Inherent damage zone model for strength evaluation of small fatigue cracks

Fujimoto, Yukio; Hamada, Koichi; Shintaku, Eiji; Pirker, Gernot

doi:10.1016/s0013-7944(00)00116-8

Cited by 19 publications

(10 citation statements)

References 16 publications

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“…This is suitable, because a small stress distance means, that the effective stress is closer to the peak stress. The shape of the resulting curves is similar to results in literature [8,9] .…”

Section: Application Of the Calculation Methodssupporting

confidence: 86%

“…To receive realistic results, the outcomes from fatigue tests [11] are taken to define the probability distribution. The stress distance was varied within their typical range [8]. The estimated parameters a s * and α* are set to a constant value.…”

Section: Simulated Experimentsmentioning

confidence: 99%

“…El Haddads approach does not perform, if the cracks originate in notches [3], therefore, a different approach is used. Fujimoto et al [8] assume that there is an inherent damage zone of size a s under the surface. The size of this zone depends on material and range from 0.03mm to 0.1mm for common steels.…”

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confidence: 99%

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Evaluation of the fatigue strength of multiphase pump components under corrosive conditions using a short crack fracture mechanics approach

Hoehbusch

Bucher

Haensel

et al. 2015

Engineering Failure Analysis

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Components of Multiphase pumps, employed in oil and gas fields, often suffer from wear and localized corrosion, which is caused by the aggressive media to be pumped. To ensure a safe operation, analytic stress assessments are required. However common guidelines do not include a general way to take the influence of corrosion into account up to now. Hence this paper presents both a calculation and an experimental method to evaluate the actual fatigue limit under the influence of pitting corrosion for components of stainless steel. The experimental method delivers material-parameters and is used to validate the calculation method. Both of these methods are applied to a weak-notched specimen. IntroductionComponents used in oil and gas production are often exposed to dynamic loads in a corrosive environment. A crack initiation caused by high load frequencies has to be avoided, since component failure can arise in short-terms. These components are usually made of stainless steel in order to prevent corrosive attack. Nevertheless aggressive media can lead to localized corrosion in many cases, i.e. pitting corrosion [2]. Thus an analytic strength assessment is required in order to ensure a safe operation. Up to now, guidelines for analytical strength assessment used in industrial environment, do not include a general way to take the influence of corrosion into account. This leads to the need for a different approach to consider the influence of corrosion on the components fatigue strength. A special type of corrosion, called pitting corrosion fatigue (PCF), the interaction of pitting corrosion and fatigue is regarded in this paper. PCF starts with the initiation and growth of corrosion pits. Both, initiation and growth of corrosion pits can occur without mechanical stress, so there is no stress value that can be defined as PCF threshold stress [2,6]. The growth of the pits leads to a change of the stress state which is characterized by increasing mechanical peak stress and decreasing stress gradients. If the stress reaches a threshold value, cracks are initiated at the corrosion pit. The first initiation of cracks at a corrosion pit is known as pit-to-crack transition [6]. This paper presents an approach to determine the conditions (stress and pit size) for a pit-tocrack transition in components. The pit-to-crack transition is regarded as the end of the safe live of a component which is exposed to high frequency loads. Due to this it may lead to an approximate estimation of the service life. The approach consists of a calculation method with special experimentally derived material parameters. These parameters are determined by an iterative newly developed experimental method using a combination of the shown calculation method and known specimen tests.

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Section: Application Of the Calculation Methodssupporting

confidence: 86%

Section: Simulated Experimentsmentioning

confidence: 99%

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Evaluation of the fatigue strength of multiphase pump components under corrosive conditions using a short crack fracture mechanics approach

Hoehbusch

Bucher

Haensel

et al. 2015

Engineering Failure Analysis

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show abstract

“…Auch den Kurzrissen läßt sich ein von der Rißgröße abhängiger Schwellenwert der zyklischen Spannungsintensität zuordnen, der der zyklischen Dauerfestigkeit mit Riß entspricht (s. dazu [1415]). 7.13.…”

Section: Formale Beschreibung Nach Sähnunclassified

“…[1415] Der vorstehend beschriebene Ansatz einer elastischen Schädigungszone kann nur die Verhältnisse in unmittelbarer Nähe der Dauerfestigkeit richtig darstellen, weil nur hier die Annahme elastischen Werkstoffverhaltens gerechtfertigt ist. [1415] Der vorstehend beschriebene Ansatz einer elastischen Schädigungszone kann nur die Verhältnisse in unmittelbarer Nähe der Dauerfestigkeit richtig darstellen, weil nur hier die Annahme elastischen Werkstoffverhaltens gerechtfertigt ist.…”

Section: Formale Beschreibung Nach Sähnunclassified