| This project is based on the key research and development project of military civilian integration in Shandong Province,and studies the fatigue crack growth and fatigue life analysis of nonlinear composite coatings based on thermal coupling.The composite coating is applied to the surface of the ship for roughening treatment to improve its anti slip performance and improve the performance of the base steel plate.Due to the wide range and long distance of ship navigation,the thermal stress generated by external environmental temperature changes can affect the performance of composite coatings.Therefore,it is necessary to study and consider the effects of extreme heat and cold temperatures on the crack growth and fatigue life of rough textured surfaces of composite coatings.The main research content and conclusions of this article are as follows:Firstly,by incorporating the unique properties of viscoelastic materials into the basic elastic element and viscous element models,while considering the creep compliance and relaxation modulus after damage,a constitutive model suitable for this composite coating material is derived,and mechanical performance tests of the composite coating are conducted.The experimental results show that the composite coating material becomes soft and tough at high temperatures,reduces its shear resistance,compressive strength,and fatigue life;At low temperatures,it becomes brittle and hard,reduces shear resistance,improves compressive strength,and reduces fatigue life.And the derived constitutive model of the composite coating has a high degree of agreement with the experimental curve after fitting,providing data support for subsequent simulation calculations.Secondly,the stochastic process function and digital filtering technology are used to characterize the composite coating Gaussian random rough surface,and the exponential autocorrelation function is used as the input,which is substituted into the height distribution function and spatial distribution function to establish the composite coating Gaussian random rough surface model.By normalizing Gaussian random rough surface and stripe texture surface,the final 3D rough texture surface is obtained,which provides a geometric modeling for simulation calculation.Thirdly,the stress intensity factors K and J-integrals of composite coating cracks were analyzed at different temperatures,surface morphology,substrate steel plate thickness,crack length,and crack location.It was found that under extreme hot and cold conditions,the cracks were open type(Type I)cracks.The risk of composite coating crack cracking also increased with increasing temperature under extreme hot conditions,and the risk of composite coating crack cracking also increased with decreasing temperature under extreme cold conditions;Under extremely hot conditions,When the surface is σ=4mm,the thickness of the steel plate is 10 mm,the crack length is 2mm,and the crack is located on the slope,the surface crack risk of the composite coating is the highest;Under extremely cold conditions,When the surface is σ=1mm,the thickness of the steel plate is 10 mm,the crack length is 2mm,and the crack is located on the slope,the surface crack risk of the composite coating is the highest,providing important reference for the fatigue crack growth trend of the composite coating.Finally,under the influence of five factors: temperature,surface morphology,substrate steel plate thickness,crack length,and crack location,the fatigue life and fatigue crack growth trend of the composite coating were analyzed,and the conclusion was drawn that under extremely cold conditions,the equivalent stress near the crack tip was greater,the deformation was greater,the fatigue life was shorter,and the crack degree was greater;At different extreme heat temperatures,the crack growth trend shows an exponential growth.The higher the extreme heat temperature,the shorter the fatigue life of the composite coating,and the greater the degree of fatigue crack growth;At different extreme cold temperatures,the crack growth trend shows a linear growth.The lower the extreme cold temperature,the shorter the fatigue life of the composite coating,and the greater the degree of fatigue crack growth;Under extremely hot conditions,When the surface is σ=8mm,the thickness of the steel plate is 10 mm,the crack length is 2mm,and the crack is located on the slope,the fatigue life of the composite coating is the shortest,and the fatigue crack growth degree is the highest;Under extremely cold conditions,When the surface is σ=4mm,the steel plate thickness is 10 mm,the crack length is 2mm,and the crack is located on the slope,the fatigue life of the composite coating is the shortest,and the fatigue crack growth degree is the highest.This provides theoretical reference for the life prediction and performance upgrading of the composite coating in practical applications. |
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