Crumpling

in strength of materials, a localized compressive stress, accompanied, as a rule, by permanent deformation (pressing down) of the material. Crumpling occurs in joints (bolted, riveted, key) in locations of structural supports, and in contact zones of compressed components.

The magnitude of crumpling stress in structures is usually kept below the allowable crumpling stress. This allowable stress is determined by the character of the surfaces in contact, the properties of the structural material, and the orientation of this material with respect to applied loads (for instance, with wood, parallel or perpendicular to the grain). Various design features aimed at reducing crumpling stresses and, more important, permanent deformation distribute the compressive stress over a large area with the aid of, for example, washers, liners, and pads. One of the most effective means for reducing deformation is the use of special inserts and fillers in the contact zones made of materials that are stronger than the structural material.