Abstract
The article presents examples of implementing the nondestructive acoustic emission (AE) strength examination technique based on long-term prediction of welded joint fracture. The technique is developed on the basis of a micromechanical fracture process model and time dependencies of the AE accompanying the fracture process. The article describes the AE test results obtained by different researchers for various samples having different stressed-and-strain patterns, with butt and fillet weld joints and having different flaws appeared during the welding process and afterwards. Conventionally used diagnostic parameters (number of impulses, amplitude, average energy of the AE impulses recorded in the elastic loading stage, and the values of the local dynamic parameter), as well as sequentially calculated diagnostic parameters following from the proposed micromechanical model were used as information-containing indicators. The correlation coefficient between the values of AE diagnostic parameters or the strength characteristics calculated from them and the experimentally determined values of time to failure or to cracking, rupture load, stress level, and flaw sizes was adopted as the information content indicator. Comparison of different AE-based diagnosing versions has shown the advisability of using the proposed diagnostic parameters, which are invariant to the type of samples, type of recording devices, type of defects, types of loading, and the generated stressed state. The obtained results create prerequisites for achieving better efficiency of AE-based production-grade material examination technology.
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