Page 75 - Biaxial Multiaxial Fatigue and Fracture

60 R LABESSEJIED ET AL.

plastic stress response model is also applied for that purpose in the case where the stress levels
exceed the material yield stress. A multiaxial critical plane criterion and the linear Miner's
damage summation technique are employed for assessing lifetimes. The ratio between
predicted results and largely scattered experimental ones are found to be less than 4.
On the basis of experimental results and lifetimes calculated by the presented fatigue
assessment procedure, the following items may be pointed out:
- All the geometrical peculiarities of the welded assembly must be considered including
angular and axial defects generated by the welding. The influence of these parameters is the
most pronounced one with respect to the fatigue behaviour of the weld,
- Fatigue predictions require to take account for S-N curves modifications involved by
metallurgical thermally dependent changes,
- The residual stresses remaining in the vicinity of the weld should be considered and
superimposed to the actual operational stress states existing within the weld,
- The cyclic plasticity correction has to be run on when stress states exceed largely the
initial material yield stress,
- A multiaxial fatigue damage model as a fatigue stress-based criterion has to be used in
order to account for multiaxial stress states generated within the weld.
The fatigue assessment procedure proposed in this work is modular and opened so that it
may include any multiaxial fatigue criterion, attended that the ductility level of materials
reveals more or less suitability of multiaxial fatigue concepts [13].

REFERENCES

1. Sonsino, C.M. (1997). "Overview of the state of the art on multiaxial fatigue of welds".
Fifth International Conference on BiaxialiMultiaxial Fatigue and Fracture, Cracow,
Poland. Macha E. and Mroz Z. Editors. Vol. I, pp. 395-419.
2. Hobbacher A. and IIW Joint Working Group XIII-XV (1 995). "Recommendations on
fatigue of welded components". Edited by the International Institute of Welding. XIII-
1539-95 I XV-845-95, 1 17 p.
3. Sonsino, C.M. and Maddox, S.J. (2001). "Multiaxial fatigue of welded structures -
Problems and present solutions". Sixth International Conference on BiaxiaVMultiaxial
Fatigue and Fracture, Lisbon, Portugal. De Freitas M. Editor. Vol. I, pp. 3-15.
4. Campion, B., Petitpas, E. and Sauveterre, M. (1999). "Determination of the fatigue
behaviour of a structure in a Gaussian random environment with the Abaqus software",
14th French Mechanics Congress, Toulouse, France. AUM Editor. No 5029.
5. Lemaitre, J. and Chaboche, J.L. (1988). Mkcanique des matkriam solides. Dunod, Paris.
188 p.
6. Bannantine, J.A. and Socie, D.F. (1 992). "Advances in Fatigue Lifetime Predictive
Techniques". ASTM STP 1122, ASTM, Philadelphia. pp. 249-275.
7. Basquin C.H. (1910). "The exponential law of endurance tests", ASTM. PV ac. 10,625 p.
8. Leese, G.E. and Socie, D.F. (1989). Multiaxial Fatigue Analysis and Experiments, SAE
AE-14. Leese G.E. and Socie D.F. Editors. 162 p.
9. Galtier, A. and SCguret, J. (1990). Revue Franqaise de Micanique 4, pp. 291-299.
10. Zenner H., Simbiirger A. and Liu J. (2000). Int. f. Fatigue 22, pp. 137-145.
11. BolIer, Chr and Seeger, T. (1987). Materials Data for Cyclic Loading, Part E : Cast and
Welded Metals. Elsevier. 201 p,
12. Petitpas, E., Lebrun, B., De Meerleer, S., Fournier, P., Charrier, P., Pollet, F. (2000). "Use
of the local approach, for the calculation of the fatigue strength". Edited by the
International Institute of Welding. XIII-I850-00. 13 D.