW SLE CWE turbines were selected as targets for conducting wake steering research. A standard loads instrumentation package and data acquisition system were installed on two turbines within the cluster to measure turbine fundamental loads. The time-series databases were used to calculate loads statistics as well as short-term and lifetime damage equivalent loads. Fatigue calculations followed the guidance in Annex H of the International Electrotechnical Commission standard 61400-1, Edition 4. Lifetime fatigue calculation results are presented in this analysis; three methods of assessing lifetime fatigue were used to determine percent difference for blade root moments, main shaft moments, main shaft torque, and tower top torque. For all three fatigue treatments, some components’ lifetime fatigue increases for the controlled turbine; however, the downwind turbine experienced a reduction in lifetime fatigue and combined effect for the turbine pair results in a reduction of fatigue when wake steering controls are applied.

The physiology of polar bear mating (Ursus maritimus)

The well‐being of any species depends on successful reproduction, so the study of mating is essential, mainly to prevent the extinction of rare animals. In the process of evolution, each new species has adapted to environmental conditions in the struggle for survival through the morphological and physiological characteristics of the reproductive anatomy. Polar bear mating lasts 10‐20 minutes and corresponds to uterine insemination, but the description of the physiology of polar bear mating is lacking due to technical difficulties. Studies of the penis of a polar bear during an erection caused by the impact of electrical impulses of an electro‐ejaculator on the pudendal and external spermatic nerves and smooth muscles of the genital organs before reaching ejaculation to obtain sperm suggest how this happens. We studied the manifestation of sexual reflexes in a male polar bear (Ursus maritimus), age 10 years. The bear was kept in the Kazan Zoo from birth and did not participate in mating. An electro‐ejaculator was used to collect sperm. We have established the following features: the penis was covered entirely with a prepuce (praeputium) in a not erect state. The length of the penis is 19 cm. It practically does not change due to the presence of the os penis, which is 18.6 cm long and extends into the head of the penis. The diameter of the body of the penis is 1.5 cm. Initially, the head was 2 cm in diameter, two plates stood out on it, filling with blood during an erection. The opening of the urogenital canal (canalis urogenitalis) extends with its free end outside the head and has soft processes at the end of the canal. The length of the processes of the free end of the canal is 6 mm, and the width of their bifurcation is 4 mm. During an erection, the shape and size of the body of the penis (corpus spondiosum glandis) change and increase. The spongy body of the glans penis swells like a conus from the main shaft with the broadest part at the end. It has a length of 4 cm. The upper part is like an ellipse inclined at an angle of 45 degrees to the plane of the cone. Further, the head of the penis (glans penis) increases and takes the form of a straight cone with swollen urogenital canal sponges about 20 mm long, 10 mm in diameter at the base, 15 mm at the end. In the upper part, the funnel has an outer diameter of 40 mm, takes an angle of almost 90 degrees to the shaft of the penis, looks like a hand pump cuff. It can be assumed that the function of the swollen sponges is to ensure maximum passage of seminal fluid through the cervix, which is 15 mm long and opens during mating, and to prevent sperm leakage during insemination. They close the backflow of seminal fluid from the body of the uterus. During intercourse, the ejaculate pours into the vagina and partly irrigates the cervix. During coitus, it occurs from 3 involuntary muscle contractions of the body, which indicate stepped ejaculation (in portions). However, polar bears should be regarded as animals with uterine type of insemination, the highly swelling glans of the male penis, poorly covered by the walls of the vagina, acts on the principle of a piston. The penis pushes ejaculate from the vagina into the uterus.

Mechanical sensitivity analysis of strain gauge configurations in the main shaft of wind turbines

Wind turbines are reaching their remaining useful life, thus it is important to guarantee the well status of its components. A common way to check the status is to measure the loads on the Low Speed Shaft with strain gauges, but not always are bonded perfectly. In this work a sensitivity analysis of strain gauge configurations is carried out, where the influence of geometric and material parameters, and misplacement and misalignment parameters is analyzed. An analytical model for a single gauge was developed, obtaining a relation between the exerted loads and the strain measured by the strain gauge. By means of Taylor approximations the estimated loads were approached in order to have into account the influence of the uncertainty of parameters. Results shown that the sensitivities with respect to the geometric and material parameters did not depend on the secondary loads while in the sensitivities with respect to the gauge bonding parameters the cross-talk effect was present. In order to obtain realistic numerical results, a horizontal-axis NREL 5-MW wind turbine was simulated in OpenFAST with two wind-speed scenarios. The uncertainty of the estimated loads by the strain gauge configurations was calculated.