Effect Of Angular Misalignment Research Articles

Fatigue crack evaluation of butt weld joints in full-scale aluminum alloy joints: Experimental and numerical study of traction structural stress

In this study, the digital image correlation technique is used to determine the inconsistent mechanical properties and microstructure non-uniformity in different regions of aluminum alloy butt welded joints. A state monitoring method is proposed based on phased-array ultrasonic total focus imaging for crack evolution. A series of surface fatigue crack propagation tests on full-scale aluminum alloy butt welds are investigated, which innovatively revealed the mechanism and evolution law of crack propagation at the surface of the weld. The analytical function for dynamic crack propagation in welded structures is proposed, which provides a new idea and data support for clarifying the state deterioration process of structures. The results show that the traction structural stress can effectively identify the critical fatigue position of the weld and effectively account for the effect of angular misalignment. The phased-array ultrasonic total-focus imaging monitoring analysis method for surface fatigue crack propagation is proposed to improve the completeness of the fatigue crack evolution law.

Fatigue performance analysis of stainless steel cruciform joint with angular misalignment

AbstractWelding distortion causes the change of stress distribution of load‐carrying cruciform stainless steel welded joints, and the weld with angle less than 90° between steel plates became the fatigue performance control weld because of stress magnification. The effect of angular misalignment on fatigue performance of stainless steel cruciform welded joint was experimentally and numerically studied. The fatigue damage evolution equations, under different stress amplitudes, were derived using relative deformation increment as damage variable based on continuum damage mechanics to explain the process of damage transformation from micro to macro crack and finally rapid fracture. The hot spot stress magnification factor was positively correlated with the welding distortion angle and exhibited two discernible stages of rise and fall with increasing nominal stress taking the proportional limit as boundary. A proposed formula considering both misalignment angle and applied stress aimed to enhance accuracy in fatigue performance evaluation compared to current methods.

Study on the effect of angular misalignment and axial preload on the mechanical properties of four-point angular contact ball bearings

Four-Point Angular Contact Ball Bearing (FPCBB) is widely used in high-speed power systems due to their capacity to withstand axial forces in two different directions, high-speed capabilities, and space-saving design. This paper presents a unified 5-degree-of-freedom quasi-static model of FPCBB, explicitly addressing the influences of axial preload and angular misalignment. Through this model, the impacts of preload and misalignment on the contact state of FPCBB are investigated. The D'Alembert principle is employed to calculate the pitch angles of balls instead of the Raceway Control Hypothesis (RCH). Furthermore, the different effects of the two preload ways on the mechanical properties of bearings under the presence of angular misalignment were comprehensively analyzed. The findings reveal that both preload and misalignment significantly affect the mechanical properties of FPCBB. Notably, under conditions of angular misalignment, the effect of fixed position preload surpasses that of constant pressure preload. These results provide valuable guidance for evaluating the performance of FPCBB in practical applications.

Modelling approach of hybrid air herringbone grooved journal bearing considering the angular misalignment and centrifugal expansion

Performance improvements can be achieved after introducing herringbone grooves into conventional plain aerostatic bearings at high speeds. However, the existing literature lacks a comprehensive model that accurately calculates the static and dynamic characteristics of this hybrid air bearing. To address this gap, this paper proposes a modeling method for high-speed hybrid air journal bearings with herringbone grooves, considering the effects of angular misalignment and centrifugal expansion. Based on the established model, effect of the grooves on the bearing performances is systematically studied. Furthermore, influences of the bearing angular misalignment and the rotor centrifugal expansion on the rotor’s vibration characteristics are illustrated through an unbalance response analysis for an industrial air spindle. The presented model provides an analysis tool for structure design and performance study of the herringbone grooved hybrid air journal bearings.

Dynamic characteristics of a spur gear pair under the coupled effects of angular misalignment fault and tooth modification

Angular misalignment is a common fault in gearbox manufacturing and installation, which directly affects the meshing characteristics of the gear pair. Tooth axial modification is considered to be a useful way to suppress angular misalignment. However, accurate determination of contact characteristics, e.g., contact stiffness and friction, caused by the coupled effects of angular misalignment and tooth modification is difficult. To settle this problem, this article put forward a method on the strength of the slice coupling and nonlinear Hertzian contact calculation. With the proposed model, the meshing errors caused by angular misalignment and tooth axial modification are derived. Then the influence of nonlinear Hertzian contact and friction on time-varying mesh stiffness (TVMS) is considered in each sliced tooth. In addition, an iterative computation method is proposed to calculate the proposed analytical model. Further, a dynamic model is developed to study the influences of angular misalignment and tooth axial modification on gear dynamic characteristics. Finally, the analytic model is validated by an experimental setup for a spur gear pair with ideal installation, misalignment and tooth axial modification. Results show that the proposed model is effective and efficient for predicting the dynamic response of the spur gear pair under the coupled effects of angular misalignment and tooth modification.

A Compact 3-D Multisector Orientation Insensitive Wireless Power Transfer System

The power conversion efficiency (PCE) in wireless power transfer (WPT) degrades due to angular misalignment between the transmitter (Tx) and the rectenna (Rx) along the azimuth plane. Therefore, a compact 3-D multisector orientation insensitive WPT system is proposed to address this problem. The optimal number of sectors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> ) is determined analytically using patch antenna design equations to mitigate the effects of angular misalignment. In addition, conditions on the receiver antenna radiation pattern are investigated to enhance the performance of the WPT system. Furthermore, the observed conditions are utilized for designing a high gain WPT system at 5.8 GHz with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> sectors. The proposed WPT system provides uniform power harvesting capability in the azimuth plane and 51.2% higher power harvesting capacity than the patch antenna WPT system.

Wear prediction and meshing characteristics for the planetary gear set considering angular misalignment and rotating carrier

This paper focuses on the effect of angular misalignment on wear prediction of the planetary gear set with the rotating carrier, which is more complex than that of the parallel-axis gear due to the position changing of the planet gears. The wear depth is calculated based on the Archard’s wear theory, the load distribution is obtained by the three dimensional loaded tooth contact analysis (3D-LTCA) method, and the effect of angular misalignment is considered by introducing the change in meshing clearance between the two engaged tooth flanks. The load distribution, the time-varying mesh stiffness (TVMS) and the backlash of gear pairs are presented under different wear levels. The results show that, with the combined effect of angular misalignment and rotating carrier, the wear depth on both sides of the face width is larger than that in the middle, and the difference is the greatest at the root. Moreover, TVMS is affected not only by the tooth wear, but also by the rotating carrier, and the cycle of TVMS and the backlash is half of that of the carrier rotation.

The stiffness characteristics analysis of the duplex angular contact ball bearings based on a comprehensive multi-degree-of-freedom mathematical model

Although the duplex angular contact ball bearings (DACBBs) are widely used in industry, the published mathematical model of DACBBs is sparse. To analyze the stiffness characteristics of DACBBs, this paper proposes a comprehensive multi-degree-of-freedom (multi-DOF) mathematical model for the DACBBs in three traditional configurations. The implicit differential method is adopted to derivate the analytical stiffness matrix formulation of DACBBs. The geometrical constraints and interactions inside the DACBBs are presented based on the vector-and-matrix method. The detailed iterative algorithm with two layers for solving the presented model is given based on the Newton-Raphson method. A systematic study for evaluating the impacts of angular misalignment on the stiffness characteristics of DACBBs has been carried out under three typical load conditions: the pure axial load condition, the pure radial load condition, and the combined-loaded condition. The results indicate that the angular misalignment remarkably affects the stiffness characteristics of DACBBs. Under the pure axial and radial load conditions, the stiffness curves of DACBBs can be divided into two segments according to the value of misalignment angle, and the angular misalignment will be the predominant factor when the angular misalignment is great. Under the combined-loaded condition, the mode (single or combined angular misalignment) and the direction of angular misalignment significantly influence the stiffness characteristics of DACBBs. Also, the angular misalignment effects depend on the radial load. The proposed model can also analyze the mechanical performance of double-row angular contact ball bearings.

Numerical simulation of the effect of angular misalignment on the dynamic behaviour of bearing

Bearing has been used extensively in numerous applications and their unplanned failure has a consequential effect on the smooth operation of the machinery. A slight misalignment in bearing has a detrimental effect on the smooth running of most machines. Hence, the paper leverages finite element technique to simulate the consequential effect of different degrees (0.1°, 0.2°, 0.3°, 0.4°, 0.5°) of misalignment on the dynamic behaviour of a cylindrical roller bearing subjected to typical operating conditions of an airflow root blower. The results of the study show that during operation, the temperature and Hertzian stress developed increased with an increase in the degree of misalignment and operating/rotating speed, and the maximum Hertzian stress was developed on the outer ring of the bearing in all the degrees of misalignments and operational speeds considered. Thus, making the outer ring of the bearing component, the most prone to failure during operation in the presence of misalignment.

Static and dynamic characteristics of a Rayleigh-steps mechanical seal with reverse steps

This paper presents a Rayleigh-steps mechanical seal with reverse steps (RS-MS), and the governing equation was solved by the finite difference method (FDM). The effects of angular misalignment, working condition parameters, and film thickness on sealing performance were discussed, including the opening force, cavitation ratio, leakage rate, frictional torque, stiffness and damping coefficients. The results indicate that the cavitation phenomenon in the reverse step groove can restrain the leakage, while it also affects the stability of the seal. The angular misalignment makes the seal have greater stiffness and damping coefficients. The stiffness and damping coefficients decrease rapidly with the increase of the film thickness, and the dynamic stability of the mechanical seal decreases with the increase of the film thickness, which is not conducive to the stable operation of the seal. The research results can guide the optimization design of mechanical seals.

Effect of angular misalignment of inner ring on the contact characteristics and stiffness coefficients of duplex angular contact ball bearings

Ring misalignment is unavoidable in most applications of bearing and significantly affects bearing performance. However, it has not been thoroughly studied for duplex angular contact ball bearings. To overcome the deficiency, this paper presents the analysis for duplex angular contact ball bearings by considering inner ring angular misalignment. A highly modular five degree-of-freedom model of duplex angular contact ball bearings is proposed based on vector-and-matrix method for back-to-back, face-to-face and tandem configurations. Five-dimensional stiffness matrix of bearing is also presented. On the basis, influences of ring misalignment on load distribution, maximum and average contact loads of bearing with back-to-back and face-to-face configurations are analyzed. Finally, translation and tilting stiffness coefficients of bearing are further discussed under misalignment condition. The results show that, ring misalignment considerable changes the contact characteristic of ball-raceway and causes uneven load distribution. Ring misalignment affects the position of maximum contact load and significantly impacts the diagonal stiffness of bearing. Contact characteristics and stiffness are also dependent on the bearing configuration. The results suggest the importance of bearing alignment and demonstrate the necessity of misalignment effect analysis.

Nonlinear Coupled Torsion/Lateral Vibration and Sommerfeld Behavior in a Double U-Joint Driveshaft

Abstract Many driveline systems are designed to accommodate angular misalignment by the use of flexible couplings or Universal Joints (U-Joints) which link individual shaft segments. The Sommerfeld effect is a nonlinear phenomenon observed in some rotor systems being driven through a critical speed when there is not enough power to accelerate the rotor through resonance. Previous studies have shown that rotor speed can become captured when transitioning through natural frequencies due to nonlinear interactions between a non-ideal driving input and rotor imbalance. This paper, for the first time, shows that this type of rotor speed capture phenomena can also be induced by driveline misalignment. During rotor spinup under constant motor torque, it is found that misalignment-induced rotor speed capture phenomena can occur as the shaft speed approaches ½ the first elastic torsional natural frequency. Depending on misalignment level and motor torque, the shaft speed will either dwell near this speed and then pass through, or the speed will become trapped. Here, a nonlinear rotordynamics model of a segmented driveshaft connected by two U-joints including effects of angular misalignment and load torque is developed for the study. This analysis also determines the minimum driveline misalignment angle for which the shaft speed capture phenomena will occur for a given motor torque and load torque condition.

Influence of angular misalignment on the tribological performance of high-speed micro ball bearings considering full multibody interactions

To study the angular misalignment effects on the high-speed micro ball bearing which is applied to the dental handpiece, an improved five-degree-of-freedom quasi-dynamic model considering full multibody interactions is established in this paper. Then the modified fatigue life model presented by Jones is adopted to further evaluate the influence of angular misalignment on the reliability of the bearing. The results show that the angular misalignment significantly influences the contact load and contact angle distributions as well as the skidding behavior under both pure axial load and combined axial and radial loads. After comprehensive comparison, it is found that the impacts of angular misalignment on total power loss and bearing fatigue life are different under the two types of loads. Under pure axial load, the total power loss increases consistently and the bearing fatigue life decreases significantly when the absolute value of angular misalignment becomes larger. However, under combined axial and radial loads, the effects of angular misalignment are rather complicated and the direction of angular misalignment turns out to be a key influencing factor.

Effect of angular misalignment on the stiffness of the double-row self-aligning ball bearing

The double-row self-aligning ball bearing commonly runs with angular misalignment between the inner and outer rings, and the angular misalignment significantly affects the bearing performance. However, the effect of angular misalignment on the dynamic characteristics of the double-row self-aligning ball bearing has not been studied thoroughly. This paper investigates the effect of angular misalignment on the stiffness of the double-row self-aligning ball bearing. The quasi-static model for the double-row self-aligning ball bearing is established with five degrees of freedom, namely, three translational displacements along x, y, and z directions and two tilting angles around x-axis and y-axis. The internal clearance between balls and raceways is included in the presented model. The formulation of the three-dimensional stiffness matrix for the double-row self-aligning ball bearing is analytically derived, and is verified by comparing with the available dada in published literature. Finally, the stiffness of the double-row self-aligning ball bearing under various angular misalignment conditions is analyzed systematically. The results show that the tilting angles vary the contact angles and contact forces of the compressed balls in the double-row self-aligning ball bearing, thus affect the bearing stiffness; the bearing stiffness decreases with the internal clearance; the angular misalignment significantly impacts the stiffness of the bearing running at a low speed.

Focal Ratio Degradation for Fiber Positioner Operation in Astronomical Spectrographs

Focal ratio degradation (FRD), the decrease of light’s focal ratio between the input into an optical fiber and the output, is important to characterize for astronomical spectrographs due to its effects on throughput and the point spread function. However, while FRD is a function of many fiber properties such as stresses, microbending, and surface imperfections, angular misalignments between the incoming light and the face of the fiber also affect the light profile and complicate this measurement. A compact experimental setup and a model separating FRD from angular misalignment was applied to a fiber subjected to varying stresses or angular misalignments to determine the magnitude of these effects. The FRD was then determined for a fiber in a fiber positioner that will be used in the Subaru Prime Focus Spectrograph (PFS). The analysis we carried out for the PFS positioner suggests that effects of angular misalignment dominate and no significant FRD increase due to stress should occur.

Effect of the angular misalignment of laser welded T-joints on fatigue curves

This paper investigates the angular misalignment of laser welded T-joints made of thin sheets of aluminium alloys and its effect on fatigue curves. The effect of welding parameters and weld dimensions on angular distortion is analysed by linear regressions. A nonlinear finite element model is set up to consider the effect of angular misalignment on stress. The fatigue curves show that the misalignment affects the scatter, slope and fatigue strength of the S-N curves. The IIW reference curves for nominal and structural stresses are suitable for the studied joints. FAT50 is recommended instead of FAT71 for effective notch stress.

Effect of angular misalignment on the dynamic characteristics of externally pressurized air journal bearing

This paper studies the effect of angular misalignment on the dynamic characteristics of externally pressurized air journal bearing with four degrees of freedom. The linear perturbation method is applied to the Reynolds equation to obtain the steady-state equation and perturbation equations, and then the finite difference method and an iterative method are used to solve the Reynolds equation. Various eccentricity ratios and rotating speeds are taken into considerations for the comparisons of dynamic stiffness coefficients and damping coefficients of the air journal bearing under different tilt angles. In addition, the influences of perturbation frequency ratio on the dynamic performances of the air journal bearing are also estimated.

Effect of angular misalignment on the static characteristics of rotating externally pressurized air journal bearing

This paper studies the effect of angular misalignment on the static characteristics of rotating externally pressurized air journal bearing with four degrees of freedom (4-DOF). A clearance function is used to describe the film thickness of air journal bearings with angular misalignment along two perpendicular directions. The finite different method (FDM) and an iterative procedure are applied to solve the Reynolds equation and obtain the air film pressure distribution. Various eccentricity ratios and rotating speeds are taken into considerations for the comparisons of static performances of the air journal bearing under different tilt angles. The results show that the air film thickness, load capacity, stiffness, load moment, attitude angle and volume flow rate are affected greatly by the angular misalignment.

Fatigue analysis of friction stir welded butt joints under bending and tension load

Friction stir welding is rapidly gaining attention for a wide range of structural applications as well as for innovations in improvement of the welding technique itself. Most of the study on friction stir welded joints has been done under uniaxial tensile loading without considering the presence of geometric or welding defects. Very few studies have been done to assess the fatigue strength of friction stir welded aluminum joints under bending load. Herein, the fatigue behavior of friction stir welded single-sided aluminum butt joints has been studied under bending and tension load through small-scale specimen testing and fracture mechanics analysis. The test results are compared with data available in the existing literature, as well as with standard design curves. The effect of angular misalignment on the fatigue life of welded joints is also studied. An analysis of the test results is performed using a strain-based fracture mechanics model. This study shows that the fatigue performance of the investigated friction stir welded joints is better than typical arc welded joints and top side of the weld has better fatigue performance as compared to the root or bottom side of the weld under bending load. It is shown that even a slight misalignment of the order of 0.5° can generate significant secondary stress, which – if ignored – can result in non-conservative fatigue life estimates under pure tension loading.

Transmission efficiency analysis and optimization of magnetically coupled resonant wireless power transfer system with misalignments

Magnetically coupled resonant (MCR) wireless power transfer (WPT) is a promising technology, which has been widely used in many practical applications. In the practical application environment the misalignments between the transmitting coil and the receiving coil can not be avoided, and it will cause a rapid decline in transmission efficiency. So the misalignments have limited the applications of MCR-WPT technology in many fields. The mathematical formula of transmission efficiency with angular misalignment and lateral misalignment was deduced. And the effects of angular misalignment and lateral misalignment on the transmission efficiency were researched by simulation experiments. And the changing regularity of the transmission efficiency with the change of the angular misalignment and lateral misalignment was obtained. The results show that when there is an angular misalignment between the transmitting coil and the receiving coil, the transmission efficiency can be optimized by adjusting the lateral misalignment between the coils. And when there is a lateral misalignment between the coils, the transmission efficiency can be optimized by adjusting the angular misalignment between the coils. An experimental prototype of MCR-WPT system was built, and experiments had been carried out to evaluate the accuracy of the theoretical analysis. Therefore, the study in this paper lay a theoretical foundation for the analysis of WPT in the complex environment, and also provide a useful reference for the design of WPT system.