Ein- und mehrstufige totaldehnungs- und spannungskontrollierte Wechselverformungsexperimente an eine

FKM 1995 Project No. 145-1
Final report
Abstract:

Components subjected to operational stresses are subject to complex load-time curves, which usually have significant mean stresses. Due to the manufacturing process, they exhibit characteristic surface topographies, surface hardening and surface residual stress states which influence the fatigue strength. The influence of the above-mentioned variables on the alternating deformation behavior, which is essential for the operationally stable dimensioning of components, has so far been investigated almost exclusively under highly simplified boundary conditions, namely under single-stage, mostly medium-stress-free cyclic loading. Studies on alternating deformation behavior with alternating amplitudes and its influence by the condition of near-surface material areas have hardly been carried out to date. As part of the research project "Alternating deformation behavior", which was a sub-project of the joint project "Component fatigue strength", one- and two-stage tensile-compression alternating deformation experiments with different mean stresses were carried out on the heat-treatable steel 42 CrMo 4 under nominal stress and total elongation control. The condition of material areas close to the surface was specifically influenced by shot peening. The investigated tempered state of 42 CrMo 4 softens continuously and does not exhibit stabilized cyclic deformation behaviour. The cyclic stress-strain curve shows larger plastic strain amplitudes at the same stress amplitudes under total strain control than under nominal stress control. Shot peening treatments under nominal stress control always lead to increased alternating strain softening if the proportion of the surface layer subject to residual compressive stress in the total cross-section is sufficiently large, whereas under total strain control this is always the case. The alternating deformation behavior under two-stage loading depends on the loading sequence, the block lengths and the test procedure and therefore cannot be derived directly from single-stage tests.


Scope of report:
159 p., 128 fig., 3 tab., 155 Ut
Start of work:
01.07.1990
End of work:
30.06.1994
Funding body:
Stiftung Stahlanwendungsforschung, A 44

Research center:
Institute of Materials Science I, University of Karlsruhe (TH)

Head:
Univ.-Prof. Dr.rer.nat. Dr.-lng. E.h.mult. E. Macherauch
Editor and author:
Univ.-Prof. Dr.rer.nat. Dr.-lng. E.h.mult. E. Macherauch, Dr.-lng. V. Schulze

Chairman of the working group:
Dr.-lng. A. Baume! Mercedes-Benz AG, Sindelfingen
Chairman of the Advisory Board:
Prof. Dr.-lng. H. Kipphan, Heidelberger Druckmaschinen AG, Heidelberg