Parameters of Acoustic Inhomogeneity for Nondestroductive Estimation of the Influence of Manufacturing Technology and Operational Damage on the Structure of Metal

An acoustic method for nondestructive evaluation of variations in the metal structure caused by violations in manufacturing technology or by accumulation of damage during operation has been proposed. The method is based on measuring microstructure-sensitive acoustic parameters, which are determined as normalized deviations of the ratios of the velocities of longitudinal and shear waves from the values characteristic of the “basic state” of the metal structure. Depending on the specific task, for the “basic” one we take the state of metal structure before the start of operation of the test object or the structure of metal in test samples whose strength characteristics are determined by the standard methods of destructive testing and are within acceptable limits. The relationship between the proposed acoustic parameters and the difference between the “basic” and real states of the material (in terms of the integral values of the compliance of microstructural inhomogeneities with respect to shear and longitudinal stresses) is discussed. The effectiveness of the proposed approach to assessing the structure of metal is demonstrated using the results of experimental studies of two essentially different types of structure—with isotropic and anisotropic inhomogeneities. Instrumental verification of the proposed parameters can be used for (1) nondestructive quality control of technological processes in the production of metallurgy and mechanical engineering products; (2) assessment of the degree of in-service metal damage accumulation; and (3) evaluation of mechanical properties, crack resistance characteristics, and other physical properties of metal.