Single toroidal roller burnishing of 2024-T3 Al alloy implemented as mixed burnishing process
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ORIGINAL ARTICLE
Single toroidal roller burnishing of 2024-T3 Al alloy implemented as mixed burnishing process G. V. Duncheva 1 & J. T. Maximov 1 & V. P. Dunchev 1 & A. P. Anchev 1 & T. P. Atanasov 1 & Jiri Capek 2 Received: 27 July 2020 / Accepted: 2 November 2020 / Published online: 13 November 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract Based on a comprehensive experimental study, single toroidal roller burnishing (STRB) of the 2024-T3 Al alloy can be successfully implemented as a mixed burnishing process. Optimum values of various governing factors provided minimum roughness and significant enhancement of the fatigue life of the treated specimens. With a planned experiment, regression analysis, and optimization procedure based on a genetic algorithm, the optimum factor values were established under a minimum roughness criterion. The derived model predicted a minimum roughness Ra = 0.074 μm. The experiment with optimal process parameters provided an average roughness (Ra) of 0.01 μm. STRB under these optimal conditions yields a relatively homogeneous surface in terms of microhardness with a surface microhardness increase coefficient of 37.6%. The parametric study of the residual surface hoop and axial stresses conducted via X-ray stress analysis shows that the STRB with near-optimal process parameters introduces significant residual stresses. STRB of the 2024-T3 Al alloy, implemented as a mixed burnishing process, produces a mirror-finish surface, improves the fatigue life by more than 2000 times, and increases the conventional fatigue limit by 35.1% compared to the reference condition. Keywords 2024-T3 Al alloy . Single toroidal roller burnishing . Roughness . Microhardness . Residual stresses . Fatigue life enhancement
Abbreviations CNC Computer numerical control HBB Hydrostatic ball burnishing LPB Low plasticity burnishing MST Mechanical surface treatment SRB Single roller burnishing STRB Single toroidal roller burnishing List of symbols A5 Elongation D External diameter of the toroidal deforming roller d Workpiece (specimen) diameter f Feed rate Fb Burnishing force kHV Surface microhardness increase coefficient n Number of passes * G. V. Duncheva [email protected] 1
Technical University of Gabrovo, 5300 Gabrovo, Bulgaria
2
Czech Technical University in Prague, Prague, Czech Republic
N r R Ra si v xi exi YRa σ−1 σu σY σres t σres z ψ
Number of cycles to failure Radius of the toroid of the toroidal deforming roller Cycle asymmetry coefficient Surface roughness X-ray elastic constant Burnishing velocity Coded variables Natural variables Objective function of the roughness Fatigue limit for symmetrical cycle Ultimate stress Yield limit Residual hoop stress Residual axial stress Transverse contraction
1 Introduction Modern structural and machine components must operate in conditions of increasing speeds and loads while minimizing their mass and size. High-strength aluminum alloys, including
3560
2024-T3, are appropriate materials because of their high strength to weight rat
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