| 摘要 |
The method is used for cold widening of holes in structural elements of tough plastic metals subsequently subjected to cyclic external action. It helps create a virtually uniform in the axial direction zone of compressive residual stresses around the worked holes, respectively the cyclically loaded structural elements worked by the method will have a longer fatigue durability. The method consists of plastic deformation of the hole under the action of axial pressing force applied to a tool with a solid work surface, whose symmetry axis coincides with the axis of the worked hole, while between the tool and the hole there is located without any clearance a thin-walled cylindrical sleeve, the lower part of which is cut along the axis into four or more parts, while its uncut top part is rigidly fixed at the side of entry of the tool. In its cut lower part, which is in contact with the working part of the tool, the hole is conical and widening in the direction of the uncut part, with a coneangle equal to the angle of the conical working surface of the tool. In order to achieve uniform radial displacement of all points of the surface of the pre-drilled hole, the outer surfaces of the working parts of the cut sleeve are conical with a small cone angle and have a rounding radius greater than the radius of the pre-drilled hole. Compressive residual stresses are formed after the tool returns to its original position around the cold expanded hole.
|
