Research On Polarization Characteristics And Image Texture Features Of Metal Surface In Fatigue Damage Process

In the industrial and engineering fields,metal materials are widely used because of their good comprehensive properties.However,metal materials are often accompanied by the occurrence of fatigue damage during service.In severe cases,the materials will break and fail.Therefore,the fatigue of metal materials has always been the focus of attention.Under the continuous action of the cyclic load,the metal material gradually cracks on the surface,and finally the material breaks.During this process,the surface morphology of the metal continues to change irreversibly.At present,the research on the surface morphology of materials under the action of fatigue load is mainly to analyze the evolution mechanism of the microscopic morphology during the crack initiation,propagation and fracture of the material surface through the optical microscope,and to reverse the initiation of micro cracks through the analysis of the material fracture And expansion mechanism.These methods are difficult to achieve online fatigue damage detection and analysis.Polarization is an inherent property of light.In recent years,optical polarization imaging technology has developed rapidly,and has the advantages that traditional optical imaging technology does not have.It can not only reflect the reflected radiation intensity of the object surface,but also reflect the physical characteristics of the surface.Compared with traditional optical images,polarized images contain multi-dimensional optical information of targets and are more sensitive to the edges,textures and details of targets.They have been widely used in military camouflage detection,material classification,biomedicine and other fields.In this paper,starting from the changes in the surface morphology of the metal material during the fatigue process,the microscopic morphology and optical polarization characteristics of the metal material surface under cyclic loading are obtained by building a fatigue test platform and a polarized image acquisition platform,and the texture texture is used to extract the polarized image.Texture information,analyze the evolution of metal surface micro-topography during fatigue damage,and study the correlation between the polarization characteristics of metal surface,image texture characteristics and fatigue damage status,to provide fatigue damage monitoring and status assessment for active metal components New theories and methods.The main contents and conclusions of this article are as follows:(1)Analysis of the status quo of subject research and basic theoretical researchThe background and significance of the subject research and the current status of fatigue damage are introduced,and the evolution mechanism and development law of the internal structure and surface morphology of metal materials during fatigue are discussed.Introduce the research status of image texture analysis technology,the main theories and methods of image texture feature extraction.Introduce the basic principles of optical polarization imaging,the polarization characteristics of light waves and their description methods.(2)Research on the polarization characteristics of metal surfacesIn-depth research and analysis of the optical polarization characteristics and modeling methods of metal surfaces.Based on the principle of polarized optics and micro-plane theory,the bidirectional polarization distribution function(PBRDF)is deduced,an improved six-parameter PBRDF model is proposed,and the influencing factors and polarizing characteristics of the reflected light on the metal surface are studied by simulation and experimental measurement methods.Characterization method.The results show that the polarization characteristics of the reflected light on the metal surface are closely related to the incident angle,observation angle,material,surface roughness and other factors.The degree of polarization increases with the increase of the incident angle or the reflection angle.The Stokes parameter S0,S1 decreases with increasing roughness.(3)Experimental study on polarization characteristics and image texture of metal surface during fatigue damageThe Q235 notched specimen was selected for fatigue test.By analyzing the threedimensional topography images of the specimen surface under different cycles,it was verified that the external load will cause the specimen surface roughness to change.A test platform for optical polarization image acquisition on the surface of metal materials under fatigue load was built to study the relationship between the surface polarization characteristics and the degree of fatigue damage through experiments.The experimental results show that the Stokes parameters S0 and S1 of the reflected light on the metal surface gradually decrease with the increase of the cycle number,and the mid-fatigue change is slower,and the initial and late changes are faster.Using the image texture feature analysis method,the texture feature parameters such as the mean and entropy of the Stokes parameter image are extracted,and the relationship between the texture feature parameter and the degree of fatigue damage is studied.The results show that both the mean and entropy of the Stokes parameter image As the number of cyclic loading increases,it decreases.It is verified that the Stokes parameters of the reflected light on the metal surface and the image texture feature parameters are closely related to the degree of fatigue damage.Figure[32] Table[6] Reference[52]...