Material Removal Mechanism of Green Machining on Powder Metallurgy Parts during Orthogonal Cutting

Abstract

Due to its energy-saving and cost-reducing characteristics, a novel green machining technique for powder metallurgy (PM) parts is attracting increasing concern. Unlike in the traditional PM machining technique, in the PM green-machining method arranges, the processing operation is performed before sintering. Since the pristine PM compacts are relatively soft because it just bonds the particles together, direct cutting on pristine PM compacts is a tool-saving and cost-effective manufacturing technique and its cutting mechanism is different from that of both solid plastic metals and conventional brittle materials because of the special characteristics of a discontinuous material. The influences of cutting parameters on machined surface roughness are investigated by orthogonal cutting experiments. The results show that the machined surface roughness decreases with increasing cutting thickness and rounded cutting edge radius and slightly increases with increasing rake angle. It is suggested that these results are contrary to the long-held notions of machined surface roughness. Moreover, a geometric model illustrating the PM green-machining process was established to reveal the mechanism of material removal and machined surface formation. This model shows that the material removal of PM is composed of particle shearing deformation, peeling, and ploughing/extruding. Finally, this machining model was validated through observations of machined surface morphology and chip morphology.

Finite Element Modeling and Optimization Analysis of Cutting Force in Powder Metallurgy Green Compacts

“…At a cutting thickness of 0.25 mm, Figure 4 reveals larger but fewer fine particles, aligning well with the experimental findings. This concurs with Yang et al's [28] conclusions regarding the mechanics of PM material removal, encompassing particle shear deformation, exfoliation, and plowing/extrusion. The congruence between the observed cutting morphologies further substantiates the model's accuracy and reliability.…”

“…The workpiece models predominantly employ rectangular meshing. However, due to the complex deformation behavior of PM materials during removal-comprising particle shear deformation, exfoliation, and plowing/extrusion [28]-a triangular mesh was adopted for this study. The workpiece was segmented into 46,646 triangular meshes.…”

“…Robert-Perron et al [27] investigated the sintering properties of cylindrical PM green compacts, demonstrating that pre-sintering machining had no impact on their tensile properties. Yang et al [28] created a geometric model for PM green machining, outlining a distinct material removal mechanism involving particle shearing, peeling, and plowing/extruding. This highlighted the unique nature of PM material removal compared to conventional materials.…”

An investigation on the material removal mechanism, surface porosity, and surface integrity in ultrasonic vibration assisted turning of porous stainless steel 316L

“…This phenomenon was also reported by other researchers. 17,18 Yang et al 19 investigated the mechanism of orthogonal machining of green powder metallurgy parts (before final hardening. Their results show that the surface roughness of the machining surface decreases with increasing the undeformed chip thickness and radius of the cutting edge of tool and it increases slightly with increasing the rake angle.…”