The study of central cracking mechanism and criterion in cross wedge rolling

Zhou, Xiaochen; Shao, Zhutao; Zhang, Chi; Sun, Fengzhen; Zhou, Wenbin; Hua, Lin; Jiang, Jun; Wang, Liliang

doi:10.1016/j.ijmachtools.2020.103647

Cited by 19 publications

(15 citation statements)

References 40 publications

(60 reference statements)

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“…In this equation, A and B are material constants, presenting the contribution ratios of the maximum shear stress τ m and the rst principal stress σ 1 to central crack formation. Zhou et al [17,22] has validated this criterion by low ductility materials, including 27 groups of pure aluminium (highly strained) CWR tests and 16 groups of CWR tests with plasticine/ our composites. When the material is at high ductility, an energy-based fracture criterion will be employed considering the severe plastic deformation occurs before nal fracture, as presented in Eq.…”

Section: Proposal Of a New Central Crack Criterionmentioning

confidence: 99%

“…( ) The robustness of the previously proposed fracture criterion for low ductility materials has been validated by 27 groups of pure aluminium AA1100 H16 CWR cases and the 16 groups of plasticine/ our composite CWR cases. The experimental data for pure aluminium can be found in Table 1 in Zhou et al [22] and Tables 3 and 4 in Zhou et al [17]. These data were revisited to validate the high robustness of the proposed fracture criterion in different materials.…”

Section: Tablementioning

confidence: 99%

“…Pater et al [15,16] revealed that the central crack mechanism in C45 steels involved void formation and shear fracture by numerically analysing the stress triaxiality (the ratio of mean stress over the von Mises stress) range. Zhou et al [17] con rmed the dominant role of the maximum shear stress in central crack formation by investigating the stress states on the plasticine workpiece under different central crack conditions. It is well known that the fracture mechanisms vary with the material property, such as ductility.…”

Section: Introductionmentioning

confidence: 99%

“…Hawryluk et al [40] compared the mechanical properties of plasticine with different compositions. Zhou et al [17] designed the novel plasticine/ our composites to build the CWR billets and investigated the underlying central crack mechanism under various stress states. Thus, using model materials is reasonable to investigate the multiple fracture mechanisms and criteria in CWR.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 9 compares the normalised damage value (D n = D /D c ) on two plasticine materials in 21 CWR cases to validate the robustness of the proposed central crack in various materials. The rst 16 cases for low ductility were obtained from Tables3 and 4in the study of Zhou et al[17], represented by green…”

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confidence: 99%

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Investigation and prediction of central cracking in cross wedge rolling

Zhou¹,

Sun²,

Wang³

et al. 2022

Preprint

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Central cracking refers to the formation of internal cavities in cross wedge rolling (CWR) products. It occurs in various materials such as aluminium/titanium alloys, steels and plasticine at room or elevated temperatures, driven by different central cracking mechanisms. However, these mechanisms are still elusive, and a unified central cracking predictive model is absent due to the complex stress states within the workpiece, including triaxial stress states, cyclic loading and severe shear effects. In this study, the underlying fracture mechanisms were revealed, and a robust unified damage model with sound physical meanings was developed using a lab-scale CWR physical model and finite element models. The physical model with the plasticine billets was built, allowing the CWR dies with different geometries rapidly 3D printed and the billets with various ductility efficiently manufactured. The central cracking transiting from brittle to ductile fracture was experimentally observed for the first time using specifically designed plasticine/flour composite samples at varying ductility. The corresponding physics-based central cracking predictive model was proposed and validated quantitatively with 60 groups of CWR tests and compared with ten existing damage models/fracture criteria. This study effectively solves the long-lasting central cracking problem in the CWR industry and enhances the scientific understanding of fracture mechanics in complex engineering applications.

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Section: Proposal Of a New Central Crack Criterionmentioning

confidence: 99%

Section: Tablementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Investigation and prediction of central cracking in cross wedge rolling

Zhou¹,

Sun²,

Wang³

et al. 2022

Preprint

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Manufacturing large shafts by a novel flexible skew rolling process

Lin

Wang

Zhou

et al. 2021

Int J Adv Manuf Technol

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When manufacturing large shafts with multi-specification and small-batch production, both the conventional forging and rolling process bring a high tooling cost due to heavy forging press or large-size specialized roller. In this study, a novel flexible skew rolling (FSR) process is proposed by adding degrees of freedom to the rollers as compared to the typical skew rolling process. Since each of the FSR rollers has three 34 degrees of freedom (circle rotating, radial rotating and radial feeding), the FSR process 35 can be divided into four stages: radial rolling, rollers inclining, skew rolling and rollers 36 levelling. Therefore, the FSR process can produce various shafts with same rollers via programming different movements. To verify the feasibility of FSR process, a physical investigation corresponding with a numerical simulation for a single-step shaft is undertaken with a Φ80×390 mm C45 steel billet. According to the results from physical experiments and numerical simulations, the FSR formed shaft has a maximum deviation of 0.99 mm, and its microstructure and properties have been improved obviously. Moreover, although there is a tendency of center crack in FSR products as predicted by numerical results, both the transverse and longitudinal section of the physical shaft are free from central cracking. The major forming defects existed on the rolled shaft are knurled pockmarks, surface threads and side cavity, which are the typical defects of the conventional skew rolling and cross-wedge rolling and can be removed by machining. To the authors' knowledge, this novel process has a good combination of flexible production and less loading, which will be of great engineering significance to reduce the tooling cost in large shafts manufacturing.

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