Fatigue crack growth (Δa/ΔN = f(K_max) data for several metallic materials were measured, using the 20 kHz ultrasonic resonance stressing method, and compared to 100-Hz frequency measurements. In a noncorrosive environment, a similar Δa/ΔN = f(K_max) dependence was found for both frequencies, Furthermore, several other features were found to be common to both, for example, (1) a ductile crack propagation mechanism. (2) a K_max and crack-tip opening displacement-governed crack growth behavior. (3) discontinuous crack propagation, and (4) the existence of a threshold stress intensity.

Therefore, the method is thought to be a useful tool in gaining crack growth data in a manner that saves time, material, and energy. It has great practical value in the low stress-intensity regime.

Measurements in 3.5 percent sodium chloride solution show an environmental influence only at crack growth rates below about 10⁻⁹ m/cycle.