Prediction of damage in small curvature bending processes of high strength steels using continuum damage mechanics model in 3D simulation

Tsoupis, Ioannis; Hildering, Sven; Merklein, Marion

doi:10.1007/s11740-012-0441-3

Cited by 7 publications

(3 citation statements)

References 9 publications

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“…Commercial software LS-OPT is used to minimise the Mean Squared Error (MSE) of experimental and re-calculated numerical uniaxial tensile test. A detailed description of the methodology can be read in [13]. The determined parameters then have to be adapted for the load case of bending since the three axial load condition over the sheet thickness and the interaction of microstructure and load yield to unequal results.…”

Section: Parameter Identification and Adaption Strategymentioning

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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Section: Parameter Identification and Adaption Strategymentioning

confidence: 99%

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

Tsoupis

Merklein

2015

KEM

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“…Crack free surfaces were observed for all other experiments within bending BL II RD as well as BL ⊥ RD. A detailed description of the validation and the calibration of the model can be found in [8].…”

Section: Experimental and Numerical Analysis Of Damage Behaviour In B...mentioning

confidence: 99%

Development of a Damage Prediction System for Bending and Cutting of High Strength Steels

Vatter

Hildering²,

Tsoupis³

et al. 2013

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Abstract. The application of modern high strength low alloyed steels (HSLA) and advanced high strength steels (AHSS) for structural and safety relevant components in the automotive industry offers the advantage of combining low specific weight with high material strength. Typical manufacturing processes for these steel grades are bending and cutting operations. The forming and cutting potential of these innovative steel grades is different to conventional steels as the process and the damage behaviour is changing. In bending operations cracks occur at the outer bending edge, whereas in cutting operations delamination can appear at the sheared edge. These damages, even though they are small, can initiate the component to fail. For a reliable use of such materials in industrial application a method for the process design is essentially needed. In particular, damages have to be predicted at an early stage. In industrial application damage is detected by a trial-and-error approach causing significant work and a high failure rate. A system for an offline assessment of the risk of failure is unknown so far. In the scope of this work, a method is presented to describe the damaging behaviour of both, bending and cutting operations, by theoretical metamodels. In order to generate a database experiments were carried out using different high strength steels. The main influence factors have been varied, such as the rolling direction, the punch-to-die clearance and the cutting contour in the cutting operation. The bending was investigated using an air-bending process varying the bending angle, the bending radius and the rolling direction. To calculate further sampling points a finite element model has been developed and validated against the experimental data. The damage criterion of Lemaître has been applied. The necessary parameters were determined by reverse identification by means of the major strain for the bending operation and by the punch force-punch stroke curve for the cutting operation. To build up a system for the prediction of the damage the gained data basis was approximated by mathematical functions. An error analysis was carried out showing good accordance. In doing so, a metamodel for the occurrence of damages could be established. The functions are implemented in a software tool which allows the user to determine the failure probability for a given parameter set.

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“…On the other hand bending tests are expensive and time consuming due to the countless number of different tooling choices that affect the deformation of the material in bending. [2] Based on experimental observations fracture in bending is usually preceded by intense strain localization in the form of deep grooves parallel to the bend axis on the convex side of the bend. Depending on the microstructure and the existence of constituent particles (e.g inclusions) shear bands form either at the bottom of these grooves or right beneath the surface and the final fracture follows the direction of these shear bands [5].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Bendability of Hot-Rolled S960 Grade Steel Using Optical Strain Measurements and FE-Modelling

Arola

Kaijalainen

Kesti³

2015

KEM

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Bending is an important forming process for ultra-high strength steel (UHSS) because it is cost-effective, fast and in many cases it can be used to replace welding in a part manufacturing processes. One major challenge in air bending of UHSS is to predict the limits for bendability since the traditional methods for failure prediction, such as forming limit diagram (FLD), cannot generally be applied to bending process. In this paper, 3D FE-modelling coupled with a CDM-damage model is used to simulate the air bending process and to determine the bendability limits for a hot-rolled 960MPa grade. Damage parameters for the CDM-model are determined by using optical strain measurements and inverse modelling of the tensile test. Three point bending tests with optical strain measuring were carried out to determine the deformation field of the outer bend in different bending angles and the results of the bending simulation are compared with the strain measurements of the bending tests. The damage model is then calibrated using the experimental results of the bending tests to adjust the crack occurrence in the simulation. A good agreement was found between simulations and experimental measurements.

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Prediction of damage in small curvature bending processes of high strength steels using continuum damage mechanics model in 3D simulation

Cited by 7 publications

References 9 publications

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

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

Development of a Damage Prediction System for Bending and Cutting of High Strength Steels

Evaluation of Bendability of Hot-Rolled S960 Grade Steel Using Optical Strain Measurements and FE-Modelling

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