Acoustic emission monitoring for rolling contact fatigue of superfinished ground surfaces

Abstract

Grinding is the key finishing process in mass production of various precision components such as bearings, cams, shafts, etc. Grinding induced surface integrity has significant impact on rolling contact fatigue life. However, the effect of grinding induced surface integrity on rolling contact fatigue (RCF) life has been poorly understood. Therefore, an effective method to in-process monitor fatigue failure is critical to study the effects of surface integrity on RCF. In situ monitoring for fatigue failure of the ground and polished AISI 52100 samples was accomplished using an acoustic emission sensor and signal processing software. A real life loading of contact pressure and rolling speed were applied to the well lubricated test samples. Analytical approaches to determine contact stress and RCF life were derived based on Hertz theory and kinematic analysis. All AE signals are sensitive in general to fatigue failure. The AE signals amplitude, absolute energy, and RMS increase sharply when fatigue occurs, while counts and average frequency decrease sharply with the onset of fatigue. A signal shoot always appears in the 3D (hit-amplitude-time) AE signal map whenever fatigue occurs. AE amplitude is the most stable signal for monitoring fatigue. The polished ground samples can achieve as many as 194 million cycles at a peak Hertz pressure of 4.6 GPa. Shearing may be the dominant mechanism for fatigue crack initiation and development.