Investigation on the effect of the vibratory peening process parameters on Almen intensity

Vibratory peening is a mechanical surface treatment process to improve both the fatigue life and smooth surface finish of metallic components in a single operation. Almen intensity is a significant parameter to relate the compressive residual stresses induced by the peening processes. In this study, the design of experiments (DOE) was used to investigate the effect of seven vibratory peening process parameters on Almen intensity. A specific vibratory peening machine, with the tub vibrating in a vertical pattern and resting on airbags, was built. Two empirical linear models were fitted. First, a screening model with primary effects showed that the media mass, airbag pressure, specimen longitudinal position, and lubrication rate have minor influence on Almen intensity. Secondly, a definitive model showed that high eccentricity, high frequency, and deep specimen immersion are required to reach high Almen intensities. The complex interactions between eccentricity, immersion depth, and frequency are described.