| In recent years,accidents such as rear-end collision,overturning and fire occurred in highway transportation tanker,which seriously affected people’s life,health and property safety,therefore,it is important to improve the impact resistance performance of transportation tank structure.Sprayed polyurea has the advantages of high strength,light texture,energy absorption and dissipation due to its excellent basic properties and mechanical characteristics,and spraying polyurea material on the surface of the structure can reduce the damage of the structure and improve the impact resistance performance.In this paper,the stainless steel tank as the base material,14-B6 impact resistant polyurea（hereinafter referred to as 14-B6 polyurea）material and modified Q413T viscoelastic polyurea（hereinafter referred to as Q413T polyurea）material as impact resistant coating are used to prepare polyurea coated tank for different working conditions.Firstly,the basic properties,anti-aging properties and thermal properties of the above two polyurea materials were studied to determine the inherent properties and high temperature stability of the materials;secondly,the dynamic mechanical properties of 14-B6 type polyurea and Q413T type polyurea under different strain rates were studied by tensile experiments at low and medium speeds and compression experiments at high speeds,and the energy dissipation mechanisms of the two materials were analyzed by dynamic thermo-mechanical property experiments Third,the polyurea materials were sprayed on the surface of the tank structure to prepare different types of coated tank composite structures,and the optimal single and composite polyurea coated tank structures were studied by using the falling ball impact experimental device;Finally,the tank structure models under different working conditions are simulated by ANSYS/LS-DYNA finite element software,and the optimal protection method is determined according to the dynamic response results to verify the reliability of the numerical simulation and the accuracy of the impact experiments.The main conclusions obtained from the experimental study are as follows:（1）The results of the basic performance experiments of 14-B6 type and Q413T type polyurea show that:the density of both is close to that of water,which is a light material;the solid content is above 95%,which is a solvent-free environmental protection material;14-B6 type polyurea is hard,which is suitable for the restraining material outside the tank structure,while Q413T type polyurea is soft and good viscoelasticity can absorb a large amount of impact energy;the adhesion between the two polyurea materials and the tank substrate meets the construction requirements;the quasi-static mechanical properties of both materials are excellent and have good fatigue and aging resistance characteristics,which can meet the requirements of impact protection of the structure;the initial degradation temperatures of 14-B6 and Q413T polyurea materials are 226.5℃and 210.7℃respectively,and both of them have good thermal stability performance.（2）The results of low and medium-high strain rate tensile experiments,high strain rate compression experiments and dynamic thermo-mechanical properties experiments of 14-B6 and Q413T polyurea show that:In the range of low strain rate from 0.001s-1to 0.1s-1and medium to high strain rate from 51.67s-1to 765.30s-1with the increase of tensile rate,the engineering stress and real stress of 14-B6 type Q413T polyurea both showed increasing trend,both materials showed obvious strain rate effect when dynamic tensile and compressive loads were applied,and the mechanical strength of 14-B6 type polyurea was greater than that of Q413T type polyurea;the peak range of energy storage modulus of 14-B6 type polyurea at different frequencies is much larger than that of Q413T type polyurea,and the loss factors of 14-B6 type and Q413T type polyurea are close to 0.23 and 0.35 respectively at the same frequency,which indicates that Q413T type polyurea has excellent flexibility and damping and is more prone to deformation energy dissipation.（3）Under the action of falling ball impact load,the residual deformation in the center area of the top surface of the blank tank is 4.25cm.For the single polyurea coating,when the coating thickness increases from 1mm to 3mm,the maximum residual deformation in the center area of the 14-B6 coated tank decreases from3.45cm to 2.25cm,while the Q413T coated tank decreases from 3.58cm to 2.34cm;for the three thicknesses The strain peaks of 14-B6 and Q413T polyurea coated cans are in the order of 1mm>2mm>3mm,both 14-B6 and Q413T single polyurea coating can effectively reduce the damage deformation of the can structure,and the coating thickness is the main factor affecting the impact resistance of the cans;while for the polyurea composite coating,the damage deformation degree of the coated tank under both construction methods I（tank+restraint layer+damping layer）and II（tank+damping layer+restraint layer）is greatly reduced,and the residual deformation in the center area of the top surface of the tank is reduced by more than30%,which indicates that the protection effect of the polyurea composite coating tank is obvious,and the impact resistance performance of the construction method II is better than that of the construction method I.When the thickness ratio between layers of composite coating is 1∶1,the peak strain and the compressive deformation of the top surface center area of the coated tank in F2 and F5 working conditions are the smallest.（4）The simulation results of ANSYS/LS-DYNA finite element software show that the structural model and material parameters of the coated tank can reasonably calculate the damage morphology,center point displacement and energy time course curve of the tank.Under the protection of single polyurea coating,with the increase of14-B6 and Q413T polyurea coating in the thickness of 1mm～3mm,the displacement at the center point of the top surface of the tank decreases by 1.0cm and 0.69cm respectively,and the peak internal energy and kinetic energy of the tank show a decreasing trend;For the polyurea composite coated tank,different degrees of depression and deformation occurred in various conditions of the coated tank under Type I（F1 to F3 conditions）and Type II（F4 to F6 conditions）construction methods,while the damage deformation at the center of the coated tank under F2 and F5（interlayer thickness ratio 1∶1）conditions was the smallest,while the displacement at the center of the coated tank under F1 and F4（interlayer thickness ratio 1∶3）,F3 and F6（interlayer thickness ratio 3∶1）conditions were 2.70cm,2.53cm,2.78cm and2.71cm,respectively.The comparative analysis determined that the optimum coating thickness for the impact resistance of the tank structure is 2 mm and the optimum composite coating layer thickness ratio is 1∶1,and it is confirmed that the developed model and the adopted material parameter are sufficiently reliable to better predict the degree of damage deformation of the coated tank under the impact load.In summary,14-B6 and Q413T polyurea materials have good physical and dynamic mechanical properties,and their spraying on the surface of tank structure can effectively reduce the degree of damage and deformation caused by impact loads on the tank,which has important and wide application prospects. |
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