Surface Crack Detection by A.C. Potential Method

该裂纹检测系统是用交流电源开发的。势滴法。在这个系统中，交流的集肤效应。被应用了。利用该系统进行了表面裂纹的测量，得到的主要结论如下。1.新的空调。开发了潜在裂纹检测系统，利用交流集肤效应对裂纹进行检测。得到了有效的应用。该系统由函数发生器、高频功率放大器、锁定放大器、FFT分析仪和微型计算机组成。系统的最大电流为5A，最大频率为20 kHz。经验证，该系统具有设计的性能。2.用交流电测仪进行了表面裂纹测量。潜在的系统。使用的是一台空调。频率在50赫兹到10千赫之间的正弦波。对于较小的裂纹，AC。频率越高，电势越大，而频率越大，电势越大。交流的皮肤效应。被成功地应用于所开发的电位系统中，有效地检测表面小裂纹。3.为提高测量效率，采用矩形交流。使用功率谱范围在50赫兹到5千赫之间的波。检测到的矩形交流。利用FFT分析仪对裂纹产生的电势进行功率谱分析。表面裂纹越小，高频的位势越大，而表面裂纹越大，低频的位势越大。空调。与正弦法相比，矩形波电位法的测试时间缩短了50倍。4.《空调》势函数法在矩形交流输电中的应用将其应用于内部缺陷检测。空调。当缺陷靠近表面时，高频电位增加较多，而当缺陷远离表面时，低频电位增加较多。

The crack detection system was developed using a.c. potential drop method. In this system, the skin effect of a.c. was applied. The surface crack measurements were carried out using the system and the main conclusions obtained are as follows. 1. The new a.c. potential crack detection system was developed, where the skin effect of a.c. was effectively applied. The system was composed of function generator, high frequency power amplifier, lockin amplifier, FFT analyzer and micro computer. The maximum current and frequency of the system are respectively 5A and 20 KHz. The system was confirmed to have a designed performance. 2. Surface crack measurements were carried out using the a.c. potential system. Used was an a.c. sinusoidal wave with frequencies between 50 Hz to 10 KHz. For the smaller crack, the a.c. potential with higher frequencies was more increased while for the larger crack, that with lower frequencies was specifically increased. The skin effect of a.c. was successfully used in the potential system developed to detect the small surface crack effectively. 3. For the efficient measurement, the rectangular a.c. wave which has the power spectrum range between 50 Hz and 5 KHz was used. The detected rectangular a.c. potential raised by cracks was analyzed by FFT analyzer into the power spectrum. The potential of higher frequencies was more increased by the smaller surface crack while that of lower frequencies was more increased by the larger surface crack. The a.c. potential method using the rectangular wave shortened the testing time 50 times in comparison with the sinusoidal method. 4. The a.c. potential method suing the rectangular a.c. was applied to the inside defect detection. The a.c. potential with higher frequencies was more increased if the defect was near the surface but that with lower frequencies was more increased when the defect was apart from the surface.