Abstract: An extrusion damper for interposing between two members to absorb energy of motion which may be induced between the two comprises an outer jacket (1) surrounding a body of plastically deformable energy absorbing material (3) such as lead and a shaft (2) which moves through the outer jacket to deform the lead during induced motion. The body of lead may be fixed relative to the outer jacket and the shaft has a portion of reduced diameter (2a) which moves through the lead. Alternatively the body of lead may be fixed to the shaft and the outer jacket has a portion of enlarged diameter (21a) through which the energy absorber passes. The body of energy absorbing material may optionally be subjected to approximately hydrostatic pressure preferably exceeding the shear yield stress of the energy absorbing material.

Abstract: An energy absorber for interposing between two members to absorb energy of motion which may be induced between the two members includes a core (3) of a plastically deformable energy absorbing material such as lead and structure surrounding the core such as layers of steel plates (2) and rubber (1) in a sandwich-like arrangement structure. The end plates (4) are formed with holes (5), into which the ends of the core (3) project. During construction, the support structure (1, 2) is stretched, allowing end caps (6) to be fitted. The support structure (1, 2) is then relaxed, which applies approximately hydrostatic pressure to the core (3). Induced motion is transferred as shear forces across the core (3). The hydrostatic pressure applied to the core (3) preferably exceeds the shear yield stress of the energy absorbing material of the core (3).