The Effect of Punch Radius on the Deformation of Ultra-High Strength Steel in Bending

Anna Maija Arola; Vili Kesti; Raimo Ruoppa

doi:10.4028/www.scientific.net/KEM.639.139

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HomeKey Engineering MaterialsKey Engineering Materials Vol. 639The Effect of Punch Radius on the Deformation of...

The Effect of Punch Radius on the Deformation of Ultra-High Strength Steel in Bending

Abstract:

Bendability is an important material property for ultra-high strength steel. The bendability of a certain material is expressed as the minimum bending radius R_min of the inner surface of the bend and expressed in multiples of the sheet thickness. Bendability is limited by either cracking on the surface or the edges of the bend or by surface waviness that usually precedes cracking on the outer surface. Surface waviness is a form of strain localization in bending and the intensity of the phenomenon is dependent on e.g. the punch radius, the lower tool width and the sheet thickness. In this study the bendability of a 960MPa grade steel was investigated using optical strain measurements of three-point bending tests to determine the strain level and the bending angle when localization starts with different punch radii. The unbent samples were marked with a grid using laser marking and the deformation was measured with the GOM ARGUS strain analysis system after bending. The quality of the bend was also evaluated visually. In addition, tensile tests were performed and evaluated with the GOM ARAMIS deformation analysis system to investigate the local mechanical properties of the studied steel. The results of strain measurements and visual evaluation were then compared. It was found that beyond a certain angle the maximum strain across the bend did not significantly change with further increases in the bending angle when the punch radius was at least three times the sheet thickness. But with smaller punch radii the maximum strain increased almost linearly with increasing bending angle until fracture appeared. With the smaller punch radii deformation localizes and surface waviness begins to form in smaller bending angles because the deformation is concentrated in a narrow zone.

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Periodical:

Key Engineering Materials (Volume 639)

Pages:

139-146

DOI:

https://doi.org/10.4028/www.scientific.net/KEM.639.139

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Online since:

March 2015

Authors:

Anna Maija Arola*, Vili Kesti, Raimo Ruoppa

Keywords:

Bendability, Strain Localization, Ultra-High Strength Steel

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* - Corresponding Author

References

[1] R. Akeret, Failure mechanisms in the Bending of Aluminum Sheets and Limits of Bendability, Alum. 55 (1978) 117-123.

Google Scholar

[2] A.J. Kaijalainen, P. Suikkanen, L.P. Karjalainen, J.J. Jonas, Effect of Austenite Pancaking on the Microstructure, Texture and Bendability of an Ultrahigh-Strength Strip Steel, Metal. Mat. Trans. A. 45A (2014) 1273-1283.

DOI: 10.1007/s11661-013-2062-7

Google Scholar

[3] C. Soyarslan, M. Malekipour Gharbi, A.E. Tekkaya, A Combined Experimental-Numerical Investigation of Ductile Fracture of a Class of Ferritic-Martensitic Steel, Int. J. Solids Struct. 49 (2012) 1608-1626.

DOI: 10.1016/j.ijsolstr.2012.03.009

Google Scholar

[4] J. Datsko, C. Yang, Correlation of Bendability of Materials with Their Tensile Properties, J. Manuf Sci. Eng. 82 (1960) 309-313.

DOI: 10.1115/1.3664236

Google Scholar

[5] D-K. Leu, A Simplified Approach for Evaluating Bendability and Springback in Plastic Bending of Anisotropic Sheet Metals, J. Mat Proc. Tech. 66 (1997) 9-17.

DOI: 10.1016/s0924-0136(96)02453-3

Google Scholar

[6] K. Yamazaki, M. Oka, H. Yasuda, Y. Mizuyama, H. Tsuchiya, Recent Advances in Ultrahigh-Strength Sheet Steels for Automotive Structural use, Nippon Steel technical Report. 64 (1995) 37-44.

DOI: 10.1016/s0142-1123(97)90062-1

Google Scholar

[7] M. Kaupper, M. Merklein, Bendability of Advanced High Strength Steels – A New Evaluation Procedure, CIRP Annals – Manufacturing Technology. 62 (2013) 247-250.

DOI: 10.1016/j.cirp.2013.03.049

Google Scholar

[8] A. Kaijalainen, P. Karjalainen, D. Porter, P. Suikkanen, J. Kömi, V. Kesti, T. Saarinen, Effect of Inclusions on the Properties of Ultra-High Strength Low-Alloy Steel with a Martensitic-Bainitic Microstructure, Proceedings of the 8th International Conference on CLEAN STEEL, 14 - 16 May, 2012, Budapest, Hungary.

Google Scholar