Bending of High-strength Low-alloyed Steel with Respect to Edge Crack Sensitivity Caused by Shearing Operations

Tsoupis, Ioannis; Hildering, Sven; Merklein, Marion

doi:10.1016/j.proeng.2014.10.065

Cited by 9 publications

(4 citation statements)

References 3 publications

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“…Looking back at the example bracket in Figure 1, the HTT procedure lacks the typical strain reversal of the safety part application [6], where a flat, stamped blank is bent into shape as a bracket which is then pulled flat again in a subsequent load scenario: The test procedure should include shear-cutting, forming and then the break load situation as a third step. Future analyses could extend the stamp+bend test in [16] with a subsequent tensile stage.…”

Section: Discussionmentioning

confidence: 99%

Modelling stamped edges in FEM breakage analyses of high-strength steel safety components

Lingbeek

Schalk-Kitting

Gruschka

et al. 2022

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

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The development process for new safety components includes break load tests, where the component undergoes very large strains. Besides the mechanical properties of the steel, which are changed by the forming process, the break load depends on the quality of the stamped edges. Target of this paper is to investigate whether a hole-tensile test with a stamped hole can demonstrate the effects of stamped-edge quality on the load bearing capacity – and secondary, how such a test procedure can be reproduced with a multi-scale FEM procedure. A series of Hole Tensile Tests (HTT) has been performed with a HSLA steel grade. Here, only minor differences in break load and total elongation were found. The local strain just prior to breakage at the edge of the stamped hole shows remarkably high values, but little difference is found when comparing a machined sample to stamped samples. The multi-scale FEM approach was demonstrated using literature data for dual-phase steel, which is known to be more sensitive to edge cracks. Indeed, a stamped edge, which includes significant hardening and pre-damage, shows earlier fracture in this FEM calculation – however, the crack propagation, which is needed to capture the full breakage of the HTT sample, is not modelled correctly – this limits the application of the method on safety components.

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Section: Discussionmentioning

confidence: 99%

Modelling stamped edges in FEM breakage analyses of high-strength steel safety components

Lingbeek

Schalk-Kitting

Gruschka

et al. 2022

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

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“…Experimental Test Set Up. A technological air bending test device is used for the experimental evaluation of the bendability [10]. The open design of the tool provides the possibility to adopt an optical strain measurement system and to study the evolution of the plastic deformation at the outer surface of the specimen.…”

Section: Methodsmentioning

confidence: 99%

“…Remarkable results in terms of damage development, damage distribution and failure prediction within bending for both mentioned models are demonstrated by several researchers like for example in [7] for Lemaitre and in [8] for Gurson, when considering the drawbacks of the models [9]. For crucial bending conditions however only very few studies on the application of the Lemaitre model [10] and the Gurson model [11] have been performed yet. In the scope of this work a methodology for the adaption of Lemaitre damage model to bending load conditions is developed in order to correctly numerically calculate damage evolution and to predict failure in terms of crack initiation.…”

Section: Introductionmentioning

confidence: 99%

Numerical Prediction of Failure within Small Curvature Bending of Advanced High Strength Steels

Tsoupis

Merklein

2015

KEM

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Within this paper a numerical study of the Continuum Damage Mechanics based damage model Lemaitre in commercial software LS-DYNA is performed in order to correctly predict failure in terms of crack occurrence within small curvature bending of AHSS steels. A strain based calibration method is used for the effective adaption of the Lemaitre model to the bending operation, which is based on the comparison and adaption of the numerically calculated and the experimentally measured deformation field on the outer surface of the bent specimen. Within this method the material dependent damage parameter S is systematically varied in the simulation in order to represent maximum major strain. The new method is proved by numerical simulation of experiments provoking crack initiation using smaller bending radii. It can be shown that failure in terms of crack initiation can be correctly predicted by the model with the damage parameters, which were determined by the method of strain based calibration and an additional optimisation of the parameter Dc. Thus, within this study a user friendly and effective way for the application of Lemaitre damage model to small curvature bending processes of AHSS steels is developed.

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“…Degner et al [5] used tailor heat treated blanks of 6000 and 7000 series aluminum alloys for their research according to ISO 16630.In addition to expanding or flanging processes further forming operations can be impacted by cut outlines. Tsoupis et al [6] investigated the influence of the burr orientation for bending of holed specimens.The different tests feature characteristic advantages and disadvantages. Nevertheless the hole expanding test according to standard ISO 16630is yet the only standardized test for analyzing edge cracking sensitivity.…”

Section: Introductionmentioning

confidence: 99%

Influence of Cutting Processes on Edge Cracking Sensitivity of Bright Finishing Alloys

Merklein

Gnibl

Tsoupis

et al. 2016

KEM

Self Cite

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The economic application of various cutting processes in product development can lead to significant forming problems when changing from prototypes to serial parts. Every cutting process causes characteristic effects on the resulting edge and consequently specific edge cracking sensitivities. For exterior trim components of premium car models various bright finishing alloys are used but were not yet focus of scientific research. Within this study influences of laser beam cutting and machining on the edge cracking sensitivity of the alloys Al99.7Mg0.8Cu and EN AW-5505 are analyzed by executing hole expanding tests according to ISO 16630 enhanced with an offline evaluation method. To assess possible impacts on the resulting hole expansion ratios material and edge characterizations are conducted. Generated knowledge can support reducing forming problems occurring while changing from prototypes to serial parts.

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Bending of High-strength Low-alloyed Steel with Respect to Edge Crack Sensitivity Caused by Shearing Operations

Cited by 9 publications

References 3 publications

Modelling stamped edges in FEM breakage analyses of high-strength steel safety components

Modelling stamped edges in FEM breakage analyses of high-strength steel safety components

Numerical Prediction of Failure within Small Curvature Bending of Advanced High Strength Steels

Influence of Cutting Processes on Edge Cracking Sensitivity of Bright Finishing Alloys

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