A new tool path with point contact and its effect on incremental sheet forming process
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ORIGINAL ARTICLE
A new tool path with point contact and its effect on incremental sheet forming process Zhidong Chang 1,2 & Wenshuai Huang 1,2 & Jun Chen 1,2 Received: 30 April 2020 / Accepted: 17 August 2020 / Published online: 24 August 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract Incremental sheet forming (ISF) is a promising and flexible sheet metal forming process, which is appropriate for small batch production of complex parts and customized sheet metal parts. Although the formability of sheet metal in ISF can be significantly improved compared with conventional stamping, some low-ductility materials still cannot be formed to specific geometry through ISF at room temperature, such as magnesium alloy and titanium alloy. Besides, geometric deviation affects industrial applications. In the present work, a novel point-contact tool path (PCTP) method free of circumferential friction is developed. For better understanding the forming characteristic and deformation mechanism of this new tool path, the surface quality, geometric accuracy, and forming limit of the sheet metal are investigated through experiment and numerical simulation for different sheet materials and compared with conventional spiral tool path. Experimental results demonstrate that PCTP can obviously improve the surface quality and geometric accuracy by using small interval length. Besides, the forming limits of AA2024 and AA7075 sheets are improved dramatically due to the absence of circumferential friction, and an updated analytical model of stress triaxiality is developed based on membrane analysis to explore the increased forming limit of PCTP. This novel tool path provides a simple and feasible solution for forming low-ductility sheet metal components at room temperature. Keywords Incremental sheet forming . Point-contact tool path . Formability . Surface quality . Geometric accuracy . Numerical simulation
Nomenclature h Offset distance of PCTP s Interval length of PCTP to Initial sheet thickness t Actual sheet thickness r Tool radius Δh Step depth σϕ Meridional stress under the tool σθ Circumferential stress under the tool σt Through-thickness stress under the tool μθ Coefficient of friction along the circumferential direction * Jun Chen [email protected] 1
Department of Plasticity Technology, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030, China
2
National Engineering Research Center of Die & Mold CAD, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030, China
μφ σ ε ηc ηp dθ
Coefficient of friction along the meridional direction Equivalent stress of the sheet metal Equivalent plastic strain Stress triaxiality of the sheet metal in CTP Stress triaxiality of the sheet metal in PCTP Circumferential angle of the small element
1 Introduction ISF is considered as an advanced and dieless forming process, which is appropriate for small batch production of complex sheet metal parts with high flexibility. To further control the
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