A Phenomenological Concept to Predict Formability in Stretch-Bending Forming Operations

Kitting, Daniela; Ofenheimer, Aldo; Pauli, Heinrich; Till, Edwin T.

doi:10.1007/s12289-010-0979-6

Cited by 18 publications

(8 citation statements)

References 6 publications

(10 reference statements)

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“…When a material is subjected to bending in addition to other loading conditions, the conventional FLD often provides inaccurate results. In these contexts, materials exhibit a higher deformation capacity than indicated by the FLD, as major strain values located above the safety limit, are in reality, below the failure limit [21,115]. Research conducted by Kitting et al [116] involved stretch-bending tests conducted on DP800 and CP800 steels under plane-strain and biaxial stretching conditions.…”

Section: Bending Influencementioning

confidence: 99%

“…Kitting et al [115] proposed a phenomenological approach that offers the ability to predict stretch-bending formability using the conventional FLC prediction method. Neuhauser et al [113] conducted angular stretch bending tests on DP600 steel and presented a methodology for quantitatively assess the formability of steel sheets subjected to stretching with superimposed bending.…”

Section: Bending Influencementioning

confidence: 99%

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A Review of Sheet Metal Forming Evaluation of Advanced High-Strength Steels (AHSS)

Pereira,

Peixinho,

Costa

2024

Metals

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This paper presents a review on the formability evaluation of AHSS, enhancing necking-based failure criteria limitations. Complementary fracture/damage constitutive modeling approaches specifically tailored to formability evaluation, validated through numerical and experimental methods, are also subjects of research. AHSS are widely processed through sheet metal forming processes. Although an excellent choice when lightweight, high-strength, and ductility are critical factors, their multi-phase microstructure accentuates forming challenges. To accurately model forming behavior, necking-based failure criteria as well as direct fracture models require improvements. As a necking-based failure model, the conventional forming limit diagram/curve (FLD/FLC) presents limitations in estimating direct fracture (surface cracks, edge cracks, shear cracks), as well as deformation histories under non-linear strain paths. Thus, significant research efforts are being made towards the development of advanced fracture constitutive models capable of predicting fracture scenarios without necking, which are more frequently observed in the realm of AHSS. Scientific community research is divided into several directions aiming at improving the forming and fracture behavior accuracy of parts subjected to sheet metal forming operations. In this review paper, a comprehensive overview of ductile fracture modeling is presented. Firstly, the limitations of FLD/FLC in modeling fracture behavior in sheet metal forming operations are studied, followed by recent trends in constitutive material modeling. Afterwards, advancements in material characterization methods to cover a broad range of stress states are discussed. Finally, damage and fracture models predicting failure in AHSS are investigated. This review paper supplies relevant information on the current issues the sheet metal forming community is challenged with due to the trend towards AHSS employment in the automotive industry.

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Section: Bending Influencementioning

confidence: 99%

Section: Bending Influencementioning

confidence: 99%

A Review of Sheet Metal Forming Evaluation of Advanced High-Strength Steels (AHSS)

Pereira,

Peixinho,

Costa

2024

Metals

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“…The above analyses demonstrate the idea and capability of the proposed localized necking criterion for identifying stable deformation limits of sheet metal under stretch-bending. In order to further explore its validity for forming limit prediction, the experimental results reported by Kitting et al [21] have been analyzed. In FE-simulations of the uniaxial and plane-strain ASBT, Eq.…”

Section: Localized Necking Criterion In Stretch-bending Conditionmentioning

confidence: 99%

“…Von Mises yield criterion is used. The static coefficient of friction for contact conditions between blank and punch is set to 0.001 (recommended by Kitting et al [21]), and that for contact conditions between blank and die is set to 0.125.…”

Section: Strain Localization Behavior Of Sheet Metal Under Stretch-be...mentioning

confidence: 99%

Study on Instability and Forming Limit of Sheet Metal under Stretch-Bending

Hou

Perdahcıoğlu

Boogaard

et al. 2014

KEM

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Under stretch-bending conditions, a significant tensile stress gradient through sheet thickness is induced, especially for a small punch radius. The traditional instability theories were developed assuming a uniform tensile stress / strain distribution through thickness; hence, may lead to unreliable prediction of stretch-bending formability. In this study, the instability behavior of sheet metal under stretch-bending is analyzed via FE-simulation of an Angular Stretch-Bend Test (ASBT). In order to reflect the influence of bending, contact normal stress etc., solid elements are used in the simulation. Three deformation stages are identified: (a). stable deformation; (b). strain localization through sheet thickness; (c). localized necking. Based on the instability characteristics, a localized necking criterion is proposed for predicting forming limits of sheet metal under stretch-bending. By combining the proposed criterion and solid element simulation, good agreement between numerical and experimental results is indicated. This work provides a new approach for predicting stretch-bend formability with sufficient accuracy and convenience.

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“…However, quantitative predictions remain elusive as compared to a body of work on the experimental front [16][17][18][19], especially when the bending radius is small relative to the thickness of the sheet metal.…”

Section: Introductionmentioning

confidence: 99%

Forming Limits of a Sheet Metal After Continuous-Bending-Under-Tension Loading

Xia²,

Zeng

et al. 2013

Journal of Engineering Materials and Technology

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Forming limit diagrams (FLD) have been widely used as a powerful tool for predicting sheet metal forming failure in the industry. The common assumption for forming limits is that the deformation is limited to in-plane loading and through-thickness bending effects are negligible. In practical sheet metal applications, however, a sheet metal blank normally undergoes a combination of stretching, bending, and unbending, so the deformation is invariably three-dimensional. To understand the localized necking phenomenon under this condition, a new extended Marciniak-Kuczynski (M-K) model is proposed in this paper, which combines the FLD theoretical model with finite element analysis to predict the forming limits after a sheet metal undergoes under continuous-bending-undertension (CBT) loading. In this hybrid approach, a finite element model is constructed to simulate the CBT process. The deformation variables after the sheet metal reaches steady state are then extracted from the simulation. They are carried over as the initial condition of the extended M-K analysis for forming limit predictions. The obtained results from proposed model are compared with experimental data from Yoshida et al. (2005, "Fracture Limits of Sheet Metals Under Stretch Bending," Int. J. Mech. Sei., 47(12), pp. 1885-1986 under plane strain deformation mode and the Hutchinson and Neale's (I978(a), "Sheet Necking-II: " Mech. Sheet Metal Forming,) M-K model under in-plane deformation assumption. Several cases are studied, and the results under the CBT loading condition show that the forming limits of post-die-entry material largely depends on the strain, stress, and hardening distributions through the thickness direction. Reduced forming limits are observed for small die radius case. Furthermore, the proposed M-K analysis provides a new understanding of the FLD after this complex bending-unbending-stretching loading condition, which also can be used to evaluate the real process design of sheet metal stamping, especially when the ratio of die entry radii to the metal thickness becomes small.

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A Phenomenological Concept to Predict Formability in Stretch-Bending Forming Operations

Cited by 18 publications

References 6 publications

A Review of Sheet Metal Forming Evaluation of Advanced High-Strength Steels (AHSS)

A Review of Sheet Metal Forming Evaluation of Advanced High-Strength Steels (AHSS)

Study on Instability and Forming Limit of Sheet Metal under Stretch-Bending

Forming Limits of a Sheet Metal After Continuous-Bending-Under-Tension Loading

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