Modeling of Drag Finishing—Influence of Abrasive Media Shape

Irati Malkorra,Joel Rech,Pedro Arrazola,Ferdinando Salvatore,Mehmet Cici,Hanène Souli,Jason Rolet,Aude Mathis

doi:10.3390/jmmp5020041

Abstract

Drag finishing is a widely used superfinishing technique in the industry to polish parts under the action of abrasive media combined with an active surrounding liquid. However, the understanding of this process is not complete. It is known that pyramidal abrasive media are more prone to rapidly improving the surface roughness compared to spherical ones. Thus, this paper aims to model how the shape of abrasive media (spherical vs. pyramidal) influences the material removal mechanisms at the interface. An Arbitrary Lagrangian–Eulerian model of drag finishing is proposed with the purpose of estimating the mechanical loadings (normal stress, shear stress) induced by both abrasive media at the interface. The rheological behavior of both abrasive slurries (media and liquid) has been characterized by means of a Casagrande direct shear test. In parallel, experimental drag finishing tests were carried out with both media to quantify the drag forces. The correlation between the numerical and experimental drag forces highlights that the abrasive media with a pyramidal shape exhibits a higher shear resistance, and this is responsible for inducing higher mechanical loadings on the surfaces and, through this, for a faster decrease of the surface roughness.

Highlights

Drag finishing is a superfinishing process leading to great improvements of surface roughness
This paper aims to understand the influence of the media shape on the induced drag forces and the mechanical loading at the interface between abrasive media and the part surface, in order to explain why pyramidal media are more efficient in decreasing surface roughness
The drag forces predicted by the numerical model and the drag forces measured experimentally reveal that the pyramidal media lead to a higher drag force than the spherical ones

Summary

Introduction

Drag finishing is a superfinishing process leading to great improvements of surface roughness. ) is known to influence the surface finish [2,3,4], since it changes the tribological conditions in the contacts, evacuates media and part debris, and can even accelerate the process thanks to a chemical reaction. Large media are well known as being able to increase contact forces, leading to a faster decrease of surface roughness [6]. It was shown by [7] that the abrasive capacity of media influences material removal rates. The drag forces that media induce when the part is moved through them may play an important role: higher stresses will result in more material removal and plastic deformation.

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