I have tested many specimens and structures over my lifetime but never encountered a test with as much extraneous noise as this test. In addition excellent correlation between the summation of acoustic emission counts and crack length was observed. Figure 2 shows these results. Note in figure 2 that quite periods occur where no crack growth or AE is observed, followed by very active AE and crack growth. This is consistent with a crack growing in a redundant structure and in the process causing stress relief and redistribution of stresses and subsequent crack arrest.
Redistributed stresses cause new crack initiation in an adjacent area.
Traditional acoustic emission instrumentation used on the same test failed to achieve the same results.