SU1516287A1 - Method of preparing composite panel - Google Patents

Abstract

The invention relates to the repair of, in particular, prefabricated panels with a fatigue crack and can be used in various fields of engineering and aircraft construction. The purpose of the invention is to increase the fatigue life and processability of the compound. In the area of the crack in the precast panel, an overlay is attached. Holes are made at the tips of the cracks. Fasteners are installed in them with tension across the entire thickness of the precast panel. In places of holes previously made in the panel, fasteners for the repair lining are set offset in the direction of the main tensile stresses. This results in a decrease in stress concentration at the crack tips. 3 hp f-ly, 5 ill.

Description

The invention relates to mechanical engineering, in particular to aircraft manufacturing, and can be used in the repair of a damaged fatigue crack panel.

The aim of the invention is to increase the durability and processability of the compound.

FIG. 1 shows a precast panel with an overlay; on league. 2 shows section A-A in FIG. one; in fig. 3 shows a section BB in FIG. one; in fig. 4 shows a section B-B in FIG. one; in fig. 5 is a view I in FIG. one.

In order to connect repair lining 1 and a damaged fatigue crack 2, panel 3 uses several rows of fasteners 4. At vertices 2, holes are made in the entire thickness of the pack of parts to be joined and fasteners 5 are installed in them. In the joint area of the skin with stringers 6, repair fasteners elements 4 are installed in holes whose axes are arranged with offset L relative to the axis of the rivets 7 of the panels in the direction of action of the main tensile stresses &. In this case, the straight line drawn through the center of the repair fastener 4 and the center of the rivet 7 of the panels is with the direction of action of the main tensile stresses on the panel угол an angle of 0-45.

By installing fasteners at the top of the tray across the entire thickness

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a package of connected parts with a repair lining achieves a decrease in stress concentration at the tip of the traction, a decrease in the stress intensity factor at the crack tip in panels, a decrease in the magnitude or amplitude of cyclic tensile stress at the crack tip, a decrease in stress intensity at the crack tip .

The location of the hole for the repair rivet with an offset from the hole for the rivet installed during the initial assembly helps to reduce the stress concentration ratio of the tensile plate with two circular holes compared to the concentration ratio of the expandable plate with a circular hole.

In addition, when setting repair rivets with offset, the rivets installed during the initial assembly are pressed in and the radial delivery of their rods increases, which increases the radial tension and increases its uniformity along the height of the package of connected parts.

When mounting the fastening elements of the outermost on the repair lining of rows with a gap in the lining and with a tension in the panel, the separation of stress concentration zones and fretti-g corrosion on the mating surfaces, the separation of the zones of action of the maximum stress concentration from the load transmitted by the fastener , and bending from one to different sections of the parts to be joined, reducing the bending stresses in the zones of extreme rows.

In conjunction with fasteners installed in the zone of extreme rows on the repair pad with a gap in the pad and with a tension in the damaged fatigue crack panel, along with a decrease in bending stresses in the zone of openings of the extreme rows, the stress concentration transmitted by the fasteners elements are also reduced. In the zone of the extreme rows of fasteners, a hole filled with a fastener unloaded on the cut is realized, the long duration of which is always loaded.

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The use of the proposed method contributes to an increase in the fatigue life of the joint of the panel damaged by the fatigue crack and the repair lining, if the repair fasteners are rationally set at least 2 times.

Claims (4)

1. A method of repairing a precast panel damaged by a fatigue crack, in which a repair pad is placed on a panel in the area of the crack, is connected to the panel by means of fasteners that are arranged in several rows, and holes are made in the tops of the crack, characterized in that , in order to increase fatigue life and the processability of the joint, fasteners with a tension across the entire thickness of the package of parts to be connected are installed in the holes formed in the cracks of the vertexes, and at the locations of the holes previously made in the assembly panel, the fasteners that connect the repair strip with the panel are installed with by displacing their axes relative to the axes of the holes in the panel in the direction of action of the main tensile stress. 2. A method according to claim 1, characterized in that the offset value is chosen to be greater than or equal to the radius of the rods of the fastening elements of the assembly panel and less than or equal to the radius of their embedded heads when using repair fastening elements of the same diameter and equal to the radius of the embedded heads when using repair fasteners of a larger diameter than the diameter of the fasteners of the precast panel. 3. Method pop. 1, characterized in that the axes of the repair fasteners are arranged on direct, passing through the axes of the fasteners of the assembly panel, which form with the direction of action of the main tensile stresses in the panel an angle a (equal to 0-45. 4. A method according to claim 1, characterized in that the outermost rows of fasteners are installed with a gap in the cover plate and with a tension in the panel. MAM-LJ-Ujj X / CST and f 4. 4 A a Fig.Z at In In