Contact Fatigue Failure Research Articles

Integrated analysis strategy for detecting gear contact fatigue before reaching failure interruption criterion

Identifying the occurrence of gear contact fatigue failure as early as possible is essential for condition-based maintenance (CBM). Vibration signals can be used to identify gear contact fatigue. However, the use of vibration signals can be challenging due to its complexity, compounded by lower levels of vibration during the initial stages of contact fatigue. The present study details a new algorithm that integrates stand-alone features to correlate the vibrational signal with early failure occurrence. The study aim is to identify the failure in the early stages, before reaching the ISO 6336-5 stopping criterion of 4% damaged area. A damage induction on the flank of helical gears is applied to simulate and characterize the failure occurrence. Damping characteristics with impact evaluation, Kurtosis analysis and the monitoring of the Gear Meshing Frequency are applied to characterize the failure signature. This strategy stands out by the integration of these stand-alone features and their behavior. The algorithm's capacity is verified through durability tests, promoting the natural evolution of this failure mode. Results show a success rate of above 80% at identifying the failure presence before the stopping criterion limit.

Influence mechanism of grinding surface quality of 20CrMnTi steel on contact failure

To reveal the influence mechanism of the grinding surface quality of 20CrMnTi steel components on the tribological characteristics and contact fatigue performance, accelerated tests for sliding friction wear and fatigue damage were carried out. Tribological characteristics and contact fatigue performance get worse with increasing surface roughness while getting better with increasing surface microhardness. Residual compressive stress is conducive to inhibiting the initiation and propagation of cracks and promoting contact fatigue performance. Additionally, mechanical friction, abrasive wear, adhesive wear and fatigue damage coexist and form a competing failure mechanism under the synergistic effect of frictional wear and contact fatigue failure. The damage process mainly manifests as wear, stress concentration induced fatigue, microcracks, pitting, and spalling in the shallow layer. This study is more beneficial to promote the 20CrMnTi steel transmission parts manufacturing products for high precision, low damage, and long life.

Capacity assessment of railway axle journal bearing addressing a localized rolling contact fatigue failure mechanism

Abstract A framework for assessing the capacity of railway axle journal bearings is presented after elaborating on the locale rolling contact fatigue (RCF) failure mechanism. Three phases are conducted, including the determination of bearing service loads, finite element analysis (FEA) on the localized RCF stresses of bearing components, and the life-related capacity assessment on the bearings and bearing components. Results prove that wheel-track (WT) contact forces inspected by an instrumented wheel set can be transferred into bearing service loads. Two-step FEA from the global wheel set to the local bearings is used to obtain localized RCF stresses at dangerous locations around the bearing contact regions. After determining the locations, a life-related capacity assessment is performed by evaluating equivalent RCF stresses and lives at the locations to determine the weakest bearing component. Typical practice is given in agreement with FEA. This method deals with the FEA of bearing structures, material cyclic stress-strain curves, and probabilistic RCF life curves. Therefore, this work greatly enhances the development of rail-bearing materials, innovative structures, and capacity assessment.

FE-analytical slice model and verification test for load distribution analysis and optimization of planetary gear train in wind turbine

Load distribution behavior of planetary gear train (PGT) is crucial for the contact and bending fatigue failure of wind turbine transmission system. With the increasing power of wind turbines, the load and failure rate of wind turbine become larger, which leads to the demand of accurate and efficient modeling, analysis and optimization for load distribution of PGT. In this paper, a new efficient and accurate FE-analytical slice model for load distribution analysis and optimization of PGT in wind turbine is proposed, which is explicitly formulated by the geometry slice model of external/internal gear contact, original FE-analytical slice model for local contact deformation, and efficient finite element (FE) model for global structural deformation. In the FE-analytical slice model, geometry errors are effectively descripted by discretizing gears into a series of slices, while gear tooth contact elasticity and structural elasticity are addressed by the FE-analytical method accurately and efficiently. Upon the proposed model, the load distribution behaviors of PGT with coupling effects of elasticity and errors are revealed and optimized by tooth modification and in-phase eccentricity arrangement strategy. The load distribution tests of PGT in wind turbine are conducted, verifying the proposed FE-analytical slice model which is significant to improve the load-bearing capacity and avoid the fatigue failure of wind turbine transmission system.

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.

Effect of surface rolling process on rolling contact fatigue behavior and failure mechanism of powder metallurgy steel

The effect of surface rolling process on the surface microstructure and rolling contact fatigue of the Fe-2Cu-0.6 C powder metallurgy steel was investigated in the present investigation. Results indicated that a densified and hardened layer with a densification depth of 330 μm and a surface hardness of 330 HV0.1 was generated in the surface layer after rolling process. Ferrite grain and pearlite lamellae became typical fibrous structures on the top surface. The microstructure of pearlite was presented by two typical features. One was that the discrete cementite plates were severely curled and wavy. The other one was that the cementite plates remained parallel to each other, but were a reticular structure at a macroscopic level. The rolling contact fatigue (RCF) test showed that the RCF life of the rolled sample was superior. The L10, L50, L63.2 life increased by 182%, 105%, 92%, respectively. Surface initiated spalling was the main fatigue failure mode. Subsurface equivalent contact stress and local equivalent stress were calculated. The results showed that surface cracks were due to the repetitive tensile stress, which caused pits. Subsurface cracks nucleated and propagated in the region where the local equivalent stress was higher than the matrix yield strength, which caused spalling as connecting with surface cracks. The surface densified layer plays an important role in improving the rolling fatigue resistance of the material.

Wear and Friction Behaviour of Additive Manufactured PEEK under Non-conformal Contact

Tribological properties of laser sintered polyether-ether-ketone (EOS PEEK HP3) were investigated using a rolling-sliding test rig. This investigation aimed to study the wear and friction failure mechanism of EOS PEEK HP3. The main objectives included to conduct wear and friction tests under non-conformal contact, to monitor surface temperature, to carry out surface characterization with microscopy. With this rolling-sliding test rig, tests were carried out on an EOS PEEK HP3 specimen running against a steel disc unlubricated, with various slip-ratios under a contact pressure of 56 MPa, 48 MPa and 39 MPa respectively. Both wear and friction were measured. The results have shown that both friction and wear were increased with an increase of either slip-ratios or the contact pressures, exacerbated by high surface temperatures. It has also been observed that both friction and wear failures were associated with the degradation of the non-conformal contact surfaces due to crystallinity changes that correlated well with working conditions. Using microscopy it was found that such failures as pitting, fatigue and surface cracking were affected by the surfaces in contact, including the degree of melting of the surface. Based on the observation on the contact surfaces, the failure mechanisms of EOS PEEK HP3 include surface melting and contact fatigue failures with the high slip-ratio and the high contact pressure conditions. The findings of this investigation have the potential to help to design & develop additive manufacturing PEEK products. Typically, these results can be used in a design process for a more effective polymeric gear system.

The influence of shot peening on gear teeth micropitting and contact fatigue failure

Case-hardened gears present a high contact fatigue load capacity in a compact and light mechanical transmission systems but sometimes, micropitting appears. This damage can lead to early contact fatigue failure called macropitting (NF ISO 10825-1). A previous study has demonstrated that an appropriate shot peening treatment could reduce the micropitting phenomenon via tests on a twin disc machine.The aim of this paper is to study the influence of shot peening on the micropitting of case-hardened gears tooth flank and its development to macropitting. Experimental tests are carried out using a back-to-back gear test rig, an interrupted test method is defined in order to monitor the micropitting initiation and its propagation on the tooth flank. Two variants of carburized spur gear specimens are tested. The reference specimen has a case-hardened ground tooth flanks which is a typical gear application. The other specimen has a case-hardened ground tooth flanks with a shot peened finishing process. The fatigue tests are run until the appearance of macropitting. The performed inspections of specimens indicate that shot peening modifies the surface roughness, the surface topography and increases the compressive residual stress. The experimental results show that micropitting occurs on both shot-peened and non-shot-peened gears after approximately the same running time. However, a difference is observed in the propagation of micropitting on the tooth flanks. In comparison to reference gears, shot peening has postponed the apparition of macropitting by more than 60%. An analytical study is also conducted to validate the prediction of micropitting using the ISO/TR 6336-22 by comparing the results with the occurrence of micropitting on the tested gears.

Calculation and Analytical Prediction of Coating Wear During Tribological Tests Based on Models of Contact Fatigue Failure

Calculation and Analytical Prediction of Coating Wear During Tribological Tests Based on Models of Contact Fatigue Failure

Modeling of Contact-Fatigue Failure of a Two-Layer Elastic Half-Space

Modeling of Contact-Fatigue Failure of a Two-Layer Elastic Half-Space

Rolling Contact Fatigue Damage Analysis of G10CrNi3Mo Steel Bearing Inner Ring by X-ray Measurements

Contact fatigue is the main failure model for bearing systems in steel rolling mills. Characterizing the degree of contact fatigue damage is important for predicting its operating life. In this paper, the X-ray diffraction method (XRD) is used to measure the residual stress state and the diffraction peak width (FWHM, full width at half maximum) of six samples with different degrees of contact fatigue failure. The results show that surface residual stress values increased by more than 70% compared with the original state, while the diffraction peak width values decreased by more than 7% and were strongly correlated with the degree of contact fatigue damage. The XRD measurement of the bearing inner ring enables the characterization of the evolution of the residual stress state and grain distortion due to damage development. FWHM values may be considered an indicator for predicting the degree of contact fatigue.

Rolling contact fatigue failure mechanism of bearing steel on different surface roughness levels under heavy load

It is inherent knowledge that rolling contact fatigue (RCF) failure of subsurface-initiated spalls usually occur under optimum surface under heavy load. However, our previous work has revealed surface-initiated RCF failure mechanism under heavy load and initial high roughness surface. The formation of surface crack caused by RCF is a complicated phenomenon that is accompanied by surface morphology and lubrication condition, as well as stress distribution and microstructure evolution. To clarify the main failure mechanism, this study carried out systematic RCF tests with different surface roughness specimens and conducted characterization of superficial microstructure for specimens of pre-service and post-service by Focused Ion Beam (FIB). The results clearly suggest precursor of collapsed morphology and nanocrystalline layer are the main factor that causes the RCF life with high roughness is lower than that with low roughness. While the spalling failure initiating from low roughness surface under heavy load are strongly relied on surface plastic deformation. Two main plastic deformation mechanisms are conductive to formation of surface cracks: the micro-plastic deformation and the local severe plastic flow. A newly failure mechanism that spalling failure initiates from surface has been proposed to link surface roughness and microstructure evolution.

Refining the mechanistic understanding of microstructural decay during rolling contact fatigue in 52100 bearing steel tempered at high temperature

Subsurface rolling contact fatigue (RCF) failure occurs beneath heavily loaded hard contacts like gears, bearings, and cams. This study investigates microstructural decay beneath a RCF-tested surface in AISI/SAE 52100 bearing steel tempered at 240 ℃. RCF tests were conducted at 100 ℃ with a maximum Hertzian contact pressure of 4 GPa for four stress cycles. Microstructural characterization utilized scanning electron microscopy, electron backscatter diffraction, transmission Kikuchi diffraction, and transmission electron microscopy. Due to high tempering temperature, white etching bands (WEBs) were observed without preceding dark etching regions. The microstructural decay sequence involved: (1) formation of elongated ferrite and ferrite microbands, (2) complete dissolution of tempered carbides and partial dissolution of residual cementite, (3) formation of WEBs composed of nano-sized ferrite grains (100–300 nm) transformed from ferrite microbands, and (4) appearance of lenticular carbides. Within the WEBs, most nano-sized grains had high-angle grain boundaries, while the fraction of low-angle grain boundaries increased in later stages of RCF. Lenticular carbides formed alongside elongated ferrite and coalesced nano-sized ferritic grains.

Experimental testing of GCr15 bearing steel with different surface treatments as passive friction energy-dissipative shims

The seismic performance of buildings can be improved by adding supplemental damping using friction dampers. The friction behavior of the metallic shims becomes more stable with increasing surface hardness ratio between the friction pair. However, as hardness increases, metallic materials tend to become more brittle, which increases the risk of accidental failure. This study investigated the performance of a friction energy dissipator using bearing steel (GCr15) treated by a grinding-strengthening process, a special manufacturing technology for bearings steel commonly used in mechanical engineering. Two base materials, Q355 and B450, were additionally compared with GCr15. Each base material used three different surface treatments, i.e., cleaned surface (CS), sand-blasting (SB), and grinding-strengthen (GS) treatments. The surface hardness of Q355-GS, B455-GS, and GCr15-GS increased by 13.62 %, 17.38 %, and 19.71% compared to their base materials, while sand-blasting didn’t have an increased effect on surface hardness. The nine specimens were quasi-statically tested to investigate the effect of surface treatment on the friction behavior of the metallic shims. For the three Q355-like and three B450-like specimens, the wear mechanism mixed abrasive and adhesive wear. The GCr15-CS experienced contact fatigue failure, while the GCr15-SB and GCr15-GS exhibited abrasive wear resulting in standard rectangular hysteretic loops with a high degree of coincidence. The friction performance of GCr15-GS was the best among the nine friction shims, because it has less loss in friction coefficient and strength during fatigue loading, the least fluctuation in bolt force, and the smallest degradation and coefficient of variation in friction strength.

Research on Rolling Contact Fatigue Failure of the Bearing Used in High-Speed Electric Multiple Units’ Axle Box Based on a Damage-Coupled Elastic–Plastic Constitutive Model

The axle box bearing is a crucial component of high-speed electric multiple units (EMU) and is exposed to harsh working conditions, making it susceptible to subsurface-induced rolling contact fatigue (RCF) under long-term alternating stress. The objective of this paper is to develop a damage-coupled elastic–plastic constitutive model that can accurately predict the RCF life of EMU axle box bearings made from AISI 52100 bearing steel. The total damage is divided into elastic damage related to the shear stress range and plastic damage associated with plastic deformation. Material parameters are determined based on experimental data from the literature, and validation is conducted to ensure the validity of the model. Finally, the RCF behavior of the EMU axle box bearing, including crack initiation, crack propagation, and spalling, is simulated, and reasonable results are obtained. This study provides valuable insights into the RCF behavior of EMU axle box bearings and contributes to the accurate prediction of the fatigue life.

Contact fatigue performance and failure mechanisms of Fe-based small-module gears fabricated using powder metallurgy technique

Gears fabricated using powder metallurgy technique (PMT) have the potential to replace traditional wrought gears due to their very high forming efficiency and relatively low cost. However, their practical applications are restricted due to the lack of understanding of their fatigue properties and failure mechanisms. This work investigates the contact fatigue performance and corresponding failure mechanism of a typical Fe-based small-module gears fabricated by PMT. The fatigue tests were conducted under grease lubrication condition, using a power-opened small-module gear testing rig. The experimental results show that the current PMT fabricated small-module gears exhibit contact fatigue properties comparable to those of traditional wrought steel gears. It has been found that the subsurface cracks induced from pores are the dominant cause of spalling of PMT fabricated small-module gears during rolling contact. The cracks tend to propagate between adjacent pores, playing a vital role in the overall fatigue life. Thus, this study suggests that PMT can be a successful method for fabricating Fe-based small-module gears with excellent contact fatigue property if formation of pores during fabrication is well inhibited.

A study on the rolling contact fatigue mechanism of ZC-L cast wheel steel

In this paper, the rolling contact fatigue (RCF) failure mechanism of ZC-L cast steel wheels was analyzed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that obvious fatigue flaking is formed on the macroscopic surface of the wheel tread after RCF failure. The RCF cracks are formed at the maximum shear stress region of the sun-surface of the wheel (1–5 mm below the tread). There are a lot of subsurface white etching microstructure (WEM) and obvious casting defects in the subsurface of the wheel tread. The RCF cracks are mainly formed at the interface between the subsurface WEM and the matrix and at the edge of the casting defects. The subsurface WEM is composed of nano-ferrite grains and residual cementite, and its hardness is about 920HV, which is much higher than that of the matrix structure. During the wear process, the plastic deformation of the subsurface WEM and the matrix is not coordinated, resulting in the formation of RCF cracks. As a hard phase, the hardness of casting defects is much higher than that of matrix. In the process of wear, under the action of subsurface stress, the casting defects can cause obvious plastic deformation in the soft orientation region at the edge of the casting defects. When the plastic deformation reaches the plastic limit, the RCF cracks are formed at the edge of the inclusions due to ratchet failure. The stress at the crack tip is caused by the RCF crack propagation at the edge of inclusions will further lead to the refinement of the microstructure at the edge of the RCF crack. Under the action of the subsurface contact stress, the subsurface WEM and casting defects are the main reasons leading to the RCF failure of the ZC-L casting wheel. Improving the microstructure uniformity and reducing casting defects are the main methods to improve the fatigue property of casting wheels.

A spalling evolution model for time-varying mesh stiffness evaluation and service life prediction of gears

Spalling is one of the most common contact fatigue failure modes on gear face. Although there are some prediction models for spalling formation, few prediction models have previously addressed the evolution from initial defects to spalling cavities. In this paper, a damage-connectivity spalling model (DCSM) is proposed to describe the formation and evolution of multiple irregular spalling cavities on the tooth face deriving from the initial defects. Subsequently, a type of TVMS-based indicator is established to represent the evolutionary severity of irregular spalling cavities. Finally, a service life prediction method is developed based on the proposed indicators. The correctness of the proposed DCSM model is verified by comparison with the extant gear spalling experiments. The effects of working load, depth ratio and quantify ratio of initial defect groups on the service life are discussed, which contributes to the service life improvements of gear pairs in the design stage.

Rolling-sliding contact fatigue failure and associated evolutions of microstructure, crystallographic orientation and residual stress of AISI 9310 gear steel

In the present study, rolling-sliding contact fatigue (RSCF) failures of AISI 9310 gear steel were analyzed systematically, in terms of characterizing the fatigue life, evolution of microstructure and crystallographic orientation, and variation of microhardness and residual stress distributions. The RSCF experiments were conducted using a twin rollers fatigue test rig. The RSCF life of AISI 9310 steel roller decreased continuously with increasing the maximum Hertzian contact pressure, however, it could be effectively improved by additional shot peening process owing to the enhanced microhardness and compressive residual stress near the roller surface. The main fatigue damage characteristics near the roller surface were consisted of inclined cracks, micropitting, spallation and plastic deformation. Although the compressive residual stress was reduced by RSCF, there was an obvious increase in the microhardness which should be attributed to the refined microstructure, increased dislocation density as well as phase transformation from retained austenite to martensite. In addition, the accumulated plastic strain during RSCF resulted into development of several preferred crystallographic orientations corresponding to ideal shear texture components of body-centered cubic (BCC) materials that has been seldom reported.

Decomposition-resistant carbonitride precipitates in X30CrMoN15-1 high-nitrogen bearing steel deformed by high-pressure torsion

The X30CrMoN15-1 high-nitrogen bearing steel is far more resistant against premature rolling contact fatigue (RCF) failures than the conventional 100Cr6 bearing steel. However, the origins of this steel's resistance against localized severe plastic deformation, which accompanies RCF failure, are still indefinite.In this work, we use multi-scale characterization techniques to investigate the microstructural changes in through-hardened X30CrMoN15-1 steel upon high-pressure torsion (HPT, maximum shear strain, Ƴmax ∼ 14.14). HPT is used to ingress severe plastic deformation in larger bulk samples mimicking the localized severe plastic deformation induced by crack face rubbing in RCF samples just below the sample surface. Upon HPT, the M23(C, N)6 and M2(N, C) carbonitride precipitates in the microstructure remain intact without decomposition, whereas the matrix martensite deforms severely. This is in contrast to pronounced M3C carbide decomposition observed in high-carbon 100Cr6 bearing steels under equivalent ingress of severe plastic deformation. Apart from the cleanliness of the X30CrMoN15-1 steel avoiding crack-initiating inclusions, we conclude that the superior stability of carbonitride precipitates largely contributes to better RCF performance. We show that the carbonitrides exhibit higher hardness (M23(C, N)6 ∼ 22 GPa, M2(N, C) ∼ 20 GPa) and increased thermodynamic stability in comparison to M3C cementite (hardness ∼ 15 GPa). We evaluate the differences in thermodynamic stability through density functional theory (DFT) calculations. Additionally, we discuss the influence of mechanical properties of the surrounding matrix microstructure on precipitate decomposition.