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Study On Impact Damage Of Steel Structure Coatings Under Impact Load And Finite Element Simulation

Posted on:2020-06-07Degree:MasterType:Thesis
Country:ChinaCandidate:X L TianFull Text:PDF
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Infrastructures such as steel structures in strong ultraviolet and sandstorm environments in Inner Mongolia have been damaged by impact of hard granular media such as sandstorm for a long time.Surface coatings serve under complex conditions such as particle impact,collision and strong ultraviolet radiation.They are prone to micro-cracks or even damage and spalling,which will cause damage and failure,and affect the durability and safety of structures.The impact damage resistance of the steel ball structure of polyurethane coating and fluorocarbon coating under impact load pressure method,UV analysis method proved the two kinds of coatings using morphology characterization and chemical structure of the aging mechanism and damage morphology,LS-DYNA software was used to analyze the stress distribution of coatings under impact.This study is subject to the National Natural Science Foundation of China(Study on damage mechanism of steel structure coatings by wind-sand erosion under high temperature difference and strong ultraviolet environment in central and Western Inner Mongolia)(No.11862022),(Study on the mechanical behavior and damage mechanism of the windshield glass under the special environment of the region)(No.11662012),The specific research contents are as follows:1.Based on Hertz contact theory and the characteristics of wind-blown sand particles in central and Western Inner Mongolia,the impact spherical pressure model of particle medium impact steel structure coatings was established,And the basic mechanical properties of two steel structure coating hardness,elastic modulus,adhesion and flexibility of the coatings were tested.2.According to the impact ball pressure test of two kinds of steel structure coatings,the impact resistance of fluorocarbon coatings is better than that of polyurethane coatings.The ultimate load of fluorocarbon coatings is greater than that of polyurethane coatings.Under the impact load,fluorocarbon coatings have better elastic recovery and plastic deformation resistance.3.The damage morphology of the coating was measured and analyzed by PXS9-T three-mesh continuum microscope and Z16 APOA ultra-depth-of-field microscope.It was found that under impact,spherical coronal impact craters were formed on the surface of steel structure coatings,material accumulation and circumferential and longitudinal cracks appeared around the indentation of polyurethane coatings,and the radial cracks produced by impact of fluorocarbon coatings were less than those of polyurethane coatings,and the crack width was finer than that of polyurethane coatings,the coating has good evenness.The impact indentation depth of fluorocarbon coatings is 31% lower than that of polyurethane coatings under impact height.4.By using scanning electron microscopy(SEM)and Fourier transform infrared spectrometer on the UV aging mechanism of coating,The results show that with the increase of ultraviolet aging time,the surface cracks,bubbles,residues and crystal deposits of fluorocarbon coatings increase gradually,and the molecular bonds in fluorocarbon coatings do not break obviously,the characteristic groups are not destroyed,and the fluorocarbon coatings do not fail during ultraviolet aging.A large number of cracks,aging residues and crystalline substances appeared in the polyurethane coating.The coating gradually peeled off the matrix.After three years of ultraviolet aging,the C-H bond disappeared.Ultraviolet light had a certain damage effect on the polyurethane coating.The aging resistance of the coating is fluorocarbon coating > polyurethane coating.5.The impact test of the coatings after ultraviolet aging shows that the impact resistance of the coatings after ultraviolet aging is better than that of polyurethane coatings,and the indentation growth rate is as follows: the non-ultraviolet aging coatings < ultraviolet aging for one year < ultraviolet aging for two years < ultraviolet aging for three years;according to the LSCM diagram of the coatings after ultraviolet aging,the indentation area of the coatings subjected to impact damage increases with the aging time.With the enlargement of domains and the increase of depth of impact craters,cracks and material heaping appeared on the coating surface.The indentation parameters of the coating increased with the aging time,and the fluorocarbon coating still showed excellent impact damage resistance.6.LS-DYNA software was used to simulate the process of spherical impact coating,and the stress distribution on the surface of spherical impact coating and along Z-direction profile was analyzed,the impact load-time curves obtained by numerical simulation and impact test are compared and analyzed.Experiment and finite element simulation results are consistent.
Keywords/Search Tags:Steel structure coating, Impact load, Ultraviolet aging, Damage morphology, LS-DYNA
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