Tham khảo tài liệu 'nondestructive evaluation and quality control (1998) part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Example 1 Acoustic Waveguide Sensors Used in Monitoring the Cooling of Molten Vitrified Nuclear Waste. Acoustic emission monitoring was used to help correlate cracking in vitrified high-level waste with cooling procedures. There was a need for a method capable of performing in an environment consisting of approximately 900 C 1650 F temperatures and 500 Gy h 50 000 rad h gamma radiation for the continuous monitoring of vitrified waste in canisters during cooling to detect glass cracking. Waveguide sensors about m 15 ft long were used one end was submerged in the glass and a sensing crystal and preamplifier were positioned on the other end. The signal from the sensor was passed through coaxial cables to the outside of the hot cell where it was received by an AE monitor system for analysis. At the end of the testing the AE sensors had been in the environment for 120 days and the accumulated dose of gamma radiation had reached 14 X 105 Gy 14 X 107 rad . The sensors were still functioning properly. Reference cited in this section 21. Standard Method for Primary Calibration of Acoustic Emission Sensors E 1106-86 Annual Book of ASTM Standards American Society for Testing and Materials Note cited in this section Example 1was provided by Phil Hutton Battelle Northwest Laboratory. Acoustic Emission Inspection Adrian A. Pollock Physical Acoustics Corporation Instrumentation Principles During an AE test the sensors on the testpiece produce any number of transient signals. A signal from a single discrete deformation event is known as a burst-type signal. This type of signal has a fast rise time and a slower decay as illustrated in Fig. 7. Burst-type signals vary widely in shape size and rate of occurrence depending on the structure and the test conditions. If there is a high rate of occurrence the individual burst-type signals combine to form a continuous emission. In some cases AE inspection relies on the detection of continuous emission see the sections Mechanisms of AE .
