| Metal material have good comprehensive performance and are widely used in industrial and engineering fields,and the accumulation of fatigue damage in service can lead to material failure.Therefore,fatigue injury has become the focus of attention and research from all walks of life.Fatigue failure is a common phenomenon in which metal materials accumulate and degrade their performance under repeated stress,which has significant suddenness and concealment.The traditional fatigue injury detection method can’t evaluate the early damage of metal components accurately and effectively,and it takes a long time and the process is cumbersome.The process of metal fatigue damage is accompanied by complex energy dissipation.When the outside world works on the metal components,it leads to irreversible plastic deformation and internal micro-defects,which causes the internal microstructure of the material to change,and the internal energy and kinetic energy in the internal deformation area to change,which is directly reflected in the temperature change of the material surface.Heat dissipation is an important energy consumption phenomenon in the process of fatigue damage,which directly causes the change of the surface temperature field of the material,and reflects the evolution process of internal micro-defects and the damage state of metal materials.Therefore,the infrared thermal imaging method provides an effective way and method for the detection of metal fatigue damage,which has the obvious advantage of real-time non-destructiveness.However,the temperature measurement accuracy of the infrared thermal imaging method still needs to be further improved,mainly in: 1)at present,when observing fatigue damage state,the emission rate of the actual surface of the default object is constant,and the metal under the action of circular load,the surface micromorphology is constantly changing,making the reflectivity of the actual surface is constantly changing,resulting in the fatigue performance of the research material directly through the temperature field changes in the fatigue process is difficult to obtain accurate and reliable results 2)Infrared thermal imaging method by obtaining spontaneous radiation on the metal surface and evaluating the damage status of the material based on the temperature change of the surface,but the acquired spontaneous radiation is susceptible to environmental or background fluctuations in the transmission process,especially when measuring small temperature changes,it is difficult to obtain sufficient measurement accuracy.The energy dissipation during metal fatigue is lost in the air in the form of thermal radiation.From the point of view of physics,thermal radiation belongs to spontaneous radiation and has polarization characteristics.In infrared imaging detection,the introduction of polarization detection can effectively suppress background clutter,improve the contrast between the target and the background,increase the amount of information of the target,is conducive to target detection and recognition,can significantly improve the detection and recognition ability of low temperature difference or low thermal contrast target,can reduce the impact of infrared polarization characteristics of weak background.On the other hand,polarization detection can effectively reveal the microphysical properties of the material,and a single imaging can obtain high-dimensional parameters such as stokes parameters,polarization and polarization angle,elliptic bias and elliptical bias angle,thus raising the target recognition from the surface structure to the spatial structure,and the interpretation ability of the target is greatly enhanced.Based on this,this paper based on the fatigue process metal surface morphological changes,respectively,to carry out the following work:(1)To explore the process and mechanism of metal fatigue damage,analyze the evolution law of metal material surface appearance under the action of circulating load,carry out metal fatigue test to demonstrate that metal surface texture is an important characteristic change in metal fatigue process.Based on this,the Q235 notch specimen is used as the research object,the fatigue stretching experimental platform and the three-dimensional morphological acquisition platform are set up,the three-dimensional morphological image of the specimen surface under different cycle cycles is analyzed,and the external load effect is verified to cause the surface roughness of the specimen to change,and the metal surface appearance will change continuously as the fatigue degree deepens.(2)Analyze the basic principles of infrared polarization detection,carry out comparative experiments,analyze the difference between infrared image and infrared polarization image,verify the effectiveness of polarization detection,and find that polarization thermal imaging can improve the contrast of the target background,enrich the amount of information,highlight the edge profile and detail information.At the same time,starting from the change of metal surface morphology in fatigue process,considering the deficiency of infrared thermal imaging method,introducing polarization detection,studying the model of infrared radiation polarization characteristics of metal surface,laying a theoretical foundation for the subsequent infrared polarization test based on metal fatigue damage,and providing effective technical methods.(3)Combined with the outstanding advantages of infrared polarization detection,Q235 steel as the research object,through the construction of fatigue test platform and polarization thermal image acquisition platform,to obtain different fatigue cycles under the metal material surface polarization thermal image,to explore the fatigue process of the metal surface infrared polarization characteristic evolution law,the results show that under the action of the circular load,different polarization angular image light strength,Stokes parameters and polarization are showing a regular change trend.In addition,the different polarization angular images、stokes image and dop images collected by the experiment are preprocessed by wavelet transformation,the image quality is improved,the edge outline and texture of the image are more highlighted,and the thermal texture information such as polarization angularity,polarization and Stokes parameters is extracted by gray-Lever Co-occurrence-Matrix,which shows that the metal surface texture changes regularly during fatigue damage.The statistics of symbiotic matrix show certain regularity.Figure[42] Table[5] Reference[65]... |
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