The influence of mean stress or on the fatigue crack threshold characteristics of steels—A review

Bulloch, J.H.

doi:10.1016/0308-0161(91)90032-w

Cited by 23 publications

(15 citation statements)

References 34 publications

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“…Comparatively, according to Eq. (3), DK I for a crack initiated from an internal defect of similar size would be between 2.85 and 3 MPa ffiffiffiffi ffi m p , which is clearly below the scatter-band of threshold DK values reported by Bulloch for this R ratio, in air [34], and also well below the smallest DK computed for any of the internal cracks observed (see Fig. 16).…”

Section: Crack Growth Threshold and Kineticsmentioning

confidence: 64%

“…7. No threshold data is available for crack growth in air at that R ratio in the paper by Suresh et al [32], but according to the extensive DK threshold versus R database gathered by Bulloch [34] for steels with a tempered martensite microstructure, these values are still compatible with crack growth and thus fatigue failure, as observed. Comparatively, according to Eq.…”

Section: Crack Growth Threshold and Kineticsmentioning

confidence: 94%

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Surface versus internal fatigue crack initiation in steel: Influence of mean stress

Gaur

Doquet

Persent

et al. 2016

International Journal of Fatigue

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International audienceStress-controlled fatigue tests were run at different R ratios (¼ r min =r max) up to at most 3 million cycles on a 2.5%Cr–1%Mo steel (ASTM A182 F22) used in riser tubes connectors for offshore oil drilling. The fatigue lives, as well as the slope of the S–N curves were found to decrease with increasing R and the endurance limit to follow Gerber's parabola. Surface crack initiation without any defect involved, was most often observed for R = À1, À0.5 and 0, while an R ratio of 0.25 triggered crack initiation from either surface or internal pores or chemically inhomogeneous areas, leading, in the latter case, to fish-eye patterns for relatively low numbers of cycles. A further increase in R ratio to 0.5 promoted only defect-initiated surface cracks, while no fatigue fracture was observed within 10 million cycles above R ¼ 0:6. These transitions in crack initiation mode are discussed based on X-ray diffraction analyses of residual stresses, elastic–plastic F.E. computations on a unit cell model containing a pore and some fracture mechanics analyses, with a particular attention to environmental effects

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Section: Crack Growth Threshold and Kineticsmentioning

confidence: 64%

Section: Crack Growth Threshold and Kineticsmentioning

confidence: 94%

Surface versus internal fatigue crack initiation in steel: Influence of mean stress

Gaur

Doquet

Persent

et al. 2016

International Journal of Fatigue

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show abstract

“…where fb=6{n(X)j 112 (1.12-1.39 (G)+7.32(x)2-13.1 (+>'+14.0(;)lj (2) for 0 < a/W<0. 6 after Brown and Srawley [9]. The bending geometry factor may be integrated to obtain the SIF calibration for mode I1 [ 101:…”

Section: Specimen and Stress Intensity Factor Calibrationmentioning

confidence: 99%

“…( 5 ) with the initial voltage readings for k, and then substituting in Eq. (6). Lead spacings were hl = 2 mm for ul, hz=40 mm for uz.…”

Section: Crack Length Measurementmentioning

confidence: 99%

The Significance of Mean Stress on the Fatigue Crack Growth Threshold for Mixed Mode I + Ii Loading

Tong

Yates

Brown

1994

Fatigue Fract Eng Mat Struct

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The effect of mean stress on near threshold fatigue crack growth behaviour under mixed mode I+II loading has been studied in a structural steel BS4360 50D in laboratory air at room temperature. It was found that the branch crack threshold decreased significantly as R ratio (P,,,/P,,,,) increased from 0.1 to 0.7. A simple model is proposed to predict the branch crack threshold behaviour for R-ratio sensitive materials. Further investigation is required to model the mode I1 dominant situations where the branch crack thresholds tend to converge on a high value. NOMENCLATURE a = crack length B = specimen thickness hl, h, = active and reference p.d. probe spacings AK,, A&, = mode I and I1 stress intensity factors AKIeq = equivalent mode I stress intensity factor AK,,, = nominal equivalent mode I threshold AK,,.,R = effective equivalent mode I threshold AK,* = intrinsic mode I threshold K, = stress intensity factor necessary to open a crack M = bending moment m = ratio of AK, and AKI, p.d. = potential drop Q = shear force R = load ratio P,,,,,,/P, W = specimen width R,, = value of R above which AK* is constant ul, u2 = active and reference potential drops 0 = branch crack angle

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“…Diversos fatores mecânicos que afetam significativamente as características da extensão da trinca por fadiga em uma grande variedade de materiais de engenharia são alvos de estudos recentes. Entre esses fatores, destacam-se a microestrutura do material e a carga de tensão R, definida como a razão entre a carga minima sobre a carga máxima utilizada durante os ciclos do ensaio de fadiga [21][22]. Bulloch realizou estudos [21][22] para analisar o comportamento de ∆Kth em função de R (relação entre a tensão máxima e mínima) para diferentes microestruturas, como pode ser visto na Figura 3.…”

Section: -Método ε-N Ou De Coffin-mansonunclassified

Caracterização Microestrutural Da Propagação De Trincas Em Aços Estruturais

PIRES¹

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Two structural steels with different chemical compositions and similar mechanical properties were selected for the research, aiming to be alternatives for the manufacture of crankshaft (DIN 34CrNiMo6 steel) of Diesel and natural gas engines of thermoelectric plants. CT-type test specimens were machined in SAE 4140 and 4340 steels and subjected to fatigue crack propagation tests, in order to obtain the respective curves of d /dN versus ΔK. After the tests, the fatigue cracks were indicated on the specimens' surfaces by means of penetrating liquid. Samples from the crack propagation region, with emphasis on the threshold (∆Kth), were removed from the specimens and analyzed by optical microscopy, in an attempt to correlate ∆Kth and the crack propagation with microstructural characteristics and metallurgical heterogeneities of the materials, such as inclusions, voids and second phase particles.

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The influence of mean stress or on the fatigue crack threshold characteristics of steels—A review

Cited by 23 publications

References 34 publications

Surface versus internal fatigue crack initiation in steel: Influence of mean stress

Surface versus internal fatigue crack initiation in steel: Influence of mean stress

The Significance of Mean Stress on the Fatigue Crack Growth Threshold for Mixed Mode I + Ii Loading

Caracterização Microestrutural Da Propagação De Trincas Em Aços Estruturais

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