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In this paper, the dynamic plastic buckling of axisymmetric circular cylindrical shells subjected to axial impact is investigated. The von Mises yield criterion is used for the elastic-plastic cylindrical shell made of linear strain hardening material in order to derive the constitutive relations between stress and strain increments. Nonlinear dynamic circular cylindrical shell equations are solved with the finite difference method for three types of boundary conditions and two types loading. Two types of loading are stationary cylindrical shells impacted axially and traveling cylindrical shells impacted on a rigid wall. The growth and improvement of axial and lateral strains and buckling shapes of cylindrical shells are investigated for different boundary and loading conditions, from the viewpoint of stress wave propagation. It is found that the total length of cylindrical shell is affected by the plastic deformation when the plastic wave reaches unimpacted end. Also it is found that shortening and energy absorption are independent of loading and boundary conditions. The buckling shapes are affected by loading and boundary conditions; also peak loads at impacted and unimpacted ends are affected by loading conditions and are independent of boundary conditions. The presented theoretical results are compared with some experimental results and good agreement is obtained.

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In this paper, the internal inversion process of metallic cylindrical shells under dynamic axial loading is investigated experimentally and numerically. Experimental tests are performed on the steel tubes in a gas gun and the required force for internal inversion is obtained using the measurement system of impact loadings. Also, numerical analysis is carried out by the finite element software ABAQUS and the accuracy of simulated models are validated with the experimental results. In this paper, all geometrical properties of the tubes and die are assumed to be constant and the effect of the projectile mass and velocity is investigated on the shortening and energy absorption of the tubes which are affected by axial impact in the internal inversion process. Therefore the projectile is shot directly to the specimen with different masses and velocities. It is observed that if the projectile mass remains constant, increasing in the impact velocity has almost no effect on the constant inversion load and just increase the tube displacement but if the impact velocity remains constant, increasing the amount of projectile mass causes increasing in the constant inversion load besides of increasing in tube displacement. Comparing the results of numerical simulations with the experimental results shows a good agreement between them.

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In this paper, the behavior of cylindrical shells with uniform thickness and functionally graded thickness distributions subjected to axial quasi-static loading is investigated experimentally and subjected to axial impact is investigated experimentally and numerically. Steel cylindrical shells with uniform thickness and functionally graded thickness distributions have same inner diameter, length and weight. Cylindrical shells are impacted by the drop hammer apparatus and experimental axial force-time curves are obtained by using a load cell; in addition, impact simulations are done by Abaqus finite element software. The effect of thickness distributions on the shortening, energy absorption, buckling shape and axial force-time curve of cylindrical shells is investigated. It is found that for axial quasi-static loading, a change in thickness distribution of cylindrical shell is able to convert the buckling shape from mixed buckling (a combination of axisymmetric and diamond modes) to progressive buckling, also for axial impact loading, a change in thickness distribution of cylindrical shell can affect the number of complete folds. The studies also suggest that at same impact energy, functionally graded thickness distribution cylindrical shell compared with uniform thickness distribution cylindrical shell absorbs approximately the same energy with more shortening and transforms less mean load and peak load to under protected specimen, thus, functionally graded thickness distribution cylindrical shell is a better energy absorption specimen. It is found that there is a good agreement between the experimental and numerical results.