SU1532265A1 - Method of retarding the growth of fatigue cracks - Google Patents

Abstract

The invention relates to repair work, in particular to the restoration of the performance of sheet materials with fatigue cracks. The purpose of the invention is to improve the braking of a branched crack. The method of inhibiting the growth of fatigue cracks in flat parts includes making holes in the zone of crack tops and grooves that intersect these holes and are made on opposite sides of the plane of the main crack, of which each is in contact with the main crack tip and opposite in direction. The grooves lie on opposite sides of the main crack and are interconnected by an open-loop curve that captures the tips of the crack. Then heated wires are pressed into the grooves and holes. The cross-sectional area of the wire S _{pr is} chosen from the following relationship: S _pr = (1 - 1.2) S _can , where S _can is the area of the groove section. As a result, compressive stresses are created in the crack zone, which enhances the effect of crack inhibition. 5 il.

Description

The invention relates to the repair work, in particular to the restoration of the performance of sheet materials with fatigue cracks.

The aim of the invention is to increase the braking efficiency of a branched crack.

FIG. 1 shows a flow chart of the method; in fig. 2 is a section A-A in FIG. 1 in the process of pressing the wire :, in FIG. 3 is a section BB in FIG. 1 :, in FIG. 4 is a section A-A in FIG. 1 after pressing the wire; ifa FIG. 5 is a section b-B in FIG. one.

A method for inhibiting the growth of fatigue cracks 1 with lateral branches 2 in flat parts 3 involves making holes 4 in the zone of the tips of the crack 1 and groove 5. intersecting these holes and formed on opposite sides of the plane of the main RF crack 1, each of which is associated with the main top of the crack and opposite in direction.

At the same time, in order to increase the effectiveness of braking the growth of branched cracks on both sides of the part, additional grooves 6 are joined, which are conjugated to the base and form

oo to

1HE

05

ate

The two branches lying on opposite sides of the main crack 1 and interconnected through a through hole 7, together with the main grooves form a closed curve that encloses a broken line that connects 8 centers of the radii of the main grooves and the tops of 9 branches of the crack, followed by pressing into the holes and additional grooves of the heated wire 10, while the cross-sectional area of the wire is in the following relation with the area of the regular cross-section of the groove

§LE. 2

from 11 ,,

The depth of the groove b is 0.2-0.3 of the thickness of the part H is optimal from the point of view of creating the necessary compressive stresses when pressing the wire into it and from the point of view of maintaining the required strength of the part.

When the depth G of the groove is less than 0.2 of the thickness H of the part, it is impossible to create the necessary compressive (compressive) stresses on the surface when the wire is pressed. When the depth of the groove is more than 0.3 of the thickness of the part H, the execution of the grooves can lead to a significant weakening of the cross section and an increase in the rate of crack development along the bottom of the groove.

It is the placement of the additional grooves and the pressed-in wire in them, as well as the ratio of the sizes and areas of the groove sections and the wire ensure, according to the method, the braking efficiency is branched.

no crack and thereby achieving

objectives of the invention.

Example. As a sample

For testing, a sample of a sheet of steel 20 with a size

A 100x100x10.8 miter was made of a kerf simulating a main crack and side cuts simulating the side branches of the main crack. The grooves and holes are made as shown in FIG. 1. The width of the grooves

3, and the depth of the grooves is 2.6 mm.

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In additional grooves were pressed steel wire with a diameter of f2 mm, preheated by a gas torch.

, Laboratory tests have shown that in samples after loads, tensile forces of 1000–1500 kN for 180–220 h owing to the effect of a compression wrap, no significant development of the main crack and its branches was observed.

Claims (1)

Invention Formula A method for inhibiting the growth of fatigue cracks in flat parts, including making holes in the zone of crack tops and grooves crossing these holes and made on opposite sides of the plane of the main crack, of which each is in contact with the main tip of the crack and opposite in the direction that that, in order to increase the braking effect of a branched crack, the grooves are joined into a closed curve that engages the tips of the crack branches, and then they are pressed into the grooves and holes This wire, wherein the cross-sectional area of the wire Spip is chosen from the following ratio 1-1.2, where is the area groove section. Figg TH / 3.5 I-8