experimental investigations on the softening and ratcheting behaviors of steel cylindrical shell under cyclic axial loading

in this research, softening and ratcheting behaviors of ck20 alloy steel cylindrical shells were studied under displacement-control and force-control cyclic axial loading and the behavior of hysteresis curves of specimens was also investigated. experimental tests were performed by a servo-hydraulic instron 8802 machine. the mechanical properties of specimens were determined according to astm e8 standard. under force-control loading with non-zero mean force, ratcheting behavior occurred on cylindrical shell and plastic strain accumulation continued up to the collapse point of cylindrical shell. the rate of ratcheting strain became higher using the higher force amplitude. softening behavior was observed under displacement control loading and, due to the occurred buckling in compression zone, this behavior became more extreme. the behavior of hysteresis curves of this alloy was not symmetrical under tensile and compressive loads. moreover, the influence of loading history was studied on the behavior of hysteresis curves of the specimens under various types of loadings.