Study Of Low Yield Point Steel's Dynamic Constitutive Relationship And Its Performance On Explosion Energy Absorption

Based on Low Yield Point (LYP) steel's lower yield strength, better plastic performance and better impact toughness than general structural steel, its advantages of dissipating explosion or impact energy through the plastic deformation were explored in this paper. Domestic 225MPa class LYP steels named AQ225 were tested by quasi-static and split Hopkinson pressure bar (SHPB) experiment. Corresponding Johnson-Cook dynamic constitutive model was obtained by fitting experimental data, and the accuracy of the model parameters was verified through numerical simulation of SHPB experiment. Then dynamic response of LYP steel square plate structure subjected to explosive loads was studied by numerical simulation.The main contents of this dissertation include the following aspects: First, specimens made of AQ225 were tested using Instron material testing machine and SHPB apparatus, and corresponding stress-strain curves under quasi-static strain rate and high strain rate were obtained. Based on the experimental data, JC model parameters were fitted. Then influence degree of adiabatic temperature rise effect in the SHPB experiment process was estimated.Second, numerical simulation of SHPB experiment was carried out. Reasonable element size and contact stiffness penalty factor were determined, and then JC model parameters were verified to be accurate and reliable by comparing with the waveforms obtained from simulation and experiments.Finally, the prospect of AQ225 used for absorbing explosion or impact energy was studied by a series of numerical simulations. Using simplified impact load method and fluid-structure coupling method respectively, the dynamic mechanical responses of square plates subjected to same blast loads were analyzed. Then the results of plates made of different steel (HQ600, Q345 and AQ225) were analyzed and compared through energy analysis method. At last, LYP steel's advantages of absorbing explosion or impact energy through the plastic deformation were confirmed.