Study On Crashworthiness Improvement Of Thin-wall Low-carbon Stell Tube With Tailor-made Axial Gradient Intensity

With the development of modern automobile industry, people are paying moreattentions on the aspects of energy saving and structural safety. Application of thin-walled structure to design safety protection system will be so helpful to get lightweightand better energy absorption capacity at the same time. As one of the common kinds ofthin-walled structures, the thin-walled tube is widely used in the development of safetyprotection devices. However, most of the present researches about energy absorptioncapacity improvement with thin-wall tubes are concentrated on structure optimization,etc. This paper applied local induction heating and then entirely rapid cooling process toQ235thin-wall tube and got the tube with various microstructures in axial direction.Then, investigations about static compression deformation behaviors andcrashworthiness performance of these tubes and original ones were systematicallyimplemented with experiments and the finite elements analysis (ABQUS).Firstly, variable intensity process of the tube was completed by high speed districtinduction heating and entirety rapid cooling through quenching agent of10%NaClsolution. Microstructure analysis and hardness measurement were taken along the axisdirection to get the hardness distribution and range. Through the hardness measurement,it was found that the effect of heat preservation time rising (30s,60s) was not obviouson the width of heat affected zone.Quasi static simulation and dynamic simulation of original tube and variableintensity tube were taken to get the stress concentration location and the difference ofplastic deformation energy absorption and it showed that when impacted the tube alongaxial direction in same kinetic energy, the compression distance of variable intensitytubes was less than the original ones. Simulations showed that changing gradientintensity within a certain range can effectively improve energy absorption ability andreasonable strength distribution was benefit to orderly pile shrinkage of tube.Quasi static compression experiment of variable intensity tubes and original tubeswith the length of100mm,150mm and200mm were done and the results shown thatenergy adoption capacity of variable intensity tubes was better. When attained the limitcompression distance, the total energy absorption capacity of variable intensity tubes of100mm and150mm was40%greater than the original ones. The effect of heatpreservation time rising on energy absorption capacity of100mm tube was unobvious.To the tube of150mm, the energy absorption capacity was improved more than10%. Itwas apt to appear compression bending during the quasi-static deformation of200mmoriginal tube and variable intensity tube which lead to low energy absorption capacity.Energy absorption failure problems during compression process were analyzed and corresponding solutions were put forward at last.