Stress range parameters for specific Initiation Sites

4.4.1 Parent material, full penetration butt welds and mechanically fastened joints (see Tables 5.1.5, 5.1.2, 5.1.3 and initiation sites 1,2,3,7 and 9 in Table 5.1.3).

(1)P Cracks initiating from weld toes, fastener holes, fraying surfaces, etc. and propagating through parent material or fully penetrated weld metal shall be assessed using the nominal principal stress range in the member at that point (see Fig.4.2.1).

(2)P The local stress concentration effects of weld profile, bolt and rivet holes, etc. shall be ignored as these are taken into account in the Aa-N strength data for the appropriate detail class. They shall not be calculated (see tables 5.1.1 to 5.1.5).

4.4.2 Fillet and partial penetration butt welds (see initiation sites 4,5,6, 8 and 11 in table 5.1.3).

(1) Cracks initiating from weld roots and propagating through the weld throat should be assessed using the vector sum of the shear forces in the weld metal based on an effective throat dimension (see figure 4.4.1).

pw and hw are forces per unit length

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III! II III If

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Fig.4.4.1 Stresses in weld throats

(2) In lapped joints in one plane the stress per unit length of weld may be calculated on the basis of the average area for axial forces and an elastic polar modulus of the weld group for in-plane moments (see figure 4.4.2).

(3)P In tee-joints any effect of different axial stiffness along the joint shall be taken into account (see Fig.4.2.1(c)).

(4) Where single fillets or incompletely penetrated butt welds are subjected to out-of-plane bending moments the stresses at the root should be calculated using a linear stress distribution through the throat (see figure 4.4.3).

(5)No allowance should be made for bearing contact on the root face in partially penetrated welded joints. 4.4.3 Adhesive bonds (see Table 5.1.5).

(1)P For lap joints failing in the bond line, the effective shear stress range Aaadh shall be based on the force per unit width of the joint divided by the effective length of the lap Ladh, where:

Ladh= lap length L, where L < 15mm (see table 5.1.5) Ladh = 15mm, where L > 15mm

Stress distribution Stress distribution due to direct load p due to moment m

Figure.4.4.2 Stresses in lapped joints Figure 4.4.3. Stresses in root of fillet weld

4.4.4 Castings

(1)P The principal structural stress shall be obtained using finite stress analysis or strain gauging in the case of complex shapes, when standard solutions are not available.

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