An Investigation into the Influence of Interrupted Loading in Improving the Stretch-Flangeability of Dual Phase Steel

Prasad, Kali; Krisnaswamy, Hariharan; Banerjee, D.; Chakkingal, Uday

doi:10.4028/p-gi07rp

Cited by 4 publications

(4 citation statements)

References 8 publications

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“…where 3 J is the devatoric third stress invariant. References [39,43,[56][57][58] have been reported, defining the relationship between the fracture strain and stress state.…”

Section: Ductile Fracture Modelingmentioning

confidence: 99%

“…Dual-phase (DP) steels, owing to their superior mechanical properties, are widely used in automotive applications [1][2][3]. However, poor stretch-flangeability is a concern associated with many advanced high strength steels (AHSS) including DP steels [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the HER was also found to depend on several metallurgical factors such as material microstructure [1,12], non-metallic inclusions [13], heat treatment condition [14,15], alloy chemistry, [5] and relative strengths of the individual phases [4,15]. Since the stress state is nearly uniaxial when deformed using a conical punch [3,8,11], attempts have been made to correlate uniaxial tensile (UT) properties with HER [16,17]. It has been shown that yield strength (YS), ultimate tensile strength (UTS), uniform elongation (UE), etc., have a positive correlation with HER [17,18].…”

Section: Introductionmentioning

confidence: 99%

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Does friction contribute to formability improvement using servo press?

et al. 2023

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Servo press forming machines are advanced forming systems that are capable of imparting interrupted punch motion, resulting in enhanced room temperature formability. The exact mechanism of the formability improvement is not yet established. The contribution of interrupted motion in the ductility improvement has been studied through stress relaxation phenomena in uniaxial tensile (UT) tests. However, the reason for improved formability observed when employing servo press is complicated due to the additional contribution from frictional effects. In the present work, an attempt is made to decouple the friction effect on formability improvement numerically. The improved formability is studied using a hole expansion test (HET). The limit of forming during hole expansion is modeled using the Hosford-Coulomb (HC) damage criteria, which is implemented as a user subroutine in a commercial explicit finite element (FE) software. Only the contribution of stress relaxation is accounted for in the evolution of the damage variable during interrupted loading. Therefore, the difference between simulation and experimental hole expansion ratio (HER) can be used to decouple the friction effect from the overall formability improvement during hole expansion. The improvement in HER due to stress relaxation and friction effect is different. The study showed that the model effectively captures the hole expansion deformation process in both monotonic and interrupted loading conditions. Compared to stress relaxation, friction effect played a major role during interrupted HET.

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“…where 3 J is the devatoric third stress invariant. References [39,43,[56][57][58] have been reported, defining the relationship between the fracture strain and stress state.…”

Section: Ductile Fracture Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Does friction contribute to formability improvement using servo press?

et al. 2023

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“…This can be understood by tracing the strain evolution in the contact region. Since the failure mechanism during ISF is by fracture rather than local necking, fracture forming limit curve (FFL) are used to represent deformation limits as opposed to the conventional forming limit curve (FLC) [5,6]. Although the overall formability of ISF is higher than the conventional forming, the process is limited by gradual IOP Publishing doi:10.1088/1757-899X/1238/1/012024 2 thinning and subsequent fracture [7,8].…”

Section: Introductionmentioning

confidence: 99%

Analytical approach to damage prediction in incremental sheet metal forming

Bharti

Raneesh

Hariharan

et al. 2022

IOP Conf. Ser.: Mater. Sci. Eng.

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Incremental sheet metal forming (ISF) is known to exhibit higher formability compared to conventional stamping. It is established that the mechanism of failure during ISF is by fracture occurring at higher effective strain than the local necking observed in traditional forming processes. The deformation limit in ISF is therefore estimated numerically using a suitable continuum damage model. However, simulation of incremental forming process including the damage model is often computationally expensive. In the present work, a simpler alternative combining finite element simulation and numerical solution outside finite element software is utilized. The finite element simulation is performed ignoring the damage model. The stress and strain history thus obtained in critical locations is utilized to estimate the damage evolution. The proposed method is useful when utilizing uncoupled continuum damage models. The proposed method is validated for typical cases by comparing it against the predictions from finite element method. Excellent correlation is observed between the proposed method and finite element simulation results.

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