Theoretical and numerical analysis on finishing mechanism by rheological properties and flow behaviors of abrasive media in micro-porous structures

Abstract

As one of the typical micro-porous structures, how to effectively finish the spray nozzles to remove the fabricated defects becomes the key problem to be urgently solved. In virtue of the unique viscoelastic characterization and excellent shear thinning nature, the abrasive media could smoothly penetrate through the micro spray holes and generate desired finishing effect. Through systemically investigating the rheological behaviors, the media obviously exhibited considerable storage modulus (around 33,000 Pa), loss modulus (around 17,000 Pa) and rather low shear viscosity, revealing the positive elasticity and fluidity equipped by media. Despite the existence of stress relaxation behavior (around 60 s), the polymer chains still remained the great stretched state resulting from the shrink of streamline when flowing into spray holes, as demonstrated by simulation results. By synthesizing the micro size effect, rheological behavior and morphology change, the finishing mechanism on spray holes was described in detail and verified by the groves and residual grains in finished surface. Besides, the bulges and burrs in the inlet of spray hole have been completely removed and the volumetric rate of finished nozzles was around 0.824 L/min, meeting the required value. In addition, by means of the yield strain-stress criteria and the grains geometry, most of grains exhibited excellent capability to initiate the plastic deformation, denoted by the critical angle range enough to generate plastic deformation. Considering both the discrete grains phase and continuous polymer phase in media, the forces on single grain were systemically investigated to establish the relevant mechanics model to theoretically describe the finish mechanism.