Fatigue,corrosion,and bolt loosening are the main causes of structural performance degradation and collapse in steel bridges.Accurate monitoring of steel bridge diseases is a basic premise for ensuring high-quality op...Fatigue,corrosion,and bolt loosening are the main causes of structural performance degradation and collapse in steel bridges.Accurate monitoring of steel bridge diseases is a basic premise for ensuring high-quality operation and maintenance of steel bridges.In this regard,a summary and analysis were conducted on the classification of steel bridge diseases,monitoring and detection methods,application statuses,and major difficulties.The main causes,research status,and development trends of steel bridge diseases are discussed.The results showed that,for fatigue crack problems,fatigue crack initiation has a small scale,high difficulty in monitoring and detection,few methods,and low accuracy.As the cracks grow,the difficulty of monitoring and detection decreases,the number of methods increases,and the accuracy improves.Fatigue crack monitoring and detection are affected by the environmental and vehicular loads.Superficial corrosion features are evident in steel bridges,and corrosion identification methods and technologies are rapidly developing.Monitoring and detecting corrosion in concealed areas is difficult and requires further improvements in monitoring and detection technologies and their accuracy.Monitoring and detection methods and supporting equipment for bolt loosening in steel bridges are rapidly developing.The development of intelligent monitoring and detection technologies and supporting equipment is an important research topic that urgently needs to be addressed for the full-lifecycle operation and maintenance of steel bridges and the sustainable development of bridge engineering.Developing new intelligent sensing components based on high-performance materials and sensing element design theory to improve the monitoring and detection perception ability is an important development direction for steel bridge monitoring and detection.Research on intelligent monitoring and detection technologies,standardized indicators,and related topics based on intelligent operations and maintenance provide great support for the development of steel-bridge disease monitoring and detection.展开更多
The hot deformation behavior of （3 vol% SiCp -4- 3 vol% Mg2B2Osw）/6061 A1 （W3P3） hybrid composite and 6 vol% SiCp/6061 A1 （P6） composite have been characterized in the temperature range of 300--450 ℃ and strain...The hot deformation behavior of （3 vol% SiCp -4- 3 vol% Mg2B2Osw）/6061 A1 （W3P3） hybrid composite and 6 vol% SiCp/6061 A1 （P6） composite have been characterized in the temperature range of 300--450 ℃ and strain rate range of 0.0001-0.1 s-1 using isothermal constant true strain rate tests. The flow behavior and processing maps have been investigated using the corrected data to eliminate the effect of friction. Under the same deformation conditions, the compressive resistance of the singular composite remains superior to that of the hybrid composites. The processing map of W3P3 hybrid composite exhibits a single hot working domain at the temperature between 350 and 450 ℃ with strain rate between 0.0001 and 0.003 s-1 （domain A）. Two hot working domains exist for P6 composite： （i） 300-400 ℃/ 0.0001-0.003 s-1 （domain B1）; （ii） 380-450 ℃/0.01-0.1 s-1 （domain B2）. The processing maps also reveal the flow instability of the two composites, which is associated with whiskers breakage, whisker/matrix interfacial debonding, SiCp/ matrix interfacial decohesion, adiabatic shear bands or flow localization, and wedge cracking in the corresponding regions. The estimated apparent activation energies are about 224 kJ mo1-1 in domain A for W3P3 hybrid composite, 177 kJ mo1-1 in domain B1 and 263 kJ mo1-1 in domain B2 for P6 composite, respectively. These values are higher than that for self-diffusion in A1 （142 kJ mol-1）, suggesting that there is a significant contribution from the back stress caused by the presence of particles and/or whiskers in the matrix. The deformation mechanisms corresponding to domain B 1 and domain B2 are dislocation climb controlled creep and cross-slip for P6 composite, respectively. For W3P3 hybrid composite, the deformation mechanisms contain dislocation climb controlled creep and grain boundary sliding caused by DRX in domain A.展开更多
基金funded by the National Key Research and Development Program of China(grant No.2022YFB3706405)National Natural Science Foundation of China(grant Nos.52378316,52278318 and 52108176)+1 种基金National Key Research and Development Program of China(grant No.2021YFB1600300)List of Scientific and Technological Key Projects in Transportation Industry(grant No.2019-MS1-011)。
文摘Fatigue,corrosion,and bolt loosening are the main causes of structural performance degradation and collapse in steel bridges.Accurate monitoring of steel bridge diseases is a basic premise for ensuring high-quality operation and maintenance of steel bridges.In this regard,a summary and analysis were conducted on the classification of steel bridge diseases,monitoring and detection methods,application statuses,and major difficulties.The main causes,research status,and development trends of steel bridge diseases are discussed.The results showed that,for fatigue crack problems,fatigue crack initiation has a small scale,high difficulty in monitoring and detection,few methods,and low accuracy.As the cracks grow,the difficulty of monitoring and detection decreases,the number of methods increases,and the accuracy improves.Fatigue crack monitoring and detection are affected by the environmental and vehicular loads.Superficial corrosion features are evident in steel bridges,and corrosion identification methods and technologies are rapidly developing.Monitoring and detecting corrosion in concealed areas is difficult and requires further improvements in monitoring and detection technologies and their accuracy.Monitoring and detection methods and supporting equipment for bolt loosening in steel bridges are rapidly developing.The development of intelligent monitoring and detection technologies and supporting equipment is an important research topic that urgently needs to be addressed for the full-lifecycle operation and maintenance of steel bridges and the sustainable development of bridge engineering.Developing new intelligent sensing components based on high-performance materials and sensing element design theory to improve the monitoring and detection perception ability is an important development direction for steel bridge monitoring and detection.Research on intelligent monitoring and detection technologies,standardized indicators,and related topics based on intelligent operations and maintenance provide great support for the development of steel-bridge disease monitoring and detection.
基金financially supported by the National Basic Research Program of China(No. 2011CB612200)
文摘The hot deformation behavior of （3 vol% SiCp -4- 3 vol% Mg2B2Osw）/6061 A1 （W3P3） hybrid composite and 6 vol% SiCp/6061 A1 （P6） composite have been characterized in the temperature range of 300--450 ℃ and strain rate range of 0.0001-0.1 s-1 using isothermal constant true strain rate tests. The flow behavior and processing maps have been investigated using the corrected data to eliminate the effect of friction. Under the same deformation conditions, the compressive resistance of the singular composite remains superior to that of the hybrid composites. The processing map of W3P3 hybrid composite exhibits a single hot working domain at the temperature between 350 and 450 ℃ with strain rate between 0.0001 and 0.003 s-1 （domain A）. Two hot working domains exist for P6 composite： （i） 300-400 ℃/ 0.0001-0.003 s-1 （domain B1）; （ii） 380-450 ℃/0.01-0.1 s-1 （domain B2）. The processing maps also reveal the flow instability of the two composites, which is associated with whiskers breakage, whisker/matrix interfacial debonding, SiCp/ matrix interfacial decohesion, adiabatic shear bands or flow localization, and wedge cracking in the corresponding regions. The estimated apparent activation energies are about 224 kJ mo1-1 in domain A for W3P3 hybrid composite, 177 kJ mo1-1 in domain B1 and 263 kJ mo1-1 in domain B2 for P6 composite, respectively. These values are higher than that for self-diffusion in A1 （142 kJ mol-1）, suggesting that there is a significant contribution from the back stress caused by the presence of particles and/or whiskers in the matrix. The deformation mechanisms corresponding to domain B 1 and domain B2 are dislocation climb controlled creep and cross-slip for P6 composite, respectively. For W3P3 hybrid composite, the deformation mechanisms contain dislocation climb controlled creep and grain boundary sliding caused by DRX in domain A.
