The quasi-static large, plastic deformation of a helical extension spring is analysed to determine its load-deflection characteristic and energy-absorbing capacity. These results along with elastic effects and other related factors are then discussed in relation to a vehicle arresting system. Formulae and diagrams for facilitating the design of such systems are given. Some experimental test results for the large plastic extension of some initially close coiled helical springs are presented and compared with the theoretical results.
