Rrrrm i

(c) Direct stress distribution in y direction across lateral symmetry axis

Fig. 9.3. Finite element analysis of a semi-infinite tension plate with a central circular hole, using triangular elements.

Further, it is known that disturbances to stress distributions due to rapid changes in geometry or load concentrations are only local in effect. Saint-Venant's principle states that the effect of stress concentrations essentially disappear within relatively small distances (approximately equal to the larger lateral dimension), from the position of the disturbance. Advantage can therefore be taken of this principle by reducing the necessary extent of a finite element model. A rule-of-thumb is that a model need only extend to one-and-a-half times the larger lateral dimension from a disturbance, see Fig. 9.4.

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