Non-circular Drawing Research Articles

Effects of deformation stress mode on twin activation of CP-Ti wire through cryogenic non-circular drawing sequence

Effects of deformation stress mode on twin activation of CP-Ti wire through cryogenic non-circular drawing sequence

Meta-Heuristics for Engineering Optimisation - Applications to Metal Forming Processes

This paper presents the use of meta-heuristics one of the most popular types of optimisation methods for solving real engineering applications. The general procedure of meta-heuristics is detailed. The applications are related to metal forming processes. Two design examples, optimisation of a strip coiling process and the non-circular wire drawing process, are demonstrated. The results obtained are compared while advantages and disadvantages of using the optimisers are discussed.

Two-stage surrogate assisted differential evolution for optimization of a non-circular drawing sequence

In this work, a two-stage surrogate assisted optimization technique is proposed for optimizing a non-circular drawing (NCD) sequence. The objective function was introduced to minimize inhomogeneity of the effective strain distribution at the cross-sections of the drawn wire which could deteriorate its delamination characteristics. The design variables introduced were die geometry and reduction of areas of the NCD sequence. Combination of Kriging (KG) models and support vector regression (SVR) which found to be an efficient technique in the literature is used as a surrogate model while a new circular sampling generation technique is proposed and applied leading to a two-stage surrogate assisted optimization strategy. The results revealed that using the proposed two-stage surrogate assisted optimization strategy can reduce surrogate model uncertainty within the same total number of training points compared to a traditional approach. The optimum results showed better effective strain homogeneity at the cross-section of the drawn wire than the original wire drawing (WD) process and NCD sequence with the same total reduction of area and less number of passes.

Residual stress characteristics in a non-circular drawing sequence of pearlitic steel wire

In this paper, characteristics of residual stress in pearlitic steel wire drawn by a non-circular drawing (NCD) sequence with two processing routes, NCDA and NCDB, were experimentally and numerically investigated up to the 12th pass in comparison with conventional wire drawing (WD). For experimental investigation of the axial residual stress at the surface of the drawn wire, destructive (deflection) and non-destructive methods were employed. According to the experimental results, axial surface residual stress of the drawn wire by the NCD sequence was lower and more homogeneous compared to the conventional WD. Based on the elasto-plastic numerical simulation results from the surface to the center of the drawn wire using a commercial DEFORM-3D, an empirical relationship between residual stress and reduction of area was determined to predict the residual stress evolution in the multi-pass WD, NCDA, and NCDB, in that order. From the results of this investigation, it can be construed that the NCD sequence, especially the NCDB, might be helpful in improving the residual stress characteristics of pearlitic steel wire to improve its mechanical behavior and service life.

Process optimization of a non-circular drawing sequence based on multi-surrogate assisted meta-heuristic algorithms

Process optimization of a Non-circular drawing (NCD) sequence of a pearlitic steel wire was performed to improve the mechanical properties of a drawn wire based on surrogate assisted meta-heuristic algorithms. The objective function was introduced to minimize inhomogeneity of effective strain distribution at the cross-section of the drawn wire, which could deteriorate delamination characteristics of the drawn wires. The design variables introduced were die geometry and reduction of area of the NCD sequence. Several surrogate models and their combinations with the weighted sum technique were utilized. In the process optimization of the NCD sequence, the surrogate models were used to predict effective strain distributions at the cross-section of the drawn wire. Optimization using Differential evolution (DE) algorithm was performed, while the objective function was calculated from the predicted effective strains. The accuracy of all surrogate models was investigated, while optimum results were compared with the previous study available in the literature. It was found that hybrid surrogate models can improve prediction accuracy compared to a single surrogate model. The best result was obtained from the combination of Kriging (KG) and Support vector regression (SVR) models, while the second best was obtained from the combination of four surrogate models: Polynomial response surface (PRS), Radial basic function (RBF), KG, and SVR. The optimum results found in this study showed better effective strain homogeneity at the cross-section of the drawn wire with the same total reduction of area of the previous work available in the literature for fewer number of passes. The multi-surrogate models with the weighted sum technique were found to be powerful in improving the delamination characteristics of the drawn wire and reducing the production cost.

The effect of a non-circular drawing sequence on spheroidization of medium carbon steel wires

A non-circular drawing (NCD) sequence was applied as a prior cold working to improve spheroidization in a medium carbon steel wire. To investigate the effect of the NCD sequence on spheroidization behavior of the medium carbon steel wire, numerical simulations and experiments were carried out up to the fourth pass and were compared with the results of the conventional wire drawing (WD). From the three-dimensional numerical results, it was found that the NCD sequence could impose higher and relatively more homogeneous plastic deformation on the wire than the WD process. Spheroidization annealing at subcritical temperature of 705°C for 2, 4, and 8h was applied for the specimens that were produced by the WD and NCD processes, respectively. Tension and Vickers micro-hardness tests were conducted to measure mechanical properties of the annealed specimens. The annealed specimen processed by the NCD sequence showed the reduced ultimate tensile strength and micro-hardness, and the enhanced reduction of area compared to those values for the WD process. According to upsetting test results, it was found that cold workability was also improved for the annealed specimen processed by the NCD process compared to the one produced by the WD process. Scanning electron microscopy (SEM) was employed to investigate the microstructure change and to quantitatively measure the spheroidization ratio of the annealed specimens processed by both processes. Owing to the SEM results, the spheroidization of the annealed specimens processed by the NCD sequence was improved compared to the one produced by the WD process. It can be construed from the current investigation that the NCD sequence might be helpful in improving the spheroidization of cementite and cold workability of medium carbon steel wires during the subcritical annealing.

비원형 신선을 이용한 고강도-고연성 펄라이트 강선의 제조

본 연구에서는 고강도-고연성 펄라이트 강선을 제조하기 위하여 비원형 신선 공정을 적용하였다. 다단 비원형 신선 공정을 A와 B로 정의한 2 종류의 가공경로를 이용하여 상온에서 12 패스까지 수행하였다. 비원형 신선 공정과의 비교를 위해서 기존의 원형 신선 공정을 수행하고 기계적 특성과 집합조직발달에 대해 비교를 수행하였다. 원형 신선 공정으로 제조된 강선은 10 패스에서부터 박리파괴가 관찰되었지만, 비원형 신선 가공경로 B의 경우는 12 패스에서도 박리파괴가 발생하지 않았으며, 이는 X-선회절로부터 측정된 집합조직 결과에서 원형집합조직의 발달이 적은 것과 연관된다. 따라서, 다단 비원형 신선 공정을 통하여 기존의 신선 공정보다 박리파괴의 발생 가능성을 저감시킴으로써 높은 비틀림 연성을 갖는 고강도 펄라이트 강선을 제조할 수 있음을 확인할 수 있었다.

The effect of a non-circular drawing sequence on delamination characteristics of pearlitic steel wire

In this study, a non-circular drawing (NCD) sequence was applied to investigate the effect of deformation behavior, microstructure and texture evolution on delamination characteristics of pearlitic steel wire under torsional deformation mode. The multi-pass NCD sequence was numerically and experimentally applied up to the 12th pass in comparison with conventional wire drawing (WD). For investigation of the deformation characteristics of the drawn wires, three-dimensional finite element and flownet analyses were carried out. These simulation results indicated that the NCD could impose relatively homogeneous plastic deformation on the wire compared to the WD. From the scanning electron microscopy and X-ray diffraction results, globular cementite and cylindrical texture component, which might increase likeliness of delamination fracture, were rarely observed in the NCD drawn wire. In the torsion test, the delamination fracture was observed in the WD drawn wire for the 10th pass while it did not occur for the 12th pass NCD. In addition, the ultimate tensile strength (UTS) of 2300MPa grade wire was manufactured by the NCD and the UTS value was 257MPa higher than the one of the WD. Therefore, it was demonstrated that the multi-pass NCD could impose relatively homogeneous plastic deformation on the wire, resulting in high-torsional ductility with better strength compared to the WD.

Manufacturing of Medium Carbon Steel Wires with Improved Spheroidization by Non-circular Drawing Sequence

A non-circular drawing sequence was investigated for manufacturing medium carbon steel wires with improved spheroidization of cementite for better cold workability compared to those produced by the conventional wire drawing. The wire drawing and non-circular drawing processes with 20% area reduction per each pass were numerically and experimentally applied up to the fourth pass (total area reduction of 59%). The drawn wire by the non-circular drawing sequence shows higher average effective strain value than the one of the wire drawing in the numerical result. To investigate the effect of prior cold working on spheroidization of the drawn wire, spheroidization annealing was conducted at subcritical temperature of 705oC for 2h for both processes. According to the present investigation, the wires subject to subcritical annealing following the non-circular drawing sequence showed the reduced ultimate tensile strength and micro-hardness, and the enhanced reduction of area compared to those for the wire drawing. From upsetting test results, cold workability was also improved for the annealed specimen processed by the non-circular drawing sequence compared to the one produced by the wire drawing. Scanning electron microscopy (SEM) was employed to investigate microstructure changes during spheroidization annealing. Owing to the SEM results, the spheroidization of the annealed specimens processed by the non-circular drawing sequence was improved than the one produced by the wire drawing. It is demonstrated that the non-circular drawing sequence could manufacture the wires with improved spheroidization of cementite and cold workability compared to the wire drawing in the present work.

The effect of the multi-pass non-circular drawing sequence on mechanical properties and microstructure evolution of low-carbon steel

In this study, the multi-pass non-circular drawing sequence was investigated for manufacturing high-strength wires with better ductility in a simple continuous way without adding additional alloys and heat treatment considering the effect of microstructure evolution and die geometry of the sequence on the mechanical properties of low-carbon steel during the process. For this purpose, the non-circular drawing sequence was designed and applied up to the 10th pass at room temperature. Mechanical properties and microstructure evolution of the specimen processed by the sequence were investigated by tension, Vickers micro-hardness, electron backscattering diffraction (EBSD), and fatigue tests compared with those for the conventional wire-drawing process. From the EBSD results, the higher low angle grain boundaries length per unit area and smaller average grain size of the specimen processed by the non-circular drawing sequence were obtained than those of the specimen processed by the wire-drawing process for the 8th pass. These results indicated that more plastic deformation was imposed in the material by the non-circular drawing sequence, resulting in grain refinement of the deformed specimen compared to the wire-drawing process. It is demonstrated that the multi-pass non-circular drawing sequence could be beneficial in producing fine-grained wires with improved ultimate tensile strength, ductility, and fatigue property by simply changing drawing dies geometry of the conventional wire-drawing process.

The effect of microstructure and texture evolution on mechanical properties of low carbon steel in a non-circular drawing sequence

In this study, a new process sequence of non-circular and circular drawing is designed using finite element simulations and is proposed to produce strengthened wires in a simple continuous way for industrial applications. The developed non-circular drawing (NCD) sequence was experimentally applied to low carbon steel at room temperature. Mechanical properties, microstructure and texture evolution of the specimen processed by the newly proposed process and conventional wire drawing (WD) were investigated by tension test, electron backscattering diffraction (EBSD), and X-ray diffraction (XRD) for comparison. According to the present investigation, the specimen processed by the NCD sequence achieved 10.7% higher ultimate tensile strength (UTS) with slightly higher reduction of area at fracture than the one processed by the WD for the two-pass with the same area reductions. Furthermore, the UTS value (612MPa) of the drawn wire by the two-pass NCD sequence was equivalent to the level of 602MPa processed by the three-pass WD. From the EBSD results, the areal fraction of the low angle grain boundaries (1.12μm−1) of the specimen processed by the NCD was higher than that (0.78μm−1) of the specimen processed by the WD for the two-pass. The pole figures and ODFs of the specimen processed by the NCD sequence showed typical drawing and rolling textures. It is demonstrated that the non-circular drawing sequence could be beneficial in producing high-strength wires with comparable ductility through grain refinement according to the observations made in the present work.