Damage mechanism of a nodular cast iron under the very high cycle fatigue regime

Xue, Hongqian; Bayraktar, E.; Bathìas, Claude

doi:10.1016/j.jmatprotec.2007.09.030

Cited by 38 publications

(17 citation statements)

References 16 publications

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“…They found a strong relation between graphite particle size and fatigue life. Also cyclic loading with variable amplitudes [36] and loading in the VHCF regime [129] were investigated. A comprehensive database for HCF behavior of NCI of type EN-GJS-400 including a study on the influence of casting defects on fatigue life is given in [108].…”

Section: Cyclic Loading and Fatiguementioning

confidence: 99%

Micromechanisms of fracture in nodular cast iron: From experimental findings towards modeling strategies – A review

Hütter

Zybell

Kuna

2015

Engineering Fracture Mechanics

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Section: Cyclic Loading and Fatiguementioning

confidence: 99%

Micromechanisms of fracture in nodular cast iron: From experimental findings towards modeling strategies – A review

Hütter

Zybell

Kuna

2015

Engineering Fracture Mechanics

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“…The nodular cast iron grade EN-GJS-400-18-LT, in which graphite spheroids or nodules in a ferritic matrix provide large ductility and fatigue strength, is widely used. Specific shape of the graphite in the ferritic microstructure acts as the crack arrester and lowers the stress intensity in front of the crack, which makes it an appropriate material for such cyclically loaded structures [1][2][3][4][5]. Therefore, in order to prevent catastrophic failures and to prolong the service lifetime of wind turbine structures, it is important to consider the influence of the graphite nodule geometrical features (size, shape and distribution of nodules) on the fatigue crack initiation and propagation at the root of a geometrical discontinuity and local notches.…”

Section: Introductionmentioning

confidence: 99%

Microstructure influence on fatigue behaviour of nodular cast iron

Čanžar

Tonković

Kodvanj

2012

Materials Science and Engineering: A

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a b s t r a c tThe present paper evaluates the fatigue life of ductile nodular cast iron EN-GJS-400-18LT with four different microstructures. Characterisation of the graphite morphology and the matrix microstructure is performed on 50 samples for every material type. Tensile stress-strain curves, symmetrical and unsymmetrical stress-strain hysteresis loops, cyclic stress-strain curves, crack resistance curves and fatigue life curves of these four microstructures are obtained. Experimental results show that size, shape and distribution of the graphite nodules has no significant influence on cyclic hardening of the material but they play a great role in the crack initiation and propagation process. It is shown that the larger irregularly shaped nodules reduce fracture toughness and fatigue strength. Furthermore, the results demonstrated that pearlitic phase does not strongly affect fatigue life if its proportion does not exceed 10%. The monitoring of crack length during the tests is performed by an optical method developed in the present work.

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“…In addition, an intermittent loading condition, i.e., 500 ms of pulse followed by 1000 ms of pause, was employed to minimize the thermal effect. As reported in [18], the thermal effect could be noticably reduced by employing cooling measures in a lower strength steel. After testing, all fracture surfaces of failed specimens were observed by scanning electron microscopy (SEM) in order to identify the crack initiation modes.…”

Section: Fatigue Testing Methodsmentioning

confidence: 78%

Failure mechanisms and fatigue strength reduction factor of a Cr-Ni-Mo-V steel welded joint up to ultra-long life regime

Zhu

Xuan

2018

MATEC Web Conf.

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Abstract. It is known that welded joint is much "weaker" than base metal due to discontinuities of geometry, materials and residual stresses. It seems current international design rules do not adopt a uniform approach to weld efficiency, which is often defined as the ratio of the strength of a welded joint to the strength of base metal, in their guidance for creep and fatigue design of welds. This appears to be a great barrier for the application of nuclear welded structures which has a prolonged design lifetime of 60 years. In this work, fatigue strength reduction factor of a Cr-Ni-Mo-V steel welded joint, machined from welded steam turbine rotors for nuclear power plant, was investigated by performing axially push-pull cyclic loads tests with both cross-weld and pure base metal specimens up to very high cycle fatigue regime under ultrasonic frequency at ambient temperature. The effects of residual stress, strain localization, and microdefects in mismatched steels on failure mechanisms of welds were discussed thoroughly. Results show that fatigue strength reduction factor is varied in the range of 0.95-0.975, and is found to be dependent on fatigue lifetime for the first time. It is indicated that variation of fatigue strength reduction factor are associated with transition of crack initiation from specimen surface in high cycle fatigue regime to interior micro-defects in very high cycle fatigue regime. Comparing existing codes and standards for fatigue design of welds with experimental data indicates the over-conservativeness of present code-based design method. This implies a micro-defect based fatigue design approach is required for long life safe and reliability of weldments.

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Damage mechanism of a nodular cast iron under the very high cycle fatigue regime

Cited by 38 publications

References 16 publications

Micromechanisms of fracture in nodular cast iron: From experimental findings towards modeling strategies – A review

Micromechanisms of fracture in nodular cast iron: From experimental findings towards modeling strategies – A review

Microstructure influence on fatigue behaviour of nodular cast iron

Failure mechanisms and fatigue strength reduction factor of a Cr-Ni-Mo-V steel welded joint up to ultra-long life regime

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