小波分析与漏磁检测信号处理

详细介绍了小波分析的基本理论,并将其引入到钢管漏磁探伤信号的分析中,可以去除噪声、压缩数据和检测奇异性,而且为缺陷的定性和定量分析提供了新的判定方法.     

含交错层叠电涡流传感器阵列的成像定位仪的研究

针对被遮盖的金属物体的可视化问题进行了研究探讨,采用交错层叠柔性电涡流传感器阵列替代线圈式电涡流传感器阵列,利用CCD摄像头拍摄遮盖物表面图像,实现金属物体与遮盖物表面的同步显示,并采用打印机将金属物体上螺纹孔中心位置标记在遮盖物表面相应位置。所研究的探测成像定位仪具有更高的定位精度,操作更简单,使用更方便。     

小波变换在管道弱超声回波奇异性检测中的应用

研究了小波变换在细尺度下检测信号奇异性的原理。通过对样管中标准缺陷的超声回波分析试验,证明6层db5小波变换可以有效地分离出湮没在噪声中的微弱缺陷信号,并可以有效地分离出信号的孤立奇异点,准确定位缺陷出现时刻。     

论半波式П形电磁轭和交叉电磁轭的磁场及提升力

半波式电磁轭组合了交流和直流电磁轭的优点。交叉半波式电磁轭可实现全方位探伤且连续可调、灵敏度高、能耗低、体积小。其提升力-F不是磁场强度峰值Bm的单值函数,因而不能反映电磁轭对工件的磁化能力,更不能反映其磁粉探伤灵敏度。     

管道中激励和接收扭转模态导波专用探头的研制与应用

超声导波检测技术是一种新兴的无损检测方法。扭转模态是管道中超声导波的模态之一,可以检测各类缺陷。采用厚度切变型压电陶瓷作为敏感元件的探头,其外形尺寸为20 mm×10 mm×20 mm,在4 m长的钢管中进行了扭转模态的激励与接收试验。结果表明,该探头能够有效地激励和接收扭转模态,抑制了其它模态导波的干扰。     

钢管漏磁探伤中孔洞缺陷的漏磁场分析

针对钢管孔洞缺陷进行了分析。分别从数学模型和仿真软件建模等方面对孔洞缺陷进行了漏磁场分析，并且将采集的漏磁信号进行处理，得出孔洞半径与漏磁信号之间的关系，为孔洞缺陷信号的识别提供了一定的参考依据。     

An experimental comparison of three wire beam electrode based methods for determining corrosion rates and patterns

Laboratory experiments have been carried out to examine the advantages and limitations of three wire beam electrode (WBE) based techniques, including the noise resistance R_n-WBE method, the overpotential-galvanic current method, and the galvanic current method, in determining corrosion rates and patterns. These techniques have been applied simultaneously to several selected corrosion systems of different characteristics. It has been found that the R_n-WBE method has advantages over other WBE based methods when applying to WBE surfaces under uniform corrosion. However, the R_n-WBE method has been found to be unsuitable for low noise level corrosion systems. It has also been found that both R_n-WBE and overpotential-galvanic current methods are similarly applicable to WBE surfaces under nonuniform corrosion. However, the galvanic current method has been found to be suitable only for WBE surfaces under highly localised corrosion. Some related issues regarding R_n calculation such as trend removal and its effects on corrosion mapping have also been discussed.     

High-frequency ultrasonic testing of young cement-based materials using the ‘prism technique’

A new technique for testing young cement paste and mortar is presented. It is based on a method, which uses unconventional prism-shaped specimens. It involves the precise measurement at fixed intervals of 24 h of the time-of-flight of both compressional and shear waves using high-frequency ultrasound. A water tank was designed that allows for easy coupling and handling of the specimens. Both waves are generated by mode conversion using the same transducer. The echoes from all the specimens were strong, and no signal processing was required. Thus, reliable and repeatable results were achieved using a very basic apparatus. Second-order elastic constants were evaluated, and correlation was made with the porosity and age of mortar. A new standard based on this method is proposed which would help in the making of prediction models for evaluating the strength of cement-based materials.     

喷气燃料银片腐蚀快速测定方法的研究

通过在喷气燃料油中加入极性溶剂改变其导电性,探讨了温度、外加直汉电源、溶剂等因素对喷气燃料银片腐蚀实验速度的影响,并对试验条件进行了优化,从而建立起喷气燃料银片文化馆快速测定方法。实验结果表明,这一快速试验方法试验时间短,结果正确、可靠,与ＳＨ／Ｔ００２３－９０所述方法有良好的相关性。     

爆炸焊接工艺参数与波形参数的关系

采用半圆柱实验法,研究了钛-钢爆炸焊接工艺参数与焊接结合波形参数间的关系.结果表明,随炸药量和复板飞行距离增加,波幅及波长均随之增大,工艺参数对波形成过程及波形参数有直接的影响,研究结果为爆炸焊接工艺参数的选择提供了可靠依据.