Simple detection method for crack growth rate of cold-drawing high-strength steel wires

Abstract

The invention discloses a simple detection method for the crack growth rate of cold-drawing high-strength steel wires, and relates to the field of bridge material detection. The detection method is combined with the relevant fracture mechanics theory for evaluating the residual service lives of cable ropes for bridges and prestress steel wires. The simple detection method for the crack growth rate of the cold-drawing high-strength steel wires is characterized by comprising the following steps: implementing fatigue loading on precracked cold-drawing high-strength steel wire test specimens until the steel wires are fractured, then measuring stripes formed by the fatigue loading on a fracture surface, drawing a crack growth rate-stress intensity factor range curve on a bilogarithmic diagram, and fitting a calculated curve by adopting a least square method, thereby obtaining Paris formula curve fitting parameters C and m of the cold-drawing high-strength steel wires, and calculating the crack growth rate of the cold drawing high-strength steel wires under any given crack length a and stress amplitude delta Sigma according to a Paris formula. The detection method provided by the invention is used for providing the technical support for the fatigue service life of the cold drawing high-strength steel wires.

Description

technical field [0001] The invention relates to the detection field of bridge materials. The detection method can be used to evaluate the remaining life of bridge cables and prestressed steel wires by combining the relevant fracture mechanics theory. Background technique [0002] Cold-drawn high-strength steel wire is a high-strength steel developed in the early 20th century. This material achieves the purpose of further improving the strength of the material by performing multiple cold drawing processes on high-strength hot-rolled steel rods. At present, the commonly used specifications of cold-drawn high-strength steel wire for bridges are ￠5mm and ￠7mm. [0003] This material is characterized by high strength, which is 3 to 5 times the strength of conventional bridge structural steel. However, since this material is obtained through multiple cold drawing, the arrangement direction of the pearlite crystals that make up the material changes during the cold drawing process...

AI Technical Summary

Problems solved by technology

However, this method is not suitable for the crack growth measurement of cold-drawn high-strength steel wire. The main limiting factors include: the material specification of cold-drawn high-strength steel wire is too small to be processed into the specimens required by the specification; the material specification of cold-drawn high-strength steel wire It is too small to install conventional sensor equipment, and if a special sensor is specially made, the test cost will be greatly increased; the side of the cold-drawn high-strength steel wire is a circular surface, and the line formed by connecting all points at the front edge of the crack when the crack propagates in the steel wire is also a curve , the crack front cannot be observed with optical equipment, and the crack length cannot be measured

[0009] Another way to determine the crack growth rate of cold-drawn high-strength steel wire is to directly use undrawn hot-rolled steel rods as substitutes to test the crack growth rate, but because the crystal arrangement of cold-drawn high-strength steel wires changes during cold drawing, Transformation of isotropic material into approximately anisotropic material, it is impossible to judge whether the crack growth rate of the alternative material can represent the crack growth rate of cold drawn high strength steel wire

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