Fretting Fatigue Damage Research Articles

The effect of phase difference and stiffness ratio on fretting fatigue behavior under variable normal load conditions

This paper investigated the effect of variable normal load on the fretting fatigue mechanism. A kinetics-based Q- P curve analysis method was proposed to assist testing system design and experiment result analysis. Based on this method, a biaxial fretting fatigue testing system was designed. Experimental and numerical investigation was carried out to discuss the effect of biaxial loading phase difference (the phase difference between bulk load and cyclic normal load) and stiffness ratio (the stiffness ratio between pad fixture and flat specimen) on the fretting fatigue mechanism. Based on the critical plane approach and proposed Q- P curves analysis method, it is found that the fretting status is partial slip regime under small stiffness ratio conditions. The stress/strain which is influenced by phase difference is the main factor of fretting fatigue damage in this condition. Furthermore, the mean stress of the normal load on the critical plane is compressive stress. It directly influences the fatigue damage under partial slip regime. With the increase of stiffness ratio and phase difference (from 0° to 90°), the fretting status changes from partial slip regime to gross slip regime, which means that the influence of wear increases. Wear inhibits the initiation of fatigue cracks, which has a positive influence on fretting fatigue life. As a result, the fretting failure mode gradually changes from fatigue to wear.

In-situ SEM and EBSD study on fretting fatigue crack initiation of a directionally solidified Ni-based superalloy

Fretting fatigue is an important cause of the failure of the turbine blade-disc dovetail joint in aero-engines. In this work in-situ scanning electron microscope (SEM) fretting fatigue experiments using dovetail shape specimens were conducted. The fretting fatigue damage process of Ni-based directionally solidified superalloys including slip trace evolution and crack initiation was captured. The misorientation and geometrically necessary dislocation (GND) density induced by fretting fatigue were quantified by electron back-scattered diffraction (EBSD). The significant correlation between crack path, slip trace, grain boundary microstructure and GND density was revealed. The EBSD analysis achieved good agreement with the in-situ SEM observation.

Research on factors affecting fretting fatigue life of high‐temperature dovetail tenon

AbstractThis paper takes the dovetail structure of an aero‐engine compressor as the research object, designs a high‐temperature dovetail fretting fatigue test, and discusses the effect of high temperature on fretting fatigue damage. Based on the fretting fatigue continuous damage accumulation model, a high‐temperature fretting fatigue life prediction model of dovetail tenon considering the temperature effect is proposed and verified by experiments. The results show that the experimental data prove that the model has good prediction accuracy and its prediction error is less than 19.24%. Finally, the relative sliding distance, contact stress, Ruiz parameters, and friction work of the dovetail structure are selected, and the dovetail structure under different actual use conditions is calculated through simulation. The influence of friction coefficient, load, temperature, arc size, and other factors on the evaluation index is analyzed. The internal law of high‐temperature fretting fatigue life of dovetail structure under multi‐factor coupling conditions is studied.

Modeling Fracture Formation, Behavior and Mechanics of Polymeric Materials: A Biomedical Implant Perspective

In industrial applications where contact behavior of materials is characterized, fretting-associated fatigue plays a vital role as a failure agitator. While considering connection, it encounters friction. Biomaterials like polytetrafluoroethylene (PTFE) and ultra-high-molecular-weight polyethylene (UHMWPE) are renowned for their low coefficient of friction and are utilized in sophisticated functions like the hip joint cup and other biomedical implants. In addition to the axial stresses, some degree of dynamic bending stress is also developed occasionally in those fretting contacts. This research investigated the fracture behavior of a polymer PTFE under bending fretting fatigue. Finite element analysis justified the experimental results. A mathematical model is proposed by developing an empirical equation for fracture characterization in polymers like PTFE. It was found that the bending stiffness exists below the loading point ratio (LPR) 3.0, near the collar section of the specimen. Along with fretting, the bending load forces the specimen to crack in a brittle-ductile mode near the sharp-edged collar where the maximum strain rate, as well as stress, builds up. For a loading point ratio of above 3, a fracture takes place near the fretting pads in a tensile-brittle mode. Strain proportionality factor, k was found as a life optimization parameter under conditional loading. The microscopic analysis revealed that the fracture striation initiates perpendicularly to the fretting load. The fretting fatigue damage characteristic of PTFE may have a new era for the biomedical application of polymer-based composite materials.

Experimental study of fretting fatigue in dovetail assembly considering temperature effect based on damage mechanics method

Fretting fatigue of dovetail structure of aero-engine compressor is a very complex phenomenon, which is affected by different factors such as temperature, load, friction coefficient, and arc radius, etc. Aiming at the problem of the high-temperature fretting fatigue life prediction of dovetail structure, the high-temperature effect on fretting fatigue life is analyzed, and then the fretting fatigue life prediction model is established considering the temperature effect by introducing temperature equivalent factor based on the circular flat contact theory and continuous damage mechanics theory. Besides, the criterion of fretting fatigue cracks initiation failure is proposed based on the displacement–strain joint monitoring method in the fretting fatigue tests. The experiment results show that the proposed fretting fatigue life prediction model has a high life prediction ability within ± 2.0 times error band. It is found that the traditional damage mechanics accumulation model cannot reflect the change of fretting fatigue damage only by changing the material performance parameters in a high-temperature environment, needing temperature correction and the proposed fretting fatigue life prediction model considering temperature effect in the exponential form of temperature ratio is feasible.

Experimental and numerical fretting fatigue using a new test fixture

A unique dovetail-based test fixture for fretting fatigue was designed and is demonstrated with a combined experimental and numerical campaign. Fretting fatigue damage is analysed and correlated with numerical analyses using a modern Ruiz formulation and Findley critical plane parameter with the Theory of Critical Distances. Initial test results show that a simple critical plane model correlates life and cracking directions with experiments; however, the Ruiz parameter only serves as a hot-spot indicator. The fixture is designed to permit testing in submerged conditions and to allow additional loads to the specimens by using a multi-axial fatigue machine.

Experimental and numerical investigation on fretting fatigue behavior of Nickel-based single crystal superalloy at high temperature

The fretting fatigue behaviors of a nickel-based single crystal superalloy in contact with a powder metallurgy alloy at 600 °C are investigated. Fretting fatigue tests are conducted by using a novel high temperature fretting fatigue test apparatus that is developed, and the crystal plasticity finite element method is used to analyze the contact stress and activations of slip systems. The results show that the fretting conditions are partial slip regime for all loading conditions, and severe wear damage occurs across the slip region, which is accompanied by surface delamination and micro crack. Fretting fatigue cracks mainly initiate at the contact leading edge area, i.e., the stress concentration zone. The cracks grow along the (100) plane when multiple octahedral slip systems are activated simultaneously, or could be eliminated by wear. Considering the effects of both crystallographic slip and wear on the fretting fatigue damage, an improved fretting fatigue damage parameter, RA , is proposed to predict the fretting fatigue life. The predicted results agree well with the test results. • A novel high temperature fretting fatigue test apparatus has been developed. • Crystal plasticity finite element method is applied to calculate the contact stress and strain. • Fretting fatigue damage mechanism is proposed considering wear and cracking. • A damage parameter, RA , is proposed to describe surface damage and predict fretting fatigue life.

Fretting fatigue and shot peening: a multiaxial fatigue criterion including residual stress relaxation

Fretting fatigue damage is a typical material damage arising in mechanical components. In such a damage condition, surface cracks can initiate at the surface contact zone, and under a fluctuating loading they can grow up to the complete failure of the component, resulting in a catastrophic failure.In order to prevent/mitigate fretting fatigue damage, shot peening is widely used in mechanical components. The improvement due to shot peening is related to different factors, but the main one is the compressive residual stress field produced by such a treatment in a region near the contact surface. Unfortunately, both the uncertainty in measurements and stability (relaxation) of residual stress field, make shot peening effects difficult to be included in models aimed to the estimation of fatigue life. Due to this lack in the literature, especially relatively to the fretting fatigue field, in the present paper a new fretting fatigue model, that is able to consider shot peening residual stress and its relaxation, is presented. A 3D elastic-plastic finite element model, which incorporates the shot peening residual stress and its relaxations, is employed. The results obtained, in terms of stress field, are used as input data of a multiaxial stress-based criterion to estimate both fatigue lifetime and crack initiation direction.

Fretting fatigue damage mechanism of Nickel-based single crystal superalloys at high temperature

A novel high temperature fretting fatigue test apparatus was developed to investigate the fretting fatigue mechanism of Nickel-based single crystal (NBSX) superalloys at elevated temperature. The fretting fatigue tests were carried out under 5 loading conditions at 600°C. Results showed that the fretting fatigue life decreased with the increase of axial load and normal load. Metallographic observations revealed that surface peeling, delamination occur at the contact area. Energy dispersive spectrum (EDS) analysis showed that the surface material was oxidized, and the oxides will be compacted onto the contact surface and form a glazed layer. Besides, many micro cracks are observed at the contact surface that are nearly perpendicular to the fretting direction. These micro cracks would either be eliminated due to the large relative displacement or grow into the main crack, which are supposed to be the dominant source of fretting fatigue failure. Multiple fretting fatigue cracks initiate at the contact leading edge area and grow along the (100) plane that is nearly perpendicular to the fretting direction. Then the crack propagation direction will deflect from (100) plane to a series of {111} planes and the specimen eventually failed. The combined effect of fretting wear and crystallographic slip is the cause of fretting fatigue failure.

Fretting Fatigue Damage Nucleation and Propagation Lifetime Using a Central Point Movement of Power Spectral Density

This paper presents a new perception in evaluating fretting fatigue damage nucleation and propagation lifetime under periodically forced circulation. A new approach, which is proposed in this paper, is to measure the change of the central point of power spectral density (CP-PSD) in different structural stiffness degradation stages. A notable aspect of this study lies in the combination between vibration amplitude and forced frequency of the fatigue-causing factors in beam structures. Additionally, it is found that randomization of the first phase from 0 to 2π yields more accurate modelling of the fatigue phenomenon. Results show that the CP-PSD parameter is significantly more sensitive compared to the regularly damage-evaluating parameters such as natural frequency, eigenvalues, or stress value. This reflects different levels of fatigue cycle effect on the structure in the experiment. At the same time, CP-PSD also categorizes the degradation level on different points on the structure under the periodically forced circulation. In addition, this paper also quantifies the relation between the changes of CP-PSD and each fatigue state. Results of this research will be a reference source to evaluate the lifespan of the structure by experimental methods.

Assessment of fretting fatigue in high strength steel bolted connections with simplified Fe modelling techniques

Abstract The fretting fatigue (FF) damage on contact surfaces constitutes a major problem in High Strength Steel (HSS) bolted connections when subjected to cyclic loadings, in that it significantly lowers the fatigue life. Moreover, the estimation of damage in the contact areas is challenging and laborious through experiments. The present paper proposes a simplified modelling technique to estimate the fretting fatigue damage in high cycle regime by considering the pretension effect and contact properties of bolted lap connections. To do so, a three-dimensional solid model is developed and validated. Afterwards, simplified FE models are validated using the three-dimensional model and test results to identify the most computationally efficient model for bolt connection in HSS under static and fatigue loading conditions. It was observed that the newly developed FE model could retain all the components on contacting surfaces while saving of up to 97% of the computational time over full solid models. These results successively provided insight into the crack initiation location and the fatigue lifetime of the joint and showed good agreement with experimental and three-dimensional solid model data.

Modeling the fretting fatigue endurance from partial to gross slip: The effect of debris layer

Abstract Fretting Fatigue (FF) appears as a key damaging process in many industrial assemblies subjected to vibrations. In this study, the “U-shape” experimental fretting fatigue endurance evolution of a 35NiCrMo16 steel cylinder/plane contact versus the applied displacement amplitudes is simulated using a complete finite element modeling. This method takes into account the crack nucleation process, the crack propagation phenomenon but also surface wear as well as the evolution of the “third body” debris layer entrapped within the interface. This dynamic simulation of the fretting fatigue endurance from partial to gross slip condition confirms that surface wear effects can be neglected under partial slip but must be taken into account including the debris layer effect, in order to predict the fretting fatigue endurance under gross slip conditions. An original “DSN“ fretting fatigue chart strategy allowing a global description of the fretting fatigue damage (wear, crack nucleation and failure) as a function of the displacement amplitude, fatigue stress and loading cycles is introduced and discussed.

A multi-scale strategy to predict fretting-fatigue endurance of overhead conductors

Abstract Overhead conductors enduring aeolian vibrations are subjected to fretting fatigue damage. To predict the fretting fatigue cracking risk along the conductor-clamp assembly involving a multitude of crossed-strands contacts, a multi-scale analysis is considered. First, a global model provides the spatial distribution of normal, tangential and fatigue loadings for every contact. “Specific” loading cases were simulated using a local FEM model involving a Crossland fatigue stress analysis and a critical distance approach to correct the stress-gradient effects. Mono-contact fretting fatigue experiments were then performed reproducing the exact same loading cases. The comparison between numerical predictions and experimental results showed that a very good prediction of crack-nucleation is achieved using this strategy. However, total failures were not systematically observed. It is believed to be related to the manufacturing process. Wire drawing induces a longitudinal microstructure which promotes cracks with a low diving angle, rather than cracks propagating directly into the bulk. 3D-surface-crack simulations confirm a crack arrest phenomenon induced by the contact-induced compressive stress field.

Very high cycle fretting fatigue damage and crack path investigation of Nimonic 80A at elevated temperature

Fretting fatigue failure generally appears in turbine blades and disk tenon joint position subjected to high frequency vibration loads at elevated temperature. To study the fretting resistance of Nickel-based super alloy at high temperature, a set of fretting rig with a special heater was integrated with ultrasonic fatigue testing machine. Fretting tests with the developed apparatus were performed in very high cycle fatigue regime at elevated temperature. The initiation site and path of the cracks were analyzed via laser confocal microscope and scanning electron microscope. The cracks have a high proportion to initiate at the trailing edge of the wear zone and tend to extend to one side of the wear zone. Critical plane method with multiaxial fatigue damage parameters was used to predict the main propagation path of fatigue cracks.

Effect of contact pressure on torsional fretting fatigue damage evolution of a 7075 aluminum alloy

Abstract Contact pressure is a crucial factor which can affect fretting fatigue (FF) life significantly. In this research, the influence of contact pressure on torsional fretting fatigue (TFF) damage of a 7075 aluminum alloy is investigated. According to the experiment results, below 72.5 N⋅m torque as the contact pressure increases, the TFF life decreases firstly and then it reaches to the lowest point at 300 N, while afterward the TFF life increases. The P-N curve shows a C shape. The damage analysis results show that with increasing the contact pressure, the damage becomes severer. The oxidative products are mainly Al2O3 and Al(OH)3, and the loading side is found to be more oxidized than the center position and fixed side.

Crack propagation simulation for ductile material under fretting fatigue loads using cohesive zone models

The object of this study is fretting fatigue cracks subjected to cyclic loading both normal and tangential. The cycle cohesive zone model (CCZM) and extended finite element method (XFEM) are used to describe the fretting behaviour. The fretting fatigue damage is described with a damage evolution equation. Both the extended finite element method as well as cohesive zone models have been implemented into the commercial FEM software ABAQUS, via the user interfaces UEL and UMAT. The CCZM parameters are obtained from a material fatigue test result and fretting fatigue experiment.

RA-based fretting fatigue life prediction method of Ni-based single crystal superalloys

Abstract Fretting fatigue damage can significantly reduce the service life of Ni-based single crystal (NBSX) superalloys turbine blades. In this work, we proposed a fretting fatigue life prediction method by considering cracking, wear and their mutual interaction. Specifically, a parameter, denoted as RA, is developed with combination of Resolved shear stress based damage factor and Accumulated dissipated energy based damage factor, by which the contribution from cracking and wear are described respectively. The proposed method is validated with experimental data in the literature. Finite element analyses are performed to study the distribution of stresses and strains. Results show that the predicted crack initiation site, failure plane and life cycles are consistent with the experimental results.

Fatigue strength evaluation for individual strands of overhead conductors using a biaxial fretting fatigue test bench

This paper presents a biaxial fretting fatigue test bench which provides the capability of performing fretting fatigue experiments on individual wires of a conductor combining the effect of both alternating tension and bending loadings to represent a more realistic state of a conductor individual strand under periodic loading caused by aeolian vibrations. Preliminary tests with only uniaxial alternating tension loading were carried out on 1350-H19 aluminum wires having the same mechanical and geometric characteristics as those of the ACSR Bersfort conductor aluminum strands. Different levels of alternating stress were tested in order to validate the performance of the apparatus. Preliminary results showed that the experimental setup allows reproducing the local loading state which leads to the fretting fatigue damage on the tested wires. Biaxial tests were also conducted at a high level of alternating loadings. The results of these tests reveals that, at high alternating stress amplitudes, the biaxial loading allows to observe some fretting fatigue failures, whereas early plain fatigue failures were observed when applying similar uniaxial loading.

Effect of Fretting on Fatigue Behavior of Al Alloys Considering Environmental Effect

Abstract In this paper fretting fatigue behavior of 6061-T4 aluminium alloy has been studied by performing fretting fatigue tests with two different pad geometries (bridge type and flat type pad) under two different environments (room temperature and 200°C). Both the contact pads and specimens were made of 6061 T4 aluminium alloys. Finite element analysis (FEA) model was also designed to understand the fretting fatigue damage mechanisms. From the results, it was found that contact pad geometry and test temperature significantly affect the fretting fatigue strength. The mechanism was discussed based on the fretting fatigue crack initiation considering the stress distribution behavior at the contact.

Analysis of Fir Tree Root of Aero-engine Disc Assembly for Simultaneous Optimization of Fretting Characteristics

An aero-engine fir tree blade disc assembly is much proven to fretting fatigue damages due to centrifugal and vibrating conditions. This paper examines the effect of disc speed, contact angle and co-efficient of friction on fretting responses such as equivalent von-Mises stress, maximum shear stress and contact pressure by adopting Taguchi based grey relational analysis and RSM. All of the fretting responses were influenced by disc speed and contact angle. Multi response optimization achieved using grey relational analysis indicated that minimum equivalent von-Mises stress (0.63 MPa), shear stress (0.36 MPa) and contact pressure (0.681 MPa) are achieved at 260 rpm of disc speed, 17.5° of contact angle and 0.3 co-efficient of friction. Significant improvement was noticed in terms of stress concentration reduction at optimal conditions. Confirmatory simulation runs were performed to ensure the grey relational analysis results.