Features of the Development of Calibration Specimens for Monitoring Ultra-Acoustic Flaw Detectors. Part 1. General Principles for the Construction of Calibration Specimens

Abstract

Special features in the use of calibration specimens (certifi ed reference materials) in nondestructive testing are considered. It is shown that calibration specimens are articles for which the coupling parameters, which express the dependence of the information signal of the nondestructive testing instruments on the geometry of the defect models and the physical properties of the test material, should be normalized. It is established that calibration specimens for use in control of the nonlinearity of the electroacoustic channel of an ultra-acoustic fl aw detector do not presently exist and that it is necessary to create a new group of calibration specimens, for example, in the form of a multi-element solid-state construction containing defect models of the same type. Through the use of such calibration specimens, it will become possible to identify poor-quality ultra-acoustic fl aw detectors. Keywords: calibration specimens, certifi ed reference materials, defect model, ultra-acoustic nondestructive testing device.The dominance of ultra-acoustic methods of nondestructive testing in industry has led to the appearance of a broad class of ultra-acoustic fl aw detectors. Each of these devices constitutes a coupled system consisting of an electronic block and primary direct-and slanted-type piezoelectric transducers. Through the use of slanted piezoelectric transducers, it is possible to achieve ultra-acoustic control by the echo method with different entry angles (from 40 to 75°) of transverse, longitudinal, and surface ultra-acoustic waves in the range of frequencies 1.8-10 MHz.Calibration specimens and analogs of such specimens, for example, simulator specimens of defects [1-3], in particular, are used for purposes of metrological assurance of the operation of certifi ed ultra-acoustic fl aw detectors (verifi cation of functionality, adjustment, calibration, and inspection) in domestic applications. The basic estimated parameters of ultra-acoustic fl aw detectors include the conventional sensitivity, resolution, error of depth gage, conversion factor of pulses of piezoelectric transducer, range of variation of detected information signal, and a number of other parameters, depending on the type of ultra-acoustic fl aw detector.We have not found any certifi ed specimens intended for use in estimation of the nonlinearity of the electroacoustic channel of an ultra-acoustic fl aw detector in the list of calibration specimens now in use or foreign analogs of these specimens.