An Analytical Method for Prediction of Cross-Sectional Deformations in Stretch Bending

Abstract:

Abstract. A method for the prediction of cross-sectional distortions of hollow sections under the action of combined bending and stretching has been developed. The model is based on classical deformation theory of plasticity combined with detailed interpretations, making the simplifications necessary to develop a practical closed-form solution while retaining basic mechanisms. The model provides the ability to assess the effect of material properties, tool and section geometry on deformation of individual cross-sectional members. The applicability of the model has been verified with a series of carefully controlled laboratory experiments done in an industry-type rotary stretch bending machine. The findings show that the main parameter with respect to (magnitude of) nominal deformations is the width of the cross section, whereas flange thickness is the main parameter with respect to controlling dimensional accuracy. Comparing the experimental and analytical results, the agreement is remarkably good - in most cases comparable to what could be achieved with more elaborate FE analyses - despite the simplifications necessary to develop the model. A new tool design concept denoted Flatness Limit Curve has been introduced, and used to demonstrate the general applicability of the approach.

• Periodical: Key Engineering Materials (Volumes 504-506)
• Pages: 809-814
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.504-506.809
• Online since: February 2012
• Authors: Togeir Welo
• Keywords: Analytical Solution, Cross-Sectional Deformations, Deformation Theory, Dimensional Tolerances, Flatness Limit Curves, Stretch Bending, Tool Design

References

[1] Hill, R.: The Mathematical Theory of Plasticity, Oxford Engineering Science Series, Oxford, (1950).

[2] Ludwik, P.: Technische Blatter, pp.133-159, (1903).

[3] Welo, T., Baringbing, H.A., On the Evaluation of Dimensional Accuracy in Rotary Stretch Forming, Int J Mater Form (2009) Vol 2 Suppl: 849-852, ESAFORM 2009, (2009).

DOI: 10.1007/s12289-009-0642-2