Revealing, identifying and assessing "non-predictable flaws", crack type IV, by quantitative acoustic emission non-destructive inspection technology, photo-elastic and metallurgical methods

QAE NDI technology has been adapted to revealing, identifying and assessing one type of previously non-predictable failure of high energy equipment and piping, known as crack type IV. The research established the following: Cracks of type IV correspond to transverse shear crack mode II, according to the classification used in fracture mechanics and the physics of solids. The length of crack mode II jumps, the velocity of it propagation are significantly higher than in case crack mode I under the same loads. The earliest quantitative statistical Acoustic Emission (AE) indications and peculiarities necessary and sufficient to reveal cracks in specimens loaded by tension or shear loads, especially the differences in the AE power, median Energy, Average Frequency and Hit Rate of the AE signals flow. etc. Based on the findings described above have been formulated requirements and technological solutions for revealing, typifying and assessing crack IV.