涡流检测技术剖析.ppt

第三章作业： 1、涡流检测的基本原理是什么？适合检测何种材料的何种缺陷？ 2、趋肤效应及其影响因素是什么？ 3、提离效应及其克服方法是什么？ 4、涡流检测信号的显示方式是什么？ 第三章作业： 1、涡流检测的基本原理是什么？适合检测何种材料的何种缺陷？ 2、趋肤效应及其影响因素是什么？ 3、提离效应及其克服方法是什么？ 4、涡流检测信号的显示方式是什么？ Multi-Frequency Eddy Current Instruments Multi-Frequency Eddy Current Instruments (cont.) Multi-Frequency instruments usually refer to equipment that can drive inspection coils at more than two frequencies either sequentially (multiplexing) or simultaneously. This type of instrumentation is used extensively for tubing inspection in the power generation, chemical and petrochemical industries. These instruments are often capable of being computer networked and may have as many as four probes attached to them at one time. Multi-Frequency Eddy Current Instruments (cont.) Advantages of Multi-frequency inspections: Allows increased inspection information to be collected from one probe pulling. Provides for comparison of same discontinuity signal at different frequencies. Allows mixing of frequencies which helps to reduce or eliminate sources of noise. Often improves detection, interpretation and sizing capabilities of discontinuities. Multi-Frequency Eddy Current Instruments (cont.) Screen of multi-frequency instrument during inspection. * Crack standards come in variety of shapes and sizes, which is controlled by the inspection application. The material should be the same or very close to the material of the component being tested. EDM notches are often used to represent the crack but it should be noted that EDM notches usually give a stronger signal that a crack will. The image on the left has EDM notches of various depths and the two on the right show EDM notches at fastener holes. 3.2.2.7 影响线圈阻抗的因素 [4] 缺陷的影响 电导率和尺寸效应的综合 模型试验 ?d-直径 ?r-电导率 %-裂纹 分离不同效应，提高灵敏度的措施 选合适频率 3.3 涡流检测仪器及设备 3.3.1 涡流检测仪 3.3.2 涡流检测探头(检测线圈) 3.3.3 对比试样 3.3 涡流检测仪器及设备 3.3.1 涡流检测仪 功能： ①产生激励信号； ②检测涡流信息； ③鉴别影响因素； ④指示检测结果。 组成（基本电路） 振荡器 信号检出电路 放大器 信号处理电路 显示器和电源电路 3.3.1 涡流检测仪 1 振荡器 高频振荡频率为2MHz一6MHz，适合于检测表面裂纹；