The Influence of the Through-Thickness Strain Gradients on the Fracture Characterization of Advanced High-Strength Steels

Cheong, K; Butcher, Cliff; Dykeman, James

doi:10.4271/2018-01-0627

Cited by 22 publications

(30 citation statements)

References 14 publications

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“…The latter can be calculated by Eq. [4] after the radii R i and R o are digitally determined using the curve fitting function provided by AutoCAD software, as shown in Figure 2(d).…”

Section: Methodology To Determine Fracture Strainmentioning

confidence: 99%

“…According to Eq. [4], e at the outer surface for each bending test that was stopped at a prescribed a L can be calculated. It should be mentioned that e is zero when a L equals Da.…”

Section: Methodology To Determine Fracture Strainmentioning

confidence: 99%

“…It should be noted that a max is not a direct measurement of bending strain at fracture, and hence it is not transferable into a finite element model to predict fracture of structure components in the vehicle crash event. [4] Previous research works had assumed that the fracture strain (true strain in the outermost fiber at fracture) in a bending test was equal to the true strain at fracture in a tensile test, which can be measured and expressed as the percentage reduction of cross-sectional area A r at fracture. [5,6] However, the application of this methodology to thin sheets might be problematic due to the inaccuracy in measuring A r .…”

Section: Introductionmentioning

confidence: 99%

“…Recently, digital image correlation (DIC) which is a powerful tool to determine full-field strain distribution, [7] had been successfully used to measure fracture strain of a variety of sheet metals following the VDA 238-100 bending test set-up. [4] However, the DIC strain measurement usually relies on many high-resolution images, thus the accuracy of this methodology is sensitive to a few factors such as integrity of surface speckle pattern, lighting configuration, and camera resolution. Finally, the standard VDA bending set-up needs to be retrofitted such that the camera will have a straight line of sight for imaging.…”

Section: Introductionmentioning

confidence: 99%

“…Finally, the standard VDA bending set-up needs to be retrofitted such that the camera will have a straight line of sight for imaging. [4] In this study, a simple methodology to determine fracture strain of press-hardened steels under plane strain bending is developed from a series of interrupted three-point bending tests per the standard VDA 238-100 procedure and extrapolation. The influences of sheet thickness and prior austenite grain size on bendability and fracture strain are subsequently investigated.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

A Simple Methodology to Determine Fracture Strain of Press-Hardened Steels Under Plane Strain Bending

Cai

Wang

et al. 2021

Metall Mater Trans A

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Many automotive body structure components are made of press-hardened steel (PHS) to ensure occupant safety, and they are often subjected to bending-dominated deformation such as axial folding and side intrusion and fracture usually occurs under plane strain bending. Therefore, fracture strain under plane strain condition is an important material property for designing mass-efficient components while maintaining vehicle crashworthiness. The VDA 238-100 standard uses bending angle to qualitatively assess fracture resistance of PHS. However, bending angle is thickness dependent and it cannot be utilized in finite element models to characterize materials' fracture limit for predicting structure failure. In this study, a methodology to determine fracture strain of PHS is developed by applying interrupted bending tests and extrapolation, without using any direct strain measurement system. Then this method is applied to determine fracture strains of bare and AlSi-coated PHS with various thicknesses and prior austenite grain sizes, and the results are compared to that obtained from direct strain measurements. An error analysis is also performed to assess factors/assumptions affecting the accuracy of the proposed methodology. The new method is easy to implement and can be broadly applied to determine fracture strain for other sheet metals whose bendability was previously evaluated by VDA bending angle.

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“…The latter can be calculated by Eq. [4] after the radii R i and R o are digitally determined using the curve fitting function provided by AutoCAD software, as shown in Figure 2(d).…”

Section: Methodology To Determine Fracture Strainmentioning

confidence: 99%

“…According to Eq. [4], e at the outer surface for each bending test that was stopped at a prescribed a L can be calculated. It should be mentioned that e is zero when a L equals Da.…”

Section: Methodology To Determine Fracture Strainmentioning

confidence: 99%