| According to the current research status and characteristics of steel structure coatings by domestic and foreign scholars,there is a lack of research on the wind-sand erosion resistance performance of steel structure protective coating under the influence of multiple factors,and the damage mechanism of different systems of coating under the dual coupling of stress and wind-sand environment.In this paper,the damage mechanism of steel structure bridge protective coating in wind-blown sand environment is studied and analyzed.The research contents and conclusions are as follows:(1)On the basis of comprehensive consideration of static load level,temperature difference and UV,the influence of environmental factors in northwest China is summarized and analyzed.The following conclusions are drawn: temperature and humidity reduce the bonding properties of molecules in the protective coating of steel structure bridge,weaken the cohesion and adhesion between coating and substrate,and thus reduce the service life of substrate.The ultraviolet light in the highlight reduces the mechanical energy of steel bridge protection materials through photodegradation and photoaging.(2)The coating system of steel structure was designed and prepared.A static loading device was developed to pressurize the coating system,and temperature difference and ultraviolet cycle aging were carried out on the loaded coating.The coatings aged by temperature difference and static load coupling were designed under different erosion angles,erosion speeds and erosion time,and sand erosion wear tests were carried out.The degradation performance of the coatings was analyzed quantitatively and qualitatively by mass wear method,and the following conclusions were obtained: When the steel structure coating system is eroded by sand erosion at different erosion angles in the range of 30°～90°,there is a critical Angle of maximum erosion wear,about 45°.The erosion resistance of the coating is between the plastic and brittle materials.The sand erosion resistance of the coating can be reduced with the increase of static load level and temperature cycle.The influence of the number of temperature cycles on the erosion wear of sand is non-uniform development process,and the temperature cycles can reduce the ultimate life of the coating against sand erosion by 26.7%.With the increase of the temperature cycle,the erosion wear area of the coating expands gradually,and the surface wear depth and wear amount also increase gradually.(3)Based on the Bitter deformation wear theory and Arrhenius model,the temperature cycle aging factor and the deterioration factor under static load in wind-blown sand environment were deduced,and the modified Neilson-Gilchrist analysis theory was established,which took into account multiple factors such as static load level,temperature environment and wind-blown sand erosion conditions.Considering the effect of temperature difference and static load in the actual environment,a coating erosion damage degradation model under the action of multiple factors was proposed.Combined with the test conditions of different erosion speeds and erosion angles of sand,the error analysis showed that the modified Neilson-Gilchrist model proposed in this paper had a high analysis accuracy.It provides a theoretical method for evaluating wear characteristics and predicting life of coatings under the action of multiple factors.The analytical solution of the model obtained from the deduced theoretical formula for predicting the remaining service life is basically consistent with the remaining service life obtained from the experimental data,which proves that the functional relationship between the remaining service life of the coating and the wear amount proposed in this paper is correct.The remaining service life of the steel structure coating decreases with the increase of the static load applied.(4)The static load,temperature difference and ultraviolet coupling aging tests were designed to analyze the corrosion conditions of the aging steel structure coating at different erosion angles,erosion rates and erosion time,and the microscopic damage features of the coating were analyzed combined with scanning electron microscopy.The conclusion is as follows: after static load,temperature difference and UV coupling,the wear of the coating in different Angle erosion process presents nonlinear changes.The sand resistance and service life of the coating at 45° are weaker than 60°,75° and 30°,and the performance is much different from that at 90°.After static loading and temperature difference aging,the erosion wear of steel structure coating increases linearly with the increase of UV radiation duration.Under the action of ultraviolet radiation,temperature difference and static loading,the structure between and inside the coating is damaged,and the life of the coating is reduced by31% after ultraviolet irradiation.At low Angle erosion,scratches were observed by electron microscopy,and the wear was mainly due to tangential force of erosion particles.At the erosion at a critical Angle of 45°,due to the tangential and normal forces of sand particles at the same time,the wear zone of the coating is wider,and the erosion zone gradually changes from shallow to deep.When the erosion exceeds the critical Angle,the wear of the coating is mainly the deformation wear caused by the normal forces.The surface erosion depth and amount of the steel structure coating increase with the increase of temperature difference and ultraviolet aging time. |
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