Eksenel darbe yükü uygulanan içiçe tüplerin çarpışma ve ezilme davranışının sayısal ve deneysel olarak incelenmesi

The crush and crashworthiness of a vehicle (airplane, automotive, ship, etc.) is today of great importance. Strict standards need to be adhered to in the industry, in particular to protect human life. In the aim for better performance, the design of vehicles has also evolved to improve protection capabilities. In order to decrease design times and ensure safe design standards regarding the crush and crashworthiness of vehicles, and their components, virtual tests are usually performed in numerical simulations. The virtual crush and crash test data are used throughout the entire development of a new design. These numerical simulations produce results without building a physical model, and can be performed relatively quickly and inexpensively. This permits optimization of the design before an actual prototype of the vehicle has to be built. The most important phenomenon in a crush or crash situation is to absorb the kinetic energy. Crash tubes are designed for that purpose and are used in many practical situations. They have the ability to absorb and convert large amounts of kinetic energy into plastic strain energy under severe loading conditions. Therefore, there has been continued interest on the axial crushing and crashing behavior of tubes. When a tube fails under progressive buckling, the initial peak force is much greater than the subsequent peak. In many instances, these tubes are used to absorb energy in cars and the high force peaks lead to high acceleration on the vehicle occupants during an accident/impact event. An ideal energy-absorbing device should therefore cause a uniform deceleration during the entire stroke. This ideal structure would absorb the shock first and then deform under progressive buckling to absorb the energy. Thus we considered a new geometric crash tube model which would be nested with different lengths. The longest tube would absorb the kinetic energy first, and they could act together with the other tube(s) after strong impact effect. This new tube would be lighter than bi tubular crash tubes and alignment of the tubes, geometric parameters would be important. Thus, we planned to investigate this event by experimentally and numerically, which was never investigated in te open literature before. First of all, material tensile tests at elevated strain rates were carried out. For a constant thickness, different (cross-section, length, constant, etc.) specimens were produced. After producing specimens, some of them will be chosen for the experiment, and new specimens for experiments were produced. The tubes were be quasi-statically and dynamically crushed. The explicit non-linear finite element code (LS-DYNA, Abaqus were used to predict the response of the crash tubes subjected to axial crushing, and will be compared with experiments. The energy absorption capacity of a sheet metal structure depends on geometric and material parameters. Thus, it was investigated a different crash tube geometry which consist of nested tubes with different lengths. Important parameters such as arrangement, material, sheet thickness, flange width, spot-weld spacing and impact velocity will be optimized. There were no studies for these kind of crash tubes in the literature. So, it would be interesting to observe final deformations and energy absorption characteristics of these kind of nested crash tubes. Optimum nested crash tubes were realized by numerical studies. These results were compared and validated by experiments.