由于超声波衍射时差法（TOFD）的扫查面盲区较大，所以在应用TOFD技术前需要准确掌握盲区的大小，才能保证受检产品得到有效检测，避免漏检。检测前除了对扫查面盲区进行计算外，还必须采用相应的对比试块进行验证。结合目前检测技术的需求，设计了一种新型的扫查面盲区对比试块，采用该试块能够得到不同工况、不同检测条件下的扫查面盲区大小，从而避免漏检。

Due to the large blind area of the scanning surface of the ultrasonic time of flight diffraction method (TOFD), it is necessary to accurately grasp the size of the blind area before applying TOFD technology to ensure that the inspected product is effectively tested and avoid missed inspections. In addition to calculating the blind area of the scanning surface before testing, the corresponding comparison test block must also be used for verification. Combining the requirements of current detection technology, a new type of scanning surface blind zone comparison test block is designed. Using this test block, the scanning surface blind zone under different working conditions and different detection conditions can be obtained, which can avoid the deviation of the scanning surface blind zone verification. Thereby avoiding missed inspection.