Surface Cracks: Size and Failure Prediction Using Long Wavelength Measurements

Long Wavelength Measurements of Surface Cracks in Silicon Nitride

Review of Progress in Quantitative Nondestructive Evaluation ◽

10.1007/978-1-4684-4262-5_72 ◽

1982 ◽

pp. 569-571 ◽

Cited By ~ 2

Author(s):

J. J. Tien ◽

B. T. Khuri-Yakub ◽

G. S. Kino ◽

A. G. Evans ◽

D. Marshall

Keyword(s):

Silicon Nitride ◽

Surface Cracks ◽

Long Wavelength

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Long Wavelength Measurement of Surface Cracks in Silicon Nitride

10.1109/ultsym.1981.197743 ◽

1981 ◽

Author(s):

J.J. Tien ◽

K. Liang ◽

B.T. Khuri-Yakub ◽

G.S. Kino ◽

D. Marshall ◽

...

Keyword(s):

Silicon Nitride ◽

Surface Cracks ◽

Long Wavelength ◽

Wavelength Measurement

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Review and Proposed Improvement of a Failure Model for SCC of Pipelines

Volume 1: Risk Assessment and Management; Emerging Issues and Innovative Projects; Operations and Maintenance; Corrosion and Integrity Management ◽

10.1115/ipc1998-2051 ◽

1998 ◽

Cited By ~ 2

Author(s):

Carl E. Jaske ◽

John A. Beavers

Keyword(s):

Fracture Toughness ◽

Prediction Models ◽

Failure Prediction ◽

The Body ◽

Material Behavior ◽

Surface Cracks ◽

Crack Interaction ◽

Failure Model ◽

Flow Strength ◽

Inelastic Material

Oil and gas pipelines are subject to stress corrosion cracking (SCC) in groundwater environments. Recent SCC failures have emphasized the need for accurate failure prediction models that can be used to assess the integrity and safety of existing pipelines. SCC is characterized by colonies of many longitudinal surface cracks in the body of the pipeline that link up to form long shallow flaws, with length-to-depth (L/d) ratios that are typically in the range of 50 to 200. Such flaws are particularly challenging for standard failure prediction models. Because inelastic material behavior is usually associated with SCC failures of pipelines, the authors previously developed a failure prediction model that utilizes both flow strength and J fracture toughness to evaluate the failure of pipelines with crack-like flaws. Failure is predicted to occur either when the applied J value is equal to the J fracture toughness or the net-section stress is equal to the flow strength. To improve the failure model, recent work has concentrated on long, deep surface cracks. Multiple surface cracks and their possible interaction also have been considered. Interactions are modeled for both flow strength and J fracture toughness failure criteria. Methods for evaluating crack interaction are proposed, and examples of crack-interaction predictions are presented. Also, existing methods for evaluating ductile tearing instability, as well as crack initiation toughness, are described. It is proposed that these methods will improve the failure model.

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Activated Prominences; Mechanisms for Activation and Eruption

International Astronomical Union Colloquium ◽

10.1017/s0252921100065714 ◽

1979 ◽

Vol 44 ◽

pp. 307-313

Author(s):

D.S. Spicer

Keyword(s):

Pressure Gradient ◽

Density Gradient ◽

Current Density ◽

Convective Instability ◽

Tearing Mode ◽

Magnetic Shear ◽

Long Wavelength ◽

Ideal Mhd ◽

Gradient Change ◽

Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

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