Investigation On Buckling Of Cylindrical Shells And Influence Of Filling Media

Thin-walled cylindrical shells are widely used in many industrial sectors as light structural elements. Determination of their buckling strength under various types of load is a crucial work for engineering design. Due to the needs of research in crashworthiness, dynamic buckling of cylindrical shells subjected to the strong axial impact becomes a frontier issue in recent years. The axial impact is a very complex dynamic process on account of the coupling of multiple effects. In this paper, the buckling mechanism of cylindrical shells subjected to axial impact and the influences of boundary conditions, filling media on the buckling mode and energy absorption properties have been investigated by experiments and numerical simulation. Major work and results are as follows:1. Experimental research of the dynamic buckling of a lot of specimens made of steel has been completed by the Drop Hammer Rig-9401. The concertina mode and the triangle diamond mode are observed, and another phenomenon is that symmetric mode transfers into asymmetric mode after one or more fold finished. Force-time curves of the reflective ends and impact ends has been recorded, the duration of the impact process is between 10ms and 25ms, the average impact force is about 30KN ~ 60KN. The oscillation frequency of force-time curves is in consistency with the number of folds of residual mode.2. Influences of boundary conditions on the buckling mode have been examined specially in this experiment, most of cylindrical shells whose"both ends are free"have asymmetric mode, all cylindrical shells whose both ends are simply supported have symmetric mode, cylindrical shells that one end is fixed and another is clamped tend to form asymmetric mode. Hence the buckling mode concerned may be induced by changing the boundary conditions3. Buckling characteristics of fluid-filled cylindrical shells subjected to axial impact are investigated by experiment. Buckling mode is all symmetric ring -waves owing to the incompressibility of liquid. The buckling process lasts about 5ms ~ 13ms and the duration increases with the increases of impact energy. This process can be divided into three stages obviously, the loading stage oscillates intensively, the plastic post-buckling stage develops steadily and the elastic unloading stage declines rapidly.4. The simulations of buckling of hallow cylindrical shells and fluid-filled cylindrical shells subjected to axial impact are accomplished by LS-DYNA. Force-time curves, buckling mode and the number of folds obtained from simulation are basically in consistency with experimental results. Simulation results of liquid-filled cylindrical shells show that liquid almost undertake the axial pressure in the process of post-buckling.