On the interplay of friction and stress relaxation to improve stretch-flangeability of dual phase (DP600) steel

Prasad, Kali; Venkatesh, Bharath; Hariharan, K.; Banerjee, D.; Chakkingal, Uday

doi:10.1016/j.cirpj.2020.11.014

Cited by 20 publications

(19 citation statements)

References 45 publications

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“…The x-and z-directional stresses used for comparison with the XRD measurements were evaluated as the element-area-averaged components in the gauge volume shown in Figure 9. Unloading simulations were also conducted so that the element-averaged x-directional stress in the FE simulation corresponded to the XRD-measured stress using Equation ( 4) during the stepwise tensile test, when the specimen was unavoidably unloaded because of mechanical gaps in the tensile machine and stress relaxation due to material viscosity [32].…”

Section: Meshes and Boundary Conditionsmentioning

confidence: 99%

Tensile deformation behavior of TRIP-aided bainitic ferrite steel in the post-necking strain region

Matsuno

Hojo

Watanabe

et al. 2021

Science and Technology of Advanced Materials: Methods

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Transformation induced plasticity (TRIP) steels present a remarkable balance of strength and ductility. However, their post-necking hardening behavior, which is required for pressforming and automobile crash simulation, is unreliable because of their stress-triaxiality dependency. Therefore, we analyzed the stress-triaxiality hardening in the post-necking strain regions of tensile loaded TRIP steel to accurately evaluate the stress and strain distribution. Tensile tests were accordingly conducted on small, round-bar specimens to evaluate the true stress vs. cross-sectional reduction ratio curves up to fracture. Additionally, the stress distribution inside each specimen was measured using synchrotron X-ray diffraction. Using these measurements, the hardening law for the TRIP steel was identified through a series of finite element (FE) simulations, in which a simplified phenomenological strain and stress-triaxiality hardening were found to agree well with the measurements in the postnecking strain region. As a result, the hardening rate of the TRIP steel showed a sudden decrease at the uniform elongation limit strain. The FE simulations including stress-triaxiality hardening successfully reproduced this hardening behavior up to the fracture, and the FE simulation including stress-triaxiality hardening and its saturation presented values closest to the XRD measurements. This simulation also agreed well with the measurements obtained in the tensile direction away from the neck center. A microstructural analysis of the retained austenite at the neck supported this result. The FE simulations revealed that a combination of the TRIP effect and its deactivation accelerates the localized deformation at the specimen neck under tensile loading.

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Section: Meshes and Boundary Conditionsmentioning

confidence: 99%

Tensile deformation behavior of TRIP-aided bainitic ferrite steel in the post-necking strain region

Matsuno

Hojo

Watanabe

et al. 2021

Science and Technology of Advanced Materials: Methods

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“…Typically, the traditional forming limit diagram (FLD) is used to evaluate formability. However, FLD is not suitable for evaluating the edge formability of sheet metal through hole expansion test (HET) data, since HET results are sensitive to hole edge conditions [10,11,12]. The test data are used to evaluate a dimensionless parameter called hole expansion ratio (HER), which is defined as the ratio of the change in the hole diameter of the specimen at failure to the initial hole diameter.…”

Section: Introductionmentioning

confidence: 99%

“…A high value of edge formability is desired for sheet materials, especially when forming flanges in complicated shapes. Hole expansion deformation behaviour has been widely studied by various groups [10,11] and it is well known that the edge formability during HET depends on the punch profile. In the case of conical punch, the hole edge deforms nearly in uniaxial condition [10,11,12].…”

Section: Introductionmentioning

confidence: 99%

“…Hole expansion deformation behaviour has been widely studied by various groups [10,11] and it is well known that the edge formability during HET depends on the punch profile. In the case of conical punch, the hole edge deforms nearly in uniaxial condition [10,11,12]. Following this observation, various researchers have correlated the tensile properties like yield strength (YS), uniform elongation (UE) and total elongation (TE) with HER [10].…”

Section: Introductionmentioning

confidence: 99%

“…Following this observation, various researchers have correlated the tensile properties like yield strength (YS), uniform elongation (UE) and total elongation (TE) with HER [10]. Majority of these studies were performed on ferrous alloys [10,11,12,13]. Aluminum alloys received less attention in this regard.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of hole expansion formability of high strength AA7075 alloy under varying temper conditions

Prasad

Ebrahim

Hariharan

et al. 2022

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

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There has been a widespread increase in the use of aluminum alloys in automotive industries for meeting ever-growing light-weighting requirements. However, edge formability is a critical manufacturing challenge that restricts their widespread use. Edge formability of sheet metal is determined using a hole expansion test (HET) and is evaluated by the hole expansion ratio (HER). The present study investigates the effect of temper conditions on the edge formability of AA7075 alloy sheets. Hole expansion tests were conducted in different temper such as W-temper (super saturated solid solution followed by water quenching), under aged (UA), and peak aged (PA) conditions. Two different hole preparation techniques, a punching and a drilling process, were used to prepare samples with varying edge conditions. The results demonstrate that the W-temper has the highest edge formability irrespective of hole edge conditions. Researchers have reported that uniaxial stress state prevails at the hole edge during the HET. Consequently, uniaxial tensile tests were conducted on for each temper condition and various tensile properties such as yield stress (YS), ultimate tensile strength (UTS), ratio of yield stress to ultimate tensile strength (YS/UTS) were determined to evaluate edge formability. Furthermore, microstructural and failure analysis of the failed specimens were performed to explain the deformation behavior during the HET.

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Stretch-Flanging Behavior of Dual-Phase Steel Using Single-Point Incremental Forming Process

Pandre

Morchhale

Kotkunde

et al. 2022

The Minerals, Metals &Amp; Materials Series

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On the interplay of friction and stress relaxation to improve stretch-flangeability of dual phase (DP600) steel

Cited by 20 publications

References 45 publications

Tensile deformation behavior of TRIP-aided bainitic ferrite steel in the post-necking strain region

Tensile deformation behavior of TRIP-aided bainitic ferrite steel in the post-necking strain region

Evaluation of hole expansion formability of high strength AA7075 alloy under varying temper conditions

Stretch-Flanging Behavior of Dual-Phase Steel Using Single-Point Incremental Forming Process

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