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Effect of pre-cut hole diameter on deformation mechanics in multi-stage incremental hole flanging of deep drawing quality steel

Gandla Praveen Kumar, Kurra Suresh, Prasad K. Sajun, Panda Sushanta Kumar, Singh Swadesh Kumar

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 1

260--282

Incremental hole flanging (IHF) is a relatively new sheet metal forming process to produce intricate shapes without using dedicated punches and dies. The present work focuses on understanding the mechanics of the multi-stage IHF process through experimental studies and the finite element approach. The IHF experiments were performed on deep drawing quality steel sheets with a pre-cut hole diameter of 45 mm, 50 mm, 60 mm, and 70 mm. The cylindrical flanges were formed in four stages with an initial wall angle of 60° to a final angle 90° with an angle increment of 10° in each stage. The maximum and minimum hole expansion ratio was found to be 2.06 and 1.17 respectively. The fracture was observed in a blank of 45 mm pre-cut hole diameter in the third stage at 40 mm depth. The fracture forming limit diagram (FFLD) was determined from incrementally formed varying wall angle conical and pyramidal frustums. Consequently, six different ductile damage models incorporating Hill48 anisotropy plastic theory were successfully calibrated. The Ayyada model showed good agreement with experimental FFLD as compared to all other models. The fracture limit determined experimentally and using the Ayyada model was implemented in the finite element simulation of the IHF process to predict the formability in terms of in-plane strain distribution, forming forces, and thickness distribution. The predicted results matched accurately with the experimental data within a 6% error for all investigated conditions. Noticeably, the strain path in IHF had three deformation modes viz. plane strain, bi-axial stretching, and uni-axial tension, which was comprehended using texture analyses. Finally, irrespective of the initial pre-cut hole diameter, the surface roughness was found to decrease with the number of stages of the IHF process.

Określenie sił w procesie walcowania poprzeczno-klinowego

Pater Z., Samołyk G.

Hutnik, Wiadomości Hutnicze

2009

Vol. 76, nr 12

860-865

W artykule skoncentrowano się na problematyce związanej z wyznaczaniem sił w procesach walcowania poprzeczno-klinowego (WPK). W tym celu zastosowano obliczenia inżynierskie (bazujące na metodzie energetycznej i oceny górnej), numeryczne (wykonane w programie DEFORM-3D, wykorzystującym metodę elementów skończonych) oraz badania doświadczalne realizowane w warunkach laboratoryjnych Politechniki Lubelskiej. Rozważano przypadki walcowania wsadów ze stali gatunku C45, kształtowanych na gorąco przy różnych parametrach procesu WPK, warunkowanych przez średnicę wsadu oraz kąt rozwarcia klina. Takie podejście umożliwiło porównanie wartości sił obliczonych i zmierzonych w próbach laboratoryjnych.

This paper concentrates on problem of determining forces in cross-wedge rolling processes (CWR). In order to this, the following steps were considered: engineering calculations (basing on energetic method and upper bound, numerical calculations (made in software DEFORM-3D, using the finite element method) and experimental research in laboratory conditions of Lublin University of Technology. Cases of rolling of billets from steel C45 were considered. These billets were formed in hot conditions at various CWR process parameters, dependant on billet diameter and spreading angle of wedge. This approach allowed comparing of values of forces calculated and measured in laboratory tests.