Fretting Fatigue under Variable Amplitude Loading below Fretting Fatigue Limit

Kondo, Yoshiyuki; Sakae, Chu; Kubota, Masanobu; Kitahara, Hiroki; Yanagihara, Kazutoshi

doi:10.1299/jsmemp.2004.12.241

Cited by 2 publications

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“…In the previous study, 7 however, it was revealed that fatigue failure occurred in some cases of fretting fatigue even when all stress amplitudes were kept within the fatigue limit diagram. In these varying stress tests, mean stress as well as stress amplitude was changed.…”

Section: Introductionmentioning

confidence: 82%

Fatigue strength of small‐notched specimens under variable amplitude loading within the fatigue limit diagram

Kondo

Sakae

Kubota

et al. 2007

Fatigue Fract Eng Mat Struct

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A B S T R A C T Although the fatigue limit diagram is defined in principle for constant stress amplitude, it is often considered that fatigue failure would not occur, even in varying loading, if applied stresses were kept within the fatigue limit diagram. However, it was shown in the case of small-notched specimens that fatigue failure occurred in some special cases of variable amplitude loading, even when all stress amplitudes were kept within the fatigue limit diagram. The cause of this phenomenon was examined using two-step stress and repeated two-step stress patterns in which the first step stress was chosen to be equal to the fatigue limit with zero mean stress and a mean stress was superposed on the second step stress. A non-propagating crack was formed by the first step stress. This crack functioned as a pre-crack for the second step stress with high mean stress. Consequently, fatigue failure occurred even when all stress amplitudes were kept within the fatigue limit diagram. It was an unexpected fracture caused by the interference effect of a non-propagating crack and a mean stress change.Keywords fatigue limit diagram; non-propagating crack; notch; repeated two-step loading; short crack; variable amplitude loading. N O M E N C L A T U R En 1 = number of cycles of 1st step stress in one block of repeated two-step stress n 2 = number of cycles of 2nd step stress in one block of repeated two-step stress R = stress ratio t = notch depth K = stress intensity factor range ( K eff ) th = effective threshold stress intensity factor range σ 0.2 = 0.2% offset stress σ 1 = 1st step stress amplitude of repeated two-step stress σ 2 = 2nd step stress amplitude of repeated two-step stress σ a = stress amplitude σ B = tensile strength σ m = mean stress σ m 1 = mean stress of 1st step stress of repeated two-step stress σ m 2 = mean stress of 2nd step stress of repeated two-step stress σ y = yield stress I N T R O D U C T I O NThe effect of mean stress on fatigue limit is usually evaluated using the fatigue limit diagram 1 as shown in Fig. 1.

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Section: Introductionmentioning

confidence: 82%

Fatigue strength of small‐notched specimens under variable amplitude loading within the fatigue limit diagram

Kondo

Sakae

Kubota

et al. 2007

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

show abstract

“…If the stress amplitude and mean stress were kept constant within fatigue limit diagram, fatigue fracture would not occur. In the previous study, however, it was shown that fatigue failure occurred in some special cases even when all stress amplitudes were kept within fatigue limit diagram 7–9 . In the previous study, 9 repeated two‐step loading pattern was examined.…”

Section: Introductionmentioning

confidence: 93%

Effect of small notch and absorbed hydrogen on the fatigue fracture in two‐step stress test within fatigue limit diagram

Kondo

Eda

Kubota

2009

Fatigue Fract Eng Mat Struct

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A B S T R A C T It is usually regarded as a common understanding that fatigue failure would not occur if all stresses were kept within fatigue limit diagram. However, it was shown that fatigue failure occurred in some special cases of variable amplitude loading condition even when all stresses were kept within fatigue limit diagram in the case of small-notched specimen.The cause of such a phenomenon was examined using two-step stress pattern for low alloy steel SCM440H. In the case of constant stress amplitude loading, non-propagating crack was formed only at low mean stress and not formed at high mean stress. However, in the case of two-step stress pattern in which the first step stress was chosen as R = −1 and the second step stress was with high mean stress, a non-propagating crack was formed by the first step stress. This crack functioned as a pre-crack for the second step stress with high mean stress. Consequently, fatigue failure occurred by the stresses within fatigue limit diagram. In this study, the effect of notch size and shape were examined. The effect of absorbed hydrogen was also investigated. Absorption of 0.3 ppm hydrogen caused more reduction of fatigue limit. R = stress ratio t = notch depth K = stress intensity factor range σ 0.2 = 0.2% offset stress σ a1 = 1st step stress amplitude of two-step stress σ a2 = 2nd step stress amplitude of two-step stress σ a = stress amplitude σ B = tensile strength σ m = mean stress σ m1 = mean stress of 1st step stress of two-step stress σ m2 = mean stress of 2nd step stress of two-step stress

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Fretting Fatigue under Variable Amplitude Loading below Fretting Fatigue Limit

Cited by 2 publications

References 0 publications

Fatigue strength of small‐notched specimens under variable amplitude loading within the fatigue limit diagram

Fatigue strength of small‐notched specimens under variable amplitude loading within the fatigue limit diagram

Effect of small notch and absorbed hydrogen on the fatigue fracture in two‐step stress test within fatigue limit diagram

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