Power spectrum density characterization of grinding wheel surface in ultrasonic vibration spiral grinding

During the ultrasonic vibration spiral grinding process, the surface topography of the grinding wheel varies complicatedly. To accurately characterize the characters of the grinding wheel surface, a power spectral density (PSD) analysis method was adopted by decomposing the microstructure of the grinding wheel surface into harmonics of different frequencies, amplitudes and phases. The wear behaviors of the grinding surfaces after conventional grinding and ultrasonic vibration grinding in different grinding stages were compared and analyzed by using the PSD analysis. The results show that the slope k of the surface PSD curve of the grinding wheel gradually decreases with the increase of the grinding stage, which means that a smaller k represents more serious surface wear of the grinding wheels. Moreover, in the early wear stage, the slope k of the ultrasonic grinding wheel surface is significantly larger than that of the conventional grinding wheel surface, but in the later wear stage, the decline rate of the slope k of the ultrasonic grinding wheel surface is significantly higher than that of the conventional grinding wheel surface. This trend reveals the variation of the effective number of abrasive grains and the wheel loading on the grinding wheel surface under two different grinding methods. Further analysis reveals that the ground flat and pulled-outs of the abrasive grains decrease the proportion of the power spectral density of them, and the wheel loading increases the overall energy value of the PSD curve. In the early wear stages, the number of effective abrasive grains on the ultrasonic vibration grinding wheel surface was larger than that of the conventional grinding surface, whereas in the later stages, the grinding wheel loading in ultrasonic vibration grinding is more significant.