Surface Texture Transformation in Micro-Cutting of AA6061-T6 with the Rehbinder Effect
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Online ISSN 2198-0810 Print ISSN 2288-6206
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Surface Texture Transformation in Micro‑Cutting of AA6061‑T6 with the Rehbinder Effect Jiayi Zhang1 · Yan Jin Lee1 · Hao Wang1 Received: 23 April 2020 / Revised: 6 August 2020 / Accepted: 12 August 2020 © Korean Society for Precision Engineering 2020
Abstract The Rehbinder effect (R-effect) on microcutting has been successful to augment machinability of ductile metals; however, there is a lack in understanding of its influence on texture evolution in the machined surfaces. This study validates the R-effect on AA6061-T6 and characterises the influence of the R-effect on the texture transformation in the machined surface. Microhardness tests reveal that the R-effect produces softer surfaces (87–96 HV) as compared with the surfaces produced conventionally (96–108 HV), which is attributed to the differences in grain types. A large fraction of substructured grains (96.4%) exists in the surfactant-affected subsurface while a higher proportion of deformed grains (42.8%) forms during conventional microcutting. In addition, the main texture components of the conventionally produced surface are Cube, Goss and S textures, which differ from the dominant volumes of Copper and R textures under the R-effect. The differences are results of the stress states induced during microcutting, which is exemplified through numerical simulations that consider the reduction in fracture toughness of the material with the R-effect. The advanced understanding of the R-effect better positions the use of surfactants as a cleaner near-dry metalworking fluid. Keywords Rehbinder effect · Surface integrity · Texture · Aluminium alloy · Ultraprecision machining Abbreviations vc Cutting speed t0 Uncut chip thickness Fc Cutting force Ft Thrust force T Temperature ρ Density β Taylor-Quinney factor (assumed to be 0.9) τ Stress γ Strain φ1 Degree along the y-axis Φ Degree along the x-axis φ2 Degree along the z-axis E Young’s modulus υ Poisson’s ratio cp Specific heat capacity k Thermal conductivity σ Flow stress * Hao Wang [email protected] 1
Department of Mechanical Engineering, Faculty of Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore
A Yield stress B Strain hardening constant n Work hardening exponent C Strain rate factor ε Equivalent plastic strain 𝜀̇ Strain rate 𝜀̇ 0 Reference strain rate Tm Melting temperature Tr Room temperature m Thermal softening exponent Di Individual damage variable σm Mean stress ω Damage initiation parameter D Overall damage variable L Element length u Equivalent plastic displacement uf Equivalent plastic displacement at failure 𝜎̄ Effective stress at the start of each increment Gf Fracture energy Gf-r Theoretical fracture energy under R-effect G’f-r Bulk uncut chip thickness theoretical fracture energy G’’f-r Surface layer theoretical fracture energy
Vol.:(0123456789) 13
International Journal of Precision Engineering and Manufacturing-Green Technology
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