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

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 characterizes 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. These are compared to experimentally gathered results for verification of the model. Impact force is shown to decrease dramatically with increasing hydration while increasing linearly with an increase in kinetic energy. Experimental findings reveal that 50% wet contact exhibits a 340% reduction in force magnitude compared to dry contact. Contact time results show an exponential increase with an increase in hydration. Research findings also show that higher hydration levels result in lower damping ratios and that higher kinetic energies (related to higher hydration levels) tend toward a decrease in damping ratio. Similarly, media damping coefficients decrease with both hydrational increases and kinetic energy increases. Results show that contact stress is reduced at higher hydration levels, which is mainly due to higher contact areas, and hence it was noticed that an increase in hydration prevents occurrence of chipping and brittle failure on the workpiece surface. Contact stress is shown to reduce by 325% from a 10% wet contact to a 50% wet contact. A high hydration of 30 to 50%, a high impinging velocity of value 31.4 m/s and above, a low stand-off distance of value 20 mm and below, a 45° polishing angle, and a polishing time of 20 to 40 min provide the most optimal parameters for efficient polishing to achieve a mirror finish on an additive manufactured Ti-6Al-4V component. The findings stipulated provide a base on which to further characterize the process and aim to promote further development and optimization of the blast polishing process.