New Methodologies for Fracture Detection of Automotive Steels in Tight Radius Bending: Application to the VDA 238–100 V-Bend Test

Noder, Jacqueline; Dykeman, James; Butcher, Cliff

doi:10.1007/s11340-020-00627-z

Cited by 16 publications

(14 citation statements)

References 17 publications

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“…The VDA 238-100 specification recommends that failure be identified from a reduction in the punch load of 30 or 60 N (depending upon the material type). Noder et al [53] highlighted limitations of this fracture detection methodology since materials with high bendability or thin gauges may not fracture in the tight-radius bend test and the punch force will decrease as a consequence of the kinematic boundary conditions of the test frame. A stress metric for fracture detection was proposed based upon the estimated bending moment, M. A reduction in the stress metric of 1% was found to provide results in agreement with the VDA force threshold for less ductile materials while it avoided false predictions of failure in ductile grades until a bend angle of 160 degrees.…”

Section: V-bend-plane Strain Fracturementioning

confidence: 99%

“…Accurate characterization of the plane strain fracture strain is vital since it represents the terminal strain state when an acute neck has formed and is the minima of the fracture locus. The VDA 238-100 [ 52 ] tight radius bend test provides an attractive alternative to conventional plane strain notch tests since fracture occurs on the specimen outer (convex) surface, where strains can directly be measured utilizing an inverted V-Bend frame equipped with a DIC set-up and thus eliminate the need for inverse finite-element analysis [ 53 , 54 , 55 ]. A schematic of the adopted test frame is depicted in Figure 25 a.…”

Section: Fracture Characterization and Calibration Of Fracture Locusmentioning

confidence: 99%

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A Comparative Evaluation of Third-Generation Advanced High-Strength Steels for Automotive Forming and Crash Applications

et al. 2021

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While the third generation of advanced high-strength steels (3rd Gen AHSS) have increasingly gained attention for automotive lightweighting, it remains unclear to what extent the developed methodologies for the conventional dual-phase (DP) steels are applicable to this new class of steels. The present paper provides a comprehensive study on the constitutive, formability, tribology, and fracture behavior of three commercial 3rd Gen AHSS with an ultimate strength level ranging from 980 to 1180 MPa which are contrasted with two DP steels of the same strength levels and the 590R AHSS. The hardening response to large strain levels was determined experimentally using tensile and shear tests and then evaluated in 3D simulations of tensile tests. In general, the strain rate sensitivity of the two 3rd Gen 1180 AHSS was significantly different as one grade exhibited larger transformation-induced behavior. The in-plane formability of the three 1180 MPa steels was similar but with a stark contrast in the local formability whereas the opposite trend was observed for the 3rd Gen 980 and the DP980 steel. The forming limit curves could be accurately predicted using the experimentally measured hardening behavior and the deterministic modified Bressan–Williams through-thickness shear model or the linearized Modified Maximum Force Criterion. The resistance to sliding of the three 3rd Gen AHSS in the Twist Compression Test revealed a comparable coefficient of friction to the 590R except for the electro-galvanized 3rd Gen 1180 V1. An efficient experimental approach to fracture characterization for AHSS was developed that exploits tool contact and bending to obtain fracture strains on the surface of the specimen by suppressing necking. Miniature conical hole expansion, biaxial punch tests, and the VDA 238-100 bend test were performed to construct stress-state dependent fracture loci for use in forming and crash simulations. It is demonstrated that, the 3rd Gen 1180 V2 can potentially replace the DP980 steel in terms of both the global and local formability.

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Section: V-bend-plane Strain Fracturementioning

confidence: 99%

Section: Fracture Characterization and Calibration Of Fracture Locusmentioning

confidence: 99%

A Comparative Evaluation of Third-Generation Advanced High-Strength Steels for Automotive Forming and Crash Applications

et al. 2021

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“…The ultimate cold bending performance affects the intrusion resistance and safety performance of hot stamping parts. Generally, the ultimate cold bending angle is required to be greater than 60° [5,6]. In this paper, we study the effect of decarburization layer thickness and carbon content on the ultimate cold bending angle of the hot stamping steel.…”

Section: Introductionmentioning

confidence: 99%

Factors Affecting Intrusion Resistance of Hot Stamping Steel

Liang¹,

Xiao²,

Liu³

et al. 2023

Atlantis Highlights in Materials Science and Technology

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In this paper, we studied the effect of decarburization layer thickness and carbon content on the ultimate cold bending angle of the hot stamping steels. The ultimate cold bending angle of hot stamping steel with 0.23 (wt. pct) carbon content and 0.35 (wt. pct) carbon content is compared. With the increase of carbon content, the ultimate cold bending angle decreases from 66.1°to 40.8°. The appearance of a completely decarburized layer in the microstructure will significantly increase the ultimate cold bending angle, from 66.1°to 77.4°. It can be found that carbon content is key factor affecting the ultimate cold bending angle of hot stamping steels, the thickness of the decarburized layer is another key factor affecting the ultimate cold bending angle of the hot stamping steels.

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“…For the same material thickness, a higher bending angle represents better ductility. It was reported [ 22 ] that the bending angle of the materials reflects the fracture strain under plane-strain bending. However, the fracture bending angle estimated by analytical formulae is thickness-dependent and is not transferable into fracture strain, which is usually applied to numerical models to predict the fracture of structural components.…”

Section: Introductionmentioning

confidence: 99%

Fracture Strain of Al–Si-Coated Press-Hardened Steels under Plane-Strain Bending

Hou

Song²,

et al. 2022

Materials

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Press-hardened steel (PHS) is widely applied to fabricate vehicle body structures for attaining mass reduction and fuel economy without sacrificing occupant safety. The VDA bendability test is often used to characterize the fracture resistance of PHS under plane-strain bending conditions. As lightweighting continues to be a design imperative in the automotive industry, it is desirable to develop and adopt more press-hardened components with higher fracture resistance. In this work, four Al–Si-coated 22MnB5 steels with various initial thicknesses and coating weights were studied. A newly developed methodology was used to calculate the fracture limit strain under plane-strain bending. The results indicate that although the four investigated 22MnB5 steels exhibit similar tensile properties under uniaxial tension, their bending performance per the VDA 238-100 standard differs significantly. The PHS with a low coating weight possesses a higher bending angle and, hence, a larger fracture limit strain. Meanwhile, the peak bending force can be 10% higher than the PHS with a standard coating weight at the same sheet thickness. Therefore, it is expected that PHS with higher fracture strain will have the potential for lightweighting due to its enhanced resistance to fracture and higher energy absorption capability.

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New Methodologies for Fracture Detection of Automotive Steels in Tight Radius Bending: Application to the VDA 238–100 V-Bend Test

Cited by 16 publications

References 17 publications

A Comparative Evaluation of Third-Generation Advanced High-Strength Steels for Automotive Forming and Crash Applications

A Comparative Evaluation of Third-Generation Advanced High-Strength Steels for Automotive Forming and Crash Applications

Factors Affecting Intrusion Resistance of Hot Stamping Steel

Fracture Strain of Al–Si-Coated Press-Hardened Steels under Plane-Strain Bending

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