Investigation of punch shape design in tube hydro-piercing processes
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ORIGINAL ARTICLE
Investigation of punch shape design in tube hydro-piercing processes Yeong-Maw Hwang 1 & Wei-Han Dai 1 & Chiao-Chou Chen 1 Received: 1 March 2020 / Accepted: 24 August 2020 / Published online: 6 September 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract This study is focused on punch shape design in tube hydro-piercing processes of SPFC590Y carbon steel tubes. The flow stresses of the carbon steel tubes obtained by tensile tests are used in the finite element simulations of tube hydro-piercing process with software “Deform 3D.” The ductile fracture criterion of Normalized Cockcroft and Latham is used during the FE simulations. The critical damage value for NCL fracture criterion is obtained by comparing simulation results and tensile test results. The effects of various parameters such as punch strokes, internal pressures, etc. on tube deformation and fracture mechanism in hydropiercing processes are investigated. Hydro-piercing experiments are conducted. The characteristics of the experimentally pierced hole sections are compared with the simulation results to validate the analytical models. The effects of various parameters on the characteristics of pierced hole sections after hydro-piercing processes are discussed numerically and experimentally. Keywords Tube hydroforming . Hydro-piercing . Finite element analysis . Punch shape design
1 Introduction The hydroforming processes have been widely applied to manufacturing parts in various fields, such as automobile, aircraft and aerospace, ship building industry, etc., due to the increasing demands for lightweight parts. Hydraulic punching or piercing is combined with hydroforming processes to save the manufacturing costs and raise the positional accuracy [1]. Generally, hydro-piercing can be conducted in two ways: outward piercing and inward piercing. In an outward piercing process, a counterpunch moves backward as a high internal pressure is reached. The process formability and the hole section characteristics are affected by the internal pressure and the corner shape of the die. The punched scrap is removed out of the tube after the process. In an inward piercing process, a punch moves forward to pierce the tube material and make the scrap drop into the tube. The hole section characteristics are affected by the internal pressure and punch shapes. The
* Yeong-Maw Hwang [email protected] 1
Department of Mechanical and Electro-mechanical Engineering, National Sun Yat-sen University, No. 70, Lein-Hai Rd., Kaohsiung 804, Taiwan
pierced hole section characteristics are different with inward and outward hydro-piercing processes. In order to improve the dimensional accuracy of the hole shape in a sheet hydro-piercing process, Shiomi et al. [2] used a hydrostatic pressure to support the sheet. The effects of punch movement types on pierced section surface quality were discussed. Wu et al. [3] used the finite element software ABAQUS with six ductile criteria to predict crack initiation and propagation in hydro-piercing p
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