New approaches to detect the onset of localised necking in sheets under through-thickness strain gradients

Martínez-Donaire, A.J.; García-Lomas, F.J.; Vallellano, C.

doi:10.1016/j.matdes.2014.01.012

Cited by 115 publications

(63 citation statements)

References 26 publications

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“…As can be seen, the bending effect is represented by means of the average necking and fracture strains (not used for obtaining the FLC and FFL) in the stretch-bending tests. Notice that although the significant enhancement of formability attained above the FLC due to this bending effect (which is further discussed in [14]), the fracture strains are placed on the FFL region. …”

Section: Forming Limit Diagrammentioning

confidence: 95%

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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: Forming Limit Diagrammentioning

confidence: 95%

“…The punch velocity was set to 1 mm/s and the lubricant at the interface punch-sheet was Vaseline + PTFE + Vaseline. The system ARAMIS ® , based on digital image correlation (DIC), was used at a rate of 12 frames per second to evaluate the onset of necking by using a methodology proposed by the authors [14].…”

Section: Forming Limit Diagrammentioning

confidence: 99%

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

Centeno

Martínez-Donaire

Bagudanch

et al. 2017

Metals

View full text Add to dashboard Cite

show abstract

“…This strategy allows delimiting the limit strains for stretched sheet metals that should not be exceeded in order to ensure a good quality of the final product. The FLDs are determined using necking or fracture criteria, which may be based on sound theoretical developments (see, e.g., Hill, 1952;Stören and Rice, 1975;Yamamoto, 1978;Abed-Meraim et al, 2014) or on finite element (FE) simulations (see, e.g., Zhang et al, 2011;Lumelskyy et al, 2012, Martínez-Donaire et al, 2014Kami et al, 2015). These criteria are generally combined with constitutive models for the prediction of limit strains in sheet metal forming.…”

Section: Determination Of Forming Limit Diagrams Based On Ductile Dammentioning

confidence: 99%

“…More specifically, the onset of strain localization is associated with the maximum of the thickness strain acceleration, which is obtained by computing the second time derivative of thickness strain in the localized zone (see, e.g., Situ et al, 2006Situ et al, , 2007Situ et al, , 2011Zhang et al, 2011;Lumelskyy et al, 2012;Martínez-Donaire et al, 2014). After the maximum in the second time derivative of thickness strain (i.e., thickness strain acceleration) is reached, the localized thinning in the sheet proceeds gradually until the onset of fracture.…”

Section: Criterion Of Maximum Second Time Derivative Of Thickness Strainmentioning

confidence: 99%

Determination of Forming Limit Diagrams Based on Ductile Damage Models and Necking Criteria

Chalal

Abed‐Meraim

2017

Lat. Am. j. solids struct.

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“…So-called time-dependent methods have recently been proposed for use in elevated temperature forming applications [2], [3], [4], [5] and are a focus of the current work.…”

Section: Introductionmentioning

confidence: 99%

Numerical and experimental investigation of the formability of AA6013-T6

DiCecco

Ciano

Butcher

et al. 2017

J. Phys.: Conf. Ser.

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Abstract. AA6013 is an age-hardenable, aluminum alloy with the potential for structural applications in weight-sensitive automotive components. The alloy is at peak strength in the T6 temper, but exhibits relatively low room temperature formability. In an effort to avoid costly post-forming heat-treatments, warm forming of the AA6013 in the T6 temper is investigated in the current work. The experimental formability of the alloy is characterized from room temperature to 250°C through limiting dome height (LDH) tests with a Nakazima hemispherical punch and in-situ stereoscopic digital image correlation (DIC) strain measurement. A forming limit diagram (FLD) is generated from the application of a curvature-based necking criterion to the elevated temperature LDH test results. The evolution of the strain distribution prior to necking is explored using models of the plane strain LDH tests at room temperature and 200°C. At 200°C, strain rate effects are explored relative to the local temporal strain evolution. Modelling efforts include development of a Barlat Yld2000 yield surface to capture the anisotropy of the alloy and use of experimentally obtained isothermal flow-stress curves. The effects of different tensile gage lengths on flow-stress and yield surface calibration for warm tensile testing are discussed. The room temperature model was found to accurately depict the thinning strain distribution consistent with the "safe" thinning strain distribution at room temperature. At 200°C, it is shown that the temporal strain evolution is strongly influenced by strain-rate effects. IntroductionThe application of aluminum in vehicle design and fabrication has seen a steady rise over the past two decades in an effort to meet increasingly stringent emissions and fuel economy mandates. To continue the trend of light-weighting, heat-treatable high-strength 6xxx and 7xxx aluminum alloys are under consideration for the fabrication of structural components that have historically been reserved for high-strength low-alloy steels. Heat-treatable aluminum alloys are at peak strength in the T6 temper, but have relatively low room temperature (RT) formability. To improve the formability of heattreatable alloys without altering the final temper, the warm forming processing route is considered [1].Before developing a warm forming processing route, the warm formability response of the intended alloy, often characterized in terms of a forming limit curve, must be established under processing parameters comparable to the intended application. So-called time-dependent methods have recently been proposed for use in elevated temperature forming applications [2], [3], [4], [5] and are a focus of the current work.

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New approaches to detect the onset of localised necking in sheets under through-thickness strain gradients

Cited by 115 publications

References 26 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

Determination of Forming Limit Diagrams Based on Ductile Damage Models and Necking Criteria

Numerical and experimental investigation of the formability of AA6013-T6

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