Generally, when a cone is directly put under axial loading as an energy absorber, a rather big peak load is observed in the linear behavior of the load-displacement curve that is considered harmful. To decrease this initial peak load, one can use some kind of initiator. This paper deals with experimental axial quasi static loading tests on the effect of stepped initiators in thin walled steel end capped conical tubes. The initiator used in this paper is in fact a solid bar with an adjustable length that applies axial loading vertically on the closed surface of the cone. In order to decrease the stiffness of initiators two to four holes with specific layouts are extruded through the end-capped part of cones. First, the initiator functions to decrease the initial stiffness. Then, a solid plate applies loading on the cone to develop the desired deformation of the cone served as energy absorption. In addition, some parameters such as the energy absorption E, specific energy absorption, SEA, and crush force efficiency, CFE have been considered to illuminate the efficiency of the initiators and constraint forces in this crash absorbers.

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