Influence of the degree and mode of forming strain on the cyclic stress-strain and strain-life behaviour of high strength sheet gauge formable steels
The stress-strain fatigue properties of various high-strength sheet steel grades were examined before and after cold working under a range of deformation modes. The different modes of pre-strain were introduced using laboratory equipment and included uniaxial, balanced biaxial, plane strain and pure shear strain. Cyclic properties were determined on small test pieces cut from appropriately deformed areas using servo-hydraulic test equipment operating under strain control. The results obtained from this test programme are described. The cyclic stress-strain behaviour of all the steels examined differed considerably from the monotonic stress-strain behaviour. In general, cyclic strength of the prestrained steels was greater than that of the corresponding unstrained, as-received material. The notch fatigue strength varied with the degree and mode of forming strain and in certain cases, no improvement over the as-received notch fatigue strength was detected. Therefore, for design purposes, it is safer to assume that no contribution to the fatigue strength at notches or discontinuities can be expected from increases in monotonic strength achieved by forming strain in pressed panels.
Bibliographic Reference: EUR 12749 EN (1990) 117 pp., FS, ECU 10
ISBN: ISBN 92-826-1507-3
Record Number: 199011285 / Last updated on: 1994-12-01
Original language: en
Available languages: en