Acoustic and Electromagnetic Properties of Civilian Gun Blanks

Abstract

The non-uniformity of acoustic properties of civilian gun barrel blanks has been studied. Four samples of civilian gun barrel blanks from the same batch, obtained after the first stage of the technological process, were subjected to the study. The blanks are of cylindrical shape with diameter of 34 mm, 210 mm in length and are made of high quality carbon steel 50A. In the research, a control echo-shadow method of multiple reflections was used with the application of an electromagnetic-acoustic transducer and a piezoelectric transducer based on a polyvinyl-dente-fluoride film for excitation and reception of waves. On the basis of the studies carried out using the echo-shadow method of multiple reflections on the samples of civilian gun barrel blanks, the following informative parameters were measured: the speed of the transverse, longitudinal and Rayleigh waves, and the elastic moduli and Poisson's ratio were calculated on their basis. The echo-shadow method of multiple reflections showed high sensitivity of the measured informative parameters of ultrasonic waves to material inhomogeneities in individual sections along the length of barrel blanks, which may be due to violations of machining processes. For transverse and Rayleigh waves, such parameters as the coefficient of detectability and dispersion are calculated, which also indicate the inhomogeneity of properties in individual sections with respect to length of the sample blanks. Using a micrometer, the diameters of the bars were measured at 17 points, and the minimum and maximum values were recorded at each point, which correlates with the results of measuring the wave velocities. The relative values of the electrical conductivity on each bar along the generatrix in 4 positions of the circle (0, 90, 180, and 270 degrees) were measured. Deviations of the obtained electric conductivity values up to 5% being the evidence of local inhomogeneities of electric properties revealing structural inhomogeneity is observed. Value inhomogeneity of coercitive force up to 0.7 A/cm along blank circumference.