Evaluation of deformation stability and fracture mechanism in incremental sheet forming

Ai, Sheng; Lü, Bin; Chen, J.; Long, Hui; Ou, Hengan

doi:10.1016/j.ijmecsci.2017.03.012

Cited by 62 publications

(33 citation statements)

References 27 publications

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“…Extensive research has been carried out to explain the deformation and fracture mechanism in ISF through theoretical analysis and experimental testing [22][23][24][25][26][27][28][29]. The results of these studies showed that the deformation and fracture in ISF part occur due to different mechanisms i.e.…”

Section: Modelling Of Ductile Fracture In Isfmentioning

confidence: 99%

Investigation of the effect of forming parameters in incremental sheet forming using a micromechanics based damage model

Gatea

Lü

et al. 2018

Int J Mater Form

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The incremental sheet forming (ISF) process is considered as a feasible solution for forming a variety of small batch and even customised sheet components. The quality of an ISF product is affected by various process parameters, e.g. sheet material, stepdown, feed rate, tool diameter and lubricant. To produce an ISF part of sufficient quality and accuracy without defects, optimal parameters of the ISF process should be selected. In the present work, experiments and FE analyses were conducted to evaluate the influence of the main ISF process parameters including the step-down, feed rate and tool diameter on the formability and fracture of two types of pure Ti (grade 1 and 2). The Gurson-Tvergaard-Needleman (GTN) damage constitutive model with consideration of stress triaxiality was developed to predict ductile fracture in the ISF process due to void nucleation, growth and coalescence. It was found that the ISF parameters have varying degrees of effect on the formability and fracture occurrence of the two types of pure Ti, and grade 2 pure Ti sheet is more sensitive than grade 1 Ti sheet to the forming parameters due to low ductility.

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Section: Modelling Of Ductile Fracture In Isfmentioning

confidence: 99%

Investigation of the effect of forming parameters in incremental sheet forming using a micromechanics based damage model

Gatea

Lü

et al. 2018

Int J Mater Form

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“…An analytical model has been developed with the consideration of strain hardening and bending to study the deformation stability and fracture in ISF process of aluminium grads, AA1100 and AA5052. It was found the bending mechanism has a significant effect on the deformation stability as well as the fracture occurs based on the material's ductility and deformation stability [16]. FE simulation was employed to analyse the deformation of SPIF.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of formability and fracture of pure titanium in incremental sheet forming

Gatea

et al. 2017

Int J Adv Manuf Technol

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A forming limit diagram (FLD) is commonly used as a useful means for characterising the formability of sheet metal forming processes. In this study, the Nakajima test was used to construct the forming limit curve at necking (FLCN) and fracture (FLCF). The results of the FLCF are compared with incremental sheet forming (ISF) to evaluate the ability of the Nakajima test to describe the fracture in ISF. Tests were carried out to construct the forming limit diagram at necking and fracture to cover the strain states from uniaxial tension to equi-biaxial tension with different stress triaxialities-from 0.33 for uniaxial tension to 0.67 for equi-biaxial tension. Due to the fact that the Gurson-Tvergaard-Needleman (GTN) model can be used to capture fracture occurrence at high stress triaxiality, and the shear modified GTN model (Nahshon-Hutchinson's shear mechanism) was developed to predict the fracture at zero stress or even negative stress triaxiality, the original GTN model and shear modified GTN model may be not suitable to predict the fracture in all samples of the Nakajima test as some samples are deformed under moderate stress triaxiality. In this study, the fractures are compared using the original GTN model, shear modified GTN model and the Nielsen-Tvergaard model with regard to stress triaxiality. To validate the ability of these models, and to assess which model is more accurate in predicting the fracture with different stress triaxialities, finite element (FE) simulations of the Nakajima test were compared with an experimental results to evaluate the applicability of the Nakajima test to characterise the fracture from ISF. The experimental and FE results showed that the shear modified GTN model could predict the fracture accurately with samples under uniaxial tension condition due to low stress triaxiality and that the original GTN model is suitable for an equi-biaxial strain state (high stress triaxiality), whereas the stress triaxiality modified GTN model should be considered for samples which have moderate stress triaxiality (from plain strain to biaxial strain). The numerical and experimental FLCF of pure titanium from the Nakajima test showed a good agreement between the experimental and numerical results of ISF.

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“…In terms of ductile fracture, Anderson [26] reported that whether necking was suppressed or not before the fracture occurrence needed to be determined by the stress and strain states. In ISF, two different types of failure modes have been observed, fracture preceded by the necking or abrupt rupture without any obvious sign of necking, reported by Gupta and Jeswiet [27] and by Ai et al [28] when testing different types of materials. The mechanism behind the transition of two fracture modes is still unclear and needs to be investigated.…”

Section: Introductionmentioning

confidence: 93%

A review on material fracture mechanism in incremental sheet forming

Long

2019

Int J Adv Manuf Technol

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In incremental sheet forming (ISF), including single point incremental forming (SPIF) and double side incremental forming (DSIF), the material formability can be significantly enhanced when compared with conventional sheet forming processes. The material deformation in ISF is far more complicated because of the combined material deformation under stretching, bending, shearing, and cyclic loading, with an additional effect of compression in DSIF. Despite extensive investigation on material deformation during ISF, no theory has yet been widely agreed to explain different types of the material fracture behavior observed in ISF experiments. This paper presents a comprehensive review on the formability enhancement in ISF and proposes possible fracture mechanisms explaining the different types of fracture behavior observed in the experimental investigations. Discussions are presented to outline the current research progress and possible solutions to overcome the current ISF process limitations because of the material processing failure due to fracture.

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Evaluation of deformation stability and fracture mechanism in incremental sheet forming

Cited by 62 publications

References 27 publications

Investigation of the effect of forming parameters in incremental sheet forming using a micromechanics based damage model

Investigation of the effect of forming parameters in incremental sheet forming using a micromechanics based damage model

Evaluation of formability and fracture of pure titanium in incremental sheet forming

A review on material fracture mechanism in incremental sheet forming

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