Quantitative fractography of fish-eye crack formation under bending–torsion fatigue

Slámečka, Karel; Pokluda, Jaroslav; Kianicová, Marta; Major, Stepan; Dvořák, Ivan

doi:10.1016/j.ijfatigue.2009.07.009

Cited by 28 publications

(19 citation statements)

References 14 publications

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“…8. This type of fatigue failure has been widely reported in gigacycle fatigue of high strength materials [16,17]. So far, less work can be referred to that has dealt with the transition of crack initiation from subsurface inclusions to the fish-eye type.…”

Section: Fractography Analysismentioning

confidence: 84%

Gigacycle fatigue behaviors of two SNCM439 steels with different tensile strengths

Duan

Shi

et al. 2011

Acta Mech Sin

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Gigacycle fatigue behaviors of two SNCM439 steels with different tensile strengthes were experimentally studied by rotating bending tests, to investigate the effects of the tensile strength obtained by different heat treatment processes on very high cycle fatigue failure mechanisms. The material with higher tensile strength of 1 710 MPa exhibited typical gigacycle fatigue failure characteristics, whereas one with lower tensile strength of 1 010 MPa showed only traditional fatigue limit during the tests and no gigacycle failure could be found even when the specimen ran up to more than 10 8 cycles. Metallographic and fractographic analysis were carried out by an optical microscope (OM) and scanning electron microscope (SEM). It showed two different crack initiation mechanisms that for the specimen with lower tensile strength the crack prefers surface initiation and for that with higher strength the crack initiates from subsurface inclusions revealed by a fish-eye like microstructure.

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Section: Fractography Analysismentioning

confidence: 84%

Gigacycle fatigue behaviors of two SNCM439 steels with different tensile strengths

Duan

Shi

et al. 2011

Acta Mech Sin

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“…Fracture surface topography is one of the basic macroscopic investigations aimed at determining the cause of the fatigue damage [1]. It allows to determine what kind of the fatigue loading material was subjected.…”

Section: Introductionmentioning

confidence: 99%

Analysis of loading history influence on fatigue and fracture surface parameters using the method of induction trees

2019

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In fatigue life testing under various loading conditions, researchers observe the profile, surface and morphology of materials. In this study authors research the fatigue life of material and the surface fracture geometry. Areal field and fractal based characterisation are evaluated for the whole fracture surfaces. Results of this test were correlated to notch geometry and loading conditions. It was confirmed, for notched specimens, that the change from torsion to proportional bending with torsion fatigue life increase significantly, the same as changing loading from bending with torsion to bending. The measurement device was equipped with a motorised nosepiece using five dedicated microscopic objective lenses from 2.5× to 100× magnification. This paper presents the application of the induction tree method for analysis of loading history influence on fatigue and fracture surface parameters. In a decision tree, nodes store tests checking values of example attributes and leaves store categories assigned to them. For each of possible test results, there is one branch coming from a node to a subtree. In this way, it is possible to represent any attributes of the hypothesis admissible for a given set. Analysis of selected parameters will estimate their impact on the surface structure.

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“…For the case of VHCF, on the other hand, cracks tend to initiate at specimen subsurface (interior). However, the process of subsurface crack initiation and propagation is still not clear and there are few theoretical models developed to analyze the different crack initiation process [8,9,13,20]. Additionally, although there have been many studies on the factors those may affect VHCF propensity of high strength steels, such as environmental medium [14][15][16], loading frequency [17,18], microstructure state [19][20][21], etc.…”

Section: Introductionmentioning

confidence: 99%

Investigation of high cycle and Very-High-Cycle Fatigue behaviors for a structural steel with smooth and notched specimens

Qian

Hong

Zhou

2010

Engineering Failure Analysis

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a b s t r a c tThe high cycle and Very-High-Cycle Fatigue (VHCF) properties of a structural steel with smooth and notched specimens were studied by employing a rotary bending machine with frequency of 52.5 Hz. For smooth specimens, VHCF failure did occur at fatigue cycles of 7.1 Â 10 8 with the related S-N curve of stepwise tendency. Scanning Electron Microscopy (SEM) was used for the observations of the fracture surfaces. It shows that for smooth specimens the crack origination is surface mode in the failure regime of less than 10 7 cycles. While at VHCF regime, the material failed from the nonmetallic inclusion lies in the interior of material, leading to the formation of fisheye pattern. The dimensions of crack initiation region were measured and discussed with respect to the number of cycles to failure. The mechanism analysis by means of low temperature fracture technique shows that the nonmetallic inclusion in the interior of specimen tends to debond from surrounding matrix and form a crack. The crack propagates and results to the final failure. The stress intensity factor and fatigue strength were calculated to investigate the crack initiation properties. VHCF study on the notched specimens shows that the obtained S-N curve decreases continuously. SEM analysis reveals that multiple crack origins are dominant on specimen surface and that fatigue crack tends to initiate from the surface of the specimen. Based on the fatigue tests and observations, a model of crack initiation was used to describe the transition of fatigue initiation site from subsurface to surface for smooth and notched specimens. The model reveals the influences of load, grain size, inclusion size and surface notch on the crack initiation transition.

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Quantitative fractography of fish-eye crack formation under bending–torsion fatigue

Cited by 28 publications

References 14 publications

Gigacycle fatigue behaviors of two SNCM439 steels with different tensile strengths

Gigacycle fatigue behaviors of two SNCM439 steels with different tensile strengths

Analysis of loading history influence on fatigue and fracture surface parameters using the method of induction trees

Investigation of high cycle and Very-High-Cycle Fatigue behaviors for a structural steel with smooth and notched specimens

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