Spring-dashpot vibrational model for the investigation of viscoelasticity in gelatinous abrasive media and subsequent control of parameters for the blast polishing of Ti-6Al-4 V alloy

Abstract

Blast polishing offers an operator-friendly solution to many of the previously encountered polishing difficulties. However, the process lacks studies into the control of key parameters, one of which is viscoelasticity (particularly present in biological based abrasive medias). Together with analytical-empirical models, a vibrational spring-dashpot model is presented, which attempts to characterize the impact force, contact time and damping ratio/coefficient of polishing media upon impact; as well as the effects of damping on contact parameters (stress, deformation, and area of contact). Impact force is shown to decrease dramatically with increasing hydration but increases linearly with an increase in kinetic energy. Contact time results show an exponential increase as hydration is increased and show a logarithmic decrease (to a limit) as kinetic energy is increased. Findings show that higher hydration levels result in lower damping ratios (with all results showing that underdamping is present). Higher kinetic energies show a decrease in damping ratio. Similarly, media damping coefficients decrease with both hydration increases and kinetic energy increases. Results show that contact stress is reduced at higher hydration levels (due to higher contact areas and lower forces) and that hydration acts to prevent brittle failure from occurring on the workpiece surface. The findings stipulated provide a base on which to further characterize the process and will help in development and further optimization of the blast polishing process.