Topic
Crack closure
About: Crack closure is a research topic. Over the lifetime, 28157 publications have been published within this topic receiving 588158 citations.
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TL;DR: In this article, the authors examined the fracture history of the Griffith theory of brittle fracture and showed that fracture initiation depended greatly on the size of the crack, particularly at smaller sizes, and that the development of the large-scale, through-going shear zone is preceded by a long history of fracture development.
162 citations
01 May 1973
TL;DR: In this article, microhardness measurements were used to determine the plane strain plastic zone sizes as a function of ΔK and to evaluate the cyclic flow stress of the material near the crack tip.
Abstract: Fatigue crack growth rates were measured in an annealed and in an aged maraging steel and in three different austenitic steels Microhardness measurements were used to determine the plane strain plastic zone sizes as a function of ΔK and to evaluate the cyclic flow stress of the material near the crack tip The presence of a reversed cyclic plastic zone within the monotonic plastic zone was confirmed The two maraging steels work soften near the tip of the crack while the three austenitic steels work harden The fatigue crack growth rates of the maraging steels are independent of the monotonic yield stress and are typical of the growth rates of steels with a bcc crystal structure The crack growth rates in the stainless steels are an order of magnitude lower than for maraging steels for ΔK< 30 ksi √in The excellent fatigue crack growth resistance of austenitic stainless steels is related to the de-formation induced phase transformations taking place in the plastic zone and to the low stacking fault energy of the alloys
162 citations
TL;DR: In this article, a 3D computational framework is proposed to model stable extension of a macroscopic crack under mode I conditions in ductile metals, where fixed-size, computational cell elements defined over a thin layer at the crack plane provide an explicit length scale for the continuum damage process.
Abstract: This study describes a 3-D computational framework to model stable extension of a macroscopic crack under mode I conditions in ductile metals. The Gurson-Tvergaard dilatant plasticity model for voided materials describes the degradation of material stress capacity. Fixed-size, computational cell elements defined over a thin layer at the crack plane provide an explicit length scale for the continuum damage process. Outside this layer, the material remains undamaged by void growth, consistent with metallurgical observations. An element vanish procedure removes highly voided cells from further consideration in the analysis, thereby creating new tractionfree surfaces which extend the macroscopic crack. The key micro-mechanics parameters are D, the thickness of the computational cell layer, and f 0 , the initial cell porosity. Calibration of these parameters proceeds through analyses of ductile tearing to match R-curves obtained from testing of deep-notch, through-crack bend specimens. The resulting computational model, coupled with refined 3-D meshes, enables the detailed study of non-uniform growth along the crack front and predictions of specimen size, geometry and loading mode effects on tearing resistance, here described by J-Δa curves. Computational and experimental studies are described for shallow and deep-notch SE(B) specimens having side grooves and for a conventional C(T) specimen without side grooves. The computational models prove capable of predicting the measured R-curves, post-test measured crack profiles, and measured load-displacement records.
162 citations
TL;DR: In this article, it was shown that the second, third and fourth terms of the stress distribution at the tip of a crack can be expanded as a power series, and the third term determines whether the maximum shear stress on the prolongation of the crack increases or decreases with distance from the crack tip.
Abstract: The stress distribution at the tip of a crack can be expanded as a power series The first term, usually called the stress intensity factor, determines the initiation of fracture in a brittle material In this paper it is shown that the second, third and fourth terms have the following effects:
(a)
the second term controls the stability of the crack's direction,
(b)
the third term controls the stability of the crack's propagation,
(c)
the fourth term determines whether the maximum shear stress on the prolongation of the crack increases or decreases with distance from the crack tip
162 citations
TL;DR: In this paper, the authors quantify the water permeability of localized cracks as a function of crack geometry (i.e., width, tortuosity, and surface roughness).
161 citations