Numerical prediction of failure in single point incremental forming using a phenomenological ductile fracture criterion

Mirnia, Mohammad Javad; Shamsari, Mohsen

doi:10.1016/j.jmatprotec.2017.01.029

Cited by 93 publications

(40 citation statements)

References 41 publications

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“…However, it is worth mentioning that there are very recent numerical works in ISF making use of more sophisticated modelling (considering material anisotropy, non-quadratic yield criteria, dynamic adaptive meshing, mixed hardening models, etc.) with the aim of reproducing more specific characteristic of the experimental procedure [24,27] or providing more accurate predictions for the onset of failure [28]. Analyzing the accumulated damage in the case of a tool of Φ10 mm diameter and a step down of 0.5 mm/pass, the case in which a direct transition from stable plastic deformation towards ductile fracture in the absence of necking was attained, the capacity of the numerical model for predicting failure by fracture in SPIF can be evaluated.…”

Section: Numerical Resultsmentioning

confidence: 99%

Section: Numerical Resultsmentioning

confidence: 99%

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Revisiting Formability and Failure of AISI304 Sheets in SPIF: Experimental Approach and Numerical Validation

Centeno

Martínez-Donaire

Bagudanch

et al. 2017

Metals

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Single Point Incremental Forming (SPIF) is a flexible and economic manufacturing process with a strong potential for manufacturing small and medium batches of highly customized parts. Formability and failure in SPIF have been intensively discussed in recent years, especially because this process allows stable plastic deformation well above the conventional forming limits, as this enhanced formability is only achievable within a certain range of process parameters depending on the material type. This paper analyzes formability and failure of AISI304-H111 sheets deformed by SPIF compared to conventional testing conditions (including Nakazima and stretch-bending tests). With this purpose, experimental tests in SPIF and stretch-bending were carried out and a numerical model of SPIF is performed. The results allow the authors to establish the following contributions regarding SPIF: (i) the setting of the limits of the formability enhancement when small tool diameters are used, (ii) the evolution of the crack when failure is attained and (iii) the determination of the conditions upon which necking is suppressed, leading directly to ductile fracture in SPIF.

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Section: Numerical Resultsmentioning

confidence: 99%

Section: Numerical Resultsmentioning

confidence: 99%

Revisiting Formability and Failure of AISI304 Sheets in SPIF: Experimental Approach and Numerical Validation

Centeno

Martínez-Donaire

Bagudanch

et al. 2017

Metals

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“…The FLCF was constructed under proportional loading (tensile test) and non-proportional loading (SPIF test). It was found the shape and value of FLCF in SPIF differ from the one of tensile test [14].…”

Section: Introductionmentioning

confidence: 87%

“…Modified MohrCoulomb (MMC) damage model was implemented in Abaqus/Explicit via user subroutine (VUMAT) to predict the ductile fracture in SPIF. According to the Lode angle parameter and stress triaxiality, it was found the loading path of SPIF is non-linear as well, the MMC model with non-linear damage accumulation can predict the SPIF fracture location accurately while there was 10% error in fracture depth prediction [14]. 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.…”

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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“…Currently employed tests are based on compression, tension and torsion, and they involve the use of specimens with shapes amplifying fracture propagation. In sheet forming, calibration tests are predominantly performed by tensile testing of sheet specimens such as dog-bone specimens, notched specimens, flat-grooved specimens and shear specimens [13][14][15][16]. The critical damage values are then validated with experimental tests using e.g.…”

Section: Introductionmentioning

confidence: 99%

Rotary compression in tool cavity—a new ductile fracture calibration test

Pater

Tomczak

Bulzak

et al. 2020

Int J Adv Manuf Technol

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Ductile fracture is one of the most common failure modes in hot metal forming. It can be predicted by means of so-called damage functions that describe the relation between stress, deformation and fracture initiation. A practical use of these functions requires the knowledge of the critical damage value of the material that is determined by calibration tests based on compression, tension and torsion. For the prediction to be correct, one must ensure that the modelled and real stresses are in agreement. Previous studies did not offer any effective test for determining critical values of damage under changing load conditions that occur in cross and skew rolling processes, among others. To compensate for this knowledge gap, researchers at the Lublin University of Technology have developed a new test consisting in rotary compression of a test-piece in a cavity between the tools, which is described in this paper. In the proposed test, a cylindrical test-piece is rolled over a cavity (impression) created by grooves on two mating tools. The cavity height is smaller than the test-piece diameter. At the critical value of the forming length, the state of stress induced thereby in the test-piece axis causes fracture. Knowing the critical forming length, it is possible to determine the critical value of damage by numerical modelling. The practical application of the proposed test is illustrated through the case of C45 grade steel subjected to forming in the temperature range 950-1150°C. The analysis makes use of the normalized Cockcroft-Latham (NCL) criterion of ductile fracture.

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Numerical prediction of failure in single point incremental forming using a phenomenological ductile fracture criterion

Cited by 93 publications

References 41 publications

Revisiting Formability and Failure of AISI304 Sheets in SPIF: Experimental Approach and Numerical Validation

Revisiting Formability and Failure of AISI304 Sheets in SPIF: Experimental Approach and Numerical Validation

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

Rotary compression in tool cavity—a new ductile fracture calibration test

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