J. Escuadra

Influence of Residual Stress Field on the Fatigue Crack Propagation in Prestressing Steel Wires

This paper deals with the effect of several residual stress profiles on the fatigue crack propagation in prestressing steel wires subjected to tension loading or bending moment. To this end, a computer program was developed to evaluate the crack front evolution on the basis of the Walker law. Results demonstrate that the absence of residual stresses makes the crack propagate towards a preferential crack path. When surface residual stresses are tensile and, correspondingly, core residual stresses are compressive, the fatigue crack fronts rapidly converge towards a quasi-straight shape. When surface residual stresses are compressive, with their corresponding tensile stresses in the core area, a preferential crack path also appears.

Evolution of crack paths and compliance in round bars under cyclic tension and bending

The aim of this paper is to calculate how the surface crack front and the dimensionless compliance evolve in cracked cylindrical bars subjected to cyclic tension or bending with different initial crack geometries (crack depths and aspect ratios). To this end, a computer application (in the Java programming language) that calculates the crack front’s geometric evolution and the dimensionless compliance was made by discretizing the crack front (characterized with elliptical shape) and assuming that every point advances perpendicularly to the crack front according to the Paris law, and using a three-parameter stress intensity factor (SIF). The results show that in fatigue crack propagation, relative crack depth influences more on dimensionless compliance than the aspect ratio, because the crack front tends to converge when the crack propagates from different initial geometries, showing greater values for tension than for bending. Furthermore, during fatigue crack growth, materials with higher values of the exponent of the Paris law produce slightly greater dimensionless compliance and a better convergence between the results for straight-fronted and circular initial cracks.

ENVIRONMENTALLY-ASSISTED FATIGUE CRACK GROWTH IN PRESTRESSING STEEL WIRES

We present the evolution of the surface crack front in prestressing reinforced-concrete steel wires subjected to fatigue in air and to corrosion fatigue in Ca(OH)2 + NaCl. To this end, a numerical modeling was performed on the basis of discretization of the crack front (with elliptic shape) by considering that the crack advance at each point is perpendicular to the analyzed front according to the Paris–Erdogan law and using a three-parameter solution for the stress intensity factor (SIF). Each analyzed case (a particular geometry of the initial crack) was characterized by the evolution of the aspect ratio of the semielliptic crack (ratio of the semiaxes of the ellipse) with the relative crack depth and by the variations of the maximum dimensionless SIF at the crack front.

Evolution of Crack Aspect Ratio in Sheets Under Tension and Bending Cyclic Loading

The aim of this paper is the numerical prediction of the cracking path followed by a surface crack front in plates constituted of different materials (determined by the exponent m of the Paris law), subjected to cyclic tension or cyclic bending loading. To this end, a numerical modelling was developed on the basis of a discretization of the crack front (characterized with elliptical shape) and the crack advance at each point perpendicular to such a front, according to a Paris law, using the stress intensity factor (SIF) calculated by Newman and Raju. Results show that the crack leads to a preferential crack path that corresponds to a very shallow initial crack with a quasi-circular crack front. The increase of the Paris exponent produces a quicker convergence during fatigue crack propagation from the different initial crack shapes.

Corrosion-Fatigue of High Strength Steel Bars: Evolution of Crack Aspect Ratio

Abstract. This paper shows the evolution of the surface crack front in prestressing steel wires subjected to fatigue in air and to corrosion-fatigue in Ca(OH)2+NaCl. To this end, a numerical modelling was made on the basis of a discretization of the crack front (characterized with elliptical shape), considering that the crack advance at each point is perpendicular to such a front according to a Paris-Erdogan law, and using a three-parameter stress intensity factor (SIF). Each analyzed case (a particular initial crack geometry) was characterized by the evolution of the semielliptical crack aspect ratio (relation between the semiaxes of the ellipse) with the relative crack depth and by the variation of the maximum dimensionless SIF at the crack front