Surface Topography Feature Extraction And Damage Assessment In Metal Fatigue Process

Fatigue damage is a typical form of metal component damage,the structure of the fatigue damage in engineering construction and production will often bring disastrous consequences,the accurate assessment of fatigue damage has become a hot topic in the field of condition monitoring and fault diagnosis.In recent years,with the development of nondestructive testing technology,people often use thermal,magnetic,and acoustic equivalent to assess damage in the fatigue process,which improves the efficiency compared with traditional methods,but the detection process will be affected by temperature,magnetic field,noise and other factors.Metal fatigue is accompanied by energy dissipation.In this process,the cyclic slip constraint on the material surface is less,and the irreversible shear displacement along the slip band changes the surface morphology of the material.Therefore,the damage assessment based on the surface topography of the damage process is expected to provide a potential method for fatigue damage detection.In order to clarify the change rule of surface morphology in the metal fatigue process,the Q235 steel is selected as the test sample,and the axial tensile fatigue tests are conducted wiht the in-situ tensile tester,and the surface morphology characteristic s of the sample processed under different fatigue cycle time are collected.Through the two dimensional and three dimensional roughness characterization,combined with the surface height distribution and fractal theory analysis,the change law of the surface morphology characteristics of metal fatigue process is obtained.The results show that the arithmetic mean deviation Sa,the mean value μ and standard deviation σ of the surface height distribution,and the multifractal spectrum width(35)α all increase nonlinearly with the increase of the number of fatigue cycles.The amplitude A of the surface height distribution decreases with the increase of the number of fatigue cycles,indicating that with the increase of the number of cycles,the height data concentration decreases and the metal surface becomes uneven.The above five characteristic quantities(arithmetic mean deviation Sa,surface height distribution amplitude A,mean value μ and standard deviationσ,multifractal spectrum width(35)α)were used as the data layer to construct the nonlinear mapping between the morphology features and the damage,and to establish the fatigue damage surface morphology feature data fusion evaluation model.The data verification error is within10%,indicating that the model is effective.Based on the microscopic mechanism,this paper studies the change law of the surface morphology characteristics in the metal fatigue process,and establishes the fusion evaluation model of the surface morphology characteristics of the fatigue damage,which provides a new idea and method for the detection and evaluation of the metal component fatigue damage,and has a certain application prospect in the industry.Figure [36] table [5] reference [85]...