Improvements of multiaxial fatigue criteria computation for a strong reduction of calculation duration

Fatigue life criteria are tools used for engineering and designing against fatigue. Even if computers capacities increase more and more, the complex g eometry of mechanical components treated nowadays require to improve the sw iftness of the calculations realized in any point of the structure. This pa per contains two proposals concerning the computation of the most commonly used fatigue criteria, whatever their formulation is based upon the critica l plane concept or upon a global approach. The application of many fatigue criteria requires to examine all the material planes passing through the co nsidered point either to find out the critical plane or to make some averag e of stress quantities over all of them. In both cases, all the possible or iented planes have to be explored. The first proposal deals with the way to obtain an homogeneous distribution of the orientation of the practically c onsidered planes. The second proposal of this paper concerns the determinat ion of the smallest circle surrounding to the loading path that describes t he tip of the shear stress vector acting on a material plane during one str ess cycle. The mean shear stress is determined by the centre of this circle ; the shear stress amplitude and the alternate component of the shear stres s are established from this circle also. The principles of these two propos als are explained in detail and the algorithms for the fastest calculations are given. The efficiency of the new proposals relatively to what is commo nly realized is assessed in terms of time saving. (C) 1999 Elsevier Science B.V. All rights reserved.