In order to monitor the basic mechanical properties and interior damage of concrete structures,the piezoelectric actuator/sensor based wave propagation method was investigated experimentally in the laboratory using a ...In order to monitor the basic mechanical properties and interior damage of concrete structures,the piezoelectric actuator/sensor based wave propagation method was investigated experimentally in the laboratory using a specifically designed test setup.The energy attenuation of stress waves was measured by the relative index between the output voltage of sensors and the excitation voltage at the actuator.Based on the experimental results of concrete cube and cylinder specimens,the effect of excitation frequencies,excitation amplitude,wave propagation paths and the curing age on the output signals of sensors are evaluated.The results show that the relative voltage attenuation coefficient RVAC is an effective indicator for measuring the attenuation of stress waves through the interior of concrete.展开更多
Civil infrastructure is continuously subject to aging and deterioration due to multiple factors,which lead to a decline in performance and impact structural health.Accumulated damage on structures increases operationa...Civil infrastructure is continuously subject to aging and deterioration due to multiple factors,which lead to a decline in performance and impact structural health.Accumulated damage on structures increases operational costs and poses significant risks to public safety.Effective maintenance,repair,and rehabilitation strategies are needed to ensure civil infrastructure’s overall safety and reliability.Non-Destructive Evaluation(NDE)methods are utilized to assess latent damage and provide decision-makers with real-time information for mitigating hazards.Within the last decade,there has been a significant increase in the research and development of innovative NDE techniques to improve data processing and promote efficient and accurate infrastructure assessment.This paper aims to review one of those methods,namely,Infrared Thermography(IRT),and its applications in civil infrastructure.A comprehensive review is presented by investigating numerous journal articles,research papers,and technical reports describing numerous IRT applications for bridges,buildings,and general civil structures made from different materials.The capability of IRT to identify and pinpoint anomalies,typically in the early stages of degradation,has excellent potential to improve the safety and shore up the dependability of civil infrastructures while reducing expenses tied to maintenance and rehabilitation.Furthermore,the non-invasive nature of IRT is beneficial in mitigating disturbances and downtime that may occur during various inspection procedures.It is highlighted that IRT is a highly versatile and effective tool for infrastructure condition assessment.With further advancement and fine-tuning of the available techniques,it is likely that IRT will continue to gain significant popularity in maintaining and monitoring civil infrastructure.展开更多
This paper presents an air-coupled impact echo(IE)technique that relies on the phase spectrum of the collected data to find the frequencies corresponding to the reflections from delaminations.The proposed technique ta...This paper presents an air-coupled impact echo(IE)technique that relies on the phase spectrum of the collected data to find the frequencies corresponding to the reflections from delaminations.The proposed technique takes advantage of the fact that the IE compression wave is not a propagating wave,but it is the 1st order symmetrical(S1)mode Lamb wave at zero group velocity(S1-ZGV).Therefore,it searches the phase spectra of the data collected by multiple sensors to locate the frequency corresponding to the lowest phase difference.As a result,the technique reduces the effect of propagating waves,including the direct acoustic wave and ambient noise.It is named the Constant Phase IE(CPIE).The performance of the CPIE is experimentally compared with the regular amplitude spectrum-based IE technique and two other multisensor IE techniques.The CPIE shows a performance advantage,especially in a noisy environment.展开更多
采用了50～200 MHz 的高频超声反射法技术,检测出含于 Si_3N_4试样中小至40～5μm 的夹杂颗粒及金属丝状缺陷。结合 X 射线探测技术,还判断出缺陷所处的深度和水平方位。但藉受入射表面光洁度影响的缺陷渡强度以判断缺陷的性质尚属难题...采用了50～200 MHz 的高频超声反射法技术,检测出含于 Si_3N_4试样中小至40～5μm 的夹杂颗粒及金属丝状缺陷。结合 X 射线探测技术,还判断出缺陷所处的深度和水平方位。但藉受入射表面光洁度影响的缺陷渡强度以判断缺陷的性质尚属难题。实验尚表明,电流导通法是验证 NDE 技术检出缺陷可信度的有效旁证手段。展开更多
基金Funded by the National Natural Science Foundation of China (No.50708065)the National High-tech R&D Program(863 Program )(No.2007-AA-11-Z-113)the Key Projects in the Science and Technology Pillar Program of Tianjin(No.11ZCKFSF00300)
文摘In order to monitor the basic mechanical properties and interior damage of concrete structures,the piezoelectric actuator/sensor based wave propagation method was investigated experimentally in the laboratory using a specifically designed test setup.The energy attenuation of stress waves was measured by the relative index between the output voltage of sensors and the excitation voltage at the actuator.Based on the experimental results of concrete cube and cylinder specimens,the effect of excitation frequencies,excitation amplitude,wave propagation paths and the curing age on the output signals of sensors are evaluated.The results show that the relative voltage attenuation coefficient RVAC is an effective indicator for measuring the attenuation of stress waves through the interior of concrete.
文摘Civil infrastructure is continuously subject to aging and deterioration due to multiple factors,which lead to a decline in performance and impact structural health.Accumulated damage on structures increases operational costs and poses significant risks to public safety.Effective maintenance,repair,and rehabilitation strategies are needed to ensure civil infrastructure’s overall safety and reliability.Non-Destructive Evaluation(NDE)methods are utilized to assess latent damage and provide decision-makers with real-time information for mitigating hazards.Within the last decade,there has been a significant increase in the research and development of innovative NDE techniques to improve data processing and promote efficient and accurate infrastructure assessment.This paper aims to review one of those methods,namely,Infrared Thermography(IRT),and its applications in civil infrastructure.A comprehensive review is presented by investigating numerous journal articles,research papers,and technical reports describing numerous IRT applications for bridges,buildings,and general civil structures made from different materials.The capability of IRT to identify and pinpoint anomalies,typically in the early stages of degradation,has excellent potential to improve the safety and shore up the dependability of civil infrastructures while reducing expenses tied to maintenance and rehabilitation.Furthermore,the non-invasive nature of IRT is beneficial in mitigating disturbances and downtime that may occur during various inspection procedures.It is highlighted that IRT is a highly versatile and effective tool for infrastructure condition assessment.With further advancement and fine-tuning of the available techniques,it is likely that IRT will continue to gain significant popularity in maintaining and monitoring civil infrastructure.
文摘This paper presents an air-coupled impact echo(IE)technique that relies on the phase spectrum of the collected data to find the frequencies corresponding to the reflections from delaminations.The proposed technique takes advantage of the fact that the IE compression wave is not a propagating wave,but it is the 1st order symmetrical(S1)mode Lamb wave at zero group velocity(S1-ZGV).Therefore,it searches the phase spectra of the data collected by multiple sensors to locate the frequency corresponding to the lowest phase difference.As a result,the technique reduces the effect of propagating waves,including the direct acoustic wave and ambient noise.It is named the Constant Phase IE(CPIE).The performance of the CPIE is experimentally compared with the regular amplitude spectrum-based IE technique and two other multisensor IE techniques.The CPIE shows a performance advantage,especially in a noisy environment.
文摘采用了50～200 MHz 的高频超声反射法技术,检测出含于 Si_3N_4试样中小至40～5μm 的夹杂颗粒及金属丝状缺陷。结合 X 射线探测技术,还判断出缺陷所处的深度和水平方位。但藉受入射表面光洁度影响的缺陷渡强度以判断缺陷的性质尚属难题。实验尚表明,电流导通法是验证 NDE 技术检出缺陷可信度的有效旁证手段。
