Contact Fatigue Life Research Articles

Contact fatigue life prediction of PEEK gears based on CTAB-GAN data augmentation

The contact fatigue life of PEEK gears is a critical fundamental data for the design of load-carrying capacity, which is significantly influenced by many factors such as material type, operating temperature, and loading level. Temperature effects must be considered during contact fatigue life prediction of PEEK gears. This article presents a predictive model for contact fatigue life of PEEK gears, utilizing the CTAB-GAN data augmentation. The CTAB-GAN data augmentation model expands the experimental dataset of contact fatigue lives of oil-lubricated PEEK gears. Then, a predictive formula was derived to estimate contact fatigue life of oil-lubricated PEEK gears considering the temperature dependent effect. Results revealed that the predicted fatigue lives of PEEK gears under different loading and temperature conditions based on the enhanced dataset are within a two-fold scatter band. The mean square error of predicted lives reduces by 30% compared to the life formula based on the original experimental data set. Furthermore a quantitative analysis was conducted on the influence of operating temperature and stress on the fatigue life of PEEK gears.

Investigation on fatigue parameters in railway wheels using a critical plane model

The contact areas between rail and wheel are critical in determining the performance of rail vehicles. Analyzing the mechanics, materials, tribology, and geometry of the interface is important to understand the contact damage mechanisms, fatigue parameter and fatigue life. Developing a simplified and novel approach to predict crack initiation and fatigue life is key for investigating contact fatigue of rail wheel interaction. This study aims to investigate rolling contact fatigue (RCF) cracks and fatigue life in railroad wheels using Finite Element Model (FEM). Using a proper material model that accounts for plastic shakedown, ratchetting, and cyclic hardening for both the rail and wheel materials, the FEM model is analyzed with the help of Abaqus 2020 tool. The submodelling technique was implemented to reduce computation demand. Stress and strain history outputs extracted from the submodel (at 0 mm, 1.3 mm, 2.6 mm, and 3.6 mm depths) were used to predict critical plane orientation, crack initiation and fatigue life using critical plane models. The orientation of critical (crack) plane was found using a novel MATLAB algorithm by searching for a plane with maximum fatigue parameter (FPmax). The investigation reveals that the location of maximum damage is the subsurface and the crack angles fall within the range of (0°, 40°), (62°, 123°) and (143°, 180°) with a 5 % margin and at a depth of 2.6 mm below the wheel surface. The determined fatigue crack initiation and life at this specific location were 6178 and 7174 cycles, respectively. Predicting the critical zone which is susceptible to shorter crack initiation and fatigue life is a crucial to prevent wheel failure.

Rolling Contact Fatigue Life and Categorization of Failure in Experiment of Flat PEEK Race-Alumina Ball Bearings in Water Lubrication under 1700 N at 1000 rpm

Abstract The rolling contact fatigue tests of flat polyether-ether-ketone (PEEK) race-alumina balls bearings in water lubrication were done. From the experiments under 1700 N at 1000 rpm, three types of failures were obtained: a crater-shaped flaking, a rhombus-shaped flaking and a large cracking failures. To research the relationships between the failures and the lives, the surface properties near the failures were measured and observed. No relationships between the surface roughness and the life were found. On the other hand, the contact width of the shorter life specimen was larger than that of the longer life specimen. Two types of the flaking holes were compared to study the differences. The crater-shaped flaking hole exceeded the contact track, but the rhombus-shaped flaking hole existed inside the contact track. In addition, the crater-shaped flaking hole was shallower than the rhombus-shaped flaking hole. This means that the flaking mechanisms were different between them, i. e. the differences of the flaking mechanisms caused the differences of the life.

Extended crack propagation in nitrided and carburised steels subject to rolling contact fatigue

To predict the Rolling Contact Fatigue life of components such as rolling element bearings, it is important to understand the failure mechanisms. A rather unusual failure was observed on integrated races into a planetary gear train. The failure of the planet of this gearbox was attributed to the very long propagation, at an unusual depth, of a crack, which probably started at the surface. The present preliminary study aims to gain a better understanding of the factors that can lead to this type of failure. Firstly, a twin-disc machine is used to reproduce the contact conditions identified in the application. A second set of more severe conditions is also tested. A comparison is made between a carburised steel (16NiCrMo13) and a nitrided one (32CrMoV13). Two distinct crack patterns and spalling characteristics between the two materials are observed. Some unusual crack characteristics are observed in the carburised sample for a specific set of contact conditions.

Gear contact fatigue prediction under mixed elastohydrodynamic lubrication with ellipsoidal asperity rough surface: Experimental and numerical investigation

A three-dimensional(3D) line-contact mixed lubrication model and contact fatigue life prediction model for gears are established, considering the elastoplastic contact of ellipsoidal asperities and their interactions. The localized lubrication states across the actual 3D rough surfaces are visually depicted. The direct asperity contact pressures calculation exhibits greater accuracy and universality. The proposed mixed lubrication model can be applied accurately and efficiently to heavy-load conditions. The synergistic mechanisms of multi-scale surface integrity parameters, such as surface morphology-lubrication coupling, hardness gradient, and residual stress, on gear contact fatigue has been revealed. The results reveal that surface roughness significantly affects the competitive failure mechanism between surface-initiated micropitting and subsurface-initiated macropitting. The increase in surface compressive residual stress is more sensitive to the enhancement of near-surface and subsurface fatigue lives, compared to the increase of peak residual stress and the depth of peak residual stress. The proposed physics-based gear contact fatigue life prediction model has been validated through gear contact fatigue experiments under various operating conditions. The maximum deviation between the predicted and experimental fatigue lives is within 10%. This paper presents theoretical methodologies and data-driven support for optimizing the design and manufacturing processes of gears, specifically focusing on enhancing anti-fatigue properties.

Pulsed Magnetic Field Treatment Effects on Undissolved Carbides in Continuous Casting Billets of GCr15 Bearing Steel

The study investigates the effect of pulsed magnetic fields on undissolved carbides in high-carbon chromium bearing steel GCr15 billets. The billets were subjected to heat treatment at 950 °C, with a pulsed magnetic field of varying durations applied during the process. The influence of the pulsed magnetic field on the distribution of undissolved carbides within the billets was investigated, and the thermodynamic and kinetic mechanisms of undissolved carbides dissolution were explored. The results indicate that the area percentage of undissolved carbides in the microstructure decreases from 1.68% to 0.06% after applying a pulsed magnetic field for 10 min, and the size of undissolved carbides decreases from 17.5 μm to 4.9 μm. When a pulsed magnetic field is applied for 30 min, all undissolved carbides dissolve. The statistics demonstrate that the average size of undissolved carbides is reduced from 14.19 μm to 0.63 μm, with a reduction percentage reaching 96%. Over the same duration, the number density of the undissolved carbides decreases from (0.19~0.55)/mm2 to (0.03~0.1)/mm2, and the percentage area of the undissolved carbides decreases from (1.26~1.68)% to (0~0.02)%. Thermodynamically, applying a pulsed magnetic field lowers the dissolution energy barrier of undissolved carbides and modifies their transformation temperature. Kinetically, the rate of alloy element diffusion is enhanced by increasing the frequency of atomic jumps. This research aims to provide new insights into enhancing the contact fatigue life of bearing steel, increasing the proportion of special steel, and optimizing the steel deep-processing process.

Research on the Influence of Wheel Tread Defects on Rolling Contact Fatigue

With the rapid development of high-speed trains, local rolling contact fatigue caused by special local defect damage forms has become more prominent. This article takes circular defects as the research object, adopts the Jiang Sehitoglu multi-axis fatigue damage criterion based on the critical plane method, establishes a finite element model of wheel tread circular defects, and studies the influence of wheel tread circular defects on wheel rail rolling contact fatigue. Based on finite element analysis to obtain fatigue damage parameters, an improved PSO-BP neural network was used to establish a neural network prediction model for fatigue damage parameters, and the feasibility of the model was demonstrated. The research results show that the main influencing factors on the rolling contact fatigue life of wheel tread defects are shear stress and shear strain; The fatigue damage parameter is maximum at the edge of the wheel tread defect; As the defect distribution moves from the center to both sides, the contact stress and damage parameters gradually decrease; As the depth of the defect increases to the size of the radius, the contact stress and damage parameters first increase and then decrease; As the diameter of the defect increases, the contact stress and damage parameters increase, but the amplitude change gradually tends to stabilize with the increase of the defect diameter. The neural network prediction results indicate that all predicted samples are within a reasonable range, and this neural network model can provide a reference for predicting fatigue damage of wheel tread.

Multi-Objective Process Parameter Optimization of Ultrasonic Rolling Combining Machine Learning and Non-Dominated Sorting Genetic Algorithm-II.

Ultrasonic rolling is an effective technique for enhancing surface integrity, and surface integrity is closely related to fatigue performance. The process parameters of ultrasonic rolling critically affect the improvement of surface integrity. This study proposes an optimization method for process parameters by combining machine learning (ML) with the NSGA-II. Five ML models were trained to establish relationships between process parameters and surface residual stress, hardness, and surface roughness by incorporating feature augmentation and physical information. The best-performing model was selected and integrated with NSGA-II for multi-objective optimization. Ultrasonic rolling tests based on a uniform design were performed, and a dataset was established. The objective was to maximize surface residual stress and hardness while minimizing surface roughness. For test specimens with an initial surface roughness of 0.54 µm, the optimized process parameters were a static pressure of 900 N, a spindle speed of 75 rpm, a feed rate of 0.19 mm/r, and rolling once. Using optimized parameters, the surface residual stress reached -920.60 MPa, surface hardness achieved 958.23 HV, surface roughness reduced to 0.32 µm, and contact fatigue life extended to 3.02 × 107 cycles, representing a 52.5% improvement compared to untreated specimens and an even more significant improvement over without parameter optimization.

Comparative analysis of rolling contact fatigue life in a wind turbine pitch bearing with different modeling approaches

The load calculation for wind turbines usually does not take pitch bearings into account, and the pitch-bearing internal load distribution is calculated in a decoupled process. In the current study, a coupled wind turbine load simulation considering the pitch bearings is proposed. Internal pitch-bearing load distribution and roller contact fatigue life are compared to a decoupled approach using a high-fidelity finite-element model. Internal pitch-bearing load distribution can be an essential variable in almost all major pitch-bearing failures. Furthermore, rolling contact fatigue is one of the major types of pitch-bearing failure that can represent the bearing service life. The results show that the flexibility of the surroundings has an effect on the contact forces. As a result, the finite element model-based life calculation of the NREL 5 MW turbine predicts a longer rolling contact fatigue life for the bearing than the multi-body system-based one. For the IWT7.5, sample load cases indicate that this behavior is different, leading to the conclusion that the life of the bearing is significantly affected by the stiffness of the bearing and its surrounding components.

Relating rolling contact fatigue (RCF) life to the microstructure evolution in aerospace grade bearing steels: A comparison of Cronidur-30 with AISI 440C

This article presents an extensive analysis of the microstructural evolution under various heat treatment conditions, mechanical properties (hardness), and rolling contact fatigue (RCF) life assessment and sub-surface crack analysis are studied on high nitrogen bearing steel Cronidur-30(Cr-30). An optimum solutionising temperature range has been identified which ensures desirable hardness as well as low retained austenite content. The microstructure consists of primary M2 (C, N) and secondary M23C6 carbides. Sizes of carbides in Cr-30 are significantly smaller than in AISI 440C and this plays a critical role in enhancing the RCF life of Cr-30. A larger area fraction of fine carbides results in branches and subsequent sub-branches of cracks in Cr-30 steel. However, the AISI 440C sample exhibits extensively interconnected cracks due to the presence of larger carbides. The tempering response of Cronidur-30 exhibited a peak hardness of 61 HRC at both lower (150 °C) and higher (475 °C) temperatures. Higher temperature tempering showed L1 life improvement of over 0.5 fold compared to lower temperature tempering.

Investigation of pad radius effects on multiaxial fretting fatigue behavior of al2024 alloy

Fretting fatigue, a critical phenomenon prevalent in engineering applications, occurs at the interface of contacting surfaces under cyclic loading, presenting significant challenges. The advent of Finite Element Analysis (FEA) has transformed the investigation of fretting fatigue by offering detailed insights into stress distributions and fatigue damage mechanisms. This study delves into the impact of pad radius on the fretting fatigue behavior of Al2024 alloy using FEA, with a focus on hot spot analysis and the Smith-Watson-Topper (SWT) criterion. The analysis aims to validate numerical results against analytical findings and explore the role of pad radius in determining contact behavior, fatigue life, and hot spot locations. By incorporating "fe-safe" software, computations are streamlined, facilitating efficient comparison of different fatigue initiation criteria. The results demonstrate that variations in pad radius significantly influence fretting fatigue behavior. Larger pad radii tend to distribute stresses more uniformly across the contact interface, resulting in reduced fatigue damage and longer fatigue life compared to smaller pad radii. Hot spot analysis reveals that smaller pad radii concentrate stresses at specific regions, accelerating fatigue damage initiation. The findings contribute to a deeper understanding of fretting fatigue mechanisms, shedding light on the importance of pad radius in designing more durable engineering components. Through professional scientific methodology, this study provides valuable insights into optimizing pad design to mitigate fretting fatigue and enhance the reliability of mechanical systems.

The effect of fine particle peening on aviation gear performance, part II: Rolling contact fatigue

AbstractFine particle peening (FPP) technology offers an effective method to achieve outstanding surface integrity and fatigue performance in aviation gears. However, the lack of sufficient research on the correlation between process parameters, surface integrity parameters, and fatigue life undermines the full potential of FPP in strengthening aviation gears. Therefore, we have developed an elastic–plastic contact fatigue life model to predict the fatigue life of AISI 9310 gear steel after different strengthening processes. This model can consider surface integrity parameters such as surface micro‐topography, residual stress gradient, and hardness gradient. To validate the model, we conducted rolling contact fatigue tests and compared the results with the predictions from our model. The influence of process parameters on the rolling contact fatigue of AISI 9310 gear steel was further investigated. A process window for FPP was established, and an optimization method was proposed in order to provide guidance for selecting process parameters for FPP on high‐performance aviation gears.

Composite effects of residual stress and hardness gradient on contact fatigue performance of rough tooth surfaces and optimization design of detailed characteristic parameters

Residual stress and hardness gradient significantly affect the contact fatigue failure process of rough tooth surfaces, and the meticulous design of their characteristic parameters can help improve the fatigue resistance of gears. In this paper, an efficient computational method for rough tooth surface contact is established based on the reconstruction modeling of asperities and mixed lubrication analysis. By comprehensively considering the effects of residual stress and hardness gradient, the Dangvan multiaxial fatigue criterion is adopted to predict and analyze the contact fatigue life of the gear surface. The correlation between the surface residual stress, maximum residual stress depth, surface hardness, and effective hardening layer depth, among other characteristic parameters, and the contact fatigue performance of tooth surfaces is established. The results show that: (1) Increasing the magnitude of surface residual compressive stress and surface hardness can significantly reduce the risk of fatigue failure in the near-surface layer of the gear. To achieve the same fatigue performance, there is a linear negative correlation between the design values of the two parameters. (2) Affected by the double stress peaks in the rough tooth surface stress field, the maximum residual stress depth significantly affects the depth at which the highest failure risk occurs. With changes in roughness, the optimal design value of the maximum residual compressive stress depth changes from about 0.5 times the Hertzian contact half-width depth in the subsurface layer (Sa < 0.2 μm) to about 15 μm in the near-surface layer (Sa > 0.4 μm). (3) Considering both process cost and gear surface fatigue resistance, the design threshold for the effective hardening layer depth should be greater than the Hertzian contact half-width. This paper establishes a composite correlation between the meticulous characteristic parameters of residual stress, hardness gradient, and the contact fatigue performance of tooth surfaces, providing theoretical support for optimal design of tooth surface anti-fatigue performance.

The effect of shot peening on the contact fatigue performance of C40 steel gears after laser surface melting

In this paper, shot peening (SP) was employed as a post-processing technique for the laser surface melted (LSMed) gear. The aim was to improve the contact fatigue performance of laser surface melting+shot peened (LSMSPed) gears. The microstructure, surface roughness, residual stress, microhardness of C40 steel gears before and after SP treatment were characterized using scanning electron microscopy, x-ray diffraction stress analyzer, contour measuring instrument, and hardness tester. Fatigue test of gear was carried out with a Forschungsstelle für Zahnräder und Getriebebau (FZG) testing machine. Following the laser surface melting (LSM) treatment, a molten layer was observed on the gear teeth surface. The experimental results indicated that SP induced a hardened layer with a certain thickness and plastic deformation on the surface of LSMed gears. Importantly, as the SP parameters increased, there’s a corresponding reduction in both the average grain diameter and the maximum grain diameter. The reduction was most pronounced when the shot diameter reached its maximum value. It’s worth noting that once the optimal threshold for SP parameters is surpassed, the residual compressive stress and microhardness on the LSMSPed gear surface do not exhibit a continuous growth trend. Furthermore, the rise in SP parameters resulted in a gradual increase in the surface roughness of LSMSPed gears, albeit to varying degrees. In light of the combined effects of grain refinement, residual compressive stress, microhardness, and surface roughness, the contact fatigue performance of LSMSPed gears improved with increasing SP parameters. Notably, when comparing the contact fatigue life of LSMed gears with that of LSMSPed gears, we observed a substantial enhancement. However, it’s essential to highlight that when the shot diameter reaches its maximum value, the contact fatigue life of the LSMSPed gear, somewhat unexpectedly, decreased. It emphasized to a certain extent the influence of surface roughness on the contact fatigue performance of LSMSP gears.

The influence of different load distribution considering geometric error on the fatigue life of ball screw

The ball screw pair is a precision drive component that converts rotary motion into linear motion. In practical applications, because the feed system usually has rotational torque and geometric errors, it may increase the contact load of the ball screw pair and reduce the fatigue life. In order to study the influence of different loads and geometric errors on the maximum contact load and fatigue life of ball screw pairs, the following research work was carried out. Firstly, based on the composite load and rotational torque, the ball load distribution model is established, and the accuracy of the model is verified by finite element modeling analysis. Then, the influence of different composite loads, rotation times and geometric errors (including ball size error, lead error and raceway tooth profile error) on the ball load distribution is analyzed. Finally, the influence of compound load, rotating torque and geometric error on the fatigue life of ball screw pairs is studied. The results show that the rotational torque and lead error have a great influence on the load distribution and fatigue life of the ball, and the influence of lead error on load distribution is greater than that of dimension error and tooth profile error. The fatigue life of the ball screw pair with non-uniform load distribution is shorter than that of the ball screw pair with uniform load distribution.

Review of rolling contact fatigue life calculation for oscillating bearings and application-dependent recommendations for use

Abstract. In contrast to the multitude of models in the literature for the calculation of rolling contact fatigue in rotating bearings, literature on oscillating bearings is sparse. This work summarizes the available literature on rolling contact fatigue in oscillating bearings. Publications which present various theoretical models are summarized and discussed. A number of errors and misunderstandings are highlighted, information gaps are filled, and common threads between publications are established. Recommendations are given for using the various models for any oscillating bearing in any industrial application. The applicability of these approaches to pitch and yaw bearings of wind turbines is discussed in detail.

Microstructure effects on improving rolling contact fatigue by a double-quenching heat treatment process for GCr15 steel

The heat treatment process is important in improving the rolling contact fatigue (RCF) life of GCr15 bearing steel by changing the microstructure. The conventional heat treatment process of GCr15 bearing only has one quenching (CQ) process, and the corresponding RCF life cannot satisfy the requirements of many applications. A double-quenching (DQ) heat treatment with two quenching processes was proposed, and it can improve the RCF life. However, the improving mechanisms are not clarified. Therefore, the authors applied the CQ and the DQ heat treatment processes on GCr15 bearing steel and performed the ball-on-disk RCF tests for the specimens heat treated by the different processes. Moreover, comparisons of the microstructure and mechanical behavior between specimens were made. The results show that the DQ heat treatment decreases the average grain size, enhances the retained austenite content, and has no special effect on the carbide distribution. It also increases the homogeneity of grains, hardness, and retained austenite distribution. Moreover, the combined effect of grain size and retained austenite evolutions is the main mechanism that decides the RCF life improvement.

Effect of dented residual stress on the surface-defect-induced pitting under rolling contact loading of M50 bearing steel

Surface-defect-induced pitting gradually becomes the limitation of the rolling contact fatigue life of the M50 bearing steel as the subsurface initiation spalling probability decreases recently. Dent formation lives residual stress (RS). However, it was ignored in past studies on surface-initiated pitting. Therefore, this study established a continuous simulation model from particle compression to cycle rolling contact loading to study the dent-induced RS effects on damage evolution. The constitutive model of damage evolution incorporated continuum damage mechanics and cohesive mechanics. The results show that the depth-width ratio of the dent and RS increases as the load and hardness increase. RS makes both subsurface-initiation-damage and surface-initiation-damage advance, and affects the direction and speed of the surface damage evolution. Moreover, the size of the pitting in the rolling direction increases as hardness increases.

A rolling contact fatigue life prediction model for bearing steel considering its gradient structure due to cyclic hardening

This paper presents a rolling contact fatigue life prediction model for bearing steel. In the initial stage of rolling contact, the gradient structure appears in the subsurface region of bearing steel and the hardness shows a gradient distribution along the contact depth direction due to the roller compaction effect. This indicates that the fatigue resistance of bearing steel varies in the subsurface region. Besides, each subsurface material volume element is subject to different stress cycles. Based on Weibull theory, the survival possibility of subsurface volume elements is formulated. Then the rolling contact fatigue life is evaluated considering the stress state and anti-fatigue performance of each elementary volume of the subsurface material. According to the phenomenon and assumption, the model proposed for gradient material was applied in the rolling contact fatigue life prediction of the bearing steel GCr15 and validated with the fatigue experiment data in the open literature. Furthermore, the accuracy of the proposed model results was compared with the traditional empirical rolling contact fatigue life prediction models.

Fatigue properties of riveted joints under different hole perpendicularity errors and squeeze forces.

Riveting is the most important method of joining sheet metal and is widely used in the assembly of aircraft components. The perpendicularity error of the holes is unavoidable during automatic drilling and riveting, which has a significant impact on the quality of the assembly. In this paper, the effects of hole perpendicularity error and squeeze force on the interference fit size, interface contact state, microstructure morphology, fatigue life, and fracture form of riveted joints were investigated experimentally. The results show that the interference fit size increases with a greater tilt angle. When the tilt angle is 0°, the rivet shank is in close contact with the inner and outer sheets, and there is no obvious gap at the interface between the rivet and the sheets. As the tilt angle increases to 2° and 4°, a gap appears at the interface of regions 1, 2, and 3, while the rivet shank at region 4 is in close contact with the outer sheet. The fatigue life decreases when the tilt angle increases from 0° to 4°. For the same tilt angle, the fatigue life of riveted joints with a 0° tilt direction is higher than that of riveted joints with a 180° tilt direction. Increasing the squeeze force can to some extent reduce the adverse effect of the tilt angle on the fatigue life. The hole perpendicularity error does not affect the failure form, while the squeeze force has a significant effect on the failure form of the specimens. RESEARCH HIGHLIGHTS: The fatigue life of riveted joints decreases as the tilt angle increases. The size of the interfacial gap increases with increasing tilt angle. Higher fatigue life at 0° tilt direction than at 180° tilt direction. Increasing the squeeze force can somewhat reduce the negative effect of tilt angle on fatigue life.