Effects of Crystallographic Anistropy on Orthogonal Micromachining of Single-Crystal Aluminum

Abstract

Anisotropy of workpiece crystals has a significant effect in micromachining since the uncut chip thickness values used in micromachining are commensurate with characteristic dimensions of crystals in crystalline materials. This paper presents an experimental investigation on orthogonal micromachining of single-crystal aluminum at different crystallographic orientations for varying uncut chip thicknesses and cutting speeds using a diamond tool. Micromachining forces, specific energies, effective coefficient of friction, shear angles, shear stresses, and chip morphology were examined for six crystallographic orientations at uncut chip thicknesses ranging from 5 �m to20�m and cutting speeds ranging from 5 mm/s to15mm/s. Three distinct types of forces were observed, including steady (Type-I), bistable (Type-II), and fluctuating (Type-III) force signatures. The forces were seen to vary by as much as threefold with crystallographic orientation. Although the effect of cutting speed was small, the uncut chip thickness was seen to have a significant orientation-dependent effect on average forces. Chip morphology, analyzed under scanning electron microscopy, showed shear-front lamella, the periodicity of which was seen to vary with crystallographic orientations and uncut chip thicknesses. �DOI: 10.1115/1.2917268�

FE/SPH modelling of orthogonal micro-machining of f.c.c. single crystal

“…Several experimental studies in f.c.c. metals reported on the effect of crystal orientation on chip morphology [1] and cutting forces [2][3][4]. Compared to the amount of available experimental data, efforts in incorporating crystal orientation into modelling of machining processes have been somewhat limited [5][6][7][8].…”

Strain-gradient crystal-plasticity modelling of micro-cutting of b.c.c. single crystal

“…In the experimental micromachining studies, such parameters as the cutting force, shear angle, dynamic shear stress and chip thickness were observed to depend on the orientation of the cutting direction and the cutting-plane normal with respect to the crystal axis. This is naturally Manuscript Click here to download Manuscript: Manuscript_Demiral_etal.doc Click here to view linked References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 explained by the fact that single crystals are highly anisotropic in their physical properties [1]. To elucidate the underlying physics for the micromachining process, different analytical and numerical models were proposed.…”

Variation of cutting forces in machining of f.c.c. single crystals

“…Selecting materials for single-crystal machining studies, mainly copper and aluminium have been preferred in the literature [3][4][5][6][7][8][9][10][11][12]. In this paper a welldeveloped computational FE/SPH model was applied for these two monocrystalline materials to fully understanding the variation of cutting forces.…”

“…Micro-plasticity modelling of machining proposed by Lee et al [6][7] is another limited research available in the literature analysing a mechanism of single-crystal machining. Shirakashi et al [8] and Kota and Ozdoganlar [9] used the Bishop and Hill's crystal plasticity model to predict shear angles and specific energies for f.c.c. single crystals.…”