By pushing lead back and forth through an orifice the process of extrusion can be used to absorb energy. When the lead is extruded it recrystallizes immediately, thereby regaining its original mechanical properties. Rather than the energy absorber being limited by the strength and work hardening of the lead it is limited by the heat capacity of the device and is therefore able to absorb energy during a number of earthquakes. To date extrusion energy absorbers of 20 kN x 2 cm stoke to 200 kN x 26 cm stroke have been tested at rates of 2 x 10-8 to 60 cm/sec and they behaved
as "coulomb dampers" with nearly rectangular hysteresis loops and little
rate dependence.