Shaft Coupling Research Articles

An analysis of abnormal vibration and noise caused by shaft coupling misalignment of high-speed train

This study conducts on-site testing and simulation analysis of the abnormal noise phenomenon generated during the operation of high-speed trains. The sound pressure characteristics in the cabin and the vibration of different vehicle components are recorded and subjected to comprehensive analysis. Test results indicate that significant abnormal noise occurs inside the cabin at the speed of 250 km/h, with frequencies of 87 Hz, 173 Hz, 259 Hz, and 346 Hz. Through sound source identification, vibration transmission analysis and theoretical derivation, it has been determined that the abnormal noise primarily originates from the transmission system, and it is further speculated that these abnormal vibrations and noises may be correlated with the shaft coupling misalignment within the transmission system. To verify the conjecture, a high-speed vehicle electromechanical coupling simulation model was established, incorporating the shaft coupling misalignment in the transmission system. The vibration characteristics of vehicle components were analyzed, confirming that shaft coupling misalignment leads to uneven meshing forces in gears, resulting in significant vibration and noise that affect the riding comfort of the vehicle. We propose replacing the shaft coupling to solve this problem, the test results showed that the abnormal vibration amplitudes of the transmission system at 87 Hz, 173 Hz, 259 Hz, and 346 Hz were significantly reduced after replacing the shaft coupling, and the amplitude of the corresponding frequencies on the cabin floor decreased by 91 %, 78 %, 98 %, and 66 %, respectively. The issue of abnormal noise has been effectively resolved.

Multivariate iterative nonlinear chirp mode decomposition: principles and applications

Abstract The rotor-bearing system (RBS) of a hydroelectric unit includes multiple components such as the rotor, rotor shaft, coupling, turbine, and main shaft. There is a strong coupling relationship between the vibration signals of multiple bearing sections. At the same time, the vibration signal of the RBS contains rich frequency components, which can effectively reflect the operating state of the shaft system of the unit. Therefore, synchronous signal analysis across multiple rotor bearing sections is required to completely grasp the operating status of the unit. In this study, the Multivariate Iterative Nonlinear Chirp Mode Decomposition (MINCMD) is proposed to analyze signals on multiple sections simultaneously. MINCMD follows the step-by-step extraction idea of Adaptive Multivariate Chirp Mode Decomposition (AMCMD), but it adopts a new algorithm framework by modifying the objective function. Furthermore, AMCMD does not converge well without a good initial instantaneous frequency (IF). Therefore, a method based on parameterized demodulation (PD) is introduced in MINCMD to solve the multi-channel frequency initialization problem. The effectiveness of the proposed algorithm is verified through a simulation test and real data from hydroelectric units.

Investigation of Lateral Vibrations in Turbine-generator Unit 5 of the Inga 2 Hydroelectric Power Plant

The article presents a case study on the Investigation of lateral vibrations in the turbine-generator unit 5 of the Inga 2 hydroelectric power plant in the Democratic Republic of the Congo. Lateral vibrations were experimentally determined using twelve proximity and eddy-current probes, positioned on each measurement plane. The results were analyzed using the Dasylab and R software. Hence, it was observed that the vibration amplitudes of the upper guide bearing, lower guide bearing, and pivot/rotor exceeded acceptable or critical limit values of the international vibration standard for a rotating speed between 100-250 rpm. These excesses can lead to rotor mass imbalances, the eccentricity of the rotor axis relative to the rotation axis of the shaft, and the deformation of the coupling shaft between the upper rotor shaft and the turbine rotor shaft. Subsequently, the means and the variances of the vibration amplitudes were evaluated and compared to the reference values of the international standard. The results of the compliance analysis revealed statistically significant differences between the measured amplitudes and the reference values. Thus, it indicates deviations from international specifications.

Rotor speed estimation for half-broken bar detection in induction motors using Kalman filtering

This study addresses the early detection of half-broken bars in induction motors (IMs). Most research on fault detection focuses on current signature analysis because it can provide online and remote monitoring at a low cost. However, errors caused by spectral leakage around the fundamental frequency supply reduce its reliability for fault diagnosis at the incipient stages. The proposed detection technique is based on a spectral analysis of the motor speed. To detect a half-broken bar, measurements of stator voltages and currents are processed by an adaptive extended Kalman filter for system state estimation. Then, a spectral analysis is applied to the estimated motor speed to obtain its power spectral distribution. Finally, the fault harmonic amplitude at 2sfs is used as fault indicator for fault diagnosis. The proposed approach has three main advantages: (1) speed estimation is unaltered by spectral leakage around the main frequency supply, (2) the cost of speed sensors is avoided, and (3) the absence of connecting shaft couplings prevents corruption of speed data by mechanical interference. Numerical simulations and experimental results were carried out for the squirrel cage IM to provide encouraging validation of the proposed early fault detection technique.

Decoupling modeling design and high-precision position control of fast steering mirror

For a two-axis fast steering mirror (FSM) based on the flexible chain structure support and voice coil motor drive, the two axes are strongly coupled. This strong coupling may decrease the system positioning accuracy. In this study, the electric kinematics model associated with the voice coil motor and the motion and frequency equations associated with the flexible chain structure were analysed. A comprehensive system model was established considering shaft coupling, a digital controller with compensation coupling was designed, and the method of active compensation was used for decoupling. The experimental results showed that compared with the traditional non-decoupling control algorithm, the decoupling control method decreased the coupling degree from 7% to 0.8% and reduced the positioning accuracy error from 1.5% to 0.3%.

Misalignment and Rub-Impact Coupling Dynamics of Power Turbine Rotor with Offset Disk

When the dual rotor system of the aircraft engine is operating, the mass eccentricity of the power turbine rotor and the misalignment of the shaft coupling or the bearing will cause too large vibration of the rotor; this vibration leads to the rub-impact between the rotor and the casing. The power turbine rotor from the dual rotor system is taken as the research object in this paper. Considering the misalignment, the resulting rub-impact faults, the imbalance of rotor and the disk offset, the equation of motion for the system is developed according to the Lagrangian Equation, and then the Range-Kutta Method is adopted to solve the equation. The influence of the key parameters such as the rotating speed, the misalignment angle and the rub-impact clearance on the dynamics of the system is studied; the finite element analysis was carried out to validate the correctness of the theoretical modeling method. The results show that the rub-impact increases the stiffness of the system; the Hopf bifurcation occurs in the misalignment and rub-impact coupling system; the vibrational stability near the half of the switching speed slumps with the increase of the misalignment angle; with increasing of the stiffness, the number of the chaotic zone increases, and the range of the chaos is widening; enlarging the rub-impact clearance is beneficial to reduce the degree of the rub-impact system and enhance the stability of the system.

Vyladenie mechanickej sústavy pohonu piestového kompresora z hľadiska veľkosti torzného kmitania

One of possible ways to change the amount of compressed air delivered by a piston compressor is to change its operating speed. However, it can cause an improper tuning of the mechanical system of piston compressor drive in terms of torsional dynamics. In order to avoid excessive torsional vibration, a suitable pneumatic flexible shaft coupling can be used in the system. An optimum air pressure value in a pneumatic coupling was determined experimentally for three various operating modes of an experimental mechanical system of piston compressor drive.

Pneumatické pružné hriadeľové spojky v pohonoch mechanických sústav

The article presents a newly developed pneumatic flexible shaft coupling with hose flexible element usable, among other applications, in drives of mechanical systems. The presented coupling uses a hose-shaped flexible element winding between the supporting surfaces of coupling’s driving and driven hub. As the torque transfer is ensured with compressed air, the torsional stiffness of coupling can be adapted to actual operating parameters (rotational speed) with change or air pressure inside the flexible elements. This makes the presented coupling suitable for semi-active torsional vibration control. A patent was also granted for the presented coupling design. The design of hose-shaped element enables reliable sealing of compression volume and it is also easy to assembly and dismantle.

Novel Design of Variable Stiffness Pneumatic Flexible Shaft Coupling: Determining the Mathematical-Physical Model and Potential Benefits

Presently, mechanical system vibroisolation is becoming increasingly important. One of the new approaches is semi-active vibroisolation using elements capable of changing a selected mechanical property. These include, among others, pneumatic flexible shaft couplings capable of changing torsional stiffness during operation. The main goal of the article is to examine the potential advantages of a newly patented pneumatic coupling over a current type with the same pneumatic element arrangement. For comparison, parameters determinable from static load characteristics were selected. These parameters are maximum twist angle and torque, average torsional stiffness, and the percentage of torque transmitted by the bellows rubber shell. In all cases, the new coupling had better properties. Since the prototype of the new coupling has not yet been produced, its parameters were determined from its mathematical-physical model. The article contains a full procedure to obtain the static load characteristic of a new coupling type, beginning with the determination of air bellows force/height and volume/height characteristics, then optimum sizes of coupling with regards to the operating range of elements, the dependency of element height on the coupling’s twist angle, and finally the computation of the static load characteristic considering isothermal gas compression. The presented procedure can be applied to any pneumatic bellows where the force/height characteristics of different pressures are given.

Dynamic modeling and analysis of two-span rotor-pedestal system with bearing tilt and extended defect: Simulation and experiment

When the rolling bearing raceway is tilted, the contact load of the raceway increases, which may greatly increase the occurrence of raceway defects. However, the evolution law of the raceway defect extension process on the system dynamic characteristics is not clear when the bearing is tilted. In this paper, considering the influence of rough surface caused by the extension of bearing defects, a mathematical model of raceway extension defects which is more consistent with the actual morphology is proposed. The model can be used to evaluate the damage degree of the bearing raceway of rotating machinery. Taking the two-span rotor-bearing-pedestal system of the test rig as the research object, a nonlinear dynamic model of the system is established considering the nonlinear supporting force of bearings and pedestal, shaft coupling looseness and other nonlinear factors. The effectiveness of the bearing fault characterization model and the system dynamics model is verified by experiments. On this basis, the influence of tilt on bearing fault and the change rule of raceway defect extension on bearing contact characteristics and system dynamic characteristics are discussed. The results indicate that raceway tilt aggravates system vibration caused by the bearing defect. With the increase of the defect range, the impact vibration characteristics weaken, and the roughness of the raceway surface in the defect area has a great influence. However, with the increase of defect depth, the influence law is just the opposite. The research results are expected to provide theoretical support for bearing fault diagnosis of rotating machinery systems.

Optimization and prediction of CBN tool life sustainability during AA1100 CNC turning by response surface methodology

The aluminium alloy (AA1100) was familiar with automotive flexible shaft coupling applications due to its high strength, good machinability, and superior thermal and resistance to corrosion characteristics. Machining tool life drives the prominent role for deciding the product quality (machining) act aims to productivity target with zero interruptions. The novelty of this present investigation is the focus on increasing tool life during the complexity of CNC turning operation for AA1100 alloy by using CBN coated insert tool with varied input parameters of spindle speed (SS), feed rate (f), and depth of cut (DOC). Design of experiment (L16), analysis of variance (ANOVA) statistical system adopted with response surface methodology (RSM) is implemented for experimental analysis. The turning input parameters of SS, f and DOC are considered as factors and its SS (900, 1100, 1300, and 1500 rpm), f (0.1, 0.15, 0.2, and 0.25), and DOC (0.1, 0.2, 0.3, and 0.4 mm) values are treated as levels. The investigational analysis was made with the ANOVA technique and the desirability of high tool life with input turning parameters was optimized by RSM, and sample no 11/16 was predicted as high tool life and performed with extended working hours compared to other samples. The RSM optimized best turning parameter combinations are 0.1 mm DOC, 0.2mm/rev to 0.25mm/rev f, and 1300 rpm–1500 rpm SS, facilitating a higher tool life of more than 20min.

Proposed Shaft Coupling Based on RPRRR Mechanism: Positional Analysis and Consequences

Proposed Shaft Coupling Based on RPRRR Mechanism: Positional Analysis and Consequences

Centrifugal Pump Shaft Coupling Durability Material S45C in the Water Treatment Plant Unit with the Destructive Test Method (impact)

The peg is a component that functions as a binder between the shaft and the hub in transmitting power and rotation. In general, the pegs are designed and made using metal materials such as mild carbon steel. In this research, the material of the coupling pin design on the centrifugal pump shaft is S45C. Where on the sample of the designed post, an impact test or the Charpy method of hitting the notch is carried out which aims to determine the amount of resistance to sudden loading and to determine the physical changes (failure modes) experienced by the post material. In this study, the sample of the post with dimensions of 6.10 mm x 6.10 mm x 55 mm obtained a large impact strength (impact strength) in the Charpy method impact test of 0.8445 Joule/mm2. And for the physical change (failure mode) experienced by the post material against the sudden loading, it is a brittle fracture that is characterized by physical characteristics in the form of granular (like sand) on the fracture surface, and the absence of plastic deformation that occurred first.

Cure kinetics and mechanical properties of carbonized chicken feather reinforced styrene butadiene rubber composites

AbstractPolymers are part and parcel of our life and society due to the immense applications resulting from their unique properties. High performing products based on bio feed stocks have gained special attention compared to non‐renewable resources. In the present research work, carbon black (CCF) prepared from waste chicken feathers has been used as reinforcement in styrene butadiene rubber (SBR). Cure kinetics of SBR‐CCF composites and their mechanical properties have been evaluated with respect to loading of filler and concentration of dicumyl peroxide crosslinking agent. The cure reaction of all compounds obeys first order kinetics and the rate constants increase with filler loading as well as temperature. A decrease in energy of activation of cure has been noted with increase of loading of CCF filler, which assists for an increase in the rate of production of articles using the filled SBR compounds. The improvement in tensile properties with CCF has been supported by the fractography of the composites and by the crosslink density values obtained using equilibrium swelling method. The performance of the developed composites points to their applications in the area of car‐tire industry, tread rubber sector and structural applications such as drive and shaft couplings.

Robotic disassembly sequence planning considering parts failure features

AbstractDisassembly is an important step in remanufacturing products. Robotic disassembly helps to improve disassembly efficiency. However, the end‐of‐life products often have the parts with uncertain quality, which is manifested as wear, fracture, deformation, corrosion, and other failure features. The parts failure features always have impacts on disassembly process. First, the evaluation method of parts failure features is researched, and the quantitative model of parts failure features is constructed using fuzzy models. Then, the disassembly information model is established by considering the influence of different failure degrees on the robotic disassembly process. Afterwards, to generate the optimal disassembly solution, deep reinforcement learning (DRL) is used to solve robotic disassembly sequence planning problem which considers parts failure features. Considering the influence of parts failure features on robotic disassembly time, the states, actions and rewards and environment are designed in DRL. Finally, a case study of the double shaft coupling as a waste product is carried out, and the proposed method is compared with the other methods to verify the effectiveness.

NEW DESIGNS OF VARIABLE STIFFNESS COUPLINGS

Flexible couplings are widely used in mechanical drives of transport and other machines. A fundamental function of flexible shaft couplings regarding torsional vibration is the optimum tuning of torsional oscillating mechanical systems. At the authors’ workplace, the focus is on the research and design of pneumatic couplings, where the torque is transmitted mainly by compressed gas (air) in their pneumatic flexible elements. The primary advantage of these couplings is that their mechanical properties can be quickly and effectively adjusted, especially the dynamic torsional stiffness, by air pressure change directly while the mechanical system is running. This allows us “to tune” the properties of the pneumatic coupling according to the current parameters of the machine drive to avoid resonance and minimize torsional vibration. Therefore, we tend to refer to them as “pneumatic tuners of torsional vibration”. This paper aims to present two new types of these “pneumatic tuners” that were recently granted patent protections, namely “Pneumatic flexible shaft coupling with hose flexible element” and “Drum pneumatic flexible shaft coupling”. Because these pneumatic tuners are not in practical use yet, this paper describes only their design and supposed benefits.

Biologically Induced Corrosion and Consequent Fracture of a Pump Shaft Coupling

Biologically Induced Corrosion and Consequent Fracture of a Pump Shaft Coupling

Virtual Shaft Control of DFIG-Based Wind Turbines for Power Oscillation Suppression

The flexible shaft coupled to the synchronous generator (SG) is critical for the doubly-fed induction generators (DFIG) based wind turbines to improve the ability to suppress system power oscillations. The rigid shaft coupling relationship between the DFIG and SG is analyzed first under the current virtual synchronous generator (VSG) control. To give the power system a vibrational degree of freedom, a novel virtual shaft is added to the VSG emulated by the DFIG-based wind turbine. The power system's two-degree-of-freedom (TDOF) coupled motion model with VSG is then established. The virtual shaft coupling adapted to a DFIG is designed using anti-resonance theory, and the amplitude-frequency characteristic of the TDOF power system is analyzed. With the additional stiffness of the virtual shaft, the power support functions of the VSG, including inertia and damping, are integrated by optimizing the oscillation amplitude at two fixed points in the frequency domain. Finally, on a controller hardware-in-the-loop platform, a typical power system with a high penetration of wind power generation is simulated. The test results demonstrate that by employing virtual shaft coupling, it is possible to suppress system frequency variation and rotor angle oscillation during transient events, significantly improving the reliability of the power support provided by wind turbines.

Design and Simulation of the Controlled Failure of Custom-Built Rigid Shaft Coupling

Design and Simulation of the Controlled Failure of Custom-Built Rigid Shaft Coupling

A precision core drill for transmission electron microscopy sample preparation produced by 3D printing

A precision core-drilling machine has been designed and constructed almost entirely from 3D printing. The purpose of the drill is to extract 3 mm diameter discs from thin slices of mainly hard brittle materials for analysis in a transmission electron microscope. Novel methods of producing a slide bearing and shaft couplings in 3D printed components have been developed. Design principles and material selection are discussed, and the drill is evaluated by preparing samples from silicon and aluminium. The device can be self-made by any laboratory with a 3D printer, can be recycled when no longer required and can help labs reach their sustainable development goals.