چكيده به لاتين
Abstract:
This dissertation studies energy absorption of circular thin wall structures under axial impact load with rupture path orientation, analytically, numerically and experimentally. The aim is to rupture thin-walled aluminum tube simultaneously in some points during the impact load application in a controlled manner and to bend the provided petals by the deviator for more energy absorption during rupture. To do so, analytical solution of the cutting process is done at first by considering the new energy loss rates including bending of the provided petals outwards and creation of swarfs at the tool’s head and correcting previous energy loss rates by calculating cutting process sensitivity to the strain rate. Then, numerical modeling is done using ABAQUS software based on the Hooputra’s criterion. Different geometries of tube including length, diameter and thickness, and the cutting tool including number of blades, depth, thickness and cross section form of the cutting edge and different impact speeds are studies and compared. The results show that the tube’s length and diameter have less effect on the rupture process than the crushing; the force increases with increase of the tube thickness, number of blades, depth and thickness of the cutting tool. Then, a specific multi-blade cutting tool with a deviator is designed and made by using analytical and numerical results. The impact test device is prepared and equipped then and the experiments were performed to gather required data. The obtained results of numerical and analytical solutions are compared with experimental results and have proper conformity; the numerical model and the analytical equation were validated in this way. Cutting and crushing modes were compared with each other and effective parameters on energy absorption like mean and maximum axial force, specific energy absorption and the force efficiency were studied. The results show that the rupture process is predictable, controllable, repeatable, stable and continuous. Less maximum force, less sensitivity to the strain rate, higher force efficiency and force variations with less range are other specifications of the rupture with the cutting tool in comparison to the crushing between two flat plates. Moreover, a designer can easily improve the energy absorption behavior and the mean force level and can change the maximum value and form of displacement during impact by changing the tool’s geometry including number of blades, edges’ thickness, form of the cutting edges and the deviator radius.
Keywords: Impact; Energy absorption; Circular thin wall structure; Rupture; Multi-blade cutting tool
