Deformation analysis in single-point incremental forming through finite element simulation

Li, Yanle; Daniel, William J.T.; Meehan, Paul A.

doi:10.1007/s00170-016-8727-9

Cited by 45 publications

(23 citation statements)

References 24 publications

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“…The results showed that the SPIF part deforms under three deformation modes, i.e. stretching, shearing and bending [17].…”

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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“…The results showed that the SPIF part deforms under three deformation modes, i.e. stretching, shearing and bending [17].…”

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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“…For the shear strains, it can be observed that PE23 and PE12 are the two dominant shear strains in the single-sided contact zone (tool-sheet), which is in accordance with the shear strain contribution in single point ISF as reported by Li et al [15]. It can be also observed that the shear strain PE13 of the A detailed through-the-thickness shear strain evolution is shown in Fig 3.10.…”

Section: Plastic Strain Componentssupporting

confidence: 84%

“…Also, the residual stresses are positive in the inner surface and negative in the outer surface of the formed truncated cone in the circumferential direction. Similarly, Li et al [15]…”

Section: Numerical Simulationmentioning

confidence: 87%

“…The forming tool moves along the clockwise direction in each contour and then moves downwards as it reaches the step down point locus. A detailed illustration of the step down and step over in a single tool pass is illustrated in The anisotropic material property of the sheet blank is not taken into consideration based on the material data obtained from previous uniaxial tensile tests of the material AA7075-O with thickness of 1.6 mm in the rolling, transverse and diagonal directions [15]. The yield locus is defined by the isotropic von Mises yield criterion, which is given by,…”

Section: Fe Modelling Of the Multi-point Isfmentioning

confidence: 99%

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Investigation of control strategies for fracture prevention in the multi-point incremental sheet forming process

Wang¹

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This thesis is focused on understanding the deformation and failure mechanisms in incremental sheet forming (ISF) and on development of effective and efficient closed-loop control strategies to delay the fracture in multi-point ISF. Incremental sheet forming is a flexible and energy-efficient rapid prototyping process for production of small-batch and customized functional sheet components. The innovation of ISF is to achieve higher formability, flexibility and process control with localized plastic deformation compared with traditional sheet metal forming processes. Multi-point incremental forming (MPIF) shows higher formability and geometric accuracy than single point incremental forming (SPIF) and has attracted interest from industry currently. In the past decades, the industry application of multi-point ISF is still limited due to the limitation of formability, especially for producing parts with complex geometric features. Experimental and numerical ISF studies show that the formability in ISF can be improved by altering some critical process parameters. However, most of the proposed methodologies are either component specific or are based on trial-and-error approaches, while limited work has been published on closed-loop feedback control strategies for formability improvement in multi-point ISF. The first research objective of this thesis is the deformation mechanism and formability investigation in multi-point ISF. The aim of this study is to identify the contribution of different deformation modes and lay a foundation of developing damage model-coupled numerical simulation for fracture prediction in multi-point ISF. To this end, a full-scale three-dimensional numerical simulation with solid finite elements is developed. The deformation modes in different layers at different contact zones along different directions are investigated and discussed in detail. It is indicated that the existence of the supporting die leads to an increase of the hydrostatic pressure and the through-thethickness shear strain, and a decrease of the stress gradient in the thickness direction in the doublesided contact zone, which may lead to smaller springback and slow the damage accumulation rate in multi-point ISF. The second objective of this thesis is focused on the fracture prediction in multi-point ISF. In particular, six damage models are coded into finite element models through ABAQUS/VUMAT subroutine and a numerical comparative study is conducted for fracture prediction in multi-point ISF with a free-formed ellipsoid shape under different loading conditions. It is indicated that the Ayada model could predict the fracture location and fracture depth more accurately than others, however, it is also found that the fracture location and fracture depth cannot be accurately predicted simultaneously with the investigated damage models in this study. In addition, it can be found that Publications included in this thesis No publications included.

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“…Without using dedicated dies, it uses a simple tool with a hemispherical end to form the sheet parts. By travelling along a 3D CAM toolpath on the surface of the sheet, the tool end deforms the sheet incrementally with the plastic deformation localised near the tool end [2] The simple dies are generally made of cheap materials like timber or resin [3] so that the cost in the fabrication and storage of dies is not huge. With the use of supporting dies, TPIF generally leads to better geometric accuracy of the formed parts than SPIF [4].…”

Section: Introductionmentioning

confidence: 99%

Part accuracy improvement in two point incremental forming with a partial die using a model predictive control algorithm

Kearney

Wang

et al. 2017

Precision Engineering

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.Part accuracy improvement in two point incremental forming with a partial die using a model predictive control algorithm.Precision Engineering http://dx.doi.org/10. 1016/j.precisioneng.2017.02.006 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Research highlights: Flexible forming technologies are becoming increasingly significant with the rise of small batch and customised production in the market. work. The enhanced control algorithm is able to correct the toolpath in both the vertical and horizontal directions. In the newly-added horizontal control module, intensive profile points in the evenly distributed radial directions of the horizontal section were used to estimate the horizontal error distribution along the horizontal sectional profile during the forming process. The toolpath correction was performed through properly adjusting the toolpath in two directions based on the optimised toolpath parameters at each step. A case study for forming a non-axisymmetric shape was conducted to experimentally validate the developed toolpath correction strategy. Experiment results indicate that the two-directional toolpath correction approach contributes to part accuracy improvement in TPIF compared with the typical TPIF process that is without toolpath correction.

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Deformation analysis in single-point incremental forming through finite element simulation

Cited by 45 publications

References 24 publications

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

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

Investigation of control strategies for fracture prevention in the multi-point incremental sheet forming process

Part accuracy improvement in two point incremental forming with a partial die using a model predictive control algorithm

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