This study aims to provide an overview of numerical and experimental work, related to crack nucleation under fretting fatigue conditions. In fretting fatigue, multiaxial loads and severe stress ...gradients are present at the contact interface, which can lead to failure. The damage process, in general, is considered as a two-phase phenomenon, namely, nucleation and propagation. Various damage models and approaches are available in literature to model each phase. In the present work, different criteria, related to nucleation phase, are classified based on the approach used to define failure. These approaches include, critical plane approach, stress invariant approach, fretting specific parameters and continuum damage mechanics. Apart from theoretical background, the work related to the applications of these approaches to fretting fatigue problems is also presented. It is observed that, to analyse various aspects, intricate details near the contact interface and mechanisms involved in fretting fatigue, the strength of finite element method can be employed. In the light of numerical and experimental observations, comparison between different approaches, common sources of errors in prediction and generalized conclusions are presented.
•Three fatigue methodologies are used to investigate the fretting fatigue of scaled railway axles.•The effect of plastic deformation and fretting wear on fretting fatigue is studied.•The influence of ...the diameter ratio on fretting behavior is studied.•The predicted results agree with the findings from the fatigue tests.
To investigate the effect of plastic deformation and fretting wear on the fretting fatigue of scaled railway axles, three fatigue assessment methodologies are developed, namely elastic-fatigue, elastoplastic-fatigue and wear-fatigue methodologies. Elastic material behaviour, elasto-plastic material behaviour and fretting wear are taken into consideration in these three methodologies, respectively. A comparison of the simulation and experimental results indicates that the profile evolution of the fretting scar is mainly caused by fretting wear. The wear-fatigue methodology provides a better prediction of the fretting scar width and crack initiation site than the elastic-fatigue and elastoplastic-fatigue methodologies. With respect to the crack initiation life prediction, a relatively accurate prediction is obtained on using the elastoplastic-fatigue and wear-fatigue methodologies in the short-life region, while the initiation life predicted using the elastoplastic-fatigue methodology is shorter than that predicted by the wear-fatigue methodology in the long-life region. The influence of the diameter ratio on the fretting fatigue of scaled railway axles is then studied. The obtained simulation results show that an increment in the diameter ratio can reduce the fretting wear and relative slip range by alleviating the stress concentration, which thereby improves the fatigue strength of scaled railway axles. There exists a critical value of diameter ratio between 1.092 and 1.116, below which the fretting scar width and relative slip range are highly influenced by variations in the diameter ratio. This is in agreement with published experimental results.
This work investigates the influence of cyclic normal contact load on the fretting fatigue behavior of the Inconel 718 alloy at room and elevated temperatures. Fretting fatigue and friction tests ...with constant and cyclic contact load were conducted at 20 °C and 540 °C. Moreover, to estimate fretting fatigue life, numerical models (including and neglecting wear) were used in conjunction with the SWT parameter and a non-local stress approach. Experiments showed that the cyclic normal contact load has a beneficial effect on fatigue life. Additionally, no significant difference was observed for the measured friction coefficient whether considering constant or cyclic contact load. However, friction coefficient was significantly reduced at 540 °C. Generally, the life estimate approaches here considered yielded satisfactory results.
•A new heating system was used to conduct fretting fatigue tests at high temperature.•Friction coefficient was measured under different testing and temperature conditions.•Tests with constant and cyclic normal load were conducted at 20 and 540 °C.•Fatigue life was estimated by FE analysis regarding and disregarding wear damage.
Nuclear power plants, working in extremely harsh environment, primarily in the form of high-speed fluid flow, circulate through complex systems. Serious tribological problems can occur when a small ...amount of nuclear energy is converted into mechanical energy in the components (e.g., fuel-rod cladding, tube of the heat exchange systems). With the increase of the service life of nuclear power equipment, a considerable number of nuclear power equipment or structure failures occur one after another. Although the influencing factors are different, fretting damage is one of the important factors. Fretting damage has strong concealment and high risk, and it is often the main cause of component failure. Thus, improving the reliability of nuclear power equipment, extending their life, and optimizing their structure are important. In recent decades, many scholars have studied fretting wear, fretting fatigue, and fretting corrosion behavior in nuclear power equipment. Accordingly, they have solved many problems, accumulated a lot of experience, and put forward many criteria. In this article, the research status of fretting damage in key equipment and structures of nuclear power plant is reviewed.
Typical positions of fretting wear in steam generator. Display omitted
•The research status of fretting method, nuclear materials damage in key equipment and structures of nuclear power plant is reviewed.•Fretting research of heat exchange materials for steam generators and fuel cladding in nuclear power systems is reviewed.•The research status of fretting wear of fuel cladding is analyzed, including the latest coating and surface strengthening technologies.
The fretting wear tests of 690 alloy tube/405 stainless steel plate under various fretting cycles have been conducted in 285 ℃ air using a self-designed elevated-temperature fretting wear rig. The ...results demonstrated that the formation of third body layer (TBL) had considerable influence on the fretting wear performances of 690 alloy tube. The presence of TBL between the interfaces protected the partial 690 alloy tube surface from being damaged. Consequently, it resulted in the discontinuity of wear scar and reduction of coefficient of friction (COF) after approximately 500th cycles. Along the thickness of TBL, the contents of oxygen, chromium and iron took on obvious stratification induced by alternating the transfer layer and oxidation layer.
•The presence of TBL in the interfaces protected the partial 690 alloy tube surface from being damaged.•The TBL was characterized by stratification that is induced by alternating the transfer layer and oxidation layer.•The thickness of TBL increased rapidly with the number of fretting cycles and then saturated after few thousand cycles.
The evolution of fretting wear behavior and damage mechanism in Alloy 690TT with cycle number was investigated via laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM), focus ...ion beam (FIB), and transmission electron microscopy (TEM). The results showed that the fretting running status underwent a transition from partial slip and mixed stick-slip to final gross slip with the transformation of Ft-D curves from the ellipse to the parallelogram. The coefficient of friction (COF) experienced three drops throughout the fretting process, which indicated the transformation from high-friction wear to low-friction wear. The first drop was due to the transition from two-body to three-body contact. The second and third drops were mainly related to the evolution of the glaze layer from a localized distribution to completely covering the whole contact surface. The competition between fretting induced fatigue cracking (FIF) and fretting induced wear (FIW) ran through the entire fretting wear process. Before the 1.2 × 10
th cycle, the fatigue crack growth was faster than wear, and FIF won the competition. As the fretting cycle continued to increase, the wear velocity was obviously faster than that of FIF, which indicated that FIW defeated FIF. The tribologically transformed structure (TTS) participated in the competition between FIF and FIW. The gain boundaries and dislocations in the TTS were a suitable pathway for crack initiation and propagation and oxygen permeation.
Fretting corrosion behavior and damage mechanism of Zr-4 alloy mated with Inconel 718 alloy under different fretting regimes in high temperature high pressure water were studied. The corresponding ...running condition fretting corrosion map (RCFM) and material response fretting corrosion map (MRFM) were established. The results showed that the change of fretting regime led to the differences of fretting corrosion behavior and damage mechanism. Based on the damage mechanism, the MRFM could be divided into partial slip regime with only slight surface damage; mixed fretting regime-I dominated by cracks; mixed fretting regime-II dominated by cracks and abrasive wear; and gross slip regime dominated by severe adhesive wear and oxidation. The transformation of fretting regime also resulted in different oxides.
•The MRFM presents four regimes: partial slip regime, mixed fretting regime-I, mixed fretting regime-II and gross slip regime.•The MRFM presents slight degration in PSR, cracks in MFR-Ⅰ, cracks and wear in MFR-Ⅱ, adhesive wear and oxidation in GSR.•The main oxides on the worn surface were monoclinic ZrO2 in PSR and MFR, NiCr2O4 and tetragonal ZrO2 in GSR.
In pressurized water reactors (PWRs), flow-induced vibration (FIV) induces the fretting wear of fuel rods and supporting grids, and the process is accompanied by corrosion, which is called fretting ...corrosion. In this paper, fretting corrosion experiments were carried out in a simulated cladding service environment, and the fretting corrosion performance of AlCrNbSiTi coating cladding, Cr coating cladding and uncoated cladding with the supporting grids were investigated using a three-dimensional white light interferometer and a scanning electron microscope (SEM). The results showed that the AlCrNbSiTi coating cladding has the strongest fretting corrosion performance, the Cr coating cladding has the second best fretting corrosion performance and the uncoated cladding has the worst fretting corrosion performance. The coating also changes the wear mechanism of the cladding and improves the corrosion resistance of the cladding, which is responsible for the improvement in the fretting corrosion performance of the cladding. By comparing the AlCrNbSiTi coating with the Cr coating, it was found that the AlCrNbSiTi coating has a better fretting corrosion performance than the Cr coating due to its higher hardness and stronger corrosion resistance.
Systematic experiments were conducted to study the fretting wear behaviors of spline connections by surface modifications used for the gauge-changeable railway. Three different surface modification ...treatments, i.e., plasma nitriding (PN), laser quenching (LQ), and laser cladding (LC), were applied on DZ2 steel. The fretting wear volume and failure mechanism were discussed. The results show that surface modified layers can improve the fretting wear resistance compared to untreated samples. The LC layer with a lowest hardness has a lowest wear volume. While for the whole tribo-pairs, the LC/D2(QT) tribo-pair has a lowest wear volume in mixed fretting regime, but the PN/D2(QT) and LQ/D2(QT) both have a lower wear volume in slip regime. The main failure mechanism is delamination, ploughing and oxidation.
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•The fretting wear depends on the nature of modified layer and the fretting running regimes.•Surface modified layers shift fretting running regimes toward the lower displacement.•Surface modification layer can significantly improve the fretting wear resistance.•In MFR, the LC/D2(QT) tribo-pair has a lowest wear volume.•In SR, the PN/D2(QT) and LQ/D2(QT) both have a lower wear volume.
An analytical description of fretting wear is proposed wherein the volume of wear debris either removed from the sliding interface or retained within these areas, is represented as a fraction of the ...freshly-produced debris in each fretting pass. In the proposed model, the volumes respectively of removed debris and of retained debris are tallied over each pass of a fretting sequence to yield a closed analytical expression relating these volumes to the number of passes. The paper provides an example of the adaptation of the proposed model to experimental wear data on steel-steel fretting interfaces.
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