A review of the effects of cyclic contact loading on fretting fatigue behaviour

A damage phenomenon called fretting fatigue frequently takes place when two contact bodies are clamped together under a normal contact load along with a small-scale oscillatory motion due to cyclic loading. In contrast to the constant contact loading, less attention has been paid to variable contact loading which was technically reviewed in this study. Emphasis was placed on the efforts made over the past decade and the future challenges including nonlinear effects of contact loads, friction, frequency, slip amplitude, wear, and contact mechanic are discussed extensively. It was revealed a need for new fatigue and contact mechanics models by identifying the aforementioned missing parameters

Fretting-Fatigue Analysis of Shot-Peened Al 7075-T651 Test Specimens

Shot peening is a mechanical treatment that induces several changes in the material: surface roughness, increased hardness close to the surface, and, the most important, compressive residual stresses. This paper analyzes the effect of this treatment on alloy Al 7075-T651 in the case of fretting fatigue with cylindrical contact through the results of 114 fretting fatigue tests. There are three independent loads applied in this type of test: a constant normal load N, pressing the contact pad against the specimen; a cyclic bulk stress σ in the specimen; and a cyclic tangential load Q through the contact. Four specimens at each of 23 different combinations of these three parameters were tested—two specimens without any treatment and two treated with shot peening. The fatigue lives, contact surface, fracture surface, and residual stresses and hardness were studied. Improvement in fatigue life ranged from 3 to 22, depending on fatigue life. The relaxation of residual-stress distribution related to the number of applied cycles was also measured. Finally, another group of specimens treated with shot peening was polished and tested, obtaining similar lives as in the tests with specimens that were shot-peened but not polished.Junta de Andalucía P12-TEP-263

Finite element analysis of fretting crack propagation

In this work, the finite elements method (FEM) is used to analyse the growth of fretting cracks. FEM can be favourably used to extract the stress intensity factors in mixed mode, a typical situation for cracks growing in the vicinity of a fretting contact. The present study is limited to straight cracks which is a simple system chosen to develop and validate the FEM analysis. The FEM model is tested and validated against popular weight functions for straight cracks perpendicular to the surface. The model is then used to study fretting crack growth and understand the effect of key parameters such as the crack angle and the friction between crack faces. Predictions achieved by this analysis match the essential features of former experimental fretting results, in particular the average crack arrest length can be predicted accurately

On the Analysis of the Contact Conditions in Temporomandibular Joint Prostheses

Temporomandibular joint replacement (TMJR) is a complex surgical procedure in which the artificial joints available must assure the anatomical reconstruction and guarantee a good range of the natural temporomandibular joint (TMJ) movements. With this aim, different types of TMJ prostheses, including the stock prosthetic system and custom-made prostheses, are being currently implanted. Although temporomandibular joint replacements (TMJRs) are expected to accomplish their function during a number of years, they might actually fail and need to be replaced. This paper analyzes different design factors affecting the contact stress distributions within the TMJ prosthesis interface, which are consequently involved in their deterioration and final failure of the prosthetic device. With this purpose, a numerical model based on finite elements has been carried out in order to evaluate the stress states attained in different prosthesis configurations corresponding to general types of TMJ prostheses. On the other hand, the actual degradation of resected implants has been evaluated via optical microscopy. The linkage between the numerical simulations performed and experimental evidence allowed the authors to establish the different wear and damage mechanisms involved in the failure of stock TMJ prostheses. Indeed, the results obtained show that the contact stresses at the interface between the mandible and the glenoid fossa components play a key role in the failure process of the TMJR devices

An investigation of fretting wear in aerospace applications

Thesis (MScEng)--Stellenbosch University, 2011.ENGLISH ABSTRACT: Fretting wear results in the loss of fit and tolerance at contact interfaces. The aerospace and aircraft industry is severely impacted by fretting wear and fretting fatigue that frequently occurs in turbo machinery and riveted structural connections. There have been numerous studies, investigating the fretting phenomenon for these aerospace applications. Literature available in regard to fretting wear encountered in these aerospace applications is limited. This study is therefore aimed at investigating the fretting wear encountered in aerospace application. An in-house fretting test apparatus was specially designed and developed in order to perform the fretting wear experiments. Ti-6Al-4V and Al7075-T6 are the two aerospace materials that were tested using the fretting test apparatus. An extensive experimental study was conducted in order to investigate the effect of the normal force on the fretting wear and friction behaviour of the two aerospace materials. The most severe of these experiments were identified and then repeated for up to 106 fretting cycles. Additional fretting wear experiments were also conducted between the two aerospace materials and cemented carbides, since the carbides are currently being utilized as coatings in some aerospace contacts that are prone to fretting induced damage. The experimental study revealed that a decrease in the normal force resulted in an increase in the severity of the fretting wear of both aerospace materials. The additional fretting wear experiments involving carbide-metal contact couples found that Ti-6Al-4V and Al7075-T6 were prone to adhesive wear.AFRIKAANSE OPSOMMING: Knaagslytasie veroorsaak materiaalverlies by die kontakoppervlakke. Die lugvaart industrie is erg geraak deur knaagslytasie en knaaguitputting wat dikwels voorkom in turbo-enjin toepassings en strukturele verbindings. Daar was al talle studies gedoen oor die effek van knaag op lugvaart toepassings. Literatuur met betrekking tot knaagslytasie in lugvaart toepassings is egter beperk. Hierdie studie was dus gemik daarop om knaagslytasie in sekere lugvaart toepassings te ondersoek. Tydens die studie is ʼn toetsopstelling ontwerp en ontwikkel om knaagslytasie eksperimente uit te voer. Ti-6Al-4V en Al7075-T6 is die twee lugvaartmateriale wat ondersoek is met behulp van die toetsopstelling. ʼn Omvattende eksperimentele studie is gedoen om die effek van die normaal krag op knaagslytasie en die wrywings gedrag van die lugvaartmateriale te ondersoek. Die eksperimente wat die ergste slytasie en hoogste wrywing getoon het, is herhaal vir 106 siklusse. Bykomende knaag eksperimente was ook tussen die twee lugvaartmateriale en sekere karbiede gedoen, aangesien karbiede tans as deklae in sommige lugvaart kontakte gebruik word. Die eksperimentele studie het getoon dat 'n afname in die normale krag gelei het tot 'n toename in wrywing vir beide lugvaartmateriale. Die bykomende knaagslytasie eksperimente op karbied metaal pare het getoon dat Ti-6Al-4V en Al7075-T6twee lugvaart materiale nie in staat was om enige van die karbide te beskadig nie. Die lug-en Ruimte-materiaal aan die ander kant ervaar het kwaadaardige dra

A review of non-destructive testing techniques for the in-situ investigation of fretting fatigue cracks

© 2020 The Authors Fretting fatigue can significantly reduce the life of components, leading to unexpected in-service failures. This phenomenon has been studied for over a century, with significant progress being made during the past decade. There are various methods that have been used to study fretting fatigue cracks in order to gain a greater understanding of the effects of fretting fatigue. Destructive methods are traditionally used to observe fretting fatigue cracks. Although useful in determining crack location, crack length, crack propagation modes, crack path and shape, it is not efficient or reliable for time based measurements. Non-destructive testing has developed in recent years and now in-situ monitoring can be used during testing in order to increase the understanding of fretting fatigue. This paper presents a review of non-destructive testing techniques used in-situ during fretting fatigue testing, which are compared in order to conclude the suitability of each technique. Recent developments in non-destructive techniques that could be also applied for fretting fatigue tests are also discussed, as well as recommendations for future research made

Critical analysis of the suitability of crack propagation direction criteria for 2D cylindrical plain fretting contact

[EN] In this work the suitability of the criterion of maximum effective amplitude of the normal stress (Delta sigma(n,eff))(max) and the criterion of minimum shear stress range (Delta tau)(min) for 2D cylindrical plain fretting contact condition has been analysed. The numerical analysis has been performed by means of the extended finite element method, which takes into account the contact between crack faces during the closing part, and the results have been compared with experiments reported in the literature. Results show that overall the (Delta tau)(min) criterion predominates in intermediate stage, while the (Delta sigma(n,eff))(max) shows less deviation in the final stage. However, the predicted crack path by the latter criterion shifts toward the outer side, which do not correlate with the experimental results reported in the literature. Additional studies should investigate the variables that are affecting this change in the behaviour along the crack in order to set a criteria that is able to predict the plain fretting condition crack paths accurately.This work was financially supported by the the Basque Government under the "Proyectos de Investigacion Basica y/o Aplicada" (Project NUSIMCO: Ref. PI2013-23), the Spanish Ministry of Science, Innovation and Universities (grant number DPI2017-89197-C22-R) and the Generalitat Valenciana (Programme PROMETEO 2016/007). Furthermore, the authors gratefully acknowledge the financial support given by the Spanish Ministry of Economy and Competitiveness and the FEDER program through the project DPI2014-56137-C2-2-R and the FPI subprogram associated to the project with the reference BES-2015-072070.Llavori, I.; Giner Maravilla, E.; Zabala, A.; Infante, D.; Aginagalde, A.; Rodríguez-Flórez, N.; Gómez, X. (2019). Critical analysis of the suitability of crack propagation direction criteria for 2D cylindrical plain fretting contact. Engineering Fracture Mechanics. 214:534-543. https://doi.org/10.1016/j.engfracmech.2019.04.035S53454321

High pressure induced precipitation in Al7075 alloy

Precipitate-matrix interactions govern the mechanical behavior of precipitate strengthened Al-based alloys. These alloys find a wide range of applications ranging from aerospace to automobile and naval industries due to their low cost and high strength to weight ratio. Structures made from Al-based alloys undergo complex loading conditions such as high strain rate impact, which involves high pressures. Here we use diamond anvil cells to study the behavior of Al-based Al7075 alloy under quasi-hydrostatic and non-hydrostatic pressure up to ~53 GPa. In situ X-ray diffraction (XRD) and pre- and post-compression transmission electron microscopy (TEM) imaging are used to analyze microstructural changes and estimate high pressure strength. We find a bulk modulus of 75.2 +- 1.9 GPa using quasi-hydrostatic pressure XRD measurements. XRD showed that non-hydrostatic pressure leads to a significant increase in defect density and peak broadening with pressure cycling. XRD mapping under non-hydrostatic pressure revealed that the region with the highest local pressure had the greatest increase in defect nucleation, whereas the region with the largest local pressure gradient underwent texturing and had larger grains. TEM analysis showed that pressure cycling led to the nucleation and growth of many precipitates. The significant increase in defect and precipitate density leads to an increase in strength for Al7075 alloy at high pressures.Comment: 15 pages, 5 figure

A Review on Fatigue Life Prediction Methods for Metals

Metallic materials are extensively used in engineering structures and fatigue failure is one of the most common failure modes of metal structures. Fatigue phenomena occur when a material is subjected to fluctuating stresses and strains, which lead to failure due to damage accumulation. Different methods, including the Palmgren-Miner linear damage rule- (LDR-) based, multiaxial and variable amplitude loading, stochastic-based, energy-based, and continuum damage mechanics methods, forecast fatigue life. This paper reviews fatigue life prediction techniques for metallic materials. An ideal fatigue life prediction model should include the main features of those already established methods, and its implementation in simulation systems could help engineers and scientists in different applications. In conclusion, LDR-based, multiaxial and variable amplitude loading, stochastic-based, continuum damage mechanics, and energy-based methods are easy, realistic, microstructure dependent, well timed, and damage connected, respectively, for the ideal prediction model.This research was made possible by a NPRP award NPRP 5-423-2-167 from the Qatar National Research Fund (a member of the Qatar Foundation)

A fretting fatigue model based on self-steered cracks

In this article a new fretting fatigue life prediction model is presented. The model can be classified as a variable crack initiation length: the crack initiation and crack propagation phases are calculated as a function of the crack initiation length, and among all the feasible crack initiation lengths and orientations, that producing the minimum fatigue life is considered. In this new proposal the crack direction is automatically determined as a function of fatigue parameters in both phases: initiation and propagation. The model is applied to a wide experimental campaign of fretting fatigue tests, and excellent correlation is obtained between experimental and predicted fretting fatigue lives and crack paths