Strategies for springback compensation regarding process robustness

Gösling, M.; Kracker, H.; Brosius, Alexander; Kuhnt, Sonja; Tekkaya, A. Erman

doi:10.1007/s11740-010-0251-4

Cited by 10 publications

(4 citation statements)

References 5 publications

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“…They investigate springback sensitivity to noise variables such as lubrication or material characteristics. In particular, in [27], the interaction between tool shape and blank yield stress variation is found as the most significant interaction in comparison with other process variables such as, for example, the blankholder force. In [28], a general overview of the optimization problems in sheet metal forming design is shown from the point of view of surrogate modeling, also known as meta-modeling.…”

Section: Introductionmentioning

confidence: 95%

Robust Die Compensation in Sheet Metal Design through the Integration of Dual Response Surface and Shape Function Optimization

Bici

Campana

Cimolin³

et al. 2019

Mathematical Problems in Engineering

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In sheet metal forming, springback represents a major drawback increasing die set-up problems, especially for ultra-high strength steels. Finite Element Analysis is a well-established method to simulate the process during design, and multicriteria optimizations, for example, via surrogate models, are investigated in order to develop integrated design. Since to take into account also springback compensation die design may involve a large number of geometric variables, this paper presents a robust design formulation, based on the adoption of the shape function optimization, to describe springback in terms of weights directly associated to global shape variations of the die shape. Doing so, multicriteria optimization, which involves also die compensation, can be set up in a more intuitive approach, as requested in the preliminary steps of die design. After the introduction of the industrial problem, the mathematical formulation of the shape function optimization is presented together with its novel extension to Robust Design, which is based on the Dual Response Surface. Through a test case derived from the head part of a B-pillar, stamped from a Dual Phase sheet 1.5 mm thick, this novel extension investigates the effect of 6% variation from nominal values of initial yield stress and thickness. Results demonstrate the feasibility of the procedure, underlying that an optimal compensation may not be optimal in terms of process robustness.

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Section: Introductionmentioning

confidence: 95%

Robust Die Compensation in Sheet Metal Design through the Integration of Dual Response Surface and Shape Function Optimization

Bici

Campana

Cimolin³

et al. 2019

Mathematical Problems in Engineering

View full text Add to dashboard Cite

show abstract

“…Additionally, strategies exists for reducing and compensating springbackmechanics-based or geometry-based -by changing the blankholder force [8] or the geometry shapes beforehand [9]. Supplementary to these approaches, a sensitivity and robustness analysis of several springback compensation methods is analyzed for several tool stiffnesses, tool modifications and blankholder controls [10]. In this robustness analysis, the springback compensated parts has standard deviations of the geometry less than 5 %.…”

Section: Previous Workmentioning

confidence: 99%

Influence of Geometrical Shapes and Sheet Thicknesses on the Dimensional Accuracy of Single and Assembled Parts

Konrad

Schöllhammer

Roll

et al. 2016

KEM

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Based on elastic stress and strain states after forming and joining processes, single and assembled parts show deviations regarding their dimensional accuracy. Therefore an analysis of selected influencing factors and their influence on the dimensional accuracy of assembled parts is performed in this paper. In this article a novel approach is presented that characterizes the impact of three geometrical shapes (convex/concave/straight) and different sheet thicknesses on the dimensional accuracy along a linked forming and joining process chain. The process chain consists of a deep drawing and a clinching process. Depending on sheet thickness, material and geometrical shape, the dimensional accuracy of single parts and joined assemblies varies. For the single parts the geometry of the specimen S-rail is used. Several types of assemblies are used for the proposed approach combining this specimen with a plane sheet or a second S-rail. The FEM-tools LS-DYNA and Abaqus, are used to demonstrate this approach. Simulations and experiments with aluminum alloy 6014, mild steel CR3 and sheet thicknesses of 0.7, 1.0 and 2.0 mm are conducted for single and assembled parts. In summary, a significant improvement of the dimensional accuracy of an S-rail assembly is demonstrated using two non-dimensional accurate single parts. Future work will be to analyze frequently occurring part segmentations for the joining technologies and to optimize material mix and sheet thicknesses in order to improve deviations of the assembly to the nominal CAD geometry.

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“…Springback addresses one major challenge in sheet metal forming due to the resulting geometric error of components and the associated assembly difficulties. 8 To compensate springback, the part and tool design can be adapted prior to the forming operation. One of the simplest examples for springback compensation is overbending in a three-point bending operation.…”

Section: Introductionmentioning

confidence: 99%

Improvement of process control in sheet metal forming by considering the gradual properties of the initial sheet metal

Zettl

Schmid

Pulvermacher

et al. 2023

The Journal of Strain Analysis for Engineering Design

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In scientific studies, sheet metal is usually considered as a two-dimensional body. Thus, it is accepted that material properties are in most cases regarded homogeneous in thickness direction. However, a gradation of certain properties becomes apparent when going beyond the standard characterization methods for sheet metals, which can for example, influence the springback behavior and the thinning of the sheet after forming. Thus, the aim of this work is to further improve the prediction accuracy of springback after forming in simulations, by implementing several inhomogeneous properties over the sheet thickness in an existing material model. For this purpose, the entire procedure from the identification of the inhomogeneous properties for describing the gradation to the implementation in a numerical model and its validation by comparing experimental and simulated bending operations is carried out on a DC04 cold-forming steel in order to prove its influence on the springback behavior. It is shown that including graded material properties in simulations does indeed have an impact on the prediction quality of springback and that the information about inhomogeneous properties can be provided by existing characterization methods with a high local resolution like electron backscatter diffraction or X-ray stress analysis. In a further step, it was possible to validate the improvement in numerical accuracy by comparing the prediction of the springback angle from both the existing and the extended model with experimental bending results. Both the initial model as well as the model supplemented with the 3D properties provide a good prediction accuracy in the solution heat treated material state. For the predeformed material, however, the initial numerical model predicts a springback angle of about 13°, which deviates remarkably from the experimentally obtained mean value of about 17°. The extended model delivers a significantly improved accuracy in springback prediction in relation to the initial prediction (deviation of 4°) with a minor deviation of only about 0.8°, which proves the importance of considering the gradation of material properties in thickness direction for an overall higher dimensional accuracy of sheet metal products.

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Strategies for springback compensation regarding process robustness

Cited by 10 publications

References 5 publications

Robust Die Compensation in Sheet Metal Design through the Integration of Dual Response Surface and Shape Function Optimization

Robust Die Compensation in Sheet Metal Design through the Integration of Dual Response Surface and Shape Function Optimization

Influence of Geometrical Shapes and Sheet Thicknesses on the Dimensional Accuracy of Single and Assembled Parts

Improvement of process control in sheet metal forming by considering the gradual properties of the initial sheet metal

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