Issue 33

M. Cova et alii, Frattura ed Integrità Strutturale, 33 (2015) 390-396; DOI: 10.3221/IGF-ESIS.33.43 395 Figure 4 : Safety factor and final result of the overall investigation. N UMERICAL APPLICATION he proposed procedure is written in an algebraic form in order to use it in a computer-assisted procedure and to apply it in fatigue damage assessment in FE models. The method computes directly the equivalent stress amplitude, without time consuming iterative or recursive algorithms. This effectiveness is quite useful in large models where effective values shall be evaluated at each node; sometimes millions of nodes shall be processed. Simply for instance, Fig. 3 and 4 show an example of an industrial application. This groove is a detail of a machine component subjected to a fatigue load history, which has two relevant states. The maximum principal stresses in these load cases are reported. Due to the complex 3D shape, the material is subjected to very different stress conditions, on a multi-axial fatigue perspective, from point to point. In these cases, it is crucial to have an automated multi-axial criterion to properly post-process the FEM results in order to identify the critical locations and the relative safety margin. Fig. 2 shows the safety factor plot according to the presented criterion. C ONCLUSIONS he paper suggests a procedure for explicit and direct assessment of an equivalent stress amplitude under multiaxial fatigue loading. The procedure is appropriate only for particular loading conditions, specifically under a static loading combined with one or several independent and separated pulsating loadings. Moreover, the proposed procedure is suitable for materials where fatigue damage is mainly dependent from principal stress values, for instance cast irons or brittle materials. Anyway, under these particular conditions, the procedure is effective and can be easily used in any FE software, by providing a fast and efficient assessment of an equivalent value for the direct valuation of fatigue damage all over a mechanical component. R EFERENCES [1] Sines, G., Behavior Of Metals Under Complex Static And Alternating Stresses, In: Metal Fatigue. Red. G. Sines A J.L. Waisman, New York, Mcgraw Hill (1959) 145-469 [2] Carpinteri, A., Macha, E., Brighenti, R., Expected Principal Stress Directions Under Multiaxial Random Loading. Part I: Theoretical Aspects Of The Weight Function Method, International Journal Of Fatigue, 21(1) (1999) 83-88. T T