Investigation On The Dynamic Response Of Square Tube With Dents Subjected To Impact Loading

Thin-walled structures have been widely used for energy absorption in the fieldssuch as automotive, high-speed trains and aero space, due to the characteristics ofhigh strength, high stiffness, small relative density, good bearing capacity and goodenergy absorption capacity. Generally, thin-walled tubes absorb plenty of energy toprotect passengers and structures efficiently, through axial collapse and plasticdeformation. However, the disadvantages of extremely high initial crash force andpoor deformation stability during the axial collapse process are not expected.Introducing proper inducing structures is the main method to solve these problems.Meanwhile, all these points are related to deformation and dynamic impact load.Therefore, it is of scientific research significance and engineering application value toinvestigate the responses of thin-walled structures under dynamic axial load. In thisdissertation, thin-walled tubes with V-shape dents are the main research objects.Axial collapse experiments under dynamic and quasi-static loads are conducted, so dothe numerical simulations. The collapse mechanism of square tube with dents isstudied, while the characteristic quantities including deformation mode, crash forceand energy absorption capacity are analyzed.Firstly, quasi-static axial compress experiments and dynamic impact experimentsare conducted, while the dynamic ones are recorded by high-speed camera. Accordingto the results, the collapse modes of different situations are analyzed. The growingprocess of the first exterior fold is revealed in detail, and its effects on the collapsesequence are investigated.Next, numerical simulations of thin-walled square tubes are carried out, andcrash force curves and energy curves of different situations are plotted. By comparingthe numerical simulations and experiment processes, the finite element models arevalidated. Aiming at collapse mode, crash force curve and energy curves, the effectsof dents on the energy absorbing properties are analyzed, and the best dent position isobtained.Finally, based on experiments and numerical simulation, with impact velocity,wall thickness, dent depth and dent number as variables, more numerical calculationsare carried out. The results are as follows. The crash force and energy absorption increase with the velocity, and the dents could control the formation of folds to keepthe stability of collapse under different velocities. The specific energy absorptionincreases with the wall thickness. The initial force decreases with the dent depth. Forthe tubes with uniform distributing dents, with the number of dents, the initial forcedecreases and the stability of deformation is undermined.