Effects Of Shaft Misalignment Research Articles

Flow characteristic analysis of a herringbone groove thrust bearing with shaft misalignment

PurposeHerringbone groove thrust bearings are typically used in high-speed, light-load applications, such as spindle motors for hard disk drives. In the past researches, the effect of shaft misalignment was little considered. This study aims to reveal effects of shaft misalignment on the microscopic flow regime in the water-lubricated herringbone groove thrust bearing.Design/methodology/approachThe liquid film in a thrust herringbone groove bearing was investigated by computational fluid dynamics. The effects of micro-grooves on the flow field were carefully explored. Two-dimensional liquid films at four different sites were examined for obtaining the rich flow field properties.FindingsThe distributions of pressure, temperature and water vapor volume fraction were obtained, the micro hydrodynamic effects were formed by the herringbone grooves and the effects of the shaft misalignment on lubrication and sealing performance could be found.Originality/valueThe influence of misalignment on the herringbone groove thrust bearing performance was investigated in detail. The obtained results could give the reference guideline for the bearing design.

Effect of Shaft Misalignment on Bending Strength of Helical Gear for Metro Vehicles

Effect of Shaft Misalignment on Bending Strength of Helical Gear for Metro Vehicles

A journal bearing performance prediction method utilizing a machine learning technique

A predictive analytics methodology is presented, utilizing machine learning algorithms to identify the performance state of marine journal bearings in terms of maximum pressure, minimum film thickness, Sommerfeld number, load and shaft speed. A dataset of different bearing operation states has been generated by solving numerically the Reynolds equation in the hydrodynamic lubrication regime, for steady-state loading conditions and assuming isothermal and isoviscous lubricant flow. The shaft has been modelled with four different values of misalignment angle, lying within the acceptable operating range, as defined in the existing regulatory framework. The journal bearing was modelled parametrically using generic geometric parameters of a marine stern tube bearing. The lift-off speed was estimated for each loading scenario to ensure operation in the hydrodynamic lubrication regime and the effect of shaft misalignment on lift-off speed has been evaluated. The generated dataset was utilised for training, testing and validation of several machine learning algorithms, as well as feature selection analysis, in order to solve several classification problems and identify the various bearing operational states.

Effect of Shaft Misalignment on Hypoid Gear Pair Driven Through a Universal Joint

An enhanced hypoid geared rotor system model incorporating a universal joint that connects driveline propeller shaft and pinion shaft is introduced in this study. The effect of shaft misalignment and pinion mass unbalance on hypoid gear dynamic response is evaluated under different assembly conditions. A nonlinear 14-DOF lumped parameter model based on coupled multi-body dynamics is applied by considering large rotational displacement in torsional direction. Results demonstrate three main influences from shaft misalignment and mass unbalance including speed and torque fluctuation as well as external bending moment on pinion shaft. It is also observed that bending moment generated can exert additional load on pinion shaft bearings which is found to be more sensitive to misalignment angle compared to dynamic response along line-of-action. Besides, shaft misalignment and mass unbalance excitation will interact with gear internal excitation from transmission error (TE) which can affect mesh parameters.

Effect of shaft misalignment and mitigation through crowning in spur gear transmission

Misalignment of gear shafts, due to manufacturing and assembly errors, has an adverse influence on gear tooth stresses, load sharing and smooth transmission. In practice, gear tooth modifications, such as crowning, are often resorted to. In this work, investigations of simultaneous effect of both misalignment and crowning on transmission error and mesh stiffness variation have been carried out. Necessary three-dimensional model is created using in-house developed code for generation of involute and trochoidal profiles. The three-dimensional stress analysis is carried out using general purpose FEM software ANSYS 12 for contact stresses. The effect of misalignment on the contact stress for different angular rotations during meshing cycle is analysed. A method to obtain contact stress pattern on the basis of a threshold value is proposed in this work. Mesh stiffness, load sharing ratio and transmission error are also evaluated over a complete mesh cycle. The results for uncrowned and crowned spur gear with misalignment errors are compared and discussed in this paper.

Effect of shaft misalignment and mitigation through crowning in spur gear transmission

Misalignment of gear shafts, due to manufacturing and assembly errors, has an adverse influence on gear tooth stresses, load sharing and smooth transmission. In practice, gear tooth modifications, such as crowning, are often resorted to. In this work, investigations of simultaneous effect of both misalignment and crowning on transmission error and mesh stiffness variation have been carried out. Necessary three-dimensional model is created using in-house developed code for generation of involute and trochoidal profiles. The three-dimensional stress analysis is carried out using general purpose FEM software ANSYS 12 for contact stresses. The effect of misalignment on the contact stress for different angular rotations during meshing cycle is analysed. A method to obtain contact stress pattern on the basis of a threshold value is proposed in this work. Mesh stiffness, load sharing ratio and transmission error are also evaluated over a complete mesh cycle. The results for uncrowned and crowned spur gear with misalignment errors are compared and discussed in this paper.

Stochastic Dynamics of a Nonlinear Misaligned Rotor System Subject to Random Fluid-Induced Forces

In this paper, stochastic responses and behaviors of a nonlinear rotor system with the fault of uncertain parallel misalignment and under random fluid-induced forces are investigated. First, the equations of motion of the rotor system are derived by taking into account the nonlinear journal bearings, the unsymmetrical section of the shaft, and the displacement constraint between the two adjacent rotors. Then, the modeling on uncertainties of misalignment and random fluid-induced forces are developed based on the polynomial chaos expansion (PCE) technique, where the misalignment is modeled as a bounded random variable with parameter η distribution and the fluid-induced force as a random variable with standard white noise process. Finally, examples on the stochastic dynamic behaviors of the nonlinear generator-rotor system are studied, and the influences of the uncertainties on the effects of shaft misalignment, the stochastic behaviors near bifurcation point as well as the distribution of the system responses are well demonstrated.

A New Approach for Including Cage Flexibility in Dynamic Bearing Models by Using Combined Explicit Finite and Discrete Element Methods

In this investigation, a new approach was developed to study the influence of cage flexibility on the dynamics of inner and outer races and balls in a bearing. A 3D explicit finite element model (EFEM) of the cage was developed and combined with an existing discrete element dynamic bearing model (DBM) with six degrees of freedom. The EFEM was used to determine the cage dynamics, deformation, and resulting stresses in a ball bearing under various operating conditions. A novel algorithm was developed to determine the contact forces between the rigid balls and the flexible (deformable) cage. In this new flexible cage dynamic bearing model, the discrete and finite element models interact at each time step to determine the position, velocity, acceleration, and forces of all bearing components. The combined model was applied to investigate the influence of cage flexibility on ball-cage interactions and the resulting ball motion, cage whirl, and the effects of shaft misalignment. The model demonstrates that cage flexibility (deflection) has a significant influence on the ball-cage interaction. The results from this investigation demonstrate that the magnitude of ball-cage impacts and the ball sliding reduced in the presence of a flexible cage; however, as expected, the cage overall motion and angular velocity were largely unaffected by the cage flexibility. During high-speed operation, centrifugal forces contribute substantially to the total cage deformation and resulting stresses. When shaft misalignment is considered, stress cycles are experienced in the bridge and rail sections of the cage where fatigue failures have been observed in practice and in experimental studies.

Thermal Analysis of Elliptic Bore Journal Bearing Considering the Effect of Shaft-Misalignment

Bore ovality or non-circularity is due to manufacturing irregularity or running in. Misalignment is the non-parallel positioning of the shaft due to the nature of non-central dynamic loading, elastic deformation and thermal distortion of shaft. Misalignment may be also due to manufacturing error of shaft or bush. Study of combined effect of bore-out-of-roundness and shaft misalignment is important in bearing design. In this paper, the steady state characteristics of elliptic bore journal bearing are analyzed considering the shaft misalignment. A case specific film profile is derived to address the bore ellipticity together with shaft misalignment in eccentric positioning. Combined solution of Reynolds equation and Energy equation is carried out considering non-Newtonian piezo-viscous behavior of lubricant. The performance parameters such as film thickness, load carrying capacity, friction force, flow rate and side leakages are analyzed taking into account the thermal effect. The combined effect of bore non-circularity and shaft misalignment on temperature rise is also presented in this paper.

Effect of Shaft Misalignment on The Stresses Distribution of Spur Gears

Effect of Shaft Misalignment on The Stresses Distribution of Spur Gears

Transient analysis of misaligned elastic tilting-pad journal bearing

For several reasons, almost all bearings operate in a misaligned condition, the present research work deals with analyzing the performance of a misaligned tilting-pad journal bearing under transient loading condition. The elastic and thermal distortions of the pad are considered and finite element analysis is used to calculate the pad’s elastic deformation. Using finite difference method, the Reynolds equation is simultaneously solved with the energy equation to calculate the pressure distribution and hence the other bearing performance characteristics. A modified fluid film thickness equation is used to take the effect of shaft misalignment and bearing elastic and thermal distortion into consideration. The results have shown that considering the thermo-elasto-hydrodynamic distortion improves the bearing performance in the case of misalignment shaft. And, at low values of shaft misalignment, the decrease in oil film thickness due to shaft misalignment is compensated by the increase in oil film thickness due to elastic and thermal distortions.

Effect of Shaft Misalignment on the Dynamic Force Response of Annular Pressure Seals

An analysis for calculation of the dynamic force and moment response in turbulent flow, annular pressure seals is presented. The fully developed flow of a cryogenic liquid within the annular thin film region is described by variable properties, bulk-flow equations with a turbulent friction factor based on Moody's formula. The analysis considers arbitrary shaft center eccentric displacements and rotor axis misalignment angles. Solution to zeroth-order flow field equations determines the seal leakage, film forces, and moments. Dynamic force and moment coefficients due to perturbations in shaft center displacements and axis rotations are obtained from the solution of first-order (linear) flow equations. Numerical results on the effect of large static misalignment angles on the dynamic force response of a liquid oxygen damper seal typical of a cryogenic application are discussed in detail. The predictions show that a static misalignment mode relative to the seal entrance plane causes a large magnitude stiffening effect on the seal, while the opposite effect, occurs for large misalignments about the seal exit plane. Alignment considerations are then shown to be of importance for adequate and predictable performance of annular pressure seals.

An Evaluation of Precision Shaft Angle Encoders

The effect of shaft misalignment on the accuracy of four types of precision digital shaft angle encoders (219 resolution elements per rotation) was determined using a special test fixture and optical techniques. The encoders and couplings were precisely aligned or misaligned by known amounts. When properly aligned to the shaft whose rotation is to be measured, the encoders exhibit rms errors of less than a single resolution element even when connected through a coupler. When the axes of shaft and encoder transducer are mutually misaligned, the different systems vary as to the amount of corresponding error introduced into the encoder output. In each case, the errors varied in a sinusoidal manner with respect to shaft angle. By the optical method alone, it was not possible to distinguish between errors caused by the associated coupler and those inherent in the encoding transducer itself. A second method of evaluation, utilized a computer to analyze the sum of two identical encoders connected so that one of them turned in a positive direction while the other turned in a negative direction (back-to-back). The large number of measurements per revolution allowed us mathematically to separate out errors due to various causes. The system evaluated by this method showed that the greatest fraction of the errors may be attributed to distortions in the coupler, amounting to the equivalent of several resolution elements. When properly aligned, all systems exhibit excellent accuracy.