Asymmetric Hole Expansion Test (aHET) for Direct Measurement of Orientation-Dependent Tensile Fracture Strain

Abstract:

The flangeability of sheared edges in sheet metal forming is commonly evaluated using the ISO 16630 Hole Expansion Test (HET), in which fracture initiates at the edge under predominantly uniaxial tensile loading. For high-quality edges, this test can be interpreted as providing the strain to fracture under proportional uniaxial tension; however, the measured fracture strain is restricted to a single material-dependent sheet orientation. In this work, a novel experimental approach is proposed to directly measure the uniaxial tensile fracture strain in a predefined sheet orientation using digital image correlation (DIC). The method, termed the Asymmetric Hole Expansion Test (aHET), is derived from the standard HET through the introduction of a novel asymmetric punch geometry. This modification promotes accelerated edge stretching along a controlled direction, enabling orientation-specific characterization of fracture strain. The capability of the aHET to characterize direction-dependent strains to fracture under uniaxial tension is demonstrated on a DP450 dual-phase steel. The consistent fracture initiation at the edge along the predefined fracture direction, combined with the low scatter of the measured fracture strains across repeated tests for all three investigated sheet orientations, demonstrates that the aHET is well suited for identifying the strain to fracture under proportional uniaxial tensile loading for the calibration of fracture initiation models.

• Periodical: Solid State Phenomena (Volume 388)
• Pages: 91-100
• DOI: https://doi.org/10.4028/p-UDAN9u
• Online since: April 2026
• Authors: Raphaël Pérot*, Vincent Grolleau, Dirk Mohr
• Keywords: Fracture Initiation Criterion, Hole Expansion, Hosford Coulomb, Uniaxial Tension

References

[1] Metallic materials - Sheet and strip - Hole expanding test, 16630, International Organization for Standardization, pp.1-7. (2017).

[2] Mohr, D., & Marcadet, S. J., Micromechanically-motivated phenomenological Hosford-Coulomb model for predicting ductile fracture initiation at low stress triaxialities. International Journal of Solids and Structures, 67–68, 40–55. (2015).

DOI: 10.1016/j.ijsolstr.2015.02.024

[3] Roth, C., & Mohr, D., Ductile fracture experiments with locally proportional loading histories. International Journal of Plasticity. (2016).

DOI: 10.1016/j.ijplas.2015.08.004

[4] Paul, S. K., A critical review on hole expansion ratio. Materialia, 9. (2020).

[5] Barnwal, V. K., Lee, S. Y., Yoon, S. Y., Kim, J. H., & Barlat, F., Fracture characteristics of advanced high strength steels during hole expansion test. International Journal of Fracture, 224(2), 217–233. (2020).

DOI: 10.1007/s10704-020-00458-y

[6] Barlo, A., Sigvant, M., Pérez, L., Islam, M. S., & Pilthammar, J., A Study of the Boundary Conditions in the ISO-16630 Hole Expansion Test. IOP Conference Series: Materials Science and Engineering, 1238(1), 012031. (2022).

DOI: 10.1088/1757-899x/1238/1/012031

[7] Li, Z., Chang, Y., Liu, W., & Lian, J., Predicting edge fracture in dual-phase steels: Significance of anisotropy-induced localization. International Journal of Mechanical Sciences, 274. (2024).

DOI: 10.1016/j.ijmecsci.2024.109255

[8] Plosila, P., Kesti, V., Hannula, J., Kömi, J., & Kaijalainen, A., A comparison between tensile and hole expansion properties in 800 MPa tensile strength grade hot-rolled steels. Materials Today Communications, 40. (2024).

DOI: 10.1016/j.mtcomm.2024.109521

[9] Park, H. S., Barlat, F., & Lee, S. Y., Comparison of anisotropic yield functions and calibrations for accurate thickness prediction in hole expansion test. Journal of Materials Processing Technology, 319. (2023).

DOI: 10.1016/j.jmatprotec.2023.118070

[10] Abedini, A., Narayanan, A., & Butcher, C., On the flat punch hole expansion test of sheet metals: Mechanics of deformation and evaluation of anisotropic plasticity models. Mechanics of Materials, 191. (2024).

DOI: 10.1016/j.mechmat.2024.104931

[11] Larour, P., Freudenthaler, J., Grünsteidl, A., & Wang, K., Evaluation of Alternative Stretch Flangeability Testing Methods to Iso 16630 Standard. Conference Proceedings - Innovations for the sheet metal industry, 188. (2014).

[12] Pathak, N., Butcher, C., Worswick, M. J., Bellhouse, E., & Gao, J., Damage evolution in complex-phase and dual-phase steels during edge stretching. Materials, 10(4). (2017).

DOI: 10.3390/ma10040346

[13] Narayanan, A., Abedini, A., Khameneh, F., & Butcher, C., An Experimental Methodology to Characterize the Uniaxial Fracture Strain of Sheet Metals Using the Conical Hole Expansion Test. Journal of Materials Engineering and Performance, 32(10), 4456–4482. (2023).

DOI: 10.1007/s11665-022-07460-6

[14] Wang, K., Luo, M., & Wierzbicki, T., Experiments and modeling of edge fracture for an AHSS sheet. International Journal of Fracture, 187(2), 245–268. (2014).

DOI: 10.1007/s10704-014-9937-5

[15] Pathak, N., Butcher, C., & Worswick, M., Assessment of the Critical Parameters Influencing the Edge Stretchability of Advanced High-Strength Steel Sheet. Journal of Materials Engineering and Performance, 25(11), 4919–4932. (2016).

DOI: 10.1007/s11665-016-2316-9

[16] Dykeman, J., Malcolm, S., Yan, B., Chintamani, J., Huang, G., Ramisetti, N., & Zhu, H., Characterization of edge fracture in various types of advanced high strength steel. SAE 2011 World Congress and Exhibition. (2011).

DOI: 10.4271/2011-01-1058