differences are observed in the value of the scaling coefficient K, the maximum value is achieved in case 1 of figure 6: 5 182 10 u K but the deviation does not exceed 2% when analysing the other cases. As a consequence the incremental G is almost the same for the 4 mechanisms. Thus it is the stress state which governs the fracture. Indeed, the spew fillet reduces the stress concentration effects but does not remove them. Three singular points remain as highlighted by the arrows on figure 5. The most singular is (a) ( 0.611 O , ' 0.781 O ) while the two others (b) are very weakly singular ( 0.985 O ) due to the angle and to the low stiffness of the epoxy compared to steel. The singular eigenmodes are normalized in order to have a traction equal to 1 ( 1 u Or ) along the lower horizontal interface. Table 3 summarizes these tractions for the two singular modes in the four cases (figure 6). TABLE 3: Normalized tractions for the two singular eigenmodes and a combination accounting for the intensity factors. Case 1 2 3 4 0.611 O 1. -0.39 -1. -0.06 0.781 O 1. 1.09 1. 1.33 Combination 1.00 0.75 0.50 1.00 For very small r , the first singularity is predominant and the case 1 is favoured but for larger r the second term plays a role and the conclusion depends on the ratio of the intensity factors of each term as shown on the bottom line. Another method consists in observing the computed traction along fractures of equal length, this is illustrated in the next figure which shows that the first case is slightly predominant on the fourth one. A fracture scenario can be derived. In a first step the horizontal interface debonds, then a strong singularity (exponent smaller than ½) develops at the right end of the micro-crack ( 0.322 O , ' 0.378 O ). It triggers in a second step the fracture of the remaining ligament of adhesive. Finally the crack can evolve as a delamination crack along the interface or kink into the joint but this is another problem. CONCLUSION New examples are proposed in this paper to validate the crack nucleation criterion defined by (1) and (2). They are more specifically dedicated to the
RkJQdWJsaXNoZXIy MjM0NDE=