Various structural defects deteriorate tunnel operation status and threaten public safety.Current tunnel inspection methods face problems of low efficiency,high equipment expense,and difficult data management.Combinin...Various structural defects deteriorate tunnel operation status and threaten public safety.Current tunnel inspection methods face problems of low efficiency,high equipment expense,and difficult data management.Combining the deep learning model and the 3D reconstruction method based on structure from motion(SfM),this paper proposes a novel SfM-Deep learning method for tunnel inspection.The high-quality 3D tunnel model is constructed by using images taken every 1 m along the longitudinal direction.The instance segmentation of leakage in longitudinal images is realized using the mask region-based convolutional neural network deep learning model.The SfM-Deep learning method projects the texture of the images after defect recognition to the 3D model and realizes the visualization of leakage defects.By projecting the model to the design cylindrical surface and expanding it,the tunnel leakage area is quantified.Through its practical application in a Shanghai metro shield tunnel,the reliability of the proposed method was verified.The novel SfM-Deep learning method can help engineers efficiently carry out intelligent tunnel detection.展开更多
A key issue, which influences the applications of magnetic flux leakage testing, is defect quantification. There have been many research on the relationship between width, depth and magnetic flux leakage of slot defec...A key issue, which influences the applications of magnetic flux leakage testing, is defect quantification. There have been many research on the relationship between width, depth and magnetic flux leakage of slot defect. However, the length factor is often ignored. The relationship between characteristics of defect leakage field and defect length was investigated. The magnetic flux leakages of a series of plate specimens with the same width, same depth and different length slot defects were tested under the same magnetizing conditions. Testing results show that defect length is an important parameter needed to consider in quantifying defects.展开更多
The presence of walls’thermal defects can lead to large deviations between predicted and actual values of energy consumption.Infrared images have been used to compare the differences in U-value(heat transfer coeffici...The presence of walls’thermal defects can lead to large deviations between predicted and actual values of energy consumption.Infrared images have been used to compare the differences in U-value(heat transfer coefficient)and heat flow between defect and normal building walls.However,the extent to which different defects affect the U-value of building walls remains to be investigated.This study proposes a method for evaluating the impact of various defects on the U-value of building wall envelopes.Infrared images were acquired for a building in Beijing,China to demonstrate the method.First,the accuracy of the method for measuring heat flow through building walls was validated using the heat flow meter method.Second,the K-means method was applied to classify wall pixel temperatures and to identify defects of building walls.The area and boundary of defects were got.Then,the validated infrared method was used to calculate the U-value for different defects.Finally,the difference in heat transfer coefficients(ΔU_(sd))was used to evaluate the impact of various defects on the building wall.The results indicated that variations in the area and temperature of defects contributed differently to the wall’s U-value.The maximum difference between the U-value of the repaired defect and the unrepaired wall is 0.42 W/(m^(2)·K).The method proposed in this study quantitatively assesses the extent to which defects affect the U-value of a building wall,providing reference data for making decisions regarding wall renovation.展开更多
Solid lubrication is an excellent option to reduce friction and wear in dry sliding conditions,as well as a secondary source of protection in fluid-lubricated systems.Considering the most widely used solid lubricants,...Solid lubrication is an excellent option to reduce friction and wear in dry sliding conditions,as well as a secondary source of protection in fluid-lubricated systems.Considering the most widely used solid lubricants,carbon-based lubricants are among the most versatile for tribological use.The reasons for this include their availability and their innate ability to adopt various nanostructures.The crystalline ordering of carbon has been identified as the main factor governing its tribological behavior.This work presents and discusses the most significant findings from an ongoing research program aimed at developing carbon-based solid lubricants.In this sense,several carbon-based materials with diverse levels of nanostructural order have been studied:three-dimensional(3D)crystalline graphite(GR);novel carbide-derived two-dimensional(2D)turbostratic carbon(CDC)produced from Fe–SiC(GSF)and B4C–Cr3C2(GBC)solid-state reactions;NH3 plasma-functionalized multilayer graphene(MLG);in situ fluorinated diamond-like carbon(DLC)(isfDLC);vertically aligned carbon nanotube(CNT)films.Initially,we present a brief description of the processing route for obtaining these materials,followed by their microstructural characterization and a synthesis of the most relevant aspects of tribological evaluation.Dry sliding tests in reciprocating motion were employed with different tribo-pair geometries,specimens and counter-body materials,varied surface topography,and diverse routes to add solid lubricants to the contact(vacuum impregnation of sintered steels,drop-casting,self-lubricating composites and vertically aligned films).The results provide a holistic view of the nature of the tribolayers formed by these materials.Finally,a new micro-Raman(µRaman)analysis technique for quantifying the point and line defects of the carbon present in tribolayers is used to correlate the lubrication and degradation mechanism of carbonaceous solid lubricants with their initial nanostructure and testing conditions.This technique provides new insights into the nature of tribolayers produced by carbon-based solid lubricants.展开更多
Carbon-based solid lubricants are excellent options to reduce friction and wear,especially with the carbon capability to adopt different allotropes forms.On the macroscale,these materials are sheared on the contact al...Carbon-based solid lubricants are excellent options to reduce friction and wear,especially with the carbon capability to adopt different allotropes forms.On the macroscale,these materials are sheared on the contact along with debris and contaminants to form tribolayers that govern the tribosystem performance.Using a recently developed advanced Raman analysis on the tribolayers,it was possible to quantify the contactinduced defects in the crystalline structure of a wide range of allotropes of carbon-based solid lubricants,from graphite and carbide-derived carbon particles to multi-layer graphene and carbon nanotubes.In addition,these materials were tested under various dry sliding conditions,with different geometries,topographies,and solid-lubricant application strategies.Regardless of the initial tribosystem conditions and allotrope level of atomic ordering,there is a remarkable trend of increasing the point and line defects density until a specific saturation limit in the same order of magnitude for all the materials tested.展开更多
基金supported by the Key Field Science and Technology Project of Yunnan Province(Grant No.202002AC080002)the National Natural-Science Foundation of China(Grant No.52078377).
文摘Various structural defects deteriorate tunnel operation status and threaten public safety.Current tunnel inspection methods face problems of low efficiency,high equipment expense,and difficult data management.Combining the deep learning model and the 3D reconstruction method based on structure from motion(SfM),this paper proposes a novel SfM-Deep learning method for tunnel inspection.The high-quality 3D tunnel model is constructed by using images taken every 1 m along the longitudinal direction.The instance segmentation of leakage in longitudinal images is realized using the mask region-based convolutional neural network deep learning model.The SfM-Deep learning method projects the texture of the images after defect recognition to the 3D model and realizes the visualization of leakage defects.By projecting the model to the design cylindrical surface and expanding it,the tunnel leakage area is quantified.Through its practical application in a Shanghai metro shield tunnel,the reliability of the proposed method was verified.The novel SfM-Deep learning method can help engineers efficiently carry out intelligent tunnel detection.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.50001006,50305017)China Postdoctoral Science Foundation.
文摘A key issue, which influences the applications of magnetic flux leakage testing, is defect quantification. There have been many research on the relationship between width, depth and magnetic flux leakage of slot defect. However, the length factor is often ignored. The relationship between characteristics of defect leakage field and defect length was investigated. The magnetic flux leakages of a series of plate specimens with the same width, same depth and different length slot defects were tested under the same magnetizing conditions. Testing results show that defect length is an important parameter needed to consider in quantifying defects.
基金funded by the China Postdoctoral Science Foundation(2024M751701).
文摘The presence of walls’thermal defects can lead to large deviations between predicted and actual values of energy consumption.Infrared images have been used to compare the differences in U-value(heat transfer coefficient)and heat flow between defect and normal building walls.However,the extent to which different defects affect the U-value of building walls remains to be investigated.This study proposes a method for evaluating the impact of various defects on the U-value of building wall envelopes.Infrared images were acquired for a building in Beijing,China to demonstrate the method.First,the accuracy of the method for measuring heat flow through building walls was validated using the heat flow meter method.Second,the K-means method was applied to classify wall pixel temperatures and to identify defects of building walls.The area and boundary of defects were got.Then,the validated infrared method was used to calculate the U-value for different defects.Finally,the difference in heat transfer coefficients(ΔU_(sd))was used to evaluate the impact of various defects on the building wall.The results indicated that variations in the area and temperature of defects contributed differently to the wall’s U-value.The maximum difference between the U-value of the repaired defect and the unrepaired wall is 0.42 W/(m^(2)·K).The method proposed in this study quantitatively assesses the extent to which defects affect the U-value of a building wall,providing reference data for making decisions regarding wall renovation.
文摘Solid lubrication is an excellent option to reduce friction and wear in dry sliding conditions,as well as a secondary source of protection in fluid-lubricated systems.Considering the most widely used solid lubricants,carbon-based lubricants are among the most versatile for tribological use.The reasons for this include their availability and their innate ability to adopt various nanostructures.The crystalline ordering of carbon has been identified as the main factor governing its tribological behavior.This work presents and discusses the most significant findings from an ongoing research program aimed at developing carbon-based solid lubricants.In this sense,several carbon-based materials with diverse levels of nanostructural order have been studied:three-dimensional(3D)crystalline graphite(GR);novel carbide-derived two-dimensional(2D)turbostratic carbon(CDC)produced from Fe–SiC(GSF)and B4C–Cr3C2(GBC)solid-state reactions;NH3 plasma-functionalized multilayer graphene(MLG);in situ fluorinated diamond-like carbon(DLC)(isfDLC);vertically aligned carbon nanotube(CNT)films.Initially,we present a brief description of the processing route for obtaining these materials,followed by their microstructural characterization and a synthesis of the most relevant aspects of tribological evaluation.Dry sliding tests in reciprocating motion were employed with different tribo-pair geometries,specimens and counter-body materials,varied surface topography,and diverse routes to add solid lubricants to the contact(vacuum impregnation of sintered steels,drop-casting,self-lubricating composites and vertically aligned films).The results provide a holistic view of the nature of the tribolayers formed by these materials.Finally,a new micro-Raman(µRaman)analysis technique for quantifying the point and line defects of the carbon present in tribolayers is used to correlate the lubrication and degradation mechanism of carbonaceous solid lubricants with their initial nanostructure and testing conditions.This technique provides new insights into the nature of tribolayers produced by carbon-based solid lubricants.
基金the following Brazilian agencies for funding this research:CNPq,CAPES,BNDES and the Chilean agency ANID Vinculación Internacional FOVI220096(No.72190023)as well as Nidec Global Appliance/Embraco.
文摘Carbon-based solid lubricants are excellent options to reduce friction and wear,especially with the carbon capability to adopt different allotropes forms.On the macroscale,these materials are sheared on the contact along with debris and contaminants to form tribolayers that govern the tribosystem performance.Using a recently developed advanced Raman analysis on the tribolayers,it was possible to quantify the contactinduced defects in the crystalline structure of a wide range of allotropes of carbon-based solid lubricants,from graphite and carbide-derived carbon particles to multi-layer graphene and carbon nanotubes.In addition,these materials were tested under various dry sliding conditions,with different geometries,topographies,and solid-lubricant application strategies.Regardless of the initial tribosystem conditions and allotrope level of atomic ordering,there is a remarkable trend of increasing the point and line defects density until a specific saturation limit in the same order of magnitude for all the materials tested.
