The effect of tool edge radius on the contact phenomenon of tool-based micromachining

The contact phenomenon during micromachining is complicated due to the tool edge radius. This paper presents investigation of the effects of tool edge radius on the frictional contact and flow stagnation phenomenon, the stick–slide behavior and contact stress distributions, the evolutions of contact length, and the relationship between material deformation and total contact length. Through the arbitrary Lagrangian–Eulerian FE modeling approach, our findings revealed that the flow stagnation during material separations could be attributed to the counterbalance of shear contact components and it appeared to be insensitive to machining magnitude where a constant stagnation point angle of 58.5±0.5° was determined for a wide range of undeformed chip thicknesses. Three distinctive sticking and sliding regions associated with the flow stagnation phenomenon on the cutting tool were discovered following the identification of two stress criteria for sticking, τf=0 and/or τf=kf. In addition, the influence of tool edge radius on contact length and material deformation was determined and a theoretical model for the contact length of tool-based micromachining was proposed. It was also observed that tool–chip contact evolved in two successive stages through a series of intermittent sticking and sliding interactions as governed by the undeformed chip thickness and the transition of effective rake angle. An ultraprecision machining setup coupled with a high-speed and small field-of-view photography technique was proposed for experimental substantiation of the numerical results.