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Shankar Mall - One of the best experts on this subject based on the ideXlab platform.
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Effects of microstructure on Fretting Fatigue behavior of IN100
Materials Science and Engineering: A, 2010Co-Authors: Shankar Mall, H.-k. Kim, E.c. Saladin, W.j. PorterAbstract:Fretting Fatigue behavior of a nickel-base superalloy, IN100, was investigated at room temperature. Two microstructures of IN100 were tested which varied primarily by the gamma grain size (3 μm versus 7 μm). Fretting Fatigue tests were conducted at various stress levels using cylinder-on-flat contact configuration. An increase in the grain size was associated with decrease in the Fretting Fatigue strength/life of IN100. Microscopic analysis showed that the 3 μm grain microstructure provided a higher microstructural barrier to the Fretting Fatigue crack nucleation and initiation. On the other hand, the 7 μm grain microstructure had a higher intrinsic crack growth resistance due to the tortuous crack path requiring more energy. These features were in agreement with the plain Fatigue where fine microstructures generally provide higher resistance to crack initiation but reduce crack propagation resistance while coarse microstructures have the opposite behavior.
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Fretting Fatigue Behavior of Cavitation Shotless Peened Ti–6Al–4V
Tribology Letters, 2009Co-Authors: Shankar Mall, Hitoshi SoyamaAbstract:Fretting Fatigue behavior of cavitation shotless peened (CSP) titanium alloy, Ti–6Al–4V was investigated. Constant amplitude Fretting Fatigue tests were conducted at several maximum stress levels, σ_max, ranging from 400 to 555 MPa with a stress ratio of 0.1. Test results showed that the Fretting Fatigue life was enhanced by CSP treatment as compared to the unpeened specimen, but the enhancement was not as large as that from the shot-peening treatment. Residual stress measurements by X-ray diffraction method before and after Fretting test showed that residual compressive stress was relaxed during Fretting Fatigue. Before Fretting, CSP specimen had higher compressive residual stress on the surface than the shot-peened specimen. However, greater residual stress relaxation occurred in CSP specimen such that the relaxed compressive residual stress profile near the contact surface of CSP specimen was lower than that of shot-peened specimen. This lower compressive residual stress from Fretting Fatigue was the reason for shorter Fretting Fatigue life of CSP specimen as compared to shot-peened specimen at the applied stress level.
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Life Prediction of Fretting Fatigue of Ti-6Al-4V
Journal of ASTM International, 2006Co-Authors: Ohchang Jin, Jeffrey Calcaterra, Shankar MallAbstract:The present study was aimed towards improving the prediction capability of Fretting Fatigue life of Ti-6Al-4V. Incremental and interrupted Fretting Fatigue tests were conducted. Based on the crack propagation pattern observed on the fractured surface Fretting Fatigue life was predicted. The disappearance of contact stresses was evidenced by the change in crack growth direction from oblique to perpendicular path to the loading direction. Thus, Fatigue crack initially propagated under the influence of the contact stress, and then it grew due to the applied stress amplitude to the substrate. The transition crack length between these two conditions varied between 20 to 30 μm and depended on the contact load. This enabled the prediction of short and long crack propagation life. There was good correlation between the predicted Fretting Fatigue life and the experimental life.
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Nondestructive Characterization of Fretting Fatigue Damage
Journal of Nondestructive Evaluation, 2004Co-Authors: C. L. Neslen, Shankar Mall, Shamachary SathishAbstract:Fretting Fatigue has been the cause of many premature failures in aerospace components. There is a growing need of nondestructive evaluation techniques to characterize damage and detect cracks due to Fretting Fatigue. This paper presents a methodology to characterize the Fretting Fatigue damage by analyzing the surface topography and to detect cracks under Fretting Fatigued surface by imaging heat generation due to high amplitude acoustic excitation. The White Light Interference Microscopy (WLIM) was used to obtain three-dimensional surface profilometry data of fretted and non-fretted regions of titanium alloy (Ti-6A1-4V) specimens subjected to different number of Fretting Fatigue cycles. Surface topography measurements were analyzed in terms of the Power Spectral Density (PSD) and Fretting Fatigue Damage Parameter (FFDP). The FFDP showed an increasing trend in magnitude with increasing numbers of Fretting Fatigue cycles, when the Fretting Fatigue damage occurred through stick-slip condition. When the Fretting Fatigue damage occurred due to gross sliding, the FFDP did not show enough change. Thus, it appears that FFDP may be used as an indicator of the degradation of fretted surface under stick-slip condition. Cracks in presence of Fretting Fatigue damage were imaged using Sonic infrared technique. This technique appears to have a capability to detect cracks with a resolution of at least 200 μm. The benefits and limitations of thes two NDE techniques for Fretting Fatigue damage evaluation and crack detection are discussed.
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Evaluation of coatings on Ti-6Al-4V substrate under Fretting Fatigue
Surface & Coatings Technology, 2004Co-Authors: Weiju Ren, Shankar Mall, J.h. Sanders, Shashi K. SharmaAbstract:Abstract Four coating systems, TiCN, CrN+MoS2, Cu–Al and Ag+ irradiated layer, were evaluated for their potential towards improving Fretting Fatigue behavior of titanium alloy, Ti–6Al–4V. Coefficients of friction (COF) and Fretting Fatigue lives of the specimens with and without coating were compared. Coating damage was characterized through scanning electron microscopy and energy dispersive spectrometry. COF may increase or decrease during the Fretting Fatigue due to generation of coating debris. The decrease in COF can be attributed to lubrication by coating debris produced during Fretting Fatigue. Further, when a coating is subjected to Fretting, it would degrade. Improvement in Fretting Fatigue life, if any, can only be achieved only when the coating degradation is reduced or eliminated.
Toshio Hattori - One of the best experts on this subject based on the ideXlab platform.
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Fretting Fatigue life estimations based on Fretting mechanisms
Tribology International, 2011Co-Authors: Toshio Hattori, Vu Trung Kien, Minoru YamashitaAbstract:Abstract Generally the Fretting Fatigue S – N curve has two regions: one is the high cycle (low stress) region and the second is the low cycle (high stress) region. In a previous paper we introduced the Fretting Fatigue life estimation methods in high cycle region by considering the wear process; with this estimation method the Fretting Fatigue limit can be estimated to be the crack initiation limit at the contact edge. In this paper we estimate the low cycle Fretting Fatigue life based on a new critical distance theory, modified for a high stress region using ultimate tensile strength σ B and fracture toughness K IC . The critical distance for estimating low cycle Fretting Fatigue strength was calculated by interpolation of the critical distance on the Fretting Fatigue limit (estimated from σ w0 and Δ K th ) with critical distance on static strength (estimated from σ B and K IC ). By unifying this low cycle Fretting Fatigue life estimation method with the high cycle Fretting Fatigue life estimation method, which was presented in the previous paper, we can estimate the total Fretting life easily. And to confirm the availability of this estimation method we perform the Fretting Fatigue test using Ni–Mo–V steel.
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Fretting Fatigue Life Estimations Based on the Critical Distance Stress Theory
Procedia Engineering, 2011Co-Authors: Toshio Hattori, Muhammad Amiruddin Bin Ab Wahab, Takuya Ishida, Minoru YamashitaAbstract:Abstract Generally Fretting Fatigue S-N curve have two stages, one is high cycle (low stress) region and second is low cycle (high stress) region. In previous paper we introduced the Fretting Fatigue life estimation methods in high cycle region by considering the wear process. And in this estimation method the Fretting Fatigue limit can be estimated as the crack initiation limit at contact edge. In this paper we estimated the low cycle Fretting Fatigue life based on new critical distance theory, which is modified for high stress region using ultimate tensile strength σB, and fracture toughness KIC. Firstly the critical distance for estimating low cycle Fatigue strength was calculated by interpolation of critical distance on Fatigue limit (estimated from σw0 and ΔKth) with critical distance on static strength (estimated from σB and KIC). The validity of this method is confirmed by the V notch specimens. And then we applied this method on estimation of low cycle Fretting Fatigue strength and life. By unifying these low cycle Fretting Fatigue life estimation method with high cycle Fretting Fatigue life estimation method which was presented previous paper we can estimate the total Fretting life easily. And to confirm the availability of this estimation method we perform the Fretting Fatigue test using Ni-Mo-V steel.
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2320 Feature of Fretting Fatigue strength/life and it's mechanical considerations
2007Co-Authors: Toshio Hattori, Minoru Yamashita, Naoya NishimuraAbstract:The Fretting Fatigue process has many features such as early stage crack initiation at the contact edge, very slow crack propagation and Fatigue failure after a very long life operation. In a previous paper we presented a new Fretting Fatigue model which can explain these Fretting Fatigue features reasonably. In this paper we try to explain many other Fretting features such as Fretting Fatigue strength and life dependence on contact pressure and contact edge shapes. Firstly we try to discuss the dependence of Fretting Fatigue strength/life on contact pressure. In accordance with the increase of the contact pressure the stress concentration at the contact edge increased and crack initiation stress level decreased. But to open these small cracks initiated at contact edges more wear or more load cycles are needed. So Fretting Fatigue strength limit decreased in accordance with the increase of contact pressure and Fretting Fatigue life increased in accordance with the increase of contact pressure. Then we discuss the Fretting Fatigue strength dependence on the contact edge shape, such as stress release projection or interference of the contact edge with the stress concentration fillet. Experimental results of Fretting Fatigue strength improvement with stress release projection can be explained analytically. The two-stage S-N curve can be shown in joint structures, in which contact edge is set near the stress concentration fillet. These features can also be explained analytically in this paper.
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Fretting Fatigue strength estimation considering the Fretting wear process
Tribology International, 2006Co-Authors: Toshio Hattori, Takashi WatanabeAbstract:Abstract In Fretting Fatigue process the wear of contact surfaces near contact edges occur in accordance with the reciprocal micro-slippages on these contact surfaces. These Fretting wear change the contact pressure near the contact edges. To estimate the Fretting Fatigue strength and life it is indispensable to analyze the accurate contact pressure distributions near the contact edges in each Fretting Fatigue process. So, in this paper we present the estimation methods of Fretting wear process and Fretting Fatigue life using this wear process. Firstly the Fretting-wear process was estimated using contact pressure and relative slippage as follows: W = K × P × S , where W is the wear volume (depth), K the wear coefficient, P the contact pressure, S the slippage. And then the stress intensity factor for cracking due to Fretting Fatigue was calculated by using contact pressure and frictional stress distributions, which were analyzed by the finite element method. The S – N curves of Fretting Fatigue were predicted by using the relationship between the calculated stress intensity factor range (Δ K ) with the threshold stress intensity factor range (Δ K th ) and the crack propagation rate (d a /d N ) obtained using CT specimens of the material. And then Fretting Fatigue tests were conducted on Ni–Cr–Mo–V steel specimens. The S – N curves of our experimental results were in good agreement with the analytical results obtained by considering Fretting wear process. Using these estimation methods we can explain many Fretting troubles in industrial fields.
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Simulation of Fretting-Fatigue life by using stress-singularity parameters and fracture mechanics
Tribology International, 2003Co-Authors: Toshio Hattori, M. Nakamura, Takashi WatanabeAbstract:Fretting-Fatigue cracks start very early in a Fretting-Fatigue life. The Fretting-Fatigue life is dominated by the propagation of small cracks. Therefore, predicting the start of Fretting-Fatigue cracking and the propagation of the cracks is a very important part of estimating Fretting-Fatigue strength and Fretting-Fatigue life. The start of a Fretting-Fatigue crack was estimated by using the stress-singularity parameters at the contact edges. The way in which the crack propagates was then estimated by using fracture-mechanics analysis, in which the wear on the contact surfaces and the direction of crack propagation were taken into account.
Magd Abdel Wahab - One of the best experts on this subject based on the ideXlab platform.
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Fretting Fatigue crack nucleation: A review
Tribology International, 2018Co-Authors: Nadeem Ali Bhatti, Magd Abdel WahabAbstract:Abstract 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.
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Roughness effects on Fretting Fatigue
Journal of Physics: Conference Series, 2017Co-Authors: Magd Abdel WahabAbstract:Fretting is a small oscillatory relative motion between two normal loaded contact surfaces. It may cause Fretting Fatigue, Fretting wear and/or Fretting corrosion damage depending on various Fretting couples and working conditions. Fretting Fatigue usually occurs at partial slip condition, and results in catastrophic failure at the stress levels below the Fatigue limit of the material. Many parameters may affect Fretting behaviour, including the applied normal load and displacement, material properties, roughness of the contact surfaces, frequency, etc. Since Fretting damage is undesirable due to contacting, the effect of rough contact surfaces on Fretting damage has been studied by many researchers. Experimental method on this topic is usually focusing on rough surface effects by finishing treatment and random rough surface effects in order to increase Fretting Fatigue life. However, most of numerical models on roughness are based on random surface. This paper reviewed both experimental and numerical methodology on the rough surface effects on Fretting Fatigue.
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On Fretting Fatigue behaviour of single bolted lap joint
2014Co-Authors: Reza Hojjati Talemi, Magd Abdel Wahab, Tong Yue, Laurent D'alviseAbstract:Fretting Fatigue failure mechanisms occurs between connected parts which are subjected to small oscillatory relative movement and bulk Fatigue loading condition at the same time. In this study, Fretting Fatigue behaviour of single bolted lap joint connection is investigated by means of finite element modelling approach. To this end, a 3-D finite element model was developed to characterize behaviour of single bolted joint subjected to Fretting Fatigue loading conditions, which consists of initial crack site estimation, stress and slip distribution at contact interface.
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Fretting Fatigue crack initiation lifetime predictor tool using damage mechanics approach
Tribology International, 2013Co-Authors: Reza Hojjatitalemi, Magd Abdel WahabAbstract:Abstract Fretting Fatigue is a combination of two complex mechanical phenomena. Fretting appears between components that are subjected to small relative oscillatory motions. Once these connected components undergo cyclic Fatigue load, Fretting Fatigue occurs. In general, Fretting Fatigue failure process can be divided into two main portions, namely crack initiation and crack propagation. Fretting Fatigue crack initiation characteristics are very difficult to detect because damages such as micro-cracks are always hidden between two contact surfaces. In this paper Continuum Damage Mechanics (CDM) approach in conjunction with Finite Element Analyses (FEA) is used to find a predictor tool for Fretting Fatigue crack initiation lifetime. For this purpose an uncoupled damage evolution law is developed to model Fretting Fatigue crack initiation lifetime at various Fretting condition such as contact geometry, axial stress, normal load and tangential load. The predicted results are validated with published experimental data from literature.
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XFEM for Fretting Fatigue: straight VS mixed mode crack propagation
2012Co-Authors: Reza Hojjati Talemi, Magd Abdel WahabAbstract:Fretting Fatigue is a combination of two complex and serious mechanical phenomena, namely Fretting and Fatigue. The combination of these two phenomena can cause sudden fracture of components that are subjected to the oscillatory motions (Fatigue) and at the same time are in contact with each other (Fretting). Fretting Fatigue lifetime can be divided to two different parts, namely crack initiation and crack propagation. In order to model Fretting Fatigue crack propagation, one of the simplifications that is widely used by researchers relies on the assumption of straight crack, normal to the contact surface. In this study a modified Fretting Fatigue contact model in conjunction with eXtended Finite Element Method (XFEM) is used to monitor the effect of mode-mixity on Fretting Fatigue crack propagation. For this purpose, Python programming language along with ABAQUS software is used to implement the application of XFEM to Fretting Fatigue crack propagation.
Minoru Yamashita - One of the best experts on this subject based on the ideXlab platform.
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Fretting Fatigue life estimations based on Fretting mechanisms
Tribology International, 2011Co-Authors: Toshio Hattori, Vu Trung Kien, Minoru YamashitaAbstract:Abstract Generally the Fretting Fatigue S – N curve has two regions: one is the high cycle (low stress) region and the second is the low cycle (high stress) region. In a previous paper we introduced the Fretting Fatigue life estimation methods in high cycle region by considering the wear process; with this estimation method the Fretting Fatigue limit can be estimated to be the crack initiation limit at the contact edge. In this paper we estimate the low cycle Fretting Fatigue life based on a new critical distance theory, modified for a high stress region using ultimate tensile strength σ B and fracture toughness K IC . The critical distance for estimating low cycle Fretting Fatigue strength was calculated by interpolation of the critical distance on the Fretting Fatigue limit (estimated from σ w0 and Δ K th ) with critical distance on static strength (estimated from σ B and K IC ). By unifying this low cycle Fretting Fatigue life estimation method with the high cycle Fretting Fatigue life estimation method, which was presented in the previous paper, we can estimate the total Fretting life easily. And to confirm the availability of this estimation method we perform the Fretting Fatigue test using Ni–Mo–V steel.
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Fretting Fatigue Life Estimations Based on the Critical Distance Stress Theory
Procedia Engineering, 2011Co-Authors: Toshio Hattori, Muhammad Amiruddin Bin Ab Wahab, Takuya Ishida, Minoru YamashitaAbstract:Abstract Generally Fretting Fatigue S-N curve have two stages, one is high cycle (low stress) region and second is low cycle (high stress) region. In previous paper we introduced the Fretting Fatigue life estimation methods in high cycle region by considering the wear process. And in this estimation method the Fretting Fatigue limit can be estimated as the crack initiation limit at contact edge. In this paper we estimated the low cycle Fretting Fatigue life based on new critical distance theory, which is modified for high stress region using ultimate tensile strength σB, and fracture toughness KIC. Firstly the critical distance for estimating low cycle Fatigue strength was calculated by interpolation of critical distance on Fatigue limit (estimated from σw0 and ΔKth) with critical distance on static strength (estimated from σB and KIC). The validity of this method is confirmed by the V notch specimens. And then we applied this method on estimation of low cycle Fretting Fatigue strength and life. By unifying these low cycle Fretting Fatigue life estimation method with high cycle Fretting Fatigue life estimation method which was presented previous paper we can estimate the total Fretting life easily. And to confirm the availability of this estimation method we perform the Fretting Fatigue test using Ni-Mo-V steel.
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2320 Feature of Fretting Fatigue strength/life and it's mechanical considerations
2007Co-Authors: Toshio Hattori, Minoru Yamashita, Naoya NishimuraAbstract:The Fretting Fatigue process has many features such as early stage crack initiation at the contact edge, very slow crack propagation and Fatigue failure after a very long life operation. In a previous paper we presented a new Fretting Fatigue model which can explain these Fretting Fatigue features reasonably. In this paper we try to explain many other Fretting features such as Fretting Fatigue strength and life dependence on contact pressure and contact edge shapes. Firstly we try to discuss the dependence of Fretting Fatigue strength/life on contact pressure. In accordance with the increase of the contact pressure the stress concentration at the contact edge increased and crack initiation stress level decreased. But to open these small cracks initiated at contact edges more wear or more load cycles are needed. So Fretting Fatigue strength limit decreased in accordance with the increase of contact pressure and Fretting Fatigue life increased in accordance with the increase of contact pressure. Then we discuss the Fretting Fatigue strength dependence on the contact edge shape, such as stress release projection or interference of the contact edge with the stress concentration fillet. Experimental results of Fretting Fatigue strength improvement with stress release projection can be explained analytically. The two-stage S-N curve can be shown in joint structures, in which contact edge is set near the stress concentration fillet. These features can also be explained analytically in this paper.
Masanobu Kubota - One of the best experts on this subject based on the ideXlab platform.
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Fretting Fatigue on thread root of premium threaded connections
Tribology International, 2017Co-Authors: Yosuke Oku, Masaaki Sugino, Yoshinori Ando, Taizo Makino, Ryosuke Komoda, Daisuke Takazaki, Masanobu KubotaAbstract:Abstract Identification of the Fatigue failure mode of the premium threaded connection for Oil Country Tubular Goods pipes was conducted via full-scale Fatigue tests. A through-wall crack was found at the imperfect thread root of the male embodiment, but the crack initiation site depended on the stress level. At relatively higher stress amplitude region, the crack originated from the thread rounded corner by stress concentration. At relatively lower stress amplitude region, the crack originated at the middle of the thread root because of Fretting Fatigue. To investigate the Fretting Fatigue mechanism in the threaded connection, a fundamental Fretting Fatigue test was conducted. This test achieved the Fretting Fatigue failure at the middle of the contact surface under large gross slip condition.
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Reduction in Fretting Fatigue Strength of Austenitic Stainless Steels due to Internal Hydrogen
Advanced Materials Research, 2014Co-Authors: Ryosuke Komoda, Masanobu Kubota, Naoto Yoshigai, Jader FurtadoAbstract:Fretting Fatigue is one of the major factors in the design of hydrogen equipment. The effect of internal hydrogen on the Fretting Fatigue strength of austenitic stainless steels was studied. The internal hydrogen reduced the Fretting Fatigue strength. The reduction in the Fretting Fatigue strength became more significant with an increase in the hydrogen content. The reason for this reduction is that the internal hydrogen assisted the crack initiation. When the Fretting Fatigue test of the hydrogen-charged material was carried out in hydrogen gas, the Fretting Fatigue strength was the lowest. Internal hydrogen and gaseous hydrogen synergistically induced the reduction in the Fretting Fatigue strength of the austenitic stainless steels. In the gaseous hydrogen, Fretting creates adhesion between contacting surfaces where severe plastic deformation occurs. The internal hydrogen is activated at the adhered part by the plastic deformation which results in further reduction of the crack initiation limit.
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Effect of contact conditions on growth of small crack in Fretting Fatigue
TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A, 2012Co-Authors: Shunsuke Kataoka, Masanobu Kubota, Hiroaki Ono, Yoshiyuki KondoAbstract:As the general features of Fretting Fatigue, initiation of Fretting Fatigue crack is in the very early stage of the Fretting Fatigue life and there are small non-propagating cracks in the test specimen that doesn't fracture at the Fretting Fatigue limit. In accordance with these experimental facts, Fretting Fatigue problem can be considered as a propagation problem of small crack. Thus, a pre-cracked specimen was used in the Fretting Fatigue test in this study. The objective was to consider the determinant factors of Fretting Fatigue strength. In the Fretting Fatigue test, the Fretting Fatigue limit of the pre-cracked specimen was once reduced and after increased with increase of the contact pressure. The reason was understood by the stress intensity factor of the pre-crack obtained by a finite element analysis. In this study, the Fretting Fatigue limit can be predicted by the comparison of ΔK of the pre-crack and the propagation threshold of the pre-crack ΔKth. The effect of the relative location of the pre-crack to the contact edge on the Fretting Fatigue strength was also discussed by both Fretting Fatigue test and FEM analysis.
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Fretting Fatigue in hydrogen gas
Tribology International, 2006Co-Authors: Masanobu Kubota, Naoki Noyama, Chu Sakae, Yoshiyuki KondoAbstract:To clarify the effect of hydrogen gas on Fretting Fatigue strength of the materials, which supposed to be used for hydrogen utilization machines, Fretting Fatigue tests were conducted in hydrogen gas. It is important to take Fretting Fatigue into account in strength design, because many Fatigue failure accidents have occurred at joints or contact parts between components. As a part of the experiments, an austenitic stainless steel was focused in this paper. The material was SUS 304. Fretting Fatigue strength in hydrogen gas decreased compared with that in air. Tangential force coefficient increased in the reverse order of Fretting Fatigue strength. Therefore, one of the reasons of the decrease of Fretting Fatigue strength was that tangential force was different depending on the environment. Absorption of hydrogen occurred during Fretting in hydrogen gas was detected. The absorption could be considered as one of the causes of the decrease of Fretting Fatigue strength, since Fretting Fatigue life of pre-charged specimen was decreased and also the crack propagation threshold of short Fatigue crack was reduced by hydrogen charge.
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evaluation of Fretting Fatigue limit based on local stress at the contact edge
Journal of The Society of Materials Science Japan, 2002Co-Authors: Yoshiyuki Kondo, Chu Sakae, Masanobu Kubota, Tomohiro Nagasue, Shinichi SatoAbstract:It was reported previously by the author that the effect of various factors influencing the Fretting Fatigue limit could be evaluated based on the local stress at the contact edge. In this report, the meaning of the local stress in Fretting Fatigue was studied. The two-step Fatigue test showed that the value of the local stress Fatigue limit was nearly the same as the Fatigue limit of an edge cracked specimen containing a non-propagating crack formed by the pre-Fretting Fatigue. The change of stress intensity factor due to the crack growth under Fretting Fatigue condition was calculated by FEM. The Fretting Fatigue limit was the condition at which a micro-crack generated by Fretting remains as a non-propagating crack. The condition to form a non-propagating crack in Fretting Fatigue was evaluated on the basis of the threshold condition of short Fatigue crack growth.
