A COMMENTARY ON THE ROLE OF NITROGEN IN ENHANCING SLOW CRACK GROWTH IN C–Mn STEEL

Östberg,

doi:10.1046/j.1460-2695.1998.00075.x

Cited by 3 publications

(3 citation statements)

References 21 publications

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“…Time‐dependent effects of environment include the phenomenon of dynamic strain ageing, 5 dynamic embrittlement, 6 hydrogen embrittlement 7 and nitrogen embrittlement 8 . According to diffusion theory, the mere presence of a gaseous environment around a solid promotes diffusion of the former into the latter.…”

Section: Environment Sensitivity Of Crack‐tip Surfacementioning

confidence: 99%

“…Intergranular diffusivity is much greater than transgranular diffusivity and is in fact referred to as ‘short‐circuit’ diffusion 9 . Most work on the subject considers the diffusion process to be time‐dependent, intergranular and as encompassing material depth of the order of at least a few grains 5–8 . Transgranular diffusion has also been studied, but under conditions that differ considerably from those associated with fatigue 10,11 .…”

Section: Environment Sensitivity Of Crack‐tip Surfacementioning

confidence: 99%

“…9 Most work on the subject considers the diffusion process to be timedependent, intergranular and as encompassing material depth of the order of at least a few grains. [5][6][7][8] Transgranular diffusion has also been studied, but under conditions that differ considerably from those associated with fatigue. 10,11 A central feature of all these studies is the recognition that gas-metal diffusion kinetics is driven by both gas pressure as well as near-surface hydrostatic stress on the side of the metal.…”

Section: E N V I R O N M E N T S E N S I T I V I T Y O F C R a C K -Tmentioning

confidence: 99%

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Fatigue as a process of cyclic brittle microfracture

Sunder¹

2005

Fatigue Fract Eng Mat Struct

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A B S T R A C T While fatigue crack growth in vacuum may occur by slip alone, environmental fatigue including crack growth in air is strongly influenced by crack-tip surface chemistry that adversely affects ductility. Cumulative diffusion, combined with adsorption and chemisorption in the loading half-cycle may promote instantaneous crack extension by brittle microfracture (BMF). Unlike slip, the BMF component will be sensitive to parameters that affect near-tip stresses, such as load history and constraint. BMF dominates near-threshold environmental fatigue. Being a surface phenomenon, it loses its significance with increasing growth rate, as slip-driven crack extension gains momentum and growth becomes less sensitive to environment. The BMF model provides for the first time, a scientific rationale for the residual stress effect as well as the related connection between stress-strain hysteresis and load-sequence sensitivity of metal fatigue including notch response. Experimental evidence obtained on a variety of materials under different loading conditions in air and vacuum appears to support the proposed model and its implications.

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