The significance of microstructural barriers during fatigue of a duplex steel in the high- and very-high-cycle-fatigue (HCF/VHCF) regime

Krupp, Ulrich; Knobbe, Helge; Christ, Hans‐Jürgen; Köster, Philipp; Fritzen, Claus‐Peter

doi:10.1016/j.ijfatigue.2009.09.010

Cited by 59 publications

(45 citation statements)

References 8 publications

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“…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. [5,8,12], the influence of notch effect has not been fully understood.…”

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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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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“…Nishijima and Kanazawa [15] attributed the reason why the fatigue life for internal failure is longer than that for surface failure to the fact that the stress intensity factor for flaws with the same size in the material interior is smaller than that at the surface. The influence of some factors, such as loading frequency [12,14,20,21], surface finishing condition [8,16,22], material microstructure state [23][24][25] and environmental media [10,11,26], on the VHCF properties of high strength steels has been widely studied. Among them, the effect of ultrasonic frequency on the estimated fatigue strength has been intensively studied in order to make sure that the fatigue results obtained by using ultrasonic testing and conventional fatigue equipment with a low frequency are comparable.…”

Section: Introductionmentioning

confidence: 99%

A model to predict S–N curves for surface and subsurface crack initiations in different environmental media

Qian

Zhou

Hong

2015

International Journal of Fatigue

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a b s t r a c tThe influence of environmental media on crack propagation of a structural steel at high-cycle and veryhigh-cycle fatigue (VHCF) regimes was investigated with the fatigue tests in air, water and 3.5% NaCl aqueous solution. The fatigue strength in water and 3.5% NaCl solution is significantly decreased and the cracking morphology due to different driving forces is presented. A model is proposed to explain the influence of environmental media on fatigue life, which reflects the variation of fatigue life with applied stress, grain size, inclusion size and material yield stress. The model prediction is in good agreement with experimental observations.

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“…In recent years, the investigation of VHCF on metallic materials has attracted an increasing number of investigators in the fatigue research field (e.g. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]) due to the growing requirements of engineering applications, including aircraft, automobile, ship, railway, bridge, etc., for which the metallic components and structures need to endure a fatigue life larger than 10 7 or 10 8 loading cycles, and even requiring 10 10 -10 11 life cycles of endurance in some vital cases.…”

Section: Introductionmentioning

confidence: 99%

“…Nishijima and Kanazawa [11] attributed the reason why the fatigue life for internal failure is longer than that for a surface failure to the fact that the stress intensity factor for flaws in the interior is smaller than that at the surface for the same size defect. Some factors, such as loading frequency [12,13], surface finishing condition [14,15], microstructure state [16][17][18], etc., may affect the VHCF properties of high-strength steels. Results in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…The studies revealed that surface notch decreases the possibility of subsurface crack initiation. Krupp et al [18] studied the effect of the microstructure of austenitic-ferritic duplex steels on the fatigue damage of VHCF. It revealed that fatigue damage in the VHCF regime causes the formation of slip bands followed by initiation and propagation of microstructurally short cracks in a very localized manner and the plastic slip occurred firstly in the softer austenite phase of the material.…”

Section: Introductionmentioning

confidence: 99%

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Experimental and theoretical investigation of environmental media on very-high-cycle fatigue behavior for a structural steel

2011

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Rotary bending fatigue tests were performed in laboratory air and 3.5% NaCl aqueous solution to investigate the influence of environmental media on fatigue properties of a structural steel in high-cycle and very-high-cycle fatigue regimes. The results show that the fatigue strength of the structural steel in 3.5% NaCl solution is remarkably degraded compared with the case tested in laboratory air. The fracture surfaces of specimens tested in different environments were examined to reveal the fatigue crack initiation characteristics. It shows that for specimens tested in 3.5% NaCl solution, cracks originate via multiple surface initiation modes and cracking is intergranular; in addition, widespread secondary cracks feature on the fracture surface. Based on fatigue tests and fractography observations, a numerical model of crack initiation is proposed to describe the transition of fatigue initiation site from subsurface to surface for specimens tested in air and 3.5% NaCl solution. The model reveals the influences of load, material strength, grain size, inclusion size and surface environmental media on the crack initiation site transition. It agrees well with the experimental observations.

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The significance of microstructural barriers during fatigue of a duplex steel in the high- and very-high-cycle-fatigue (HCF/VHCF) regime

Cited by 59 publications

References 8 publications

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

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

A model to predict S–N curves for surface and subsurface crack initiations in different environmental media

Experimental and theoretical investigation of environmental media on very-high-cycle fatigue behavior for a structural steel

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