Statischer Festigkeitsnachweis für Maschinenbauteile auf der Grundlage örtlicher Grenzdehnungen im R

FKM 2004 Issue No. 284 Project No. 247


Final report
Abstract:
Static strength tests were carried out on non-welded components, on large notched flat and round specimens under tension, bending and torsion and on material specimens. Very different materials such as ductile structural steel (St 37), ductile quenched and tempered steel (42 CrMo 4), a ductile wrought aluminum alloy (AIMg3) as well as ductile and non-ductile cast iron materials (GGG-40 and GG-25) were examined. In addition, elastic-plastic FE calculations were carried out to determine notch strains (locally bearable strains). It was found that the low recoverable strains ertr (up to 5%) previously used in the FKM guideline and thus also the plastic support numbers n pl for local failure can be significantly increased. For the verification with local elastically calculated stresses, it is proposed to calculate ertr as the true elongation at fracture from the constriction at fracture for ductile materials (As? 12.5 %). Only for quenched and tempered steels in the tempered condition with high yield strength ratios should ertr be set equal to the elongation at fracture A s due to the sensitivity to multiaxiality. For all non-ductile materials (A s < 12.5 %), i.e. also for those previously classified as very brittle (A s < 8 %), ertr = A s , if necessary with the addition of the elastic component R m / E. Although there is potential to also increase the plastic support numbers n pl for global failure by raising the yield point R p , open questions regarding the general safety concept must first be resolved for practical implementation. In future, the nominal stress verification can be carried out up to a shape number K t = 5 (previously K t = 3). The research report contains a brief update on the application of the new static strength verification for non-welded components. It is emphasized that future research work must continue to deal with the influence of internal multiaxiality and with the improvement of the model for notch strain calculation. The objective of the research project was achieved.


Scope of report:
139 pages and 23 pages of appendices

Start of work:
01.03.2001

End of work:
31.08.2003

Funding body:
BMWi / AiF-Nr. B 12749/ 1

Research centers:
IMA Materialforschung und Anwendungstechnik GmbH, Dresden
Managing Director:
Prof. Dr.-Ing. W. Hane1 Technische Universität Darmstadt Fachgebiet Werkstoffmechanik Prof. Dr.-Ing. Häne1, Dresden Dip1.-lng. P. Leis , Darmstadt

Project supervisors:
Prof. Dr.-Ing. E. Haibach Dr.-Ing. Gerdes
Chairman of the Advisory Board:
Prof. Dr.-Ing. habil. Dr.h.c. H. Kipphan