Elastic-constant variability in stainless-steel 304

Abstract

Variability of elastic constants in stainless‐steel 304 was determined by measuring longitudinal and transverse ultrasonic velocities in 20 samples acquired randomly. Three kinds of variations—sample to sample, directional within a sample, and repeated measurements on a single sample—are reported for four elastic constants: the bulk modulus, Young’s modulus, shear modulus, and Poisson’s ratio. Because of surprisingly small variations, 1% or less, the principal problem became measurement sensitivity and reproducibility. To overcome this problem, a high‐resolution measurement system was devised using general‐purpose equipment augmented with a very simple impedance‐transforming amplifier and an FET transmission gate. With this system the often‐reported troublesome transit‐time correction disappeared. Effects due to frequency and directionality were negligible.