A Computational investigation of local material strength and toughness on crack growth

Probabilistic methods have been used to develop the basis for free-span inspection of a gas pipeline system in the South China Sea. The objective of the probabilistic analysis was to study the probability of fatigue failure associated with postulated planar flaws in the HAZ of repair welds performed on some of the girth welds. The impact of flaws on the fatigue life under different free-span conditions were studied. Conventional free-span analysis involves computation of allowable free-span lengths based on onset of in-line vibrations and does not normally consider fatigue crack growth. To consider the effect of the weld flaws on the failure probability a combined probabilistic fatigue and fracture model is required. For the particular pipelines analysed automatic ultrasonic testing (AUT) was used replacing the conventional radiography of the girth welds. Conservatism in the free-span assessment can then be significantly reduced by taking into account detailed flaw sizing information from the AUT. The inspection records provide distribution of flaw height, length and position. Combined with information on current distribution, material strength and fracture toughness distribution, a detailed probabilistic fatigue crack growth and unstable fracture assessment can be conducted as per the Det Norske Veritas (DNV) 2000 Rules for Submarine Pipeline Systems [1] using the response models of the DNV Guideline 14 for free-span analyses [2]. The objective of this analysis is to estimate the critical free-span lengths and the time for fatigue cracks to penetrate the pipe wall.

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Fatigue Crack Growth under Non-Proportional Mixed Mode Loading in Rail and Wheel Steel Part 2: Sequential Mode I and Mode III Loading

Applied Sciences ◽

10.3390/app9142866 ◽

2019 ◽

Vol 9 (14) ◽

pp. 2866 ◽

Cited By ~ 1

Author(s):

Makoto Akama ◽

Akira Kiuchi

Keyword(s):

Crack Growth ◽

Mixed Mode ◽

Fatigue Cracks ◽

Rolling Contact ◽

Material Strength ◽

Shear Mode ◽

Mode I ◽

Mode Iii ◽

Plane Shear ◽

Branch Crack

Rolling contact fatigue cracks in rail and wheel undergo non-proportional mixed mode I/II/III loading. Fatigue tests were performed to determine the coplanar and branch crack growth rates on these materials. Sequential and overlapping mode I and III loading cycles were applied to single cracks in round bar specimens. Experiments in which this is done have been rarely performed. The fracture surface observations and the finite element analysis results suggested that the growth of long (does not branch but grown stably and straight) coplanar cracks was driven mainly by mode III loading. The cracks tended to branch when increasing the material strength and/or the degree of overlap between the mode I and III loading cycles. The equivalent stress intensity factor range that can consider the crack face contact and successfully regressed the crack growth rate data is proposed for the branch crack. Based on the results obtained in this study, the mechanism of long coplanar shear-mode crack growth turned out to be the same regardless of whether the main driving force is in-plane shear or out-of-plane shear.

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A Computational investigation of Crack Growth in Multiple Fiber Ceramic Matrix Composites

Computational Mechanics ’95 ◽

10.1007/978-3-642-79654-8_341 ◽

1995 ◽

pp. 2051-2056

Author(s):

F. W. Brust ◽

N. Bonora ◽

G. M. Newaz

Keyword(s):

Crack Growth ◽

Ceramic Matrix Composites ◽

Ceramic Matrix ◽

Matrix Composites ◽

Computational Investigation

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A Statistical Model for Brittle Fracture of Functionally Graded Materials

Volume 6: Materials and Fabrication ◽

10.1115/pvp2005-71152 ◽

2005 ◽

Cited By ~ 2

Author(s):

Bostjan Bezensek ◽

Anuradha Banerjee ◽

John W. Hancock

Keyword(s):

Yield Strength ◽

Functionally Graded Materials ◽

Weibull Model ◽

Functionally Graded ◽

Graded Materials ◽

Crack Propagation Direction ◽

Local Material ◽

The Mean ◽

Two Parameter ◽

Strength And Toughness

A model has been developed to assess the structural assessment of functionally graded materials in which yield strength and toughness vary spatially. The yield strength of the material at any point is deterministic, but varies spatially. The local cleavage toughness also varies spatially, but is statistically distributed following a two parameter Weibull model. The Weibull moduli quantify reliability and the second Weibull parameter is interpreted in terms of the mean toughness of the local material. The model intended to determine the crack propagation direction and failure probabilities of a stationary pre-crack. The effect of simple yield strength and toughness gradients are discussed, before the model is applied to experimental data on laser welded joints.

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Corrosion-Fatigue Performance of High-Strength Riser Steels in Seawater and Sour Brine Environments

Volume 3: Materials Technology; Jan Vugts Symposium on Design Methodology of Offshore Structures; Jo Pinkster Symposium on Second Order Wave Drift Forces on Floating Structures; Johan Wichers Symposium on Mooring of Floating Structures in Waves ◽

10.1115/omae2011-50171 ◽

2011 ◽

Cited By ~ 1

Author(s):

Stephen J. Hudak ◽

Guadalupe B. Robledo ◽

Jeffrey Hawk

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Corrosion Fatigue ◽

Cathodic Protection ◽

High Strength Steels ◽

High Strength ◽

Fatigue Performance ◽

Material Strength ◽

Loading Frequency

Although new high-strength steels have recently been developed to meet the demands of increased reservoir pressures, and sour production fluids, the corrosion-fatigue performance of these new higher-strength materials is largely unknown. The goal of this study was to fill this knowledge gap by generating corrosion-fatigue data in two aggressive environments: 1) a sour production brine, and 2) seawater with cathodic protection. The focus of the current paper is on stress-life (S-N) corrosion-fatigue results in these environments, as well as a baseline air environment. Experiments were performed on five different steels with yield strengths ranging from 848 MPa to 1080 MPa. Prior frequency-scan results based on corrosion-fatigue crack growth rate data demonstrated that not all of these material-environment combinations exhibit a saturation frequency where the detrimental environmental effect approached a constant value as the cyclic loading frequency is decreased. Consequently, S-N tests were performed at different frequencies (0.01 Hz, 0.17 Hz, and 1 Hz), depending on the fatigue life regime, in attempting to match the loading frequencies experienced in service. Corrosion-fatigue occurred at stresses well below the fatigue endurance limit in laboratory air, and cyclic lives in the seawater with cathodic protection environment were found to be 2X to 10X less than those in the baseline air environment, while cyclic lives in the sour brine environment were found to be 30X to 100X less than those in the baseline air environment. In both environments, degradation was greatest at lower stresses in the high cycle fatigue regime. The effect of material strength level had little or no measurable effect on the S-N corrosion-fatigue performance, and the effect of cyclic frequency on the corrosion-fatigue performance was mixed. The S-N response to these two variables differed significantly from recently measured fatigue crack growth kinetics in these same materials that were performed in a companion study. Possible reasons for these differences are discussed.

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Damage Characterisation for Cement and Concrete Using Microwave Induced Damage

Proceedings ◽

10.3390/icem18-05418 ◽

2018 ◽

Vol 2 (8) ◽

pp. 525 ◽

Cited By ~ 1

Author(s):

Gareth R. Tear ◽

Amitay H. Cohen ◽

Danyal Magnus ◽

David R. Sory ◽

William G. Proud

Keyword(s):

High Strain Rate ◽

Granular Flow ◽

High Strain ◽

Ballistic Impact ◽

Material Strength ◽

Material Failure ◽

Complex Behavior ◽

Local Material ◽

Impact Experiments ◽

Numerical Approaches

Damage leading to failure in concrete and related materials is a complex behavior. Whilst many numerical approaches are available for simulating the degradation of material strength, it is difficult to discriminate between these models experimentally in the high strain rate ballistic impact regime. An experimental method has been developed to determine when local material failure has occurred, and whether the failure can be classed as fracture or granular flow. This method is tested on Kolsky bar and ballistic impact experiments. Comparison with numerical simulations is presented.

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