脉冲涡流检测技术作为当前无损检测技术中的一种新技术,能够快速方便地检测金属构件中的缺陷;文中根据脉冲涡流检测信号源的特点,采用Direct Digital Frequency Synthesis(直接数字频率合成,简称DDS)技术,设计了一种参数可调式脉冲波形...脉冲涡流检测技术作为当前无损检测技术中的一种新技术,能够快速方便地检测金属构件中的缺陷;文中根据脉冲涡流检测信号源的特点,采用Direct Digital Frequency Synthesis(直接数字频率合成,简称DDS)技术,设计了一种参数可调式脉冲波形信号源的脉冲涡流检测系统;系统由脉冲涡流检测硬件电路、上位机、数据采集卡和相关软件组成;最后使用AD9850芯片产生1kHz、50%占空比的方波激励对标准缺陷试件进行实验,并提取特征值对试件的三种定量缺陷区分进行了研究。展开更多
基于虚拟仪器的概念 ,通过 GPIB接口总线实现 PC机与可编程仪器之间的通讯。本文介绍了以图形化编程环境 L ab VIEW作为开发平台 ,组建基于 GPIB接口总线的虚拟仪器的方法 ,并提出了用 L ab VIEW软件设计提高 GPIB性能的解决方案。该设...基于虚拟仪器的概念 ,通过 GPIB接口总线实现 PC机与可编程仪器之间的通讯。本文介绍了以图形化编程环境 L ab VIEW作为开发平台 ,组建基于 GPIB接口总线的虚拟仪器的方法 ,并提出了用 L ab VIEW软件设计提高 GPIB性能的解决方案。该设计提高了测试的自动化程度、测试效率和精度 。展开更多
In this paper, a detection technique for locating and determining the extent of defects and cracks in oil pipelines based on Hilbert-Huang time-frequency analysis is proposed. The ultrasonic signals reflected from def...In this paper, a detection technique for locating and determining the extent of defects and cracks in oil pipelines based on Hilbert-Huang time-frequency analysis is proposed. The ultrasonic signals reflected from defect-free pipelines and from pipelines with defects were processed using Hilbert-Huang transform, a recently developed signal processing technique based on direct extraction of the energy associated with the intrinsic time scales in the signal. Experimental results showed that the proposed method is feasible and can accurately and efficiently determine the location and size of defects in pipelines.展开更多
The precise detection of flaw echoes buried in backscattefing noise caused by material microstructure is a problem of great importance in uhrasonic non-destructive testing （NDT）. In this work, empirical mode decompo...The precise detection of flaw echoes buried in backscattefing noise caused by material microstructure is a problem of great importance in uhrasonic non-destructive testing （NDT）. In this work, empirical mode decomposition （EMD） is proposed to deal with ultrasonic signal. A time-frequency filtering method based on EMD is designed to suppress noise and enhance flaw signals. Simulated results are presented, showing that the proposed method has an excellent performance even for a very low signal-to-noise ratio （SNR）. The improvement in flaw detection was experimentally verified using stainless steel pipe sample with artificial flaws.展开更多
To enhance the measurement precision of eddy current sensor in particular environments such asextreme temperature changes and limited available space in aerospace, we optimized the structural parameters ofthe traditio...To enhance the measurement precision of eddy current sensor in particular environments such asextreme temperature changes and limited available space in aerospace, we optimized the structural parameters ofthe traditional dual-coil eddy current sensor probe by electromagnetic field analysis and finite element simulationmodeling, and further presented the criteria for determining the optimal coil distance of the dual-coil probe. Thesimulation results are verified by setting up an experimental platform. For the extreme temperature environment,the displacement measurement error caused by the full range temperature variation of the dual-coil sensor underthe optimal distance is less than 21.0% of that of the single-coil sensor. On this basis, we analyzed and verified thethermal stability of the structurally optimized dual-coil eddy current sensor. After temperature compensation,the displacement measurement accuracy can reach 14.9 times more accurate than that of the single-coil sensor.The method proposed in this paper can provide a design reference for the structural optimization of the axialdual-coil eddy current sensor probe.展开更多
文摘脉冲涡流检测技术作为当前无损检测技术中的一种新技术,能够快速方便地检测金属构件中的缺陷;文中根据脉冲涡流检测信号源的特点,采用Direct Digital Frequency Synthesis(直接数字频率合成,简称DDS)技术,设计了一种参数可调式脉冲波形信号源的脉冲涡流检测系统;系统由脉冲涡流检测硬件电路、上位机、数据采集卡和相关软件组成;最后使用AD9850芯片产生1kHz、50%占空比的方波激励对标准缺陷试件进行实验,并提取特征值对试件的三种定量缺陷区分进行了研究。
文摘基于虚拟仪器的概念 ,通过 GPIB接口总线实现 PC机与可编程仪器之间的通讯。本文介绍了以图形化编程环境 L ab VIEW作为开发平台 ,组建基于 GPIB接口总线的虚拟仪器的方法 ,并提出了用 L ab VIEW软件设计提高 GPIB性能的解决方案。该设计提高了测试的自动化程度、测试效率和精度 。
基金Project (No. 2001AA602021) supported by the Hi-Tech Researchand Development Program (863) of China
文摘In this paper, a detection technique for locating and determining the extent of defects and cracks in oil pipelines based on Hilbert-Huang time-frequency analysis is proposed. The ultrasonic signals reflected from defect-free pipelines and from pipelines with defects were processed using Hilbert-Huang transform, a recently developed signal processing technique based on direct extraction of the energy associated with the intrinsic time scales in the signal. Experimental results showed that the proposed method is feasible and can accurately and efficiently determine the location and size of defects in pipelines.
文摘The precise detection of flaw echoes buried in backscattefing noise caused by material microstructure is a problem of great importance in uhrasonic non-destructive testing （NDT）. In this work, empirical mode decomposition （EMD） is proposed to deal with ultrasonic signal. A time-frequency filtering method based on EMD is designed to suppress noise and enhance flaw signals. Simulated results are presented, showing that the proposed method has an excellent performance even for a very low signal-to-noise ratio （SNR）. The improvement in flaw detection was experimentally verified using stainless steel pipe sample with artificial flaws.
基金the National Natural Science Foundation of China(No.51975367)。
文摘To enhance the measurement precision of eddy current sensor in particular environments such asextreme temperature changes and limited available space in aerospace, we optimized the structural parameters ofthe traditional dual-coil eddy current sensor probe by electromagnetic field analysis and finite element simulationmodeling, and further presented the criteria for determining the optimal coil distance of the dual-coil probe. Thesimulation results are verified by setting up an experimental platform. For the extreme temperature environment,the displacement measurement error caused by the full range temperature variation of the dual-coil sensor underthe optimal distance is less than 21.0% of that of the single-coil sensor. On this basis, we analyzed and verified thethermal stability of the structurally optimized dual-coil eddy current sensor. After temperature compensation,the displacement measurement accuracy can reach 14.9 times more accurate than that of the single-coil sensor.The method proposed in this paper can provide a design reference for the structural optimization of the axialdual-coil eddy current sensor probe.
