Dynamic Detecting The Mechanical Response Of Metal By Organic Mechanoresponsive AIE Luminogen

As the foundation of national economic development,equipment manufacturing industry has become a critical manifestation of a country's comprehensive national strength.The equipment develops towards large size and complicated to satisfy the industrial requirements,meanwhile it put forward higher requirements on guaranteeing equipment operation safely.This research invents a large-scale,full-field,on-site method to detect the mechanical response of metal structures based on an organic mechanoresponsive luminescent material(TPE-4N).This method can detect the stress/strain distribution of complicated metal structure components with simple devices.This detecting method is very meaningful to insure safe operation of equipment.The main research content and conclusions in this dissertation are as follows:(1)The feasibility that a pure organic mechanoresponsive fluorescent material can detect the stress/strain of metal specimens is proved by processing mechanics experiments.Surface analysis shows that the change of fluorescence response is resulted from TPE-4N coating cracks into fragments upon mechanical force.Therefore the invisible information of the stress/strain distribution of the metal specimens is transformed into visible fluorescent signals for directly observation by naked eyes.Besides,through fatigue test the initial fatigue crack can be observed and predicted by the fluorescence detecting method.In addition,the coating fragments are directly related to the strain or deformation of the substrate metal.(2)The mechanism of fluorescence response change is clarified by processing uniaxial tensile tests and microscopic analysis with a series of specimens.There are two factors that affect fluorescence response intensity: strain and grain size of substrate metal.The concept of surface roughness is proposed to establish the formulation between metal strain and fluorescence response intensity,the formulation can be used to calculate the strain of different metal by fluorescence response intensity accurately.(3)The heterogeneous local strain concentration of X80 weld joints is investigated by using fluorescent detecting method.The microstructure and mechanical property of weld joints are found heterogeneous through micro observation and hardness test.The heterogeneous deformation of the weld joints is visualized and calculated accurately by fluorescence intensity.The heterogeneity of local strain increases with elongation of weld joints under uniaxial tension and cyclic loading.Besides,the higher mean stress and stress amplitude can induce significantly higher accumulated ratcheting strain in the fusion zone of weld joints.